Merge pull request #4232 from ctiller/connected-subchannel

Change subchannel connectivity state transition graph

43 files changed, 958 insertions, 1284 deletions

diff --git a/src/core/channel/channel_stack.c b/src/core/channel/channel_stack.c
index 7f7fbf420f..5e09a050ee 100644
--- a/src/core/channel/channel_stack.c
+++ b/src/core/channel/channel_stack.c
@@ -101,11 +101,12 @@ grpc_call_element *grpc_call_stack_element(grpc_call_stack *call_stack,
   return CALL_ELEMS_FROM_STACK(call_stack) + index;
 }
 
-void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx,
+void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx, int initial_refs,
+                             grpc_iomgr_cb_func destroy, void *destroy_arg,
                              const grpc_channel_filter **filters,
-                             size_t filter_count, grpc_channel *master,
+                             size_t filter_count,
                              const grpc_channel_args *channel_args,
-                             grpc_channel_stack *stack) {
+                             const char *name, grpc_channel_stack *stack) {
   size_t call_size =
       ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(grpc_call_stack)) +
       ROUND_UP_TO_ALIGNMENT_SIZE(filter_count * sizeof(grpc_call_element));
@@ -115,6 +116,8 @@ void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx,
   size_t i;
 
   stack->count = filter_count;
+  GRPC_STREAM_REF_INIT(&stack->refcount, initial_refs, destroy, destroy_arg,
+                       name);
   elems = CHANNEL_ELEMS_FROM_STACK(stack);
   user_data =
       ((char *)elems) +
@@ -122,7 +125,7 @@ void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx,
 
   /* init per-filter data */
   for (i = 0; i < filter_count; i++) {
-    args.master = master;
+    args.channel_stack = stack;
     args.channel_args = channel_args;
     args.is_first = i == 0;
     args.is_last = i == (filter_count - 1);
@@ -166,15 +169,15 @@ void grpc_call_stack_init(grpc_exec_ctx *exec_ctx,
   size_t i;
 
   call_stack->count = count;
-  gpr_ref_init(&call_stack->refcount.refs, initial_refs);
-  grpc_closure_init(&call_stack->refcount.destroy, destroy, destroy_arg);
+  GRPC_STREAM_REF_INIT(&call_stack->refcount, initial_refs, destroy,
+                       destroy_arg, "CALL_STACK");
   call_elems = CALL_ELEMS_FROM_STACK(call_stack);
   user_data = ((char *)call_elems) +
               ROUND_UP_TO_ALIGNMENT_SIZE(count * sizeof(grpc_call_element));
 
   /* init per-filter data */
   for (i = 0; i < count; i++) {
-    args.refcount = &call_stack->refcount;
+    args.call_stack = call_stack;
     args.server_transport_data = transport_server_data;
     args.context = context;
     call_elems[i].filter = channel_elems[i].filter;
diff --git a/src/core/channel/channel_stack.h b/src/core/channel/channel_stack.h
index 1db12ead7e..c01050e717 100644
--- a/src/core/channel/channel_stack.h
+++ b/src/core/channel/channel_stack.h
@@ -51,15 +51,18 @@
 typedef struct grpc_channel_element grpc_channel_element;
 typedef struct grpc_call_element grpc_call_element;
 
+typedef struct grpc_channel_stack grpc_channel_stack;
+typedef struct grpc_call_stack grpc_call_stack;
+
 typedef struct {
-  grpc_channel *master;
+  grpc_channel_stack *channel_stack;
   const grpc_channel_args *channel_args;
   int is_first;
   int is_last;
 } grpc_channel_element_args;
 
 typedef struct {
-  grpc_stream_refcount *refcount;
+  grpc_call_stack *call_stack;
   const void *server_transport_data;
   grpc_call_context_element *context;
 } grpc_call_element_args;
@@ -144,23 +147,24 @@ struct grpc_call_element {
 
 /* A channel stack tracks a set of related filters for one channel, and
    guarantees they live within a single malloc() allocation */
-typedef struct {
+struct grpc_channel_stack {
+  grpc_stream_refcount refcount;
   size_t count;
   /* Memory required for a call stack (computed at channel stack
      initialization) */
   size_t call_stack_size;
-} grpc_channel_stack;
+};
 
 /* A call stack tracks a set of related filters for one call, and guarantees
    they live within a single malloc() allocation */
-typedef struct {
+struct grpc_call_stack {
   /* shared refcount for this channel stack.
      MUST be the first element: the underlying code calls destroy
      with the address of the refcount, but higher layers prefer to think
      about the address of the call stack itself. */
   grpc_stream_refcount refcount;
   size_t count;
-} grpc_call_stack;
+};
 
 /* Get a channel element given a channel stack and its index */
 grpc_channel_element *grpc_channel_stack_element(grpc_channel_stack *stack,
@@ -175,11 +179,11 @@ grpc_call_element *grpc_call_stack_element(grpc_call_stack *stack, size_t i);
 size_t grpc_channel_stack_size(const grpc_channel_filter **filters,
                                size_t filter_count);
 /* Initialize a channel stack given some filters */
-void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx,
+void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx, int initial_refs,
+                             grpc_iomgr_cb_func destroy, void *destroy_arg,
                              const grpc_channel_filter **filters,
-                             size_t filter_count, grpc_channel *master,
-                             const grpc_channel_args *args,
-                             grpc_channel_stack *stack);
+                             size_t filter_count, const grpc_channel_args *args,
+                             const char *name, grpc_channel_stack *stack);
 /* Destroy a channel stack */
 void grpc_channel_stack_destroy(grpc_exec_ctx *exec_ctx,
                                 grpc_channel_stack *stack);
@@ -199,14 +203,23 @@ void grpc_call_stack_set_pollset(grpc_exec_ctx *exec_ctx,
                                  grpc_pollset *pollset);
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
-#define grpc_call_stack_ref(call_stack, reason) \
+#define GRPC_CALL_STACK_REF(call_stack, reason) \
   grpc_stream_ref(&(call_stack)->refcount, reason)
-#define grpc_call_stack_unref(exec_ctx, call_stack, reason) \
+#define GRPC_CALL_STACK_UNREF(exec_ctx, call_stack, reason) \
   grpc_stream_unref(exec_ctx, &(call_stack)->refcount, reason)
+#define GRPC_CHANNEL_STACK_REF(channel_stack, reason) \
+  grpc_stream_ref(&(channel_stack)->refcount, reason)
+#define GRPC_CHANNEL_STACK_UNREF(exec_ctx, channel_stack, reason) \
+  grpc_stream_unref(exec_ctx, &(channel_stack)->refcount, reason)
 #else
-#define grpc_call_stack_ref(call_stack) grpc_stream_ref(&(call_stack)->refcount)
-#define grpc_call_stack_unref(exec_ctx, call_stack) \
+#define GRPC_CALL_STACK_REF(call_stack, reason) \
+  grpc_stream_ref(&(call_stack)->refcount)
+#define GRPC_CALL_STACK_UNREF(exec_ctx, call_stack, reason) \
   grpc_stream_unref(exec_ctx, &(call_stack)->refcount)
+#define GRPC_CHANNEL_STACK_REF(channel_stack, reason) \
+  grpc_stream_ref(&(channel_stack)->refcount)
+#define GRPC_CHANNEL_STACK_UNREF(exec_ctx, channel_stack, reason) \
+  grpc_stream_unref(exec_ctx, &(channel_stack)->refcount)
 #endif
 
 /* Destroy a call stack */
diff --git a/src/core/channel/client_channel.c b/src/core/channel/client_channel.c
index 020138bf15..9f993b39d6 100644
--- a/src/core/channel/client_channel.c
+++ b/src/core/channel/client_channel.c
@@ -59,11 +59,6 @@ typedef struct client_channel_channel_data {
   grpc_resolver *resolver;
   /** have we started resolving this channel */
   int started_resolving;
-  /** master channel - the grpc_channel instance that ultimately owns
-      this channel_data via its channel stack.
-      We occasionally use this to bump the refcount on the master channel
-      to keep ourselves alive through an asynchronous operation. */
-  grpc_channel *master;
 
   /** mutex protecting client configuration, including all
       variables below in this data structure */
@@ -81,8 +76,10 @@ typedef struct client_channel_channel_data {
   grpc_connectivity_state_tracker state_tracker;
   /** when an lb_policy arrives, should we try to exit idle */
   int exit_idle_when_lb_policy_arrives;
-  /** pollset_set of interested parties in a new connection */
-  grpc_pollset_set pollset_set;
+  /** owning stack */
+  grpc_channel_stack *owning_stack;
+  /** interested parties */
+  grpc_pollset_set interested_parties;
 } channel_data;
 
 /** We create one watcher for each new lb_policy that is returned from a
@@ -103,9 +100,7 @@ typedef struct {
 } waiting_call;
 
 static char *cc_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
-  channel_data *chand = elem->channel_data;
-  return grpc_subchannel_call_holder_get_peer(exec_ctx, elem->call_data,
-                                              chand->master);
+  return grpc_subchannel_call_holder_get_peer(exec_ctx, elem->call_data);
 }
 
 static void cc_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
@@ -121,10 +116,18 @@ static void watch_lb_policy(grpc_exec_ctx *exec_ctx, channel_data *chand,
 
 static void on_lb_policy_state_changed_locked(
     grpc_exec_ctx *exec_ctx, lb_policy_connectivity_watcher *w) {
+  grpc_connectivity_state publish_state = w->state;
   /* check if the notification is for a stale policy */
   if (w->lb_policy != w->chand->lb_policy) return;
 
-  grpc_connectivity_state_set(exec_ctx, &w->chand->state_tracker, w->state,
+  if (publish_state == GRPC_CHANNEL_FATAL_FAILURE &&
+      w->chand->resolver != NULL) {
+    publish_state = GRPC_CHANNEL_TRANSIENT_FAILURE;
+    grpc_resolver_channel_saw_error(exec_ctx, w->chand->resolver);
+    GRPC_LB_POLICY_UNREF(exec_ctx, w->chand->lb_policy, "channel");
+    w->chand->lb_policy = NULL;
+  }
+  grpc_connectivity_state_set(exec_ctx, &w->chand->state_tracker, publish_state,
                               "lb_changed");
   if (w->state != GRPC_CHANNEL_FATAL_FAILURE) {
     watch_lb_policy(exec_ctx, w->chand, w->lb_policy, w->state);
@@ -139,7 +142,7 @@ static void on_lb_policy_state_changed(grpc_exec_ctx *exec_ctx, void *arg,
   on_lb_policy_state_changed_locked(exec_ctx, w);
   gpr_mu_unlock(&w->chand->mu_config);
 
-  GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, w->chand->master, "watch_lb_policy");
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, w->chand->owning_stack, "watch_lb_policy");
   gpr_free(w);
 }
 
@@ -147,7 +150,7 @@ static void watch_lb_policy(grpc_exec_ctx *exec_ctx, channel_data *chand,
                             grpc_lb_policy *lb_policy,
                             grpc_connectivity_state current_state) {
   lb_policy_connectivity_watcher *w = gpr_malloc(sizeof(*w));
-  GRPC_CHANNEL_INTERNAL_REF(chand->master, "watch_lb_policy");
+  GRPC_CHANNEL_STACK_REF(chand->owning_stack, "watch_lb_policy");
 
   w->chand = chand;
   grpc_closure_init(&w->on_changed, on_lb_policy_state_changed, w);
@@ -179,6 +182,11 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
 
   chand->incoming_configuration = NULL;
 
+  if (lb_policy != NULL) {
+    grpc_pollset_set_add_pollset_set(exec_ctx, &lb_policy->interested_parties,
+                                     &chand->interested_parties);
+  }
+
   gpr_mu_lock(&chand->mu_config);
   old_lb_policy = chand->lb_policy;
   chand->lb_policy = lb_policy;
@@ -200,7 +208,7 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
       watch_lb_policy(exec_ctx, chand, lb_policy, state);
     }
     gpr_mu_unlock(&chand->mu_config);
-    GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
+    GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
     grpc_resolver_next(exec_ctx, resolver, &chand->incoming_configuration,
                        &chand->on_config_changed);
     GRPC_RESOLVER_UNREF(exec_ctx, resolver, "channel-next");
@@ -222,7 +230,9 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
   }
 
   if (old_lb_policy != NULL) {
-    grpc_lb_policy_shutdown(exec_ctx, old_lb_policy);
+    grpc_pollset_set_del_pollset_set(exec_ctx,
+                                     &old_lb_policy->interested_parties,
+                                     &chand->interested_parties);
     GRPC_LB_POLICY_UNREF(exec_ctx, old_lb_policy, "channel");
   }
 
@@ -230,13 +240,12 @@ static void cc_on_config_changed(grpc_exec_ctx *exec_ctx, void *arg,
     GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "config_change");
   }
 
-  GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, chand->master, "resolver");
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, chand->owning_stack, "resolver");
 }
 
 static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
                                   grpc_channel_element *elem,
                                   grpc_transport_op *op) {
-  grpc_lb_policy *lb_policy = NULL;
   channel_data *chand = elem->channel_data;
   grpc_resolver *destroy_resolver = NULL;
 
@@ -254,18 +263,15 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
     op->connectivity_state = NULL;
   }
 
-  lb_policy = chand->lb_policy;
-  if (lb_policy) {
-    GRPC_LB_POLICY_REF(lb_policy, "broadcast");
-  }
-
   if (op->disconnect && chand->resolver != NULL) {
     grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
                                 GRPC_CHANNEL_FATAL_FAILURE, "disconnect");
     destroy_resolver = chand->resolver;
     chand->resolver = NULL;
     if (chand->lb_policy != NULL) {
-      grpc_lb_policy_shutdown(exec_ctx, chand->lb_policy);
+      grpc_pollset_set_del_pollset_set(exec_ctx,
+                                       &chand->lb_policy->interested_parties,
+                                       &chand->interested_parties);
       GRPC_LB_POLICY_UNREF(exec_ctx, chand->lb_policy, "channel");
       chand->lb_policy = NULL;
     }
@@ -276,16 +282,11 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
     grpc_resolver_shutdown(exec_ctx, destroy_resolver);
     GRPC_RESOLVER_UNREF(exec_ctx, destroy_resolver, "channel");
   }
-
-  if (lb_policy) {
-    grpc_lb_policy_broadcast(exec_ctx, lb_policy, op);
-    GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "broadcast");
-  }
 }
 
 typedef struct {
   grpc_metadata_batch *initial_metadata;
-  grpc_subchannel **subchannel;
+  grpc_connected_subchannel **connected_subchannel;
   grpc_closure *on_ready;
   grpc_call_element *elem;
   grpc_closure closure;
@@ -293,17 +294,17 @@ typedef struct {
 
 static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
                               grpc_metadata_batch *initial_metadata,
-                              grpc_subchannel **subchannel,
+                              grpc_connected_subchannel **connected_subchannel,
                               grpc_closure *on_ready);
 
 static void continue_picking(grpc_exec_ctx *exec_ctx, void *arg, int success) {
   continue_picking_args *cpa = arg;
   if (!success) {
     grpc_exec_ctx_enqueue(exec_ctx, cpa->on_ready, 0);
-  } else if (cpa->subchannel == NULL) {
+  } else if (cpa->connected_subchannel == NULL) {
     /* cancelled, do nothing */
   } else if (cc_pick_subchannel(exec_ctx, cpa->elem, cpa->initial_metadata,
-                                cpa->subchannel, cpa->on_ready)) {
+                                cpa->connected_subchannel, cpa->on_ready)) {
     grpc_exec_ctx_enqueue(exec_ctx, cpa->on_ready, 1);
   }
   gpr_free(cpa);
@@ -311,7 +312,7 @@ static void continue_picking(grpc_exec_ctx *exec_ctx, void *arg, int success) {
 
 static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
                               grpc_metadata_batch *initial_metadata,
-                              grpc_subchannel **subchannel,
+                              grpc_connected_subchannel **connected_subchannel,
                               grpc_closure *on_ready) {
   grpc_call_element *elem = elemp;
   channel_data *chand = elem->channel_data;
@@ -319,18 +320,19 @@ static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
   continue_picking_args *cpa;
   grpc_closure *closure;
 
-  GPR_ASSERT(subchannel);
+  GPR_ASSERT(connected_subchannel);
 
   gpr_mu_lock(&chand->mu_config);
   if (initial_metadata == NULL) {
     if (chand->lb_policy != NULL) {
-      grpc_lb_policy_cancel_pick(exec_ctx, chand->lb_policy, subchannel);
+      grpc_lb_policy_cancel_pick(exec_ctx, chand->lb_policy,
+                                 connected_subchannel);
     }
     for (closure = chand->waiting_for_config_closures.head; closure != NULL;
          closure = grpc_closure_next(closure)) {
       cpa = closure->cb_arg;
-      if (cpa->subchannel == subchannel) {
-        cpa->subchannel = NULL;
+      if (cpa->connected_subchannel == connected_subchannel) {
+        cpa->connected_subchannel = NULL;
         grpc_exec_ctx_enqueue(exec_ctx, cpa->on_ready, 0);
       }
     }
@@ -338,21 +340,22 @@ static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
     return 1;
   }
   if (chand->lb_policy != NULL) {
-    int r = grpc_lb_policy_pick(exec_ctx, chand->lb_policy, calld->pollset,
-                                initial_metadata, subchannel, on_ready);
+    int r =
+        grpc_lb_policy_pick(exec_ctx, chand->lb_policy, calld->pollset,
+                            initial_metadata, connected_subchannel, on_ready);
     gpr_mu_unlock(&chand->mu_config);
     return r;
   }
   if (chand->resolver != NULL && !chand->started_resolving) {
     chand->started_resolving = 1;
-    GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
+    GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
     grpc_resolver_next(exec_ctx, chand->resolver,
                        &chand->incoming_configuration,
                        &chand->on_config_changed);
   }
   cpa = gpr_malloc(sizeof(*cpa));
   cpa->initial_metadata = initial_metadata;
-  cpa->subchannel = subchannel;
+  cpa->connected_subchannel = connected_subchannel;
   cpa->on_ready = on_ready;
   cpa->elem = elem;
   grpc_closure_init(&cpa->closure, continue_picking, cpa);
@@ -364,7 +367,8 @@ static int cc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *elemp,
 /* Constructor for call_data */
 static void init_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                            grpc_call_element_args *args) {
-  grpc_subchannel_call_holder_init(elem->call_data, cc_pick_subchannel, elem);
+  grpc_subchannel_call_holder_init(elem->call_data, cc_pick_subchannel, elem,
+                                   args->call_stack);
 }
 
 /* Destructor for call_data */
@@ -385,12 +389,12 @@ static void init_channel_elem(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(elem->filter == &grpc_client_channel_filter);
 
   gpr_mu_init(&chand->mu_config);
-  chand->master = args->master;
-  grpc_pollset_set_init(&chand->pollset_set);
   grpc_closure_init(&chand->on_config_changed, cc_on_config_changed, chand);
+  chand->owning_stack = args->channel_stack;
 
   grpc_connectivity_state_init(&chand->state_tracker, GRPC_CHANNEL_IDLE,
                                "client_channel");
+  grpc_pollset_set_init(&chand->interested_parties);
 }
 
 /* Destructor for channel_data */
@@ -403,10 +407,13 @@ static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
     GRPC_RESOLVER_UNREF(exec_ctx, chand->resolver, "channel");
   }
   if (chand->lb_policy != NULL) {
+    grpc_pollset_set_del_pollset_set(exec_ctx,
+                                     &chand->lb_policy->interested_parties,
+                                     &chand->interested_parties);
     GRPC_LB_POLICY_UNREF(exec_ctx, chand->lb_policy, "channel");
   }
   grpc_connectivity_state_destroy(exec_ctx, &chand->state_tracker);
-  grpc_pollset_set_destroy(&chand->pollset_set);
+  grpc_pollset_set_destroy(&chand->interested_parties);
   gpr_mu_destroy(&chand->mu_config);
 }
 
@@ -435,7 +442,7 @@ void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
   if (!grpc_closure_list_empty(chand->waiting_for_config_closures) ||
       chand->exit_idle_when_lb_policy_arrives) {
     chand->started_resolving = 1;
-    GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
+    GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
     grpc_resolver_next(exec_ctx, resolver, &chand->incoming_configuration,
                        &chand->on_config_changed);
   }
@@ -454,7 +461,7 @@ grpc_connectivity_state grpc_client_channel_check_connectivity_state(
     } else {
       chand->exit_idle_when_lb_policy_arrives = 1;
       if (!chand->started_resolving && chand->resolver != NULL) {
-        GRPC_CHANNEL_INTERNAL_REF(chand->master, "resolver");
+        GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
         chand->started_resolving = 1;
         grpc_resolver_next(exec_ctx, chand->resolver,
                            &chand->incoming_configuration,
@@ -466,32 +473,39 @@ grpc_connectivity_state grpc_client_channel_check_connectivity_state(
   return out;
 }
 
+typedef struct {
+  channel_data *chand;
+  grpc_pollset *pollset;
+  grpc_closure *on_complete;
+  grpc_closure my_closure;
+} external_connectivity_watcher;
+
+static void on_external_watch_complete(grpc_exec_ctx *exec_ctx, void *arg,
+                                       int iomgr_success) {
+  external_connectivity_watcher *w = arg;
+  grpc_closure *follow_up = w->on_complete;
+  grpc_pollset_set_del_pollset(exec_ctx, &w->chand->interested_parties,
+                               w->pollset);
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, w->chand->owning_stack,
+                           "external_connectivity_watcher");
+  gpr_free(w);
+  follow_up->cb(exec_ctx, follow_up->cb_arg, iomgr_success);
+}
+
 void grpc_client_channel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
     grpc_connectivity_state *state, grpc_closure *on_complete) {
   channel_data *chand = elem->channel_data;
+  external_connectivity_watcher *w = gpr_malloc(sizeof(*w));
+  w->chand = chand;
+  w->pollset = pollset;
+  w->on_complete = on_complete;
+  grpc_pollset_set_add_pollset(exec_ctx, &chand->interested_parties, pollset);
+  grpc_closure_init(&w->my_closure, on_external_watch_complete, w);
+  GRPC_CHANNEL_STACK_REF(w->chand->owning_stack,
+                         "external_connectivity_watcher");
   gpr_mu_lock(&chand->mu_config);
   grpc_connectivity_state_notify_on_state_change(
-      exec_ctx, &chand->state_tracker, state, on_complete);
+      exec_ctx, &chand->state_tracker, state, &w->my_closure);
   gpr_mu_unlock(&chand->mu_config);
 }
-
-grpc_pollset_set *grpc_client_channel_get_connecting_pollset_set(
-    grpc_channel_element *elem) {
-  channel_data *chand = elem->channel_data;
-  return &chand->pollset_set;
-}
-
-void grpc_client_channel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                              grpc_channel_element *elem,
-                                              grpc_pollset *pollset) {
-  channel_data *chand = elem->channel_data;
-  grpc_pollset_set_add_pollset(exec_ctx, &chand->pollset_set, pollset);
-}
-
-void grpc_client_channel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                              grpc_channel_element *elem,
-                                              grpc_pollset *pollset) {
-  channel_data *chand = elem->channel_data;
-  grpc_pollset_set_del_pollset(exec_ctx, &chand->pollset_set, pollset);
-}
diff --git a/src/core/channel/client_channel.h b/src/core/channel/client_channel.h
index 5103f07a43..d9bc4971f1 100644
--- a/src/core/channel/client_channel.h
+++ b/src/core/channel/client_channel.h
@@ -57,17 +57,7 @@ grpc_connectivity_state grpc_client_channel_check_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect);
 
 void grpc_client_channel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
     grpc_connectivity_state *state, grpc_closure *on_complete);
 
-grpc_pollset_set *grpc_client_channel_get_connecting_pollset_set(
-    grpc_channel_element *elem);
-
-void grpc_client_channel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                              grpc_channel_element *channel,
-                                              grpc_pollset *pollset);
-void grpc_client_channel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                              grpc_channel_element *channel,
-                                              grpc_pollset *pollset);
-
 #endif /* GRPC_INTERNAL_CORE_CHANNEL_CLIENT_CHANNEL_H */
diff --git a/src/core/channel/client_uchannel.c b/src/core/channel/client_uchannel.c
index 456ffb7371..2c0b07d8bf 100644
--- a/src/core/channel/client_uchannel.c
+++ b/src/core/channel/client_uchannel.c
@@ -58,13 +58,13 @@ typedef struct client_uchannel_channel_data {
       this channel_data via its channel stack.
       We occasionally use this to bump the refcount on the master channel
       to keep ourselves alive through an asynchronous operation. */
-  grpc_channel *master;
+  grpc_channel_stack *owning_stack;
 
   /** connectivity state being tracked */
   grpc_connectivity_state_tracker state_tracker;
 
   /** the subchannel wrapped by the microchannel */
-  grpc_subchannel *subchannel;
+  grpc_connected_subchannel *connected_subchannel;
 
   /** the callback used to stay subscribed to subchannel connectivity
    * notifications */
@@ -84,15 +84,13 @@ static void monitor_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
                               chand->subchannel_connectivity,
                               "uchannel_monitor_subchannel");
-  grpc_subchannel_notify_on_state_change(exec_ctx, chand->subchannel,
-                                         &chand->subchannel_connectivity,
-                                         &chand->connectivity_cb);
+  grpc_connected_subchannel_notify_on_state_change(
+      exec_ctx, chand->connected_subchannel, NULL,
+      &chand->subchannel_connectivity, &chand->connectivity_cb);
 }
 
 static char *cuc_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
-  channel_data *chand = elem->channel_data;
-  return grpc_subchannel_call_holder_get_peer(exec_ctx, elem->call_data,
-                                              chand->master);
+  return grpc_subchannel_call_holder_get_peer(exec_ctx, elem->call_data);
 }
 
 static void cuc_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
@@ -128,11 +126,11 @@ static void cuc_start_transport_op(grpc_exec_ctx *exec_ctx,
 
 static int cuc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
                                grpc_metadata_batch *initial_metadata,
-                               grpc_subchannel **subchannel,
+                               grpc_connected_subchannel **connected_subchannel,
                                grpc_closure *on_ready) {
   channel_data *chand = arg;
   GPR_ASSERT(initial_metadata != NULL);
-  *subchannel = chand->subchannel;
+  *connected_subchannel = chand->connected_subchannel;
   return 1;
 }
 
@@ -140,7 +138,7 @@ static int cuc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
 static void cuc_init_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                                grpc_call_element_args *args) {
   grpc_subchannel_call_holder_init(elem->call_data, cuc_pick_subchannel,
-                                   elem->channel_data);
+                                   elem->channel_data, args->call_stack);
 }
 
 /* Destructor for call_data */
@@ -158,7 +156,7 @@ static void cuc_init_channel_elem(grpc_exec_ctx *exec_ctx,
   grpc_closure_init(&chand->connectivity_cb, monitor_subchannel, chand);
   GPR_ASSERT(args->is_last);
   GPR_ASSERT(elem->filter == &grpc_client_uchannel_filter);
-  chand->master = args->master;
+  chand->owning_stack = args->channel_stack;
   grpc_connectivity_state_init(&chand->state_tracker, GRPC_CHANNEL_IDLE,
                                "client_uchannel");
   gpr_mu_init(&chand->mu_state);
@@ -168,10 +166,14 @@ static void cuc_init_channel_elem(grpc_exec_ctx *exec_ctx,
 static void cuc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
                                      grpc_channel_element *elem) {
   channel_data *chand = elem->channel_data;
-  grpc_subchannel_state_change_unsubscribe(exec_ctx, chand->subchannel,
-                                           &chand->connectivity_cb);
+  /* cancel subscription */
+  grpc_connected_subchannel_notify_on_state_change(
+      exec_ctx, chand->connected_subchannel, NULL, NULL,
+      &chand->connectivity_cb);
   grpc_connectivity_state_destroy(exec_ctx, &chand->state_tracker);
   gpr_mu_destroy(&chand->mu_state);
+  GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, chand->connected_subchannel,
+                                  "uchannel");
 }
 
 static void cuc_set_pollset(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
@@ -191,23 +193,14 @@ grpc_connectivity_state grpc_client_uchannel_check_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect) {
   channel_data *chand = elem->channel_data;
   grpc_connectivity_state out;
-  out = grpc_connectivity_state_check(&chand->state_tracker);
   gpr_mu_lock(&chand->mu_state);
-  if (out == GRPC_CHANNEL_IDLE && try_to_connect) {
-    grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
-                                GRPC_CHANNEL_CONNECTING,
-                                "uchannel_connecting_changed");
-    chand->subchannel_connectivity = out;
-    grpc_subchannel_notify_on_state_change(exec_ctx, chand->subchannel,
-                                           &chand->subchannel_connectivity,
-                                           &chand->connectivity_cb);
-  }
+  out = grpc_connectivity_state_check(&chand->state_tracker);
   gpr_mu_unlock(&chand->mu_state);
   return out;
 }
 
 void grpc_client_uchannel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
     grpc_connectivity_state *state, grpc_closure *on_complete) {
   channel_data *chand = elem->channel_data;
   gpr_mu_lock(&chand->mu_state);
@@ -216,40 +209,11 @@ void grpc_client_uchannel_watch_connectivity_state(
   gpr_mu_unlock(&chand->mu_state);
 }
 
-grpc_pollset_set *grpc_client_uchannel_get_connecting_pollset_set(
-    grpc_channel_element *elem) {
-  channel_data *chand = elem->channel_data;
-  grpc_channel_element *parent_elem;
-  gpr_mu_lock(&chand->mu_state);
-  parent_elem = grpc_channel_stack_last_element(grpc_channel_get_channel_stack(
-      grpc_subchannel_get_master(chand->subchannel)));
-  gpr_mu_unlock(&chand->mu_state);
-  return grpc_client_channel_get_connecting_pollset_set(parent_elem);
-}
-
-void grpc_client_uchannel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                               grpc_channel_element *elem,
-                                               grpc_pollset *pollset) {
-  grpc_pollset_set *master_pollset_set =
-      grpc_client_uchannel_get_connecting_pollset_set(elem);
-  grpc_pollset_set_add_pollset(exec_ctx, master_pollset_set, pollset);
-}
-
-void grpc_client_uchannel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                               grpc_channel_element *elem,
-                                               grpc_pollset *pollset) {
-  grpc_pollset_set *master_pollset_set =
-      grpc_client_uchannel_get_connecting_pollset_set(elem);
-  grpc_pollset_set_del_pollset(exec_ctx, master_pollset_set, pollset);
-}
-
 grpc_channel *grpc_client_uchannel_create(grpc_subchannel *subchannel,
                                           grpc_channel_args *args) {
   grpc_channel *channel = NULL;
 #define MAX_FILTERS 3
   const grpc_channel_filter *filters[MAX_FILTERS];
-  grpc_channel *master = grpc_subchannel_get_master(subchannel);
-  char *target = grpc_channel_get_target(master);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   size_t n = 0;
 
@@ -261,19 +225,19 @@ grpc_channel *grpc_client_uchannel_create(grpc_subchannel *subchannel,
   GPR_ASSERT(n <= MAX_FILTERS);
 
   channel =
-      grpc_channel_create_from_filters(&exec_ctx, target, filters, n, args, 1);
+      grpc_channel_create_from_filters(&exec_ctx, NULL, filters, n, args, 1);
 
-  gpr_free(target);
   return channel;
 }
 
-void grpc_client_uchannel_set_subchannel(grpc_channel *uchannel,
-                                         grpc_subchannel *subchannel) {
+void grpc_client_uchannel_set_connected_subchannel(
+    grpc_channel *uchannel, grpc_connected_subchannel *connected_subchannel) {
   grpc_channel_element *elem =
       grpc_channel_stack_last_element(grpc_channel_get_channel_stack(uchannel));
   channel_data *chand = elem->channel_data;
   GPR_ASSERT(elem->filter == &grpc_client_uchannel_filter);
   gpr_mu_lock(&chand->mu_state);
-  chand->subchannel = subchannel;
+  chand->connected_subchannel = connected_subchannel;
+  GRPC_CONNECTED_SUBCHANNEL_REF(connected_subchannel, "uchannel");
   gpr_mu_unlock(&chand->mu_state);
 }
diff --git a/src/core/channel/client_uchannel.h b/src/core/channel/client_uchannel.h
index dfe6695ae3..92a831493c 100644
--- a/src/core/channel/client_uchannel.h
+++ b/src/core/channel/client_uchannel.h
@@ -48,23 +48,13 @@ grpc_connectivity_state grpc_client_uchannel_check_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect);
 
 void grpc_client_uchannel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
     grpc_connectivity_state *state, grpc_closure *on_complete);
 
-grpc_pollset_set *grpc_client_uchannel_get_connecting_pollset_set(
-    grpc_channel_element *elem);
-
-void grpc_client_uchannel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                               grpc_channel_element *channel,
-                                               grpc_pollset *pollset);
-void grpc_client_uchannel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                               grpc_channel_element *channel,
-                                               grpc_pollset *pollset);
-
 grpc_channel *grpc_client_uchannel_create(grpc_subchannel *subchannel,
                                           grpc_channel_args *args);
 
-void grpc_client_uchannel_set_subchannel(grpc_channel *uchannel,
-                                         grpc_subchannel *subchannel);
+void grpc_client_uchannel_set_connected_subchannel(
+    grpc_channel *uchannel, grpc_connected_subchannel *connected_subchannel);
 
 #endif /* GRPC_INTERNAL_CORE_CHANNEL_CLIENT_MICROCHANNEL_H */
diff --git a/src/core/channel/compress_filter.c b/src/core/channel/compress_filter.c
index d7d1c189fe..cc8e191628 100644
--- a/src/core/channel/compress_filter.c
+++ b/src/core/channel/compress_filter.c
@@ -288,8 +288,7 @@ static void init_channel_elem(grpc_exec_ctx *exec_ctx,
 
 /* Destructor for channel data */
 static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
-                                 grpc_channel_element *elem) {
-}
+                                 grpc_channel_element *elem) {}
 
 const grpc_channel_filter grpc_compress_filter = {
     compress_start_transport_stream_op, grpc_channel_next_op, sizeof(call_data),
diff --git a/src/core/channel/connected_channel.c b/src/core/channel/connected_channel.c
index 0e1efd965a..e8eb9dcfc5 100644
--- a/src/core/channel/connected_channel.c
+++ b/src/core/channel/connected_channel.c
@@ -89,9 +89,9 @@ static void init_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
   int r;
 
   GPR_ASSERT(elem->filter == &grpc_connected_channel_filter);
-  r = grpc_transport_init_stream(exec_ctx, chand->transport,
-                                 TRANSPORT_STREAM_FROM_CALL_DATA(calld),
-                                 args->refcount, args->server_transport_data);
+  r = grpc_transport_init_stream(
+      exec_ctx, chand->transport, TRANSPORT_STREAM_FROM_CALL_DATA(calld),
+      &args->call_stack->refcount, args->server_transport_data);
   GPR_ASSERT(r == 0);
 }
 
diff --git a/src/core/channel/http_server_filter.c b/src/core/channel/http_server_filter.c
index bc3a56cbf0..ae8660da92 100644
--- a/src/core/channel/http_server_filter.c
+++ b/src/core/channel/http_server_filter.c
@@ -224,8 +224,7 @@ static void init_channel_elem(grpc_exec_ctx *exec_ctx,
 
 /* Destructor for channel data */
 static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
-                                 grpc_channel_element *elem) {
-}
+                                 grpc_channel_element *elem) {}
 
 const grpc_channel_filter grpc_http_server_filter = {
     hs_start_transport_op, grpc_channel_next_op, sizeof(call_data),
diff --git a/src/core/channel/subchannel_call_holder.c b/src/core/channel/subchannel_call_holder.c
index 7251714519..f5da41f3cd 100644
--- a/src/core/channel/subchannel_call_holder.c
+++ b/src/core/channel/subchannel_call_holder.c
@@ -44,7 +44,6 @@
 
 static void subchannel_ready(grpc_exec_ctx *exec_ctx, void *holder,
                              int success);
-static void call_ready(grpc_exec_ctx *exec_ctx, void *holder, int success);
 static void retry_ops(grpc_exec_ctx *exec_ctx, void *retry_ops_args,
                       int success);
 
@@ -58,16 +57,17 @@ static void retry_waiting_locked(grpc_exec_ctx *exec_ctx,
 void grpc_subchannel_call_holder_init(
     grpc_subchannel_call_holder *holder,
     grpc_subchannel_call_holder_pick_subchannel pick_subchannel,
-    void *pick_subchannel_arg) {
+    void *pick_subchannel_arg, grpc_call_stack *owning_call) {
   gpr_atm_rel_store(&holder->subchannel_call, 0);
   holder->pick_subchannel = pick_subchannel;
   holder->pick_subchannel_arg = pick_subchannel_arg;
   gpr_mu_init(&holder->mu);
-  holder->subchannel = NULL;
+  holder->connected_subchannel = NULL;
   holder->waiting_ops = NULL;
   holder->waiting_ops_count = 0;
   holder->waiting_ops_capacity = 0;
   holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
+  holder->owning_call = owning_call;
 }
 
 void grpc_subchannel_call_holder_destroy(grpc_exec_ctx *exec_ctx,
@@ -125,13 +125,9 @@ retry:
         case GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING:
           fail_locked(exec_ctx, holder);
           break;
-        case GRPC_SUBCHANNEL_CALL_HOLDER_CREATING_CALL:
-          grpc_subchannel_cancel_create_call(exec_ctx, holder->subchannel,
-                                             &holder->subchannel_call);
-          break;
         case GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL:
           holder->pick_subchannel(exec_ctx, holder->pick_subchannel_arg, NULL,
-                                  &holder->subchannel, NULL);
+                                  &holder->connected_subchannel, NULL);
           break;
       }
       gpr_mu_unlock(&holder->mu);
@@ -142,28 +138,27 @@ retry:
   }
   /* if we don't have a subchannel, try to get one */
   if (holder->creation_phase == GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING &&
-      holder->subchannel == NULL && op->send_initial_metadata != NULL) {
+      holder->connected_subchannel == NULL &&
+      op->send_initial_metadata != NULL) {
     holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL;
     grpc_closure_init(&holder->next_step, subchannel_ready, holder);
-    if (holder->pick_subchannel(exec_ctx, holder->pick_subchannel_arg,
-                                op->send_initial_metadata, &holder->subchannel,
-                                &holder->next_step)) {
+    GRPC_CALL_STACK_REF(holder->owning_call, "pick_subchannel");
+    if (holder->pick_subchannel(
+            exec_ctx, holder->pick_subchannel_arg, op->send_initial_metadata,
+            &holder->connected_subchannel, &holder->next_step)) {
       holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
+      GRPC_CALL_STACK_UNREF(exec_ctx, holder->owning_call, "pick_subchannel");
     }
   }
   /* if we've got a subchannel, then let's ask it to create a call */
   if (holder->creation_phase == GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING &&
-      holder->subchannel != NULL) {
-    holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_CREATING_CALL;
-    grpc_closure_init(&holder->next_step, call_ready, holder);
-    if (grpc_subchannel_create_call(exec_ctx, holder->subchannel,
-                                    holder->pollset, &holder->subchannel_call,
-                                    &holder->next_step)) {
-      /* got one immediately - continue the op (and any waiting ops) */
-      holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
-      retry_waiting_locked(exec_ctx, holder);
-      goto retry;
-    }
+      holder->connected_subchannel != NULL) {
+    gpr_atm_rel_store(
+        &holder->subchannel_call,
+        (gpr_atm)(gpr_uintptr)grpc_connected_subchannel_create_call(
+            exec_ctx, holder->connected_subchannel, holder->pollset));
+    retry_waiting_locked(exec_ctx, holder);
+    goto retry;
   }
   /* nothing to be done but wait */
   add_waiting_locked(holder, op);
@@ -179,36 +174,18 @@ static void subchannel_ready(grpc_exec_ctx *exec_ctx, void *arg, int success) {
              GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL);
   call = GET_CALL(holder);
   GPR_ASSERT(call == NULL || call == CANCELLED_CALL);
-  if (holder->subchannel == NULL) {
-    holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
+  holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
+  if (holder->connected_subchannel == NULL) {
     fail_locked(exec_ctx, holder);
   } else {
-    grpc_closure_init(&holder->next_step, call_ready, holder);
-    if (grpc_subchannel_create_call(exec_ctx, holder->subchannel,
-                                    holder->pollset, &holder->subchannel_call,
-                                    &holder->next_step)) {
-      holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
-      /* got one immediately - continue the op (and any waiting ops) */
-      retry_waiting_locked(exec_ctx, holder);
-    }
-  }
-  gpr_mu_unlock(&holder->mu);
-}
-
-static void call_ready(grpc_exec_ctx *exec_ctx, void *arg, int success) {
-  grpc_subchannel_call_holder *holder = arg;
-  GPR_TIMER_BEGIN("call_ready", 0);
-  gpr_mu_lock(&holder->mu);
-  GPR_ASSERT(holder->creation_phase ==
-             GRPC_SUBCHANNEL_CALL_HOLDER_CREATING_CALL);
-  holder->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
-  if (GET_CALL(holder) != NULL) {
+    gpr_atm_rel_store(
+        &holder->subchannel_call,
+        (gpr_atm)(gpr_uintptr)grpc_connected_subchannel_create_call(
+            exec_ctx, holder->connected_subchannel, holder->pollset));
     retry_waiting_locked(exec_ctx, holder);
-  } else {
-    fail_locked(exec_ctx, holder);
   }
   gpr_mu_unlock(&holder->mu);
-  GPR_TIMER_END("call_ready", 0);
+  GRPC_CALL_STACK_UNREF(exec_ctx, holder->owning_call, "pick_subchannel");
 }
 
 typedef struct {
@@ -270,14 +247,13 @@ static void fail_locked(grpc_exec_ctx *exec_ctx,
   holder->waiting_ops_count = 0;
 }
 
-char *grpc_subchannel_call_holder_get_peer(grpc_exec_ctx *exec_ctx,
-                                           grpc_subchannel_call_holder *holder,
-                                           grpc_channel *master) {
+char *grpc_subchannel_call_holder_get_peer(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel_call_holder *holder) {
   grpc_subchannel_call *subchannel_call = GET_CALL(holder);
 
   if (subchannel_call) {
     return grpc_subchannel_call_get_peer(exec_ctx, subchannel_call);
   } else {
-    return grpc_channel_get_target(master);
+    return NULL;
   }
 }
diff --git a/src/core/channel/subchannel_call_holder.h b/src/core/channel/subchannel_call_holder.h
index bda051c566..9cf72c6cf7 100644
--- a/src/core/channel/subchannel_call_holder.h
+++ b/src/core/channel/subchannel_call_holder.h
@@ -42,12 +42,11 @@
     called when the subchannel is available) */
 typedef int (*grpc_subchannel_call_holder_pick_subchannel)(
     grpc_exec_ctx *exec_ctx, void *arg, grpc_metadata_batch *initial_metadata,
-    grpc_subchannel **subchannel, grpc_closure *on_ready);
+    grpc_connected_subchannel **connected_subchannel, grpc_closure *on_ready);
 
 typedef enum {
   GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING,
-  GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL,
-  GRPC_SUBCHANNEL_CALL_HOLDER_CREATING_CALL
+  GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL
 } grpc_subchannel_call_holder_creation_phase;
 
 /** Wrapper for holding a pointer to grpc_subchannel_call, and the
@@ -71,7 +70,7 @@ typedef struct grpc_subchannel_call_holder {
   gpr_mu mu;
 
   grpc_subchannel_call_holder_creation_phase creation_phase;
-  grpc_subchannel *subchannel;
+  grpc_connected_subchannel *connected_subchannel;
   grpc_pollset *pollset;
 
   grpc_transport_stream_op *waiting_ops;
@@ -79,12 +78,14 @@ typedef struct grpc_subchannel_call_holder {
   size_t waiting_ops_capacity;
 
   grpc_closure next_step;
+
+  grpc_call_stack *owning_call;
 } grpc_subchannel_call_holder;
 
 void grpc_subchannel_call_holder_init(
     grpc_subchannel_call_holder *holder,
     grpc_subchannel_call_holder_pick_subchannel pick_subchannel,
-    void *pick_subchannel_arg);
+    void *pick_subchannel_arg, grpc_call_stack *owning_call);
 void grpc_subchannel_call_holder_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_subchannel_call_holder *holder);
 
@@ -92,7 +93,6 @@ void grpc_subchannel_call_holder_perform_op(grpc_exec_ctx *exec_ctx,
                                             grpc_subchannel_call_holder *holder,
                                             grpc_transport_stream_op *op);
 char *grpc_subchannel_call_holder_get_peer(grpc_exec_ctx *exec_ctx,
-                                           grpc_subchannel_call_holder *holder,
-                                           grpc_channel *master);
+                                           grpc_subchannel_call_holder *holder);
 
 #endif
diff --git a/src/core/client_config/lb_policies/pick_first.c b/src/core/client_config/lb_policies/pick_first.c
index 93312abb00..b91f0609d2 100644
--- a/src/core/client_config/lb_policies/pick_first.c
+++ b/src/core/client_config/lb_policies/pick_first.c
@@ -42,7 +42,7 @@
 typedef struct pending_pick {
   struct pending_pick *next;
   grpc_pollset *pollset;
-  grpc_subchannel **target;
+  grpc_connected_subchannel **target;
   grpc_closure *on_complete;
 } pending_pick;
 
@@ -60,7 +60,7 @@ typedef struct {
   /** the selected channel
       TODO(ctiller): this should be atomically set so we don't
                      need to take a mutex in the common case */
-  grpc_subchannel *selected;
+  grpc_connected_subchannel *selected;
   /** have we started picking? */
   int started_picking;
   /** are we shut down? */
@@ -76,24 +76,6 @@ typedef struct {
   grpc_connectivity_state_tracker state_tracker;
 } pick_first_lb_policy;
 
-static void del_interested_parties_locked(grpc_exec_ctx *exec_ctx,
-                                          pick_first_lb_policy *p) {
-  pending_pick *pp;
-  for (pp = p->pending_picks; pp; pp = pp->next) {
-    grpc_subchannel_del_interested_party(
-        exec_ctx, p->subchannels[p->checking_subchannel], pp->pollset);
-  }
-}
-
-static void add_interested_parties_locked(grpc_exec_ctx *exec_ctx,
-                                          pick_first_lb_policy *p) {
-  pending_pick *pp;
-  for (pp = p->pending_picks; pp; pp = pp->next) {
-    grpc_subchannel_add_interested_party(
-        exec_ctx, p->subchannels[p->checking_subchannel], pp->pollset);
-  }
-}
-
 void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   size_t i;
@@ -102,7 +84,7 @@ void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
     GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[i], "pick_first");
   }
   if (p->selected) {
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, p->selected, "picked_first");
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, p->selected, "picked_first");
   }
   grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
   gpr_free(p->subchannels);
@@ -114,16 +96,26 @@ void pf_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   pending_pick *pp;
   gpr_mu_lock(&p->mu);
-  del_interested_parties_locked(exec_ctx, p);
   p->shutdown = 1;
   pp = p->pending_picks;
   p->pending_picks = NULL;
   grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                               GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  /* cancel subscription */
+  if (p->selected != NULL) {
+    grpc_connected_subchannel_notify_on_state_change(
+        exec_ctx, p->selected, NULL, NULL, &p->connectivity_changed);
+  } else {
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, p->subchannels[p->checking_subchannel], NULL, NULL,
+        &p->connectivity_changed);
+  }
   gpr_mu_unlock(&p->mu);
   while (pp != NULL) {
     pending_pick *next = pp->next;
     *pp->target = NULL;
+    grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
+                                 pp->pollset);
     grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
     gpr_free(pp);
     pp = next;
@@ -131,7 +123,7 @@ void pf_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 static void pf_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                           grpc_subchannel **target) {
+                           grpc_connected_subchannel **target) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   pending_pick *pp;
   gpr_mu_lock(&p->mu);
@@ -140,8 +132,8 @@ static void pf_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
   while (pp != NULL) {
     pending_pick *next = pp->next;
     if (pp->target == target) {
-      grpc_subchannel_del_interested_party(
-          exec_ctx, p->subchannels[p->checking_subchannel], pp->pollset);
+      grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
+                                   pp->pollset);
       *target = NULL;
       grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 0);
       gpr_free(pp);
@@ -158,10 +150,11 @@ static void start_picking(grpc_exec_ctx *exec_ctx, pick_first_lb_policy *p) {
   p->started_picking = 1;
   p->checking_subchannel = 0;
   p->checking_connectivity = GRPC_CHANNEL_IDLE;
-  GRPC_LB_POLICY_REF(&p->base, "pick_first_connectivity");
+  GRPC_LB_POLICY_WEAK_REF(&p->base, "pick_first_connectivity");
   grpc_subchannel_notify_on_state_change(
       exec_ctx, p->subchannels[p->checking_subchannel],
-      &p->checking_connectivity, &p->connectivity_changed);
+      &p->base.interested_parties, &p->checking_connectivity,
+      &p->connectivity_changed);
 }
 
 void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
@@ -174,8 +167,8 @@ void pf_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
-            grpc_metadata_batch *initial_metadata, grpc_subchannel **target,
-            grpc_closure *on_complete) {
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   pending_pick *pp;
   gpr_mu_lock(&p->mu);
@@ -187,8 +180,8 @@ int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
     if (!p->started_picking) {
       start_picking(exec_ctx, p);
     }
-    grpc_subchannel_add_interested_party(
-        exec_ctx, p->subchannels[p->checking_subchannel], pollset);
+    grpc_pollset_set_add_pollset(exec_ctx, &p->base.interested_parties,
+                                 pollset);
     pp = gpr_malloc(sizeof(*pp));
     pp->next = p->pending_picks;
     pp->pollset = pollset;
@@ -204,25 +197,17 @@ static void destroy_subchannels(grpc_exec_ctx *exec_ctx, void *arg,
                                 int iomgr_success) {
   pick_first_lb_policy *p = arg;
   size_t i;
-  grpc_transport_op op;
   size_t num_subchannels = p->num_subchannels;
   grpc_subchannel **subchannels;
-  grpc_subchannel *exclude_subchannel;
 
   gpr_mu_lock(&p->mu);
   subchannels = p->subchannels;
   p->num_subchannels = 0;
   p->subchannels = NULL;
-  exclude_subchannel = p->selected;
   gpr_mu_unlock(&p->mu);
-  GRPC_LB_POLICY_UNREF(exec_ctx, &p->base, "destroy_subchannels");
+  GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "destroy_subchannels");
 
   for (i = 0; i < num_subchannels; i++) {
-    if (subchannels[i] != exclude_subchannel) {
-      memset(&op, 0, sizeof(op));
-      op.disconnect = 1;
-      grpc_subchannel_process_transport_op(exec_ctx, subchannels[i], &op);
-    }
     GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannels[i], "pick_first");
   }
 
@@ -232,23 +217,28 @@ static void destroy_subchannels(grpc_exec_ctx *exec_ctx, void *arg,
 static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                     int iomgr_success) {
   pick_first_lb_policy *p = arg;
+  grpc_subchannel *selected_subchannel;
   pending_pick *pp;
 
   gpr_mu_lock(&p->mu);
 
   if (p->shutdown) {
     gpr_mu_unlock(&p->mu);
-    GRPC_LB_POLICY_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
     return;
   } else if (p->selected != NULL) {
+    if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+      /* if the selected channel goes bad, we're done */
+      p->checking_connectivity = GRPC_CHANNEL_FATAL_FAILURE;
+    }
     grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                 p->checking_connectivity, "selected_changed");
     if (p->checking_connectivity != GRPC_CHANNEL_FATAL_FAILURE) {
-      grpc_subchannel_notify_on_state_change(exec_ctx, p->selected,
-                                             &p->checking_connectivity,
-                                             &p->connectivity_changed);
+      grpc_connected_subchannel_notify_on_state_change(
+          exec_ctx, p->selected, &p->base.interested_parties,
+          &p->checking_connectivity, &p->connectivity_changed);
     } else {
-      GRPC_LB_POLICY_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+      GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
     }
   } else {
   loop:
@@ -256,39 +246,41 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
       case GRPC_CHANNEL_READY:
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                     GRPC_CHANNEL_READY, "connecting_ready");
-        p->selected = p->subchannels[p->checking_subchannel];
-        GRPC_SUBCHANNEL_REF(p->selected, "picked_first");
+        selected_subchannel = p->subchannels[p->checking_subchannel];
+        p->selected =
+            grpc_subchannel_get_connected_subchannel(selected_subchannel);
+        GPR_ASSERT(p->selected);
+        GRPC_CONNECTED_SUBCHANNEL_REF(p->selected, "picked_first");
         /* drop the pick list: we are connected now */
-        GRPC_LB_POLICY_REF(&p->base, "destroy_subchannels");
+        GRPC_LB_POLICY_WEAK_REF(&p->base, "destroy_subchannels");
         grpc_exec_ctx_enqueue(exec_ctx,
                               grpc_closure_create(destroy_subchannels, p), 1);
         /* update any calls that were waiting for a pick */
         while ((pp = p->pending_picks)) {
           p->pending_picks = pp->next;
           *pp->target = p->selected;
-          grpc_subchannel_del_interested_party(exec_ctx, p->selected,
-                                               pp->pollset);
+          grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
+                                       pp->pollset);
           grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
           gpr_free(pp);
         }
-        grpc_subchannel_notify_on_state_change(exec_ctx, p->selected,
-                                               &p->checking_connectivity,
-                                               &p->connectivity_changed);
+        grpc_connected_subchannel_notify_on_state_change(
+            exec_ctx, p->selected, &p->base.interested_parties,
+            &p->checking_connectivity, &p->connectivity_changed);
         break;
       case GRPC_CHANNEL_TRANSIENT_FAILURE:
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                     GRPC_CHANNEL_TRANSIENT_FAILURE,
                                     "connecting_transient_failure");
-        del_interested_parties_locked(exec_ctx, p);
         p->checking_subchannel =
             (p->checking_subchannel + 1) % p->num_subchannels;
         p->checking_connectivity = grpc_subchannel_check_connectivity(
             p->subchannels[p->checking_subchannel]);
-        add_interested_parties_locked(exec_ctx, p);
         if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
           grpc_subchannel_notify_on_state_change(
               exec_ctx, p->subchannels[p->checking_subchannel],
-              &p->checking_connectivity, &p->connectivity_changed);
+              &p->base.interested_parties, &p->checking_connectivity,
+              &p->connectivity_changed);
         } else {
           goto loop;
         }
@@ -300,13 +292,13 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                     "connecting_changed");
         grpc_subchannel_notify_on_state_change(
             exec_ctx, p->subchannels[p->checking_subchannel],
-            &p->checking_connectivity, &p->connectivity_changed);
+            &p->base.interested_parties, &p->checking_connectivity,
+            &p->connectivity_changed);
         break;
       case GRPC_CHANNEL_FATAL_FAILURE:
-        del_interested_parties_locked(exec_ctx, p);
-        GPR_SWAP(grpc_subchannel *, p->subchannels[p->checking_subchannel],
-                 p->subchannels[p->num_subchannels - 1]);
         p->num_subchannels--;
+        GPR_SWAP(grpc_subchannel *, p->subchannels[p->checking_subchannel],
+                 p->subchannels[p->num_subchannels]);
         GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[p->num_subchannels],
                               "pick_first");
         if (p->num_subchannels == 0) {
@@ -319,7 +311,8 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
             grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
             gpr_free(pp);
           }
-          GRPC_LB_POLICY_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
+          GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base,
+                                    "pick_first_connectivity");
         } else {
           grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                       GRPC_CHANNEL_TRANSIENT_FAILURE,
@@ -327,7 +320,6 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
           p->checking_subchannel %= p->num_subchannels;
           p->checking_connectivity = grpc_subchannel_check_connectivity(
               p->subchannels[p->checking_subchannel]);
-          add_interested_parties_locked(exec_ctx, p);
           goto loop;
         }
     }
@@ -336,39 +328,6 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
   gpr_mu_unlock(&p->mu);
 }
 
-static void pf_broadcast(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                         grpc_transport_op *op) {
-  pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
-  size_t i;
-  size_t n;
-  grpc_subchannel **subchannels;
-  grpc_subchannel *selected;
-
-  gpr_mu_lock(&p->mu);
-  n = p->num_subchannels;
-  subchannels = gpr_malloc(n * sizeof(*subchannels));
-  selected = p->selected;
-  if (selected) {
-    GRPC_SUBCHANNEL_REF(selected, "pf_broadcast_to_selected");
-  }
-  for (i = 0; i < n; i++) {
-    subchannels[i] = p->subchannels[i];
-    GRPC_SUBCHANNEL_REF(subchannels[i], "pf_broadcast");
-  }
-  gpr_mu_unlock(&p->mu);
-
-  for (i = 0; i < n; i++) {
-    if (selected == subchannels[i]) continue;
-    grpc_subchannel_process_transport_op(exec_ctx, subchannels[i], op);
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannels[i], "pf_broadcast");
-  }
-  if (p->selected) {
-    grpc_subchannel_process_transport_op(exec_ctx, selected, op);
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, selected, "pf_broadcast_to_selected");
-  }
-  gpr_free(subchannels);
-}
-
 static grpc_connectivity_state pf_check_connectivity(grpc_exec_ctx *exec_ctx,
                                                      grpc_lb_policy *pol) {
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
@@ -391,7 +350,7 @@ void pf_notify_on_state_change(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
 
 static const grpc_lb_policy_vtable pick_first_lb_policy_vtable = {
     pf_destroy, pf_shutdown, pf_pick, pf_cancel_pick, pf_exit_idle,
-    pf_broadcast, pf_check_connectivity, pf_notify_on_state_change};
+    pf_check_connectivity, pf_notify_on_state_change};
 
 static void pick_first_factory_ref(grpc_lb_policy_factory *factory) {}
 
diff --git a/src/core/client_config/lb_policies/round_robin.c b/src/core/client_config/lb_policies/round_robin.c
index 1ffe32fff2..b86dba20ee 100644
--- a/src/core/client_config/lb_policies/round_robin.c
+++ b/src/core/client_config/lb_policies/round_robin.c
@@ -38,6 +38,8 @@
 #include <grpc/support/alloc.h>
 #include "src/core/transport/connectivity_state.h"
 
+typedef struct round_robin_lb_policy round_robin_lb_policy;
+
 int grpc_lb_round_robin_trace = 0;
 
 /** List of entities waiting for a pick.
@@ -46,7 +48,7 @@ int grpc_lb_round_robin_trace = 0;
 typedef struct pending_pick {
   struct pending_pick *next;
   grpc_pollset *pollset;
-  grpc_subchannel **target;
+  grpc_connected_subchannel **target;
   grpc_closure *on_complete;
 } pending_pick;
 
@@ -58,22 +60,27 @@ typedef struct ready_list {
 } ready_list;
 
 typedef struct {
-  size_t subchannel_idx; /**< Index over p->subchannels */
-  void *p;               /**< round_robin_lb_policy instance */
-} connectivity_changed_cb_arg;
-
-typedef struct {
+  /** index within policy->subchannels */
+  size_t index;
+  /** backpointer to owning policy */
+  round_robin_lb_policy *policy;
+  /** subchannel itself */
+  grpc_subchannel *subchannel;
+  /** notification that connectivity has changed on subchannel */
+  grpc_closure connectivity_changed_closure;
+  /** this subchannels current position in subchannel->ready_list */
+  ready_list *ready_list_node;
+  /** last observed connectivity */
+  grpc_connectivity_state connectivity_state;
+} subchannel_data;
+
+struct round_robin_lb_policy {
   /** base policy: must be first */
   grpc_lb_policy base;
 
   /** all our subchannels */
-  grpc_subchannel **subchannels;
   size_t num_subchannels;
-
-  /** Callbacks, one per subchannel being watched, to be called when their
-   * respective connectivity changes */
-  grpc_closure *connectivity_changed_cbs;
-  connectivity_changed_cb_arg *cb_args;
+  subchannel_data **subchannels;
 
   /** mutex protecting remaining members */
   gpr_mu mu;
@@ -81,8 +88,6 @@ typedef struct {
   int started_picking;
   /** are we shutting down? */
   int shutdown;
-  /** Connectivity state of the subchannels being watched */
-  grpc_connectivity_state *subchannel_connectivity;
   /** List of picks that are waiting on connectivity */
   pending_pick *pending_picks;
 
@@ -93,13 +98,7 @@ typedef struct {
   ready_list ready_list;
   /** Last pick from the ready list. */
   ready_list *ready_list_last_pick;
-
-  /** Subchannel index to ready_list node.
-   *
-   * Kept in order to remove nodes from the ready list associated with a
-   * subchannel */
-  ready_list **subchannel_index_to_readylist_node;
-} round_robin_lb_policy;
+};
 
 /** Returns the next subchannel from the connected list or NULL if the list is
  * empty.
@@ -144,9 +143,9 @@ static void advance_last_picked_locked(round_robin_lb_policy *p) {
 /** Prepends (relative to the root at p->ready_list) the connected subchannel \a
  * csc to the list of ready subchannels. */
 static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
-                                           grpc_subchannel *csc) {
+                                           grpc_subchannel *sc) {
   ready_list *new_elem = gpr_malloc(sizeof(ready_list));
-  new_elem->subchannel = csc;
+  new_elem->subchannel = sc;
   if (p->ready_list.prev == NULL) {
     /* first element */
     new_elem->next = &p->ready_list;
@@ -160,7 +159,7 @@ static ready_list *add_connected_sc_locked(round_robin_lb_policy *p,
     p->ready_list.prev = new_elem;
   }
   if (grpc_lb_round_robin_trace) {
-    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (SC %p)", new_elem, csc);
+    gpr_log(GPR_DEBUG, "[READYLIST] ADDING NODE %p (SC %p)", new_elem, sc);
   }
   return new_elem;
 }
@@ -200,28 +199,15 @@ static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
   gpr_free(node);
 }
 
-static void del_interested_parties_locked(grpc_exec_ctx *exec_ctx,
-                                          round_robin_lb_policy *p,
-                                          const size_t subchannel_idx) {
-  pending_pick *pp;
-  for (pp = p->pending_picks; pp; pp = pp->next) {
-    grpc_subchannel_del_interested_party(
-        exec_ctx, p->subchannels[subchannel_idx], pp->pollset);
-  }
-}
-
 void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   size_t i;
   ready_list *elem;
   for (i = 0; i < p->num_subchannels; i++) {
-    del_interested_parties_locked(exec_ctx, p, i);
+    subchannel_data *sd = p->subchannels[i];
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+    gpr_free(sd);
   }
-  for (i = 0; i < p->num_subchannels; i++) {
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[i], "round_robin");
-  }
-  gpr_free(p->connectivity_changed_cbs);
-  gpr_free(p->subchannel_connectivity);
 
   grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
   gpr_free(p->subchannels);
@@ -237,20 +223,15 @@ void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
     gpr_free(elem);
     elem = tmp;
   }
-  gpr_free(p->subchannel_index_to_readylist_node);
-  gpr_free(p->cb_args);
   gpr_free(p);
 }
 
 void rr_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
-  size_t i;
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   pending_pick *pp;
-  gpr_mu_lock(&p->mu);
+  size_t i;
 
-  for (i = 0; i < p->num_subchannels; i++) {
-    del_interested_parties_locked(exec_ctx, p, i);
-  }
+  gpr_mu_lock(&p->mu);
 
   p->shutdown = 1;
   while ((pp = p->pending_picks)) {
@@ -261,24 +242,26 @@ void rr_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   }
   grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                               GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
+  for (i = 0; i < p->num_subchannels; i++) {
+    subchannel_data *sd = p->subchannels[i];
+    grpc_subchannel_notify_on_state_change(exec_ctx, sd->subchannel, NULL, NULL,
+                                           &sd->connectivity_changed_closure);
+  }
   gpr_mu_unlock(&p->mu);
 }
 
 static void rr_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                           grpc_subchannel **target) {
+                           grpc_connected_subchannel **target) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   pending_pick *pp;
-  size_t i;
   gpr_mu_lock(&p->mu);
   pp = p->pending_picks;
   p->pending_picks = NULL;
   while (pp != NULL) {
     pending_pick *next = pp->next;
     if (pp->target == target) {
-      for (i = 0; i < p->num_subchannels; i++) {
-        grpc_subchannel_add_interested_party(exec_ctx, p->subchannels[i],
-                                             pp->pollset);
-      }
+      grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
+                                   pp->pollset);
       *target = NULL;
       grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 0);
       gpr_free(pp);
@@ -295,12 +278,16 @@ static void start_picking(grpc_exec_ctx *exec_ctx, round_robin_lb_policy *p) {
   size_t i;
   p->started_picking = 1;
 
+  gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%d", p,
+          p->num_subchannels);
+
   for (i = 0; i < p->num_subchannels; i++) {
-    p->subchannel_connectivity[i] = GRPC_CHANNEL_IDLE;
-    grpc_subchannel_notify_on_state_change(exec_ctx, p->subchannels[i],
-                                           &p->subchannel_connectivity[i],
-                                           &p->connectivity_changed_cbs[i]);
-    GRPC_LB_POLICY_REF(&p->base, "round_robin_connectivity");
+    subchannel_data *sd = p->subchannels[i];
+    sd->connectivity_state = GRPC_CHANNEL_IDLE;
+    grpc_subchannel_notify_on_state_change(
+        exec_ctx, sd->subchannel, &p->base.interested_parties,
+        &sd->connectivity_state, &sd->connectivity_changed_closure);
+    GRPC_LB_POLICY_WEAK_REF(&p->base, "round_robin_connectivity");
   }
 }
 
@@ -314,18 +301,18 @@ void rr_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 }
 
 int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
-            grpc_metadata_batch *initial_metadata, grpc_subchannel **target,
-            grpc_closure *on_complete) {
-  size_t i;
+            grpc_metadata_batch *initial_metadata,
+            grpc_connected_subchannel **target, grpc_closure *on_complete) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   pending_pick *pp;
   ready_list *selected;
   gpr_mu_lock(&p->mu);
   if ((selected = peek_next_connected_locked(p))) {
     gpr_mu_unlock(&p->mu);
-    *target = selected->subchannel;
+    *target = grpc_subchannel_get_connected_subchannel(selected->subchannel);
     if (grpc_lb_round_robin_trace) {
-      gpr_log(GPR_DEBUG, "[RR PICK] TARGET <-- SUBCHANNEL %p (NODE %p)",
+      gpr_log(GPR_DEBUG,
+              "[RR PICK] TARGET <-- CONNECTED SUBCHANNEL %p (NODE %p)",
               selected->subchannel, selected);
     }
     /* only advance the last picked pointer if the selection was used */
@@ -335,10 +322,8 @@ int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
     if (!p->started_picking) {
       start_picking(exec_ctx, p);
     }
-    for (i = 0; i < p->num_subchannels; i++) {
-      grpc_subchannel_add_interested_party(exec_ctx, p->subchannels[i],
-                                           pollset);
-    }
+    grpc_pollset_set_add_pollset(exec_ctx, &p->base.interested_parties,
+                                 pollset);
     pp = gpr_malloc(sizeof(*pp));
     pp->next = p->pending_picks;
     pp->pollset = pollset;
@@ -352,33 +337,25 @@ int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
 
 static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                     int iomgr_success) {
-  connectivity_changed_cb_arg *cb_arg = arg;
-  round_robin_lb_policy *p = cb_arg->p;
-  /* index over p->subchannels of this cb's subchannel */
-  const size_t this_idx = cb_arg->subchannel_idx;
+  subchannel_data *sd = arg;
+  round_robin_lb_policy *p = sd->policy;
   pending_pick *pp;
   ready_list *selected;
 
   int unref = 0;
 
-  /* connectivity state of this cb's subchannel */
-  grpc_connectivity_state *this_connectivity;
-
   gpr_mu_lock(&p->mu);
 
-  this_connectivity = &p->subchannel_connectivity[this_idx];
-
   if (p->shutdown) {
     unref = 1;
   } else {
-    switch (*this_connectivity) {
+    switch (sd->connectivity_state) {
       case GRPC_CHANNEL_READY:
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                     GRPC_CHANNEL_READY, "connecting_ready");
         /* add the newly connected subchannel to the list of connected ones.
          * Note that it goes to the "end of the line". */
-        p->subchannel_index_to_readylist_node[this_idx] =
-            add_connected_sc_locked(p, p->subchannels[this_idx]);
+        sd->ready_list_node = add_connected_sc_locked(p, sd->subchannel);
         /* at this point we know there's at least one suitable subchannel. Go
          * ahead and pick one and notify the pending suitors in
          * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
@@ -390,60 +367,60 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
         }
         while ((pp = p->pending_picks)) {
           p->pending_picks = pp->next;
-          *pp->target = selected->subchannel;
+          *pp->target =
+              grpc_subchannel_get_connected_subchannel(selected->subchannel);
           if (grpc_lb_round_robin_trace) {
             gpr_log(GPR_DEBUG,
                     "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
                     selected->subchannel, selected);
           }
-          grpc_subchannel_del_interested_party(exec_ctx, selected->subchannel,
-                                               pp->pollset);
+          grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
+                                       pp->pollset);
           grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
           gpr_free(pp);
         }
         grpc_subchannel_notify_on_state_change(
-            exec_ctx, p->subchannels[this_idx], this_connectivity,
-            &p->connectivity_changed_cbs[this_idx]);
+            exec_ctx, sd->subchannel, &p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
         break;
       case GRPC_CHANNEL_CONNECTING:
       case GRPC_CHANNEL_IDLE:
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
-                                    *this_connectivity, "connecting_changed");
+                                    sd->connectivity_state,
+                                    "connecting_changed");
         grpc_subchannel_notify_on_state_change(
-            exec_ctx, p->subchannels[this_idx], this_connectivity,
-            &p->connectivity_changed_cbs[this_idx]);
+            exec_ctx, sd->subchannel, &p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
         break;
       case GRPC_CHANNEL_TRANSIENT_FAILURE:
-        del_interested_parties_locked(exec_ctx, p, this_idx);
         /* renew state notification */
         grpc_subchannel_notify_on_state_change(
-            exec_ctx, p->subchannels[this_idx], this_connectivity,
-            &p->connectivity_changed_cbs[this_idx]);
+            exec_ctx, sd->subchannel, &p->base.interested_parties,
+            &sd->connectivity_state, &sd->connectivity_changed_closure);
 
         /* remove from ready list if still present */
-        if (p->subchannel_index_to_readylist_node[this_idx] != NULL) {
-          remove_disconnected_sc_locked(
-              p, p->subchannel_index_to_readylist_node[this_idx]);
-          p->subchannel_index_to_readylist_node[this_idx] = NULL;
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
         }
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                     GRPC_CHANNEL_TRANSIENT_FAILURE,
                                     "connecting_transient_failure");
         break;
       case GRPC_CHANNEL_FATAL_FAILURE:
-        del_interested_parties_locked(exec_ctx, p, this_idx);
-        if (p->subchannel_index_to_readylist_node[this_idx] != NULL) {
-          remove_disconnected_sc_locked(
-              p, p->subchannel_index_to_readylist_node[this_idx]);
-          p->subchannel_index_to_readylist_node[this_idx] = NULL;
+        if (sd->ready_list_node != NULL) {
+          remove_disconnected_sc_locked(p, sd->ready_list_node);
+          sd->ready_list_node = NULL;
         }
 
-        GPR_SWAP(grpc_subchannel *, p->subchannels[this_idx],
-                 p->subchannels[p->num_subchannels - 1]);
         p->num_subchannels--;
-        GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[p->num_subchannels],
-                              "round_robin");
+        GPR_SWAP(subchannel_data *, p->subchannels[sd->index],
+                 p->subchannels[p->num_subchannels]);
+        GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
+        p->subchannels[sd->index]->index = sd->index;
+        gpr_free(sd);
 
+        unref = 1;
         if (p->num_subchannels == 0) {
           grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                       GRPC_CHANNEL_FATAL_FAILURE,
@@ -454,7 +431,6 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
             grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
             gpr_free(pp);
           }
-          unref = 1;
         } else {
           grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                       GRPC_CHANNEL_TRANSIENT_FAILURE,
@@ -466,31 +442,8 @@ static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
   gpr_mu_unlock(&p->mu);
 
   if (unref) {
-    GRPC_LB_POLICY_UNREF(exec_ctx, &p->base, "round_robin_connectivity");
-  }
-}
-
-static void rr_broadcast(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
-                         grpc_transport_op *op) {
-  round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
-  size_t i;
-  size_t n;
-  grpc_subchannel **subchannels;
-
-  gpr_mu_lock(&p->mu);
-  n = p->num_subchannels;
-  subchannels = gpr_malloc(n * sizeof(*subchannels));
-  for (i = 0; i < n; i++) {
-    subchannels[i] = p->subchannels[i];
-    GRPC_SUBCHANNEL_REF(subchannels[i], "rr_broadcast");
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "round_robin_connectivity");
   }
-  gpr_mu_unlock(&p->mu);
-
-  for (i = 0; i < n; i++) {
-    grpc_subchannel_process_transport_op(exec_ctx, subchannels[i], op);
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannels[i], "rr_broadcast");
-  }
-  gpr_free(subchannels);
 }
 
 static grpc_connectivity_state rr_check_connectivity(grpc_exec_ctx *exec_ctx,
@@ -516,7 +469,7 @@ static void rr_notify_on_state_change(grpc_exec_ctx *exec_ctx,
 
 static const grpc_lb_policy_vtable round_robin_lb_policy_vtable = {
     rr_destroy, rr_shutdown, rr_pick, rr_cancel_pick, rr_exit_idle,
-    rr_broadcast, rr_check_connectivity, rr_notify_on_state_change};
+    rr_check_connectivity, rr_notify_on_state_change};
 
 static void round_robin_factory_ref(grpc_lb_policy_factory *factory) {}
 
@@ -529,27 +482,22 @@ static grpc_lb_policy *create_round_robin(grpc_lb_policy_factory *factory,
   GPR_ASSERT(args->num_subchannels > 0);
   memset(p, 0, sizeof(*p));
   grpc_lb_policy_init(&p->base, &round_robin_lb_policy_vtable);
-  p->subchannels =
-      gpr_malloc(sizeof(grpc_subchannel *) * args->num_subchannels);
   p->num_subchannels = args->num_subchannels;
+  p->subchannels = gpr_malloc(sizeof(*p->subchannels) * p->num_subchannels);
+  memset(p->subchannels, 0, sizeof(*p->subchannels) * p->num_subchannels);
   grpc_connectivity_state_init(&p->state_tracker, GRPC_CHANNEL_IDLE,
                                "round_robin");
-  memcpy(p->subchannels, args->subchannels,
-         sizeof(grpc_subchannel *) * args->num_subchannels);
 
   gpr_mu_init(&p->mu);
-  p->connectivity_changed_cbs =
-      gpr_malloc(sizeof(grpc_closure) * args->num_subchannels);
-  p->subchannel_connectivity =
-      gpr_malloc(sizeof(grpc_connectivity_state) * args->num_subchannels);
-
-  p->cb_args =
-      gpr_malloc(sizeof(connectivity_changed_cb_arg) * args->num_subchannels);
   for (i = 0; i < args->num_subchannels; i++) {
-    p->cb_args[i].subchannel_idx = i;
-    p->cb_args[i].p = p;
-    grpc_closure_init(&p->connectivity_changed_cbs[i], rr_connectivity_changed,
-                      &p->cb_args[i]);
+    subchannel_data *sd = gpr_malloc(sizeof(*sd));
+    memset(sd, 0, sizeof(*sd));
+    p->subchannels[i] = sd;
+    sd->policy = p;
+    sd->index = i;
+    sd->subchannel = args->subchannels[i];
+    grpc_closure_init(&sd->connectivity_changed_closure,
+                      rr_connectivity_changed, sd);
   }
 
   /* The (dummy node) root of the ready list */
@@ -558,10 +506,6 @@ static grpc_lb_policy *create_round_robin(grpc_lb_policy_factory *factory,
   p->ready_list.next = NULL;
   p->ready_list_last_pick = &p->ready_list;
 
-  p->subchannel_index_to_readylist_node =
-      gpr_malloc(sizeof(grpc_subchannel *) * args->num_subchannels);
-  memset(p->subchannel_index_to_readylist_node, 0,
-         sizeof(grpc_subchannel *) * args->num_subchannels);
   return &p->base;
 }
 
diff --git a/src/core/client_config/lb_policy.c b/src/core/client_config/lb_policy.c
index 36a2454309..d254161546 100644
--- a/src/core/client_config/lb_policy.c
+++ b/src/core/client_config/lb_policy.c
@@ -33,59 +33,85 @@
 
 #include "src/core/client_config/lb_policy.h"
 
+#define WEAK_REF_BITS 16
+
 void grpc_lb_policy_init(grpc_lb_policy *policy,
                          const grpc_lb_policy_vtable *vtable) {
   policy->vtable = vtable;
-  gpr_ref_init(&policy->refs, 1);
+  gpr_atm_no_barrier_store(&policy->ref_pair, 1 << WEAK_REF_BITS);
+  grpc_pollset_set_init(&policy->interested_parties);
 }
 
 #ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
-void grpc_lb_policy_ref(grpc_lb_policy *policy, const char *file, int line,
-                        const char *reason) {
-  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "LB_POLICY:%p   ref %d -> %d %s",
-          policy, (int)policy->refs.count, (int)policy->refs.count + 1, reason);
+#define REF_FUNC_EXTRA_ARGS , const char *file, int line, const char *reason
+#define REF_MUTATE_EXTRA_ARGS REF_FUNC_EXTRA_ARGS, const char *purpose
+#define REF_FUNC_PASS_ARGS(new_reason) , file, line, new_reason
+#define REF_MUTATE_PASS_ARGS(purpose) , file, line, reason, purpose
 #else
-void grpc_lb_policy_ref(grpc_lb_policy *policy) {
+#define REF_FUNC_EXTRA_ARGS
+#define REF_MUTATE_EXTRA_ARGS
+#define REF_FUNC_PASS_ARGS(new_reason)
+#define REF_MUTATE_PASS_ARGS(x)
 #endif
-  gpr_ref(&policy->refs);
-}
 
+static gpr_atm ref_mutate(grpc_lb_policy *c, gpr_atm delta,
+                          int barrier REF_MUTATE_EXTRA_ARGS) {
+  gpr_atm old_val = barrier ? gpr_atm_full_fetch_add(&c->ref_pair, delta)
+                            : gpr_atm_no_barrier_fetch_add(&c->ref_pair, delta);
 #ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
-void grpc_lb_policy_unref(grpc_lb_policy *policy,
-                          grpc_closure_list *closure_list, const char *file,
-                          int line, const char *reason) {
-  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "LB_POLICY:%p unref %d -> %d %s",
-          policy, (int)policy->refs.count, (int)policy->refs.count - 1, reason);
-#else
-void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+          "LB_POLICY: %p % 12s 0x%08x -> 0x%08x [%s]", c, purpose, old_val,
+          old_val + delta, reason);
 #endif
-  if (gpr_unref(&policy->refs)) {
-    policy->vtable->destroy(exec_ctx, policy);
+  return old_val;
+}
+
+void grpc_lb_policy_ref(grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  ref_mutate(policy, 1 << WEAK_REF_BITS, 0 REF_MUTATE_PASS_ARGS("STRONG_REF"));
+}
+
+void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx,
+                          grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  gpr_atm old_val =
+      ref_mutate(policy, (gpr_atm)1 - (gpr_atm)(1 << WEAK_REF_BITS),
+                 1 REF_MUTATE_PASS_ARGS("STRONG_UNREF"));
+  gpr_atm mask = ~(gpr_atm)((1 << WEAK_REF_BITS) - 1);
+  gpr_atm check = 1 << WEAK_REF_BITS;
+  if ((old_val & mask) == check) {
+    policy->vtable->shutdown(exec_ctx, policy);
   }
+  grpc_lb_policy_weak_unref(exec_ctx,
+                            policy REF_FUNC_PASS_ARGS("strong-unref"));
 }
 
-void grpc_lb_policy_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
-  policy->vtable->shutdown(exec_ctx, policy);
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  ref_mutate(policy, 1, 0 REF_MUTATE_PASS_ARGS("WEAK_REF"));
+}
+
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx,
+                               grpc_lb_policy *policy REF_FUNC_EXTRA_ARGS) {
+  gpr_atm old_val =
+      ref_mutate(policy, -(gpr_atm)1, 1 REF_MUTATE_PASS_ARGS("WEAK_UNREF"));
+  if (old_val == 1) {
+    grpc_pollset_set_destroy(&policy->interested_parties);
+    policy->vtable->destroy(exec_ctx, policy);
+  }
 }
 
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                         grpc_pollset *pollset,
                         grpc_metadata_batch *initial_metadata,
-                        grpc_subchannel **target, grpc_closure *on_complete) {
+                        grpc_connected_subchannel **target,
+                        grpc_closure *on_complete) {
   return policy->vtable->pick(exec_ctx, policy, pollset, initial_metadata,
                               target, on_complete);
 }
 
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                                grpc_subchannel **target) {
+                                grpc_connected_subchannel **target) {
   policy->vtable->cancel_pick(exec_ctx, policy, target);
 }
 
-void grpc_lb_policy_broadcast(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                              grpc_transport_op *op) {
-  policy->vtable->broadcast(exec_ctx, policy, op);
-}
-
 void grpc_lb_policy_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy) {
   policy->vtable->exit_idle(exec_ctx, policy);
 }
diff --git a/src/core/client_config/lb_policy.h b/src/core/client_config/lb_policy.h
index a696c3ce64..2f8d655558 100644
--- a/src/core/client_config/lb_policy.h
+++ b/src/core/client_config/lb_policy.h
@@ -47,7 +47,8 @@ typedef void (*grpc_lb_completion)(void *cb_arg, grpc_subchannel *subchannel,
 
 struct grpc_lb_policy {
   const grpc_lb_policy_vtable *vtable;
-  gpr_refcount refs;
+  gpr_atm ref_pair;
+  grpc_pollset_set interested_parties;
 };
 
 struct grpc_lb_policy_vtable {
@@ -58,17 +59,13 @@ struct grpc_lb_policy_vtable {
   /** implement grpc_lb_policy_pick */
   int (*pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
               grpc_pollset *pollset, grpc_metadata_batch *initial_metadata,
-              grpc_subchannel **target, grpc_closure *on_complete);
+              grpc_connected_subchannel **target, grpc_closure *on_complete);
   void (*cancel_pick)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                      grpc_subchannel **target);
+                      grpc_connected_subchannel **target);
 
   /** try to enter a READY connectivity state */
   void (*exit_idle)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 
-  /** broadcast a transport op to all subchannels */
-  void (*broadcast)(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                    grpc_transport_op *op);
-
   /** check the current connectivity of the lb_policy */
   grpc_connectivity_state (*check_connectivity)(grpc_exec_ctx *exec_ctx,
                                                 grpc_lb_policy *policy);
@@ -81,29 +78,39 @@ struct grpc_lb_policy_vtable {
                                  grpc_closure *closure);
 };
 
+/*#define GRPC_LB_POLICY_REFCOUNT_DEBUG*/
 #ifdef GRPC_LB_POLICY_REFCOUNT_DEBUG
 #define GRPC_LB_POLICY_REF(p, r) \
   grpc_lb_policy_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_LB_POLICY_UNREF(exec_ctx, p, r) \
   grpc_lb_policy_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
+#define GRPC_LB_POLICY_WEAK_REF(p, r) \
+  grpc_lb_policy_weak_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, p, r) \
+  grpc_lb_policy_weak_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
 void grpc_lb_policy_ref(grpc_lb_policy *policy, const char *file, int line,
                         const char *reason);
 void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                           const char *file, int line, const char *reason);
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy, const char *file, int line,
+                             const char *reason);
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
+                               const char *file, int line, const char *reason);
 #else
 #define GRPC_LB_POLICY_REF(p, r) grpc_lb_policy_ref((p))
 #define GRPC_LB_POLICY_UNREF(cl, p, r) grpc_lb_policy_unref((cl), (p))
+#define GRPC_LB_POLICY_WEAK_REF(p, r) grpc_lb_policy_weak_ref((p))
+#define GRPC_LB_POLICY_WEAK_UNREF(cl, p, r) grpc_lb_policy_weak_unref((cl), (p))
 void grpc_lb_policy_ref(grpc_lb_policy *policy);
 void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
+void grpc_lb_policy_weak_ref(grpc_lb_policy *policy);
+void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 #endif
 
 /** called by concrete implementations to initialize the base struct */
 void grpc_lb_policy_init(grpc_lb_policy *policy,
                          const grpc_lb_policy_vtable *vtable);
 
-/** Start shutting down (fail any pending picks) */
-void grpc_lb_policy_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
-
 /** Given initial metadata in \a initial_metadata, find an appropriate
     target for this rpc, and 'return' it by calling \a on_complete after setting
     \a target.
@@ -111,13 +118,11 @@ void grpc_lb_policy_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
                         grpc_pollset *pollset,
                         grpc_metadata_batch *initial_metadata,
-                        grpc_subchannel **target, grpc_closure *on_complete);
+                        grpc_connected_subchannel **target,
+                        grpc_closure *on_complete);
 
 void grpc_lb_policy_cancel_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                                grpc_subchannel **target);
-
-void grpc_lb_policy_broadcast(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
-                              grpc_transport_op *op);
+                                grpc_connected_subchannel **target);
 
 void grpc_lb_policy_exit_idle(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy);
 
diff --git a/src/core/client_config/resolver.c b/src/core/client_config/resolver.c
index 081097eb19..eda01e72ba 100644
--- a/src/core/client_config/resolver.c
+++ b/src/core/client_config/resolver.c
@@ -71,11 +71,8 @@ void grpc_resolver_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver) {
 }
 
 void grpc_resolver_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                     grpc_resolver *resolver,
-                                     struct sockaddr *failing_address,
-                                     int failing_address_len) {
-  resolver->vtable->channel_saw_error(exec_ctx, resolver, failing_address,
-                                      failing_address_len);
+                                     grpc_resolver *resolver) {
+  resolver->vtable->channel_saw_error(exec_ctx, resolver);
 }
 
 void grpc_resolver_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
diff --git a/src/core/client_config/resolver.h b/src/core/client_config/resolver.h
index 7ba0cd5bd4..e612eaf3b3 100644
--- a/src/core/client_config/resolver.h
+++ b/src/core/client_config/resolver.h
@@ -35,8 +35,8 @@
 #define GRPC_INTERNAL_CORE_CLIENT_CONFIG_RESOLVER_H
 
 #include "src/core/client_config/client_config.h"
+#include "src/core/client_config/subchannel.h"
 #include "src/core/iomgr/iomgr.h"
-#include "src/core/iomgr/sockaddr.h"
 
 typedef struct grpc_resolver grpc_resolver;
 typedef struct grpc_resolver_vtable grpc_resolver_vtable;
@@ -51,9 +51,7 @@ struct grpc_resolver {
 struct grpc_resolver_vtable {
   void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
   void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
-  void (*channel_saw_error)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
-                            struct sockaddr *failing_address,
-                            int failing_address_len);
+  void (*channel_saw_error)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
   void (*next)(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
                grpc_client_config **target_config, grpc_closure *on_complete);
 };
@@ -81,9 +79,7 @@ void grpc_resolver_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver);
 /** Notification that the channel has seen an error on some address.
     Can be used as a hint that re-resolution is desirable soon. */
 void grpc_resolver_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                     grpc_resolver *resolver,
-                                     struct sockaddr *failing_address,
-                                     int failing_address_len);
+                                     grpc_resolver *resolver);
 
 /** Get the next client config. Called by the channel to fetch a new
     configuration. Expected to set *target_config with a new configuration,
diff --git a/src/core/client_config/resolvers/dns_resolver.c b/src/core/client_config/resolvers/dns_resolver.c
index b40c41544a..28ca30b946 100644
--- a/src/core/client_config/resolvers/dns_resolver.c
+++ b/src/core/client_config/resolvers/dns_resolver.c
@@ -80,9 +80,7 @@ static void dns_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
                                          dns_resolver *r);
 
 static void dns_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
-static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
-                                  struct sockaddr *failing_address,
-                                  int failing_address_len);
+static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
 static void dns_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
                      grpc_client_config **target_config,
                      grpc_closure *on_complete);
@@ -102,8 +100,7 @@ static void dns_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver) {
 }
 
 static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                  grpc_resolver *resolver, struct sockaddr *sa,
-                                  int len) {
+                                  grpc_resolver *resolver) {
   dns_resolver *r = (dns_resolver *)resolver;
   gpr_mu_lock(&r->mu);
   if (!r->resolving) {
diff --git a/src/core/client_config/resolvers/sockaddr_resolver.c b/src/core/client_config/resolvers/sockaddr_resolver.c
index 0b017f06c7..fd0212a1e7 100644
--- a/src/core/client_config/resolvers/sockaddr_resolver.c
+++ b/src/core/client_config/resolvers/sockaddr_resolver.c
@@ -83,9 +83,7 @@ static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
 
 static void sockaddr_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
 static void sockaddr_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                       grpc_resolver *r,
-                                       struct sockaddr *failing_address,
-                                       int failing_address_len);
+                                       grpc_resolver *r);
 static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
                           grpc_client_config **target_config,
                           grpc_closure *on_complete);
@@ -107,8 +105,13 @@ static void sockaddr_shutdown(grpc_exec_ctx *exec_ctx,
 }
 
 static void sockaddr_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                       grpc_resolver *resolver,
-                                       struct sockaddr *sa, int len) {}
+                                       grpc_resolver *resolver) {
+  sockaddr_resolver *r = (sockaddr_resolver *)resolver;
+  gpr_mu_lock(&r->mu);
+  r->published = 0;
+  sockaddr_maybe_finish_next_locked(exec_ctx, r);
+  gpr_mu_unlock(&r->mu);
+}
 
 static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
                           grpc_client_config **target_config,
diff --git a/src/core/client_config/resolvers/zookeeper_resolver.c b/src/core/client_config/resolvers/zookeeper_resolver.c
index 136197d4c6..4924ca77d6 100644
--- a/src/core/client_config/resolvers/zookeeper_resolver.c
+++ b/src/core/client_config/resolvers/zookeeper_resolver.c
@@ -96,9 +96,7 @@ static void zookeeper_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
 
 static void zookeeper_shutdown(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
 static void zookeeper_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                        grpc_resolver *r,
-                                        struct sockaddr *failing_address,
-                                        int failing_address_len);
+                                        grpc_resolver *r);
 static void zookeeper_next(grpc_exec_ctx *exec_ctx, grpc_resolver *r,
                            grpc_client_config **target_config,
                            grpc_closure *on_complete);
@@ -125,8 +123,7 @@ static void zookeeper_shutdown(grpc_exec_ctx *exec_ctx,
 }
 
 static void zookeeper_channel_saw_error(grpc_exec_ctx *exec_ctx,
-                                        grpc_resolver *resolver,
-                                        struct sockaddr *sa, int len) {
+                                        grpc_resolver *resolver) {
   zookeeper_resolver *r = (zookeeper_resolver *)resolver;
   gpr_mu_lock(&r->mu);
   if (r->resolving == 0) {
diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index 28496ac2c9..6631e9bae2 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -47,39 +47,44 @@
 #include "src/core/transport/connectivity_state.h"
 #include "src/core/transport/connectivity_state.h"
 
+#define INTERNAL_REF_BITS 16
+#define STRONG_REF_MASK (~(gpr_atm)((1 << INTERNAL_REF_BITS) - 1))
+
 #define GRPC_SUBCHANNEL_MIN_CONNECT_TIMEOUT_SECONDS 20
 #define GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS 1
 #define GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER 1.6
 #define GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS 120
 #define GRPC_SUBCHANNEL_RECONNECT_JITTER 0.2
 
-typedef struct {
-  /* all fields protected by subchannel->mu */
-  /** refcount */
-  int refs;
-  /** parent subchannel */
-  grpc_subchannel *subchannel;
-} connection;
+#define GET_CONNECTED_SUBCHANNEL(subchannel, barrier)      \
+  ((grpc_connected_subchannel *)(gpr_atm_##barrier##_load( \
+      &(subchannel)->connected_subchannel)))
 
 typedef struct {
   grpc_closure closure;
-  size_t version;
   grpc_subchannel *subchannel;
   grpc_connectivity_state connectivity_state;
 } state_watcher;
 
-typedef struct waiting_for_connect {
-  struct waiting_for_connect *next;
-  grpc_closure *notify;
-  grpc_pollset *pollset;
-  gpr_atm *target;
+typedef struct external_state_watcher {
   grpc_subchannel *subchannel;
-  grpc_closure continuation;
-} waiting_for_connect;
+  grpc_pollset_set *pollset_set;
+  grpc_closure *notify;
+  grpc_closure closure;
+  struct external_state_watcher *next;
+  struct external_state_watcher *prev;
+} external_state_watcher;
 
 struct grpc_subchannel {
   grpc_connector *connector;
 
+  /** refcount
+      - lower INTERNAL_REF_BITS bits are for internal references:
+        these do not keep the subchannel open.
+      - upper remaining bits are for public references: these do
+        keep the subchannel open */
+  gpr_atm ref_pair;
+
   /** non-transport related channel filters */
   const grpc_channel_filter **filters;
   size_t num_filters;
@@ -88,15 +93,9 @@ struct grpc_subchannel {
   /** address to connect to */
   struct sockaddr *addr;
   size_t addr_len;
+
   /** initial string to send to peer */
   gpr_slice initial_connect_string;
-  /** master channel - the grpc_channel instance that ultimately owns
-      this channel_data via its channel stack.
-      We occasionally use this to bump the refcount on the master channel
-      to keep ourselves alive through an asynchronous operation. */
-  grpc_channel *master;
-  /** have we seen a disconnection? */
-  int disconnected;
 
   /** set during connection */
   grpc_connect_out_args connecting_result;
@@ -105,27 +104,24 @@ struct grpc_subchannel {
   grpc_closure connected;
 
   /** pollset_set tracking who's interested in a connection
-      being setup - owned by the master channel (in particular the
-     client_channel
-      filter there-in) */
-  grpc_pollset_set *pollset_set;
+      being setup */
+  grpc_pollset_set pollset_set;
+
+  /** active connection, or null; of type grpc_connected_subchannel */
+  gpr_atm connected_subchannel;
 
   /** mutex protecting remaining elements */
   gpr_mu mu;
 
-  /** active connection */
-  connection *active;
-  /** version number for the active connection */
-  size_t active_version;
-  /** refcount */
-  int refs;
+  /** have we seen a disconnection? */
+  int disconnected;
   /** are we connecting */
   int connecting;
-  /** things waiting for a connection */
-  waiting_for_connect *waiting;
   /** connectivity state tracking */
   grpc_connectivity_state_tracker state_tracker;
 
+  external_state_watcher root_external_state_watcher;
+
   /** next connect attempt time */
   gpr_timespec next_attempt;
   /** amount to backoff each failure */
@@ -139,151 +135,141 @@ struct grpc_subchannel {
 };
 
 struct grpc_subchannel_call {
-  connection *connection;
+  grpc_connected_subchannel *connection;
 };
 
 #define SUBCHANNEL_CALL_TO_CALL_STACK(call) ((grpc_call_stack *)((call) + 1))
-#define CHANNEL_STACK_FROM_CONNECTION(con) ((grpc_channel_stack *)((con) + 1))
+#define CHANNEL_STACK_FROM_CONNECTION(con) ((grpc_channel_stack *)(con))
 #define CALLSTACK_TO_SUBCHANNEL_CALL(callstack) \
   (((grpc_subchannel_call *)(callstack)) - 1)
 
-static grpc_subchannel_call *create_call(grpc_exec_ctx *exec_ctx,
-                                         connection *con,
-                                         grpc_pollset *pollset);
-static void connectivity_state_changed_locked(grpc_exec_ctx *exec_ctx,
-                                              grpc_subchannel *c,
-                                              const char *reason);
-static grpc_connectivity_state compute_connectivity_locked(grpc_subchannel *c);
 static gpr_timespec compute_connect_deadline(grpc_subchannel *c);
 static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *subchannel,
                                  int iomgr_success);
 
-static void subchannel_ref_locked(grpc_subchannel *c
-                                      GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
-static int subchannel_unref_locked(
-    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) GRPC_MUST_USE_RESULT;
-static void connection_ref_locked(connection *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
-static grpc_subchannel *connection_unref_locked(
-    grpc_exec_ctx *exec_ctx,
-    connection *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) GRPC_MUST_USE_RESULT;
-static void subchannel_destroy(grpc_exec_ctx *exec_ctx, grpc_subchannel *c);
-
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
-#define SUBCHANNEL_REF_LOCKED(p, r) \
-  subchannel_ref_locked((p), __FILE__, __LINE__, (r))
-#define SUBCHANNEL_UNREF_LOCKED(p, r) \
-  subchannel_unref_locked((p), __FILE__, __LINE__, (r))
-#define CONNECTION_REF_LOCKED(p, r) \
-  connection_ref_locked((p), __FILE__, __LINE__, (r))
-#define CONNECTION_UNREF_LOCKED(cl, p, r) \
-  connection_unref_locked((cl), (p), __FILE__, __LINE__, (r))
-#define REF_PASS_ARGS , file, line, reason
-#define REF_PASS_REASON , reason
+#define REF_REASON reason
 #define REF_LOG(name, p)                                                  \
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "%s: %p   ref %d -> %d %s", \
-          (name), (p), (p)->refs, (p)->refs + 1, reason)
+          (name), (p), (p)->refs.count, (p)->refs.count + 1, reason)
 #define UNREF_LOG(name, p)                                                \
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "%s: %p unref %d -> %d %s", \
-          (name), (p), (p)->refs, (p)->refs - 1, reason)
+          (name), (p), (p)->refs.count, (p)->refs.count - 1, reason)
+#define REF_MUTATE_EXTRA_ARGS \
+  GRPC_SUBCHANNEL_REF_EXTRA_ARGS, const char *purpose
+#define REF_MUTATE_PURPOSE(x) , file, line, reason, x
 #else
-#define SUBCHANNEL_REF_LOCKED(p, r) subchannel_ref_locked((p))
-#define SUBCHANNEL_UNREF_LOCKED(p, r) subchannel_unref_locked((p))
-#define CONNECTION_REF_LOCKED(p, r) connection_ref_locked((p))
-#define CONNECTION_UNREF_LOCKED(cl, p, r) connection_unref_locked((cl), (p))
-#define REF_PASS_ARGS
-#define REF_PASS_REASON
+#define REF_REASON ""
 #define REF_LOG(name, p) \
   do {                   \
   } while (0)
 #define UNREF_LOG(name, p) \
   do {                     \
   } while (0)
+#define REF_MUTATE_EXTRA_ARGS
+#define REF_MUTATE_PURPOSE(x)
 #endif
 
 /*
  * connection implementation
  */
 
-static void connection_destroy(grpc_exec_ctx *exec_ctx, connection *c) {
-  GPR_ASSERT(c->refs == 0);
+static void connection_destroy(grpc_exec_ctx *exec_ctx, void *arg,
+                               int success) {
+  grpc_connected_subchannel *c = arg;
   grpc_channel_stack_destroy(exec_ctx, CHANNEL_STACK_FROM_CONNECTION(c));
   gpr_free(c);
 }
 
-static void connection_ref_locked(connection *c
-                                      GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  REF_LOG("CONNECTION", c);
-  subchannel_ref_locked(c->subchannel REF_PASS_ARGS);
-  ++c->refs;
+void grpc_connected_subchannel_ref(grpc_connected_subchannel *c
+                                       GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CHANNEL_STACK_REF(CHANNEL_STACK_FROM_CONNECTION(c), REF_REASON);
 }
 
-static grpc_subchannel *connection_unref_locked(
-    grpc_exec_ctx *exec_ctx, connection *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  grpc_subchannel *destroy = NULL;
-  UNREF_LOG("CONNECTION", c);
-  if (subchannel_unref_locked(c->subchannel REF_PASS_ARGS)) {
-    destroy = c->subchannel;
-  }
-  if (--c->refs == 0 && c->subchannel->active != c) {
-    connection_destroy(exec_ctx, c);
-  }
-  return destroy;
+void grpc_connected_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                                     grpc_connected_subchannel *c
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, CHANNEL_STACK_FROM_CONNECTION(c),
+                           REF_REASON);
 }
 
 /*
  * grpc_subchannel implementation
  */
 
-static void subchannel_ref_locked(grpc_subchannel *c
-                                      GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  REF_LOG("SUBCHANNEL", c);
-  ++c->refs;
+static void subchannel_destroy(grpc_exec_ctx *exec_ctx, void *arg,
+                               int success) {
+  grpc_subchannel *c = arg;
+  gpr_free((void *)c->filters);
+  grpc_channel_args_destroy(c->args);
+  gpr_free(c->addr);
+  gpr_slice_unref(c->initial_connect_string);
+  grpc_connectivity_state_destroy(exec_ctx, &c->state_tracker);
+  grpc_connector_unref(exec_ctx, c->connector);
+  grpc_pollset_set_destroy(&c->pollset_set);
+  gpr_free(c);
 }
 
-static int subchannel_unref_locked(grpc_subchannel *c
-                                       GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  UNREF_LOG("SUBCHANNEL", c);
-  return --c->refs == 0;
+static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
+                          int barrier REF_MUTATE_EXTRA_ARGS) {
+  gpr_atm old_val = barrier ? gpr_atm_full_fetch_add(&c->ref_pair, delta)
+                            : gpr_atm_no_barrier_fetch_add(&c->ref_pair, delta);
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+  gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+          "SUBCHANNEL: %p % 12s 0x%08x -> 0x%08x [%s]", c, purpose, old_val,
+          old_val + delta, reason);
+#endif
+  return old_val;
 }
 
 void grpc_subchannel_ref(grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  gpr_mu_lock(&c->mu);
-  subchannel_ref_locked(c REF_PASS_ARGS);
-  gpr_mu_unlock(&c->mu);
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, (1 << INTERNAL_REF_BITS),
+                        0 REF_MUTATE_PURPOSE("STRONG_REF"));
+  GPR_ASSERT((old_refs & STRONG_REF_MASK) != 0);
 }
 
-void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
-                           grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-  int destroy;
-  gpr_mu_lock(&c->mu);
-  destroy = subchannel_unref_locked(c REF_PASS_ARGS);
-  gpr_mu_unlock(&c->mu);
-  if (destroy) subchannel_destroy(exec_ctx, c);
+void grpc_subchannel_weak_ref(grpc_subchannel *c
+                                  GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, 1, 0 REF_MUTATE_PURPOSE("WEAK_REF"));
+  GPR_ASSERT(old_refs != 0);
 }
 
-static void subchannel_destroy(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
-  if (c->active != NULL) {
-    connection_destroy(exec_ctx, c->active);
+static void disconnect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
+  grpc_connected_subchannel *con;
+  gpr_mu_lock(&c->mu);
+  GPR_ASSERT(!c->disconnected);
+  c->disconnected = 1;
+  grpc_connector_shutdown(exec_ctx, c->connector);
+  con = GET_CONNECTED_SUBCHANNEL(c, no_barrier);
+  if (con != NULL) {
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, con, "connection");
+    gpr_atm_no_barrier_store(&c->connected_subchannel, 0xdeadbeef);
   }
-  gpr_free((void *)c->filters);
-  grpc_channel_args_destroy(c->args);
-  gpr_free(c->addr);
-  gpr_slice_unref(c->initial_connect_string);
-  grpc_connectivity_state_destroy(exec_ctx, &c->state_tracker);
-  grpc_connector_unref(exec_ctx, c->connector);
-  gpr_free(c);
+  gpr_mu_unlock(&c->mu);
 }
 
-void grpc_subchannel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *c,
-                                          grpc_pollset *pollset) {
-  grpc_pollset_set_add_pollset(exec_ctx, c->pollset_set, pollset);
+void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                           grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, (gpr_atm)1 - (gpr_atm)(1 << INTERNAL_REF_BITS),
+                        1 REF_MUTATE_PURPOSE("STRONG_UNREF"));
+  if ((old_refs & STRONG_REF_MASK) == (1 << INTERNAL_REF_BITS)) {
+    disconnect(exec_ctx, c);
+  }
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "strong-unref");
 }
 
-void grpc_subchannel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *c,
-                                          grpc_pollset *pollset) {
-  grpc_pollset_set_del_pollset(exec_ctx, c->pollset_set, pollset);
+void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel *c
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  gpr_atm old_refs;
+  old_refs = ref_mutate(c, -(gpr_atm)1, 1 REF_MUTATE_PURPOSE("WEAK_UNREF"));
+  if (old_refs == 1) {
+    grpc_exec_ctx_enqueue(exec_ctx, grpc_closure_create(subchannel_destroy, c),
+                          1);
+  }
 }
 
 static gpr_uint32 random_seed() {
@@ -293,10 +279,8 @@ static gpr_uint32 random_seed() {
 grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
                                         grpc_subchannel_args *args) {
   grpc_subchannel *c = gpr_malloc(sizeof(*c));
-  grpc_channel_element *parent_elem = grpc_channel_stack_last_element(
-      grpc_channel_get_channel_stack(args->master));
   memset(c, 0, sizeof(*c));
-  c->refs = 1;
+  gpr_atm_no_barrier_store(&c->ref_pair, 1 << INTERNAL_REF_BITS);
   c->connector = connector;
   grpc_connector_ref(c->connector);
   c->num_filters = args->filter_count;
@@ -305,13 +289,14 @@ grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
          sizeof(grpc_channel_filter *) * c->num_filters);
   c->addr = gpr_malloc(args->addr_len);
   memcpy(c->addr, args->addr, args->addr_len);
+  grpc_pollset_set_init(&c->pollset_set);
   c->addr_len = args->addr_len;
   grpc_set_initial_connect_string(&c->addr, &c->addr_len,
                                   &c->initial_connect_string);
   c->args = grpc_channel_args_copy(args->args);
-  c->master = args->master;
-  c->pollset_set = grpc_client_channel_get_connecting_pollset_set(parent_elem);
   c->random = random_seed();
+  c->root_external_state_watcher.next = c->root_external_state_watcher.prev =
+      &c->root_external_state_watcher;
   grpc_closure_init(&c->connected, subchannel_connected, c);
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
                                "subchannel");
@@ -319,70 +304,18 @@ grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
   return c;
 }
 
-static void cancel_waiting_calls(grpc_exec_ctx *exec_ctx,
-                                 grpc_subchannel *subchannel,
-                                 int iomgr_success) {
-  waiting_for_connect *w4c;
-  gpr_mu_lock(&subchannel->mu);
-  w4c = subchannel->waiting;
-  subchannel->waiting = NULL;
-  gpr_mu_unlock(&subchannel->mu);
-  while (w4c != NULL) {
-    waiting_for_connect *next = w4c->next;
-    grpc_subchannel_del_interested_party(exec_ctx, w4c->subchannel,
-                                         w4c->pollset);
-    if (w4c->notify) {
-      w4c->notify->cb(exec_ctx, w4c->notify->cb_arg, iomgr_success);
-    }
-
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, w4c->subchannel, "waiting_for_connect");
-    gpr_free(w4c);
-
-    w4c = next;
-  }
-}
-
-void grpc_subchannel_cancel_create_call(grpc_exec_ctx *exec_ctx,
-                                        grpc_subchannel *subchannel,
-                                        gpr_atm *target) {
-  waiting_for_connect *w4c;
-  int unref_count = 0;
-  gpr_mu_lock(&subchannel->mu);
-  w4c = subchannel->waiting;
-  subchannel->waiting = NULL;
-  while (w4c != NULL) {
-    waiting_for_connect *next = w4c->next;
-    if (w4c->target == target) {
-      grpc_subchannel_del_interested_party(exec_ctx, w4c->subchannel,
-                                           w4c->pollset);
-      grpc_exec_ctx_enqueue(exec_ctx, w4c->notify, 0);
-
-      unref_count++;
-      gpr_free(w4c);
-    } else {
-      w4c->next = subchannel->waiting;
-      subchannel->waiting = w4c;
-    }
-
-    w4c = next;
-  }
-  gpr_mu_unlock(&subchannel->mu);
-
-  while (unref_count-- > 0) {
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannel, "waiting_for_connect");
-  }
-}
-
 static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   grpc_connect_in_args args;
 
-  args.interested_parties = c->pollset_set;
+  args.interested_parties = &c->pollset_set;
   args.addr = c->addr;
   args.addr_len = c->addr_len;
   args.deadline = compute_connect_deadline(c);
   args.channel_args = c->args;
   args.initial_connect_string = c->initial_connect_string;
 
+  grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                              GRPC_CHANNEL_CONNECTING, "state_change");
   grpc_connector_connect(exec_ctx, c->connector, &args, &c->connecting_result,
                          &c->connected);
 }
@@ -395,66 +328,6 @@ static void start_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   continue_connect(exec_ctx, c);
 }
 
-static void continue_creating_call(grpc_exec_ctx *exec_ctx, void *arg,
-                                   int iomgr_success) {
-  int call_creation_finished_ok;
-  waiting_for_connect *w4c = arg;
-  grpc_subchannel_del_interested_party(exec_ctx, w4c->subchannel, w4c->pollset);
-  call_creation_finished_ok = grpc_subchannel_create_call(
-      exec_ctx, w4c->subchannel, w4c->pollset, w4c->target, w4c->notify);
-  GPR_ASSERT(call_creation_finished_ok == 1);
-  w4c->notify->cb(exec_ctx, w4c->notify->cb_arg, iomgr_success);
-  GRPC_SUBCHANNEL_UNREF(exec_ctx, w4c->subchannel, "waiting_for_connect");
-  gpr_free(w4c);
-}
-
-int grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
-                                grpc_pollset *pollset, gpr_atm *target,
-                                grpc_closure *notify) {
-  connection *con;
-  grpc_subchannel_call *call;
-  GPR_TIMER_BEGIN("grpc_subchannel_create_call", 0);
-  gpr_mu_lock(&c->mu);
-  if (c->active != NULL) {
-    con = c->active;
-    CONNECTION_REF_LOCKED(con, "call");
-    gpr_mu_unlock(&c->mu);
-
-    call = create_call(exec_ctx, con, pollset);
-    if (!gpr_atm_rel_cas(target, 0, (gpr_atm)(gpr_uintptr)call)) {
-      GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, call, "failed to set");
-    }
-    GPR_TIMER_END("grpc_subchannel_create_call", 0);
-    return 1;
-  } else {
-    waiting_for_connect *w4c = gpr_malloc(sizeof(*w4c));
-    w4c->next = c->waiting;
-    w4c->notify = notify;
-    w4c->pollset = pollset;
-    w4c->target = target;
-    w4c->subchannel = c;
-    /* released when clearing w4c */
-    SUBCHANNEL_REF_LOCKED(c, "waiting_for_connect");
-    grpc_closure_init(&w4c->continuation, continue_creating_call, w4c);
-    c->waiting = w4c;
-    grpc_subchannel_add_interested_party(exec_ctx, c, pollset);
-    if (!c->connecting) {
-      c->connecting = 1;
-      connectivity_state_changed_locked(exec_ctx, c, "create_call");
-      /* released by connection */
-      SUBCHANNEL_REF_LOCKED(c, "connecting");
-      GRPC_CHANNEL_INTERNAL_REF(c->master, "connecting");
-      gpr_mu_unlock(&c->mu);
-
-      start_connect(exec_ctx, c);
-    } else {
-      gpr_mu_unlock(&c->mu);
-    }
-    GPR_TIMER_END("grpc_subchannel_create_call", 0);
-    return 0;
-  }
-}
-
 grpc_connectivity_state grpc_subchannel_check_connectivity(grpc_subchannel *c) {
   grpc_connectivity_state state;
   gpr_mu_lock(&c->mu);
@@ -463,153 +336,138 @@ grpc_connectivity_state grpc_subchannel_check_connectivity(grpc_subchannel *c) {
   return state;
 }
 
-void grpc_subchannel_notify_on_state_change(grpc_exec_ctx *exec_ctx,
-                                            grpc_subchannel *c,
-                                            grpc_connectivity_state *state,
-                                            grpc_closure *notify) {
-  int do_connect = 0;
-  gpr_mu_lock(&c->mu);
-  if (grpc_connectivity_state_notify_on_state_change(
-          exec_ctx, &c->state_tracker, state, notify)) {
-    do_connect = 1;
-    c->connecting = 1;
-    /* released by connection */
-    SUBCHANNEL_REF_LOCKED(c, "connecting");
-    GRPC_CHANNEL_INTERNAL_REF(c->master, "connecting");
-    connectivity_state_changed_locked(exec_ctx, c, "state_change");
+static void on_external_state_watcher_done(grpc_exec_ctx *exec_ctx, void *arg,
+                                           int success) {
+  external_state_watcher *w = arg;
+  grpc_closure *follow_up = w->notify;
+  if (w->pollset_set != NULL) {
+    grpc_pollset_set_del_pollset_set(exec_ctx, &w->subchannel->pollset_set,
+                                     w->pollset_set);
   }
-  gpr_mu_unlock(&c->mu);
-
-  if (do_connect) {
-    start_connect(exec_ctx, c);
-  }
-}
-
-int grpc_subchannel_state_change_unsubscribe(grpc_exec_ctx *exec_ctx,
-                                             grpc_subchannel *c,
-                                             grpc_closure *subscribed_notify) {
-  int success;
-  gpr_mu_lock(&c->mu);
-  success = grpc_connectivity_state_change_unsubscribe(
-      exec_ctx, &c->state_tracker, subscribed_notify);
-  gpr_mu_unlock(&c->mu);
-  return success;
-}
-
-void grpc_subchannel_process_transport_op(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *c,
-                                          grpc_transport_op *op) {
-  connection *con = NULL;
-  grpc_subchannel *destroy;
-  int cancel_alarm = 0;
-  gpr_mu_lock(&c->mu);
-  if (c->active != NULL) {
-    con = c->active;
-    CONNECTION_REF_LOCKED(con, "transport-op");
-  }
-  if (op->disconnect) {
-    c->disconnected = 1;
-    connectivity_state_changed_locked(exec_ctx, c, "disconnect");
-    if (c->have_alarm) {
-      cancel_alarm = 1;
-    }
-  }
-  gpr_mu_unlock(&c->mu);
-
-  if (con != NULL) {
-    grpc_channel_stack *channel_stack = CHANNEL_STACK_FROM_CONNECTION(con);
-    grpc_channel_element *top_elem =
-        grpc_channel_stack_element(channel_stack, 0);
-    top_elem->filter->start_transport_op(exec_ctx, top_elem, op);
+  gpr_mu_lock(&w->subchannel->mu);
+  w->next->prev = w->prev;
+  w->prev->next = w->next;
+  gpr_mu_unlock(&w->subchannel->mu);
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, w->subchannel, "external_state_watcher");
+  gpr_free(w);
+  follow_up->cb(exec_ctx, follow_up->cb_arg, success);
+}
+
+void grpc_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify) {
+  int do_connect = 0;
+  external_state_watcher *w;
 
+  if (state == NULL) {
     gpr_mu_lock(&c->mu);
-    destroy = CONNECTION_UNREF_LOCKED(exec_ctx, con, "transport-op");
+    for (w = c->root_external_state_watcher.next;
+         w != &c->root_external_state_watcher; w = w->next) {
+      if (w->notify == notify) {
+        grpc_connectivity_state_notify_on_state_change(
+            exec_ctx, &c->state_tracker, NULL, &w->closure);
+      }
+    }
     gpr_mu_unlock(&c->mu);
-    if (destroy) {
-      subchannel_destroy(exec_ctx, destroy);
+  } else {
+    w = gpr_malloc(sizeof(*w));
+    w->subchannel = c;
+    w->pollset_set = interested_parties;
+    w->notify = notify;
+    grpc_closure_init(&w->closure, on_external_state_watcher_done, w);
+    if (interested_parties != NULL) {
+      grpc_pollset_set_add_pollset_set(exec_ctx, &c->pollset_set,
+                                       interested_parties);
     }
+    GRPC_SUBCHANNEL_WEAK_REF(c, "external_state_watcher");
+    gpr_mu_lock(&c->mu);
+    w->next = &c->root_external_state_watcher;
+    w->prev = w->next->prev;
+    w->next->prev = w->prev->next = w;
+    if (grpc_connectivity_state_notify_on_state_change(
+            exec_ctx, &c->state_tracker, state, &w->closure)) {
+      do_connect = 1;
+      c->connecting = 1;
+      /* released by connection */
+      GRPC_SUBCHANNEL_WEAK_REF(c, "connecting");
+    }
+    gpr_mu_unlock(&c->mu);
   }
 
-  if (cancel_alarm) {
-    grpc_timer_cancel(exec_ctx, &c->alarm);
+  if (do_connect) {
+    start_connect(exec_ctx, c);
   }
+}
 
-  if (op->disconnect) {
-    grpc_connector_shutdown(exec_ctx, c->connector);
-  }
+void grpc_connected_subchannel_process_transport_op(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_transport_op *op) {
+  grpc_channel_stack *channel_stack = CHANNEL_STACK_FROM_CONNECTION(con);
+  grpc_channel_element *top_elem = grpc_channel_stack_element(channel_stack, 0);
+  top_elem->filter->start_transport_op(exec_ctx, top_elem, op);
 }
 
-static void on_state_changed(grpc_exec_ctx *exec_ctx, void *p,
-                             int iomgr_success) {
+static void subchannel_on_child_state_changed(grpc_exec_ctx *exec_ctx, void *p,
+                                              int iomgr_success) {
   state_watcher *sw = p;
   grpc_subchannel *c = sw->subchannel;
   gpr_mu *mu = &c->mu;
-  int destroy;
-  grpc_transport_op op;
-  grpc_channel_element *elem;
-  connection *destroy_connection = NULL;
 
   gpr_mu_lock(mu);
 
-  /* if we failed or there is a version number mismatch, just leave
-     this closure */
-  if (!iomgr_success || sw->subchannel->active_version != sw->version) {
-    goto done;
-  }
-
-  switch (sw->connectivity_state) {
-    case GRPC_CHANNEL_CONNECTING:
-    case GRPC_CHANNEL_READY:
-    case GRPC_CHANNEL_IDLE:
-      /* all is still good: keep watching */
-      memset(&op, 0, sizeof(op));
-      op.connectivity_state = &sw->connectivity_state;
-      op.on_connectivity_state_change = &sw->closure;
-      elem = grpc_channel_stack_element(
-          CHANNEL_STACK_FROM_CONNECTION(c->active), 0);
-      elem->filter->start_transport_op(exec_ctx, elem, &op);
-      /* early out */
-      gpr_mu_unlock(mu);
-      return;
-    case GRPC_CHANNEL_FATAL_FAILURE:
-    case GRPC_CHANNEL_TRANSIENT_FAILURE:
-      /* things have gone wrong, deactivate and enter idle */
-      if (sw->subchannel->active->refs == 0) {
-        destroy_connection = sw->subchannel->active;
-      }
-      sw->subchannel->active = NULL;
-      grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
-                                  c->disconnected
-                                      ? GRPC_CHANNEL_FATAL_FAILURE
-                                      : GRPC_CHANNEL_TRANSIENT_FAILURE,
-                                  "connection_failed");
-      break;
+  /* if we failed just leave this closure */
+  if (iomgr_success) {
+    if (sw->connectivity_state == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+      /* any errors on a subchannel ==> we're done, create a new one */
+      sw->connectivity_state = GRPC_CHANNEL_FATAL_FAILURE;
+    }
+    grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                                sw->connectivity_state, "reflect_child");
+    if (sw->connectivity_state != GRPC_CHANNEL_FATAL_FAILURE) {
+      grpc_connected_subchannel_notify_on_state_change(
+          exec_ctx, GET_CONNECTED_SUBCHANNEL(c, no_barrier), NULL,
+          &sw->connectivity_state, &sw->closure);
+      GRPC_SUBCHANNEL_WEAK_REF(c, "state_watcher");
+      sw = NULL;
+    }
   }
 
-done:
-  connectivity_state_changed_locked(exec_ctx, c, "transport_state_changed");
-  destroy = SUBCHANNEL_UNREF_LOCKED(c, "state_watcher");
-  gpr_free(sw);
   gpr_mu_unlock(mu);
-  if (destroy) {
-    subchannel_destroy(exec_ctx, c);
-  }
-  if (destroy_connection != NULL) {
-    connection_destroy(exec_ctx, destroy_connection);
-  }
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "state_watcher");
+  gpr_free(sw);
+}
+
+static void connected_subchannel_state_op(grpc_exec_ctx *exec_ctx,
+                                          grpc_connected_subchannel *con,
+                                          grpc_pollset_set *interested_parties,
+                                          grpc_connectivity_state *state,
+                                          grpc_closure *closure) {
+  grpc_transport_op op;
+  grpc_channel_element *elem;
+  memset(&op, 0, sizeof(op));
+  op.connectivity_state = state;
+  op.on_connectivity_state_change = closure;
+  op.bind_pollset_set = interested_parties;
+  elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
+  elem->filter->start_transport_op(exec_ctx, elem, &op);
+}
+
+void grpc_connected_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *closure) {
+  connected_subchannel_state_op(exec_ctx, con, interested_parties, state,
+                                closure);
 }
 
 static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   size_t channel_stack_size;
-  connection *con;
+  grpc_connected_subchannel *con;
   grpc_channel_stack *stk;
   size_t num_filters;
   const grpc_channel_filter **filters;
-  waiting_for_connect *w4c;
-  grpc_transport_op op;
-  state_watcher *sw;
-  connection *destroy_connection = NULL;
-  grpc_channel_element *elem;
+  state_watcher *sw_subchannel;
 
   /* build final filter list */
   num_filters = c->num_filters + c->connecting_result.num_filters + 1;
@@ -621,74 +479,52 @@ static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
 
   /* construct channel stack */
   channel_stack_size = grpc_channel_stack_size(filters, num_filters);
-  con = gpr_malloc(sizeof(connection) + channel_stack_size);
-  stk = (grpc_channel_stack *)(con + 1);
-  con->refs = 0;
-  con->subchannel = c;
-  grpc_channel_stack_init(exec_ctx, filters, num_filters, c->master, c->args,
-                          stk);
+  con = gpr_malloc(channel_stack_size);
+  stk = CHANNEL_STACK_FROM_CONNECTION(con);
+  grpc_channel_stack_init(exec_ctx, 1, connection_destroy, con, filters,
+                          num_filters, c->args, "CONNECTED_SUBCHANNEL", stk);
   grpc_connected_channel_bind_transport(stk, c->connecting_result.transport);
   gpr_free((void *)c->connecting_result.filters);
   memset(&c->connecting_result, 0, sizeof(c->connecting_result));
 
   /* initialize state watcher */
-  sw = gpr_malloc(sizeof(*sw));
-  grpc_closure_init(&sw->closure, on_state_changed, sw);
-  sw->subchannel = c;
-  sw->connectivity_state = GRPC_CHANNEL_READY;
+  sw_subchannel = gpr_malloc(sizeof(*sw_subchannel));
+  sw_subchannel->subchannel = c;
+  sw_subchannel->connectivity_state = GRPC_CHANNEL_READY;
+  grpc_closure_init(&sw_subchannel->closure, subchannel_on_child_state_changed,
+                    sw_subchannel);
 
   gpr_mu_lock(&c->mu);
 
   if (c->disconnected) {
     gpr_mu_unlock(&c->mu);
-    gpr_free(sw);
+    gpr_free(sw_subchannel);
     gpr_free((void *)filters);
     grpc_channel_stack_destroy(exec_ctx, stk);
-    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, c->master, "connecting");
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, c, "connecting");
+    gpr_free(con);
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
     return;
   }
 
   /* publish */
-  if (c->active != NULL && c->active->refs == 0) {
-    destroy_connection = c->active;
-  }
-  c->active = con;
-  c->active_version++;
-  sw->version = c->active_version;
+  GPR_ASSERT(gpr_atm_no_barrier_cas(&c->connected_subchannel, 0, (gpr_atm)con));
   c->connecting = 0;
 
-  /* watch for changes; subchannel ref for connecting is donated
+  /* setup subchannel watching connected subchannel for changes; subchannel ref
+     for connecting is donated
      to the state watcher */
-  memset(&op, 0, sizeof(op));
-  op.connectivity_state = &sw->connectivity_state;
-  op.on_connectivity_state_change = &sw->closure;
-  op.bind_pollset_set = c->pollset_set;
-  SUBCHANNEL_REF_LOCKED(c, "state_watcher");
-  GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, c->master, "connecting");
-  GPR_ASSERT(!SUBCHANNEL_UNREF_LOCKED(c, "connecting"));
-  elem =
-      grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(c->active), 0);
-  elem->filter->start_transport_op(exec_ctx, elem, &op);
+  GRPC_SUBCHANNEL_WEAK_REF(c, "state_watcher");
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
+  grpc_connected_subchannel_notify_on_state_change(
+      exec_ctx, con, &c->pollset_set, &sw_subchannel->connectivity_state,
+      &sw_subchannel->closure);
 
   /* signal completion */
-  connectivity_state_changed_locked(exec_ctx, c, "connected");
-  w4c = c->waiting;
-  c->waiting = NULL;
+  grpc_connectivity_state_set(exec_ctx, &c->state_tracker, GRPC_CHANNEL_READY,
+                              "connected");
 
   gpr_mu_unlock(&c->mu);
-
-  while (w4c != NULL) {
-    waiting_for_connect *next = w4c->next;
-    grpc_exec_ctx_enqueue(exec_ctx, &w4c->continuation, 1);
-    w4c = next;
-  }
-
   gpr_free((void *)filters);
-
-  if (destroy_connection != NULL) {
-    connection_destroy(exec_ctx, destroy_connection);
-  }
 }
 
 /* Generate a random number between 0 and 1. */
@@ -742,29 +578,31 @@ static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, int iomgr_success) {
   if (c->disconnected) {
     iomgr_success = 0;
   }
-  connectivity_state_changed_locked(exec_ctx, c, "alarm");
   gpr_mu_unlock(&c->mu);
   if (iomgr_success) {
     update_reconnect_parameters(c);
     continue_connect(exec_ctx, c);
   } else {
-    cancel_waiting_calls(exec_ctx, c, iomgr_success);
-    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, c->master, "connecting");
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, c, "connecting");
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
   }
 }
 
 static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *arg,
                                  int iomgr_success) {
   grpc_subchannel *c = arg;
+
   if (c->connecting_result.transport != NULL) {
     publish_transport(exec_ctx, c);
+  } else if (c->disconnected) {
+    GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
   } else {
     gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
     gpr_mu_lock(&c->mu);
     GPR_ASSERT(!c->have_alarm);
     c->have_alarm = 1;
-    connectivity_state_changed_locked(exec_ctx, c, "connect_failed");
+    grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
+                                GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                "connect_failed");
     grpc_timer_init(exec_ctx, &c->alarm, c->next_attempt, on_alarm, c, now);
     gpr_mu_unlock(&c->mu);
   }
@@ -781,29 +619,6 @@ static gpr_timespec compute_connect_deadline(grpc_subchannel *c) {
                                                           : min_deadline;
 }
 
-static grpc_connectivity_state compute_connectivity_locked(grpc_subchannel *c) {
-  if (c->disconnected) {
-    return GRPC_CHANNEL_FATAL_FAILURE;
-  }
-  if (c->connecting) {
-    if (c->have_alarm) {
-      return GRPC_CHANNEL_TRANSIENT_FAILURE;
-    }
-    return GRPC_CHANNEL_CONNECTING;
-  }
-  if (c->active) {
-    return GRPC_CHANNEL_READY;
-  }
-  return GRPC_CHANNEL_IDLE;
-}
-
-static void connectivity_state_changed_locked(grpc_exec_ctx *exec_ctx,
-                                              grpc_subchannel *c,
-                                              const char *reason) {
-  grpc_connectivity_state current = compute_connectivity_locked(c);
-  grpc_connectivity_state_set(exec_ctx, &c->state_tracker, current, reason);
-}
-
 /*
  * grpc_subchannel_call implementation
  */
@@ -811,37 +626,22 @@ static void connectivity_state_changed_locked(grpc_exec_ctx *exec_ctx,
 static void subchannel_call_destroy(grpc_exec_ctx *exec_ctx, void *call,
                                     int success) {
   grpc_subchannel_call *c = call;
-  gpr_mu *mu = &c->connection->subchannel->mu;
-  grpc_subchannel *destroy;
   GPR_TIMER_BEGIN("grpc_subchannel_call_unref.destroy", 0);
   grpc_call_stack_destroy(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c));
-  gpr_mu_lock(mu);
-  destroy = CONNECTION_UNREF_LOCKED(exec_ctx, c->connection, "call");
-  gpr_mu_unlock(mu);
+  GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, c->connection, "subchannel_call");
   gpr_free(c);
-  if (destroy != NULL) {
-    subchannel_destroy(exec_ctx, destroy);
-  }
   GPR_TIMER_END("grpc_subchannel_call_unref.destroy", 0);
 }
 
 void grpc_subchannel_call_ref(grpc_subchannel_call *c
                                   GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-#ifdef GRPC_STREAM_REFCOUNT_DEBUG
-  grpc_call_stack_ref(SUBCHANNEL_CALL_TO_CALL_STACK(c), reason);
-#else
-  grpc_call_stack_ref(SUBCHANNEL_CALL_TO_CALL_STACK(c));
-#endif
+  GRPC_CALL_STACK_REF(SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
 }
 
 void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
                                 grpc_subchannel_call *c
                                     GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
-#ifdef GRPC_STREAM_REFCOUNT_DEBUG
-  grpc_call_stack_unref(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c), reason);
-#else
-  grpc_call_stack_unref(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c));
-#endif
+  GRPC_CALL_STACK_UNREF(exec_ctx, SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
 }
 
 char *grpc_subchannel_call_get_peer(grpc_exec_ctx *exec_ctx,
@@ -859,24 +659,26 @@ void grpc_subchannel_call_process_op(grpc_exec_ctx *exec_ctx,
   top_elem->filter->start_transport_stream_op(exec_ctx, top_elem, op);
 }
 
-static grpc_subchannel_call *create_call(grpc_exec_ctx *exec_ctx,
-                                         connection *con,
-                                         grpc_pollset *pollset) {
+grpc_connected_subchannel *grpc_subchannel_get_connected_subchannel(
+    grpc_subchannel *c) {
+  return GET_CONNECTED_SUBCHANNEL(c, acq);
+}
+
+grpc_subchannel_call *grpc_connected_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
+    grpc_pollset *pollset) {
   grpc_channel_stack *chanstk = CHANNEL_STACK_FROM_CONNECTION(con);
   grpc_subchannel_call *call =
       gpr_malloc(sizeof(grpc_subchannel_call) + chanstk->call_stack_size);
   grpc_call_stack *callstk = SUBCHANNEL_CALL_TO_CALL_STACK(call);
   call->connection = con;
+  GRPC_CONNECTED_SUBCHANNEL_REF(con, "subchannel_call");
   grpc_call_stack_init(exec_ctx, chanstk, 1, subchannel_call_destroy, call,
                        NULL, NULL, callstk);
   grpc_call_stack_set_pollset(exec_ctx, callstk, pollset);
   return call;
 }
 
-grpc_channel *grpc_subchannel_get_master(grpc_subchannel *subchannel) {
-  return subchannel->master;
-}
-
 grpc_call_stack *grpc_subchannel_call_get_call_stack(
     grpc_subchannel_call *subchannel_call) {
   return SUBCHANNEL_CALL_TO_CALL_STACK(subchannel_call);
diff --git a/src/core/client_config/subchannel.h b/src/core/client_config/subchannel.h
index 85ea3739e4..74ebcecfba 100644
--- a/src/core/client_config/subchannel.h
+++ b/src/core/client_config/subchannel.h
@@ -41,6 +41,7 @@
 /** A (sub-)channel that knows how to connect to exactly one target
     address. Provides a target for load balancing. */
 typedef struct grpc_subchannel grpc_subchannel;
+typedef struct grpc_connected_subchannel grpc_connected_subchannel;
 typedef struct grpc_subchannel_call grpc_subchannel_call;
 typedef struct grpc_subchannel_args grpc_subchannel_args;
 
@@ -49,6 +50,14 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
   grpc_subchannel_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) \
   grpc_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_WEAK_REF(p, r) \
+  grpc_subchannel_weak_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
+  grpc_subchannel_weak_unref((cl), (p), __FILE__, __LINE__, (r))
+#define GRPC_CONNECTED_SUBCHANNEL_REF(p, r) \
+  grpc_connected_subchannel_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_CONNECTED_SUBCHANNEL_UNREF(cl, p, r) \
+  grpc_connected_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_CALL_REF(p, r) \
   grpc_subchannel_call_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_CALL_UNREF(cl, p, r) \
@@ -58,6 +67,12 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
 #else
 #define GRPC_SUBCHANNEL_REF(p, r) grpc_subchannel_ref((p))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) grpc_subchannel_unref((cl), (p))
+#define GRPC_SUBCHANNEL_WEAK_REF(p, r) grpc_subchannel_weak_ref((p))
+#define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
+  grpc_subchannel_weak_unref((cl), (p))
+#define GRPC_CONNECTED_SUBCHANNEL_REF(p, r) grpc_connected_subchannel_ref((p))
+#define GRPC_CONNECTED_SUBCHANNEL_UNREF(cl, p, r) \
+  grpc_connected_subchannel_unref((cl), (p))
 #define GRPC_SUBCHANNEL_CALL_REF(p, r) grpc_subchannel_call_ref((p))
 #define GRPC_SUBCHANNEL_CALL_UNREF(cl, p, r) \
   grpc_subchannel_call_unref((cl), (p))
@@ -69,33 +84,31 @@ void grpc_subchannel_ref(grpc_subchannel *channel
 void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
                            grpc_subchannel *channel
                                GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_weak_ref(grpc_subchannel *channel
+                                  GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
+                                grpc_subchannel *channel
+                                    GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_connected_subchannel_ref(grpc_connected_subchannel *channel
+                                       GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+void grpc_connected_subchannel_unref(grpc_exec_ctx *exec_ctx,
+                                     grpc_connected_subchannel *channel
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_call_ref(grpc_subchannel_call *call
                                   GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
                                 grpc_subchannel_call *call
                                     GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 
-/** construct a subchannel call (possibly asynchronously).
- *
- * If the returned status is 1, the call will return immediately and \a target
- * will point to a connected \a subchannel_call instance. Note that \a notify
- * will \em not be invoked in this case.
- * Otherwise, if the returned status is 0, the subchannel call will be created
- * asynchronously, invoking the \a notify callback upon completion. */
-int grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx,
-                                grpc_subchannel *subchannel,
-                                grpc_pollset *pollset, gpr_atm *target,
-                                grpc_closure *notify);
-
-/** cancel \a call in the waiting state. */
-void grpc_subchannel_cancel_create_call(grpc_exec_ctx *exec_ctx,
-                                        grpc_subchannel *subchannel,
-                                        gpr_atm *target);
+/** construct a subchannel call */
+grpc_subchannel_call *grpc_connected_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *connected_subchannel,
+    grpc_pollset *pollset);
 
 /** process a transport level op */
-void grpc_subchannel_process_transport_op(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *subchannel,
-                                          grpc_transport_op *op);
+void grpc_connected_subchannel_process_transport_op(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *subchannel,
+    grpc_transport_op *op);
 
 /** poll the current connectivity state of a channel */
 grpc_connectivity_state grpc_subchannel_check_connectivity(
@@ -103,26 +116,19 @@ grpc_connectivity_state grpc_subchannel_check_connectivity(
 
 /** call notify when the connectivity state of a channel changes from *state.
     Updates *state with the new state of the channel */
-void grpc_subchannel_notify_on_state_change(grpc_exec_ctx *exec_ctx,
-                                            grpc_subchannel *channel,
-                                            grpc_connectivity_state *state,
-                                            grpc_closure *notify);
-
-/** Remove \a subscribed_notify from the list of closures to be called on a
- * state change if present, returning 1. Otherwise, nothing is done and return
- * 0. */
-int grpc_subchannel_state_change_unsubscribe(grpc_exec_ctx *exec_ctx,
-                                             grpc_subchannel *channel,
-                                             grpc_closure *subscribed_notify);
-
-/** express interest in \a channel's activities through \a pollset. */
-void grpc_subchannel_add_interested_party(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *channel,
-                                          grpc_pollset *pollset);
-/** stop following \a channel's activity through \a pollset. */
-void grpc_subchannel_del_interested_party(grpc_exec_ctx *exec_ctx,
-                                          grpc_subchannel *channel,
-                                          grpc_pollset *pollset);
+void grpc_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *channel,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify);
+void grpc_connected_subchannel_notify_on_state_change(
+    grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *channel,
+    grpc_pollset_set *interested_parties, grpc_connectivity_state *state,
+    grpc_closure *notify);
+
+/** retrieve the grpc_connected_subchannel - or NULL if called before
+    the subchannel becomes connected */
+grpc_connected_subchannel *grpc_subchannel_get_connected_subchannel(
+    grpc_subchannel *subchannel);
 
 /** continue processing a transport op */
 void grpc_subchannel_call_process_op(grpc_exec_ctx *exec_ctx,
@@ -147,15 +153,10 @@ struct grpc_subchannel_args {
   /** Address to connect to */
   struct sockaddr *addr;
   size_t addr_len;
-  /** master channel */
-  grpc_channel *master;
 };
 
 /** create a subchannel given a connector */
 grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
                                         grpc_subchannel_args *args);
 
-/** Return the master channel associated with the subchannel */
-grpc_channel *grpc_subchannel_get_master(grpc_subchannel *subchannel);
-
 #endif /* GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_H */
diff --git a/src/core/iomgr/fd_posix.c b/src/core/iomgr/fd_posix.c
index 2be0ea235f..00710d83bd 100644
--- a/src/core/iomgr/fd_posix.c
+++ b/src/core/iomgr/fd_posix.c
@@ -43,6 +43,7 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
 
 #define CLOSURE_NOT_READY ((grpc_closure *)0)
@@ -158,7 +159,10 @@ void grpc_fd_global_shutdown(void) {
 
 grpc_fd *grpc_fd_create(int fd, const char *name) {
   grpc_fd *r = alloc_fd(fd);
-  grpc_iomgr_register_object(&r->iomgr_object, name);
+  char *name2;
+  gpr_asprintf(&name2, "%s fd=%d", name, fd);
+  grpc_iomgr_register_object(&r->iomgr_object, name2);
+  gpr_free(name2);
 #ifdef GRPC_FD_REF_COUNT_DEBUG
   gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, r, name);
 #endif
diff --git a/src/core/iomgr/fd_posix.h b/src/core/iomgr/fd_posix.h
index d628ef3aaf..df4eb64d4c 100644
--- a/src/core/iomgr/fd_posix.h
+++ b/src/core/iomgr/fd_posix.h
@@ -170,6 +170,7 @@ void grpc_fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd);
 void grpc_fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd);
 
 /* Reference counting for fds */
+/*#define GRPC_FD_REF_COUNT_DEBUG*/
 #ifdef GRPC_FD_REF_COUNT_DEBUG
 void grpc_fd_ref(grpc_fd *fd, const char *reason, const char *file, int line);
 void grpc_fd_unref(grpc_fd *fd, const char *reason, const char *file, int line);
diff --git a/src/core/iomgr/pollset_set.h b/src/core/iomgr/pollset_set.h
index 0fdcba01a4..09c04438f7 100644
--- a/src/core/iomgr/pollset_set.h
+++ b/src/core/iomgr/pollset_set.h
@@ -49,13 +49,19 @@
 #include "src/core/iomgr/pollset_set_windows.h"
 #endif
 
-void grpc_pollset_set_init(grpc_pollset_set* pollset_set);
-void grpc_pollset_set_destroy(grpc_pollset_set* pollset_set);
-void grpc_pollset_set_add_pollset(grpc_exec_ctx* exec_ctx,
-                                  grpc_pollset_set* pollset_set,
-                                  grpc_pollset* pollset);
-void grpc_pollset_set_del_pollset(grpc_exec_ctx* exec_ctx,
-                                  grpc_pollset_set* pollset_set,
-                                  grpc_pollset* pollset);
+void grpc_pollset_set_init(grpc_pollset_set *pollset_set);
+void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set);
+void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+void grpc_pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
+                                  grpc_pollset_set *pollset_set,
+                                  grpc_pollset *pollset);
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item);
 
 #endif /* GRPC_INTERNAL_CORE_IOMGR_POLLSET_H */
diff --git a/src/core/iomgr/pollset_set_posix.c b/src/core/iomgr/pollset_set_posix.c
index c86ed3d5da..4ec92202e3 100644
--- a/src/core/iomgr/pollset_set_posix.c
+++ b/src/core/iomgr/pollset_set_posix.c
@@ -52,9 +52,10 @@ void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set) {
   size_t i;
   gpr_mu_destroy(&pollset_set->mu);
   for (i = 0; i < pollset_set->fd_count; i++) {
-    GRPC_FD_UNREF(pollset_set->fds[i], "pollset");
+    GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
   }
   gpr_free(pollset_set->pollsets);
+  gpr_free(pollset_set->pollset_sets);
   gpr_free(pollset_set->fds);
 }
 
@@ -73,7 +74,7 @@ void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
   pollset_set->pollsets[pollset_set->pollset_count++] = pollset;
   for (i = 0, j = 0; i < pollset_set->fd_count; i++) {
     if (grpc_fd_is_orphaned(pollset_set->fds[i])) {
-      GRPC_FD_UNREF(pollset_set->fds[i], "pollset");
+      GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
     } else {
       grpc_pollset_add_fd(exec_ctx, pollset, pollset_set->fds[i]);
       pollset_set->fds[j++] = pollset_set->fds[i];
@@ -99,6 +100,46 @@ void grpc_pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
   gpr_mu_unlock(&pollset_set->mu);
 }
 
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item) {
+  size_t i, j;
+  gpr_mu_lock(&bag->mu);
+  if (bag->pollset_set_count == bag->pollset_set_capacity) {
+    bag->pollset_set_capacity = GPR_MAX(8, 2 * bag->pollset_set_capacity);
+    bag->pollset_sets =
+        gpr_realloc(bag->pollset_sets,
+                    bag->pollset_set_capacity * sizeof(*bag->pollset_sets));
+  }
+  bag->pollset_sets[bag->pollset_set_count++] = item;
+  for (i = 0, j = 0; i < bag->fd_count; i++) {
+    if (grpc_fd_is_orphaned(bag->fds[i])) {
+      GRPC_FD_UNREF(bag->fds[i], "pollset_set");
+    } else {
+      grpc_pollset_set_add_fd(exec_ctx, item, bag->fds[i]);
+      bag->fds[j++] = bag->fds[i];
+    }
+  }
+  bag->fd_count = j;
+  gpr_mu_unlock(&bag->mu);
+}
+
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
+                                      grpc_pollset_set *bag,
+                                      grpc_pollset_set *item) {
+  size_t i;
+  gpr_mu_lock(&bag->mu);
+  for (i = 0; i < bag->pollset_set_count; i++) {
+    if (bag->pollset_sets[i] == item) {
+      bag->pollset_set_count--;
+      GPR_SWAP(grpc_pollset_set *, bag->pollset_sets[i],
+               bag->pollset_sets[bag->pollset_set_count]);
+      break;
+    }
+  }
+  gpr_mu_unlock(&bag->mu);
+}
+
 void grpc_pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
                              grpc_pollset_set *pollset_set, grpc_fd *fd) {
   size_t i;
@@ -113,6 +154,9 @@ void grpc_pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
   for (i = 0; i < pollset_set->pollset_count; i++) {
     grpc_pollset_add_fd(exec_ctx, pollset_set->pollsets[i], fd);
   }
+  for (i = 0; i < pollset_set->pollset_set_count; i++) {
+    grpc_pollset_set_add_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
+  }
   gpr_mu_unlock(&pollset_set->mu);
 }
 
@@ -129,6 +173,9 @@ void grpc_pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
       break;
     }
   }
+  for (i = 0; i < pollset_set->pollset_set_count; i++) {
+    grpc_pollset_set_del_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
+  }
   gpr_mu_unlock(&pollset_set->mu);
 }
 
diff --git a/src/core/iomgr/pollset_set_posix.h b/src/core/iomgr/pollset_set_posix.h
index 05234fb642..4820a61e4b 100644
--- a/src/core/iomgr/pollset_set_posix.h
+++ b/src/core/iomgr/pollset_set_posix.h
@@ -44,6 +44,10 @@ typedef struct grpc_pollset_set {
   size_t pollset_capacity;
   grpc_pollset **pollsets;
 
+  size_t pollset_set_count;
+  size_t pollset_set_capacity;
+  struct grpc_pollset_set **pollset_sets;
+
   size_t fd_count;
   size_t fd_capacity;
   grpc_fd **fds;
diff --git a/src/core/iomgr/pollset_set_windows.c b/src/core/iomgr/pollset_set_windows.c
index 53d5d3dcd4..157b46ec32 100644
--- a/src/core/iomgr/pollset_set_windows.c
+++ b/src/core/iomgr/pollset_set_windows.c
@@ -49,4 +49,12 @@ void grpc_pollset_set_del_pollset(grpc_exec_ctx* exec_ctx,
                                   grpc_pollset_set* pollset_set,
                                   grpc_pollset* pollset) {}
 
+void grpc_pollset_set_add_pollset_set(grpc_exec_ctx* exec_ctx,
+                                      grpc_pollset_set* bag,
+                                      grpc_pollset_set* item) {}
+
+void grpc_pollset_set_del_pollset_set(grpc_exec_ctx* exec_ctx,
+                                      grpc_pollset_set* bag,
+                                      grpc_pollset_set* item) {}
+
 #endif /* GPR_WINSOCK_SOCKET */
diff --git a/src/core/security/credentials.c b/src/core/security/credentials.c
index 543c75044b..38a6710cd4 100644
--- a/src/core/security/credentials.c
+++ b/src/core/security/credentials.c
@@ -39,7 +39,7 @@
 #include "src/core/channel/channel_args.h"
 #include "src/core/channel/http_client_filter.h"
 #include "src/core/httpcli/httpcli.h"
-#include "src/core/iomgr/iomgr.h"
+#include "src/core/iomgr/executor.h"
 #include "src/core/json/json.h"
 #include "src/core/support/string.h"
 #include "src/core/surface/api_trace.h"
@@ -48,7 +48,6 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/sync.h>
-#include <grpc/support/thd.h>
 #include <grpc/support/time.h>
 
 /* -- Common. -- */
@@ -792,15 +791,14 @@ static void md_only_test_destruct(grpc_call_credentials *creds) {
   grpc_credentials_md_store_unref(c->md_store);
 }
 
-static void on_simulated_token_fetch_done(void *user_data) {
+static void on_simulated_token_fetch_done(grpc_exec_ctx *exec_ctx,
+                                          void *user_data, int success) {
   grpc_credentials_metadata_request *r =
       (grpc_credentials_metadata_request *)user_data;
   grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)r->creds;
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  r->cb(&exec_ctx, r->user_data, c->md_store->entries, c->md_store->num_entries,
+  r->cb(exec_ctx, r->user_data, c->md_store->entries, c->md_store->num_entries,
         GRPC_CREDENTIALS_OK);
   grpc_credentials_metadata_request_destroy(r);
-  grpc_exec_ctx_finish(&exec_ctx);
 }
 
 static void md_only_test_get_request_metadata(
@@ -810,10 +808,10 @@ static void md_only_test_get_request_metadata(
   grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)creds;
 
   if (c->is_async) {
-    gpr_thd_id thd_id;
     grpc_credentials_metadata_request *cb_arg =
         grpc_credentials_metadata_request_create(creds, cb, user_data);
-    gpr_thd_new(&thd_id, on_simulated_token_fetch_done, cb_arg, NULL);
+    grpc_executor_enqueue(
+        grpc_closure_create(on_simulated_token_fetch_done, cb_arg), 1);
   } else {
     cb(exec_ctx, user_data, c->md_store->entries, 1, GRPC_CREDENTIALS_OK);
   }
diff --git a/src/core/surface/call.c b/src/core/surface/call.c
index 84b9daaa28..8672478cb2 100644
--- a/src/core/surface/call.c
+++ b/src/core/surface/call.c
@@ -341,21 +341,18 @@ grpc_completion_queue *grpc_call_get_completion_queue(grpc_call *call) {
 }
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
-void grpc_call_internal_ref(grpc_call *c, const char *reason) {
-  grpc_call_stack_ref(CALL_STACK_FROM_CALL(c), reason);
-}
-void grpc_call_internal_unref(grpc_exec_ctx *exec_ctx, grpc_call *c,
-                              const char *reason) {
-  grpc_call_stack_unref(exec_ctx, CALL_STACK_FROM_CALL(c), reason);
-}
+#define REF_REASON reason
+#define REF_ARG , const char *reason
 #else
-void grpc_call_internal_ref(grpc_call *c) {
-  grpc_call_stack_ref(CALL_STACK_FROM_CALL(c));
+#define REF_REASON ""
+#define REF_ARG
+#endif
+void grpc_call_internal_ref(grpc_call *c REF_ARG) {
+  GRPC_CALL_STACK_REF(CALL_STACK_FROM_CALL(c), REF_REASON);
 }
-void grpc_call_internal_unref(grpc_exec_ctx *exec_ctx, grpc_call *c) {
-  grpc_call_stack_unref(exec_ctx, CALL_STACK_FROM_CALL(c));
+void grpc_call_internal_unref(grpc_exec_ctx *exec_ctx, grpc_call *c REF_ARG) {
+  GRPC_CALL_STACK_UNREF(exec_ctx, CALL_STACK_FROM_CALL(c), REF_REASON);
 }
-#endif
 
 static void destroy_call(grpc_exec_ctx *exec_ctx, void *call, int success) {
   size_t i;
@@ -742,8 +739,15 @@ static void execute_op(grpc_exec_ctx *exec_ctx, grpc_call *call,
 char *grpc_call_get_peer(grpc_call *call) {
   grpc_call_element *elem = CALL_ELEM_FROM_CALL(call, 0);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  char *result = elem->filter->get_peer(&exec_ctx, elem);
+  char *result;
   GRPC_API_TRACE("grpc_call_get_peer(%p)", 1, (call));
+  result = elem->filter->get_peer(&exec_ctx, elem);
+  if (result == NULL) {
+    result = grpc_channel_get_target(call->channel);
+  }
+  if (result == NULL) {
+    result = gpr_strdup("unknown");
+  }
   grpc_exec_ctx_finish(&exec_ctx);
   return result;
 }
diff --git a/src/core/surface/channel.c b/src/core/surface/channel.c
index 14fe97c30d..573a0e742f 100644
--- a/src/core/surface/channel.c
+++ b/src/core/surface/channel.c
@@ -63,7 +63,6 @@ typedef struct registered_call {
 
 struct grpc_channel {
   int is_client;
-  gpr_refcount refs;
   gpr_uint32 max_message_length;
   grpc_mdelem *default_authority;
 
@@ -81,6 +80,8 @@ struct grpc_channel {
 /* the protobuf library will (by default) start warning at 100megs */
 #define DEFAULT_MAX_MESSAGE_LENGTH (100 * 1024 * 1024)
 
+static void destroy_channel(grpc_exec_ctx *exec_ctx, void *arg, int success);
+
 grpc_channel *grpc_channel_create_from_filters(
     grpc_exec_ctx *exec_ctx, const char *target,
     const grpc_channel_filter **filters, size_t num_filters,
@@ -93,8 +94,6 @@ grpc_channel *grpc_channel_create_from_filters(
   channel->target = gpr_strdup(target);
   GPR_ASSERT(grpc_is_initialized() && "call grpc_init()");
   channel->is_client = is_client;
-  /* decremented by grpc_channel_destroy */
-  gpr_ref_init(&channel->refs, 1);
   gpr_mu_init(&channel->registered_call_mu);
   channel->registered_calls = NULL;
 
@@ -153,7 +152,9 @@ grpc_channel *grpc_channel_create_from_filters(
     gpr_free(default_authority);
   }
 
-  grpc_channel_stack_init(exec_ctx, filters, num_filters, channel, args,
+  grpc_channel_stack_init(exec_ctx, 1, destroy_channel, channel, filters,
+                          num_filters, args,
+                          is_client ? "CLIENT_CHANNEL" : "SERVER_CHANNEL",
                           CHANNEL_STACK_FROM_CHANNEL(channel));
 
   return channel;
@@ -250,17 +251,25 @@ grpc_call *grpc_channel_create_registered_call(
       rc->authority ? GRPC_MDELEM_REF(rc->authority) : NULL, deadline);
 }
 
-#ifdef GRPC_CHANNEL_REF_COUNT_DEBUG
-void grpc_channel_internal_ref(grpc_channel *c, const char *reason) {
-  gpr_log(GPR_DEBUG, "CHANNEL:   ref %p %d -> %d [%s]", c, c->refs.count,
-          c->refs.count + 1, reason);
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+#define REF_REASON reason
+#define REF_ARG , const char *reason
 #else
-void grpc_channel_internal_ref(grpc_channel *c) {
+#define REF_REASON ""
+#define REF_ARG
 #endif
-  gpr_ref(&c->refs);
+void grpc_channel_internal_ref(grpc_channel *c REF_ARG) {
+  GRPC_CHANNEL_STACK_REF(CHANNEL_STACK_FROM_CHANNEL(c), REF_REASON);
 }
 
-static void destroy_channel(grpc_exec_ctx *exec_ctx, grpc_channel *channel) {
+void grpc_channel_internal_unref(grpc_exec_ctx *exec_ctx,
+                                 grpc_channel *c REF_ARG) {
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, CHANNEL_STACK_FROM_CHANNEL(c), REF_REASON);
+}
+
+static void destroy_channel(grpc_exec_ctx *exec_ctx, void *arg,
+                            int iomgr_success) {
+  grpc_channel *channel = arg;
   grpc_channel_stack_destroy(exec_ctx, CHANNEL_STACK_FROM_CHANNEL(channel));
   while (channel->registered_calls) {
     registered_call *rc = channel->registered_calls;
@@ -279,20 +288,6 @@ static void destroy_channel(grpc_exec_ctx *exec_ctx, grpc_channel *channel) {
   gpr_free(channel);
 }
 
-#ifdef GRPC_CHANNEL_REF_COUNT_DEBUG
-void grpc_channel_internal_unref(grpc_exec_ctx *exec_ctx, grpc_channel *channel,
-                                 const char *reason) {
-  gpr_log(GPR_DEBUG, "CHANNEL: unref %p %d -> %d [%s]", channel,
-          channel->refs.count, channel->refs.count - 1, reason);
-#else
-void grpc_channel_internal_unref(grpc_exec_ctx *exec_ctx,
-                                 grpc_channel *channel) {
-#endif
-  if (gpr_unref(&channel->refs)) {
-    destroy_channel(exec_ctx, channel);
-  }
-}
-
 void grpc_channel_destroy(grpc_channel *channel) {
   grpc_transport_op op;
   grpc_channel_element *elem;
diff --git a/src/core/surface/channel.h b/src/core/surface/channel.h
index 7dea609ebc..3d2ff23542 100644
--- a/src/core/surface/channel.h
+++ b/src/core/surface/channel.h
@@ -53,7 +53,7 @@ grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_channel *channel,
                                                  int status_code);
 gpr_uint32 grpc_channel_get_max_message_length(grpc_channel *channel);
 
-#ifdef GRPC_CHANNEL_REF_COUNT_DEBUG
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
 void grpc_channel_internal_ref(grpc_channel *channel, const char *reason);
 void grpc_channel_internal_unref(grpc_exec_ctx *exec_ctx, grpc_channel *channel,
                                  const char *reason);
diff --git a/src/core/surface/channel_connectivity.c b/src/core/surface/channel_connectivity.c
index df2774b527..ad1c9b334e 100644
--- a/src/core/surface/channel_connectivity.c
+++ b/src/core/surface/channel_connectivity.c
@@ -83,7 +83,6 @@ typedef struct {
   gpr_mu mu;
   callback_phase phase;
   int success;
-  int removed;
   grpc_closure on_complete;
   grpc_timer alarm;
   grpc_connectivity_state state;
@@ -135,30 +134,15 @@ static void finished_completion(grpc_exec_ctx *exec_ctx, void *pw,
 static void partly_done(grpc_exec_ctx *exec_ctx, state_watcher *w,
                         int due_to_completion) {
   int delete = 0;
-  grpc_channel_element *client_channel_elem = NULL;
 
-  gpr_mu_lock(&w->mu);
-  if (w->removed == 0) {
-    w->removed = 1;
-    client_channel_elem = grpc_channel_stack_last_element(
-        grpc_channel_get_channel_stack(w->channel));
-    if (client_channel_elem->filter == &grpc_client_channel_filter) {
-      grpc_client_channel_del_interested_party(exec_ctx, client_channel_elem,
-                                               grpc_cq_pollset(w->cq));
-    } else {
-      grpc_client_uchannel_del_interested_party(exec_ctx, client_channel_elem,
-                                                grpc_cq_pollset(w->cq));
-    }
-  }
-  gpr_mu_unlock(&w->mu);
   if (due_to_completion) {
-    gpr_mu_lock(&w->mu);
-    w->success = 1;
-    gpr_mu_unlock(&w->mu);
     grpc_timer_cancel(exec_ctx, &w->alarm);
   }
 
   gpr_mu_lock(&w->mu);
+  if (due_to_completion) {
+    w->success = 1;
+  }
   switch (w->phase) {
     case WAITING:
       w->phase = CALLING_BACK;
@@ -212,7 +196,6 @@ void grpc_channel_watch_connectivity_state(
   w->phase = WAITING;
   w->state = last_observed_state;
   w->success = 0;
-  w->removed = 0;
   w->cq = cq;
   w->tag = tag;
   w->channel = channel;
@@ -223,16 +206,14 @@ void grpc_channel_watch_connectivity_state(
 
   if (client_channel_elem->filter == &grpc_client_channel_filter) {
     GRPC_CHANNEL_INTERNAL_REF(channel, "watch_channel_connectivity");
-    grpc_client_channel_add_interested_party(&exec_ctx, client_channel_elem,
-                                             grpc_cq_pollset(cq));
     grpc_client_channel_watch_connectivity_state(&exec_ctx, client_channel_elem,
-                                                 &w->state, &w->on_complete);
+                                                 grpc_cq_pollset(cq), &w->state,
+                                                 &w->on_complete);
   } else if (client_channel_elem->filter == &grpc_client_uchannel_filter) {
     GRPC_CHANNEL_INTERNAL_REF(channel, "watch_uchannel_connectivity");
-    grpc_client_uchannel_add_interested_party(&exec_ctx, client_channel_elem,
-                                              grpc_cq_pollset(cq));
     grpc_client_uchannel_watch_connectivity_state(
-        &exec_ctx, client_channel_elem, &w->state, &w->on_complete);
+        &exec_ctx, client_channel_elem, grpc_cq_pollset(cq), &w->state,
+        &w->on_complete);
   }
 
   grpc_exec_ctx_finish(&exec_ctx);
diff --git a/src/core/surface/channel_create.c b/src/core/surface/channel_create.c
index fe7e1072ac..97ec23408f 100644
--- a/src/core/surface/channel_create.c
+++ b/src/core/surface/channel_create.c
@@ -171,7 +171,6 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   c->base.vtable = &connector_vtable;
   gpr_ref_init(&c->refs, 1);
   args->args = final_args;
-  args->master = f->master;
   s = grpc_subchannel_create(&c->base, args);
   grpc_connector_unref(exec_ctx, &c->base);
   grpc_channel_args_destroy(final_args);
diff --git a/src/core/surface/lame_client.c b/src/core/surface/lame_client.c
index 4a55544ac1..a60e9d20da 100644
--- a/src/core/surface/lame_client.c
+++ b/src/core/surface/lame_client.c
@@ -49,7 +49,6 @@ typedef struct {
 } call_data;
 
 typedef struct {
-  grpc_channel *master;
   grpc_status_code error_code;
   const char *error_message;
 } channel_data;
@@ -84,8 +83,7 @@ static void lame_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
 }
 
 static char *lame_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
-  channel_data *chand = elem->channel_data;
-  return grpc_channel_get_target(chand->master);
+  return NULL;
 }
 
 static void lame_start_transport_op(grpc_exec_ctx *exec_ctx,
@@ -111,10 +109,8 @@ static void destroy_call_elem(grpc_exec_ctx *exec_ctx,
 static void init_channel_elem(grpc_exec_ctx *exec_ctx,
                               grpc_channel_element *elem,
                               grpc_channel_element_args *args) {
-  channel_data *chand = elem->channel_data;
   GPR_ASSERT(args->is_first);
   GPR_ASSERT(args->is_last);
-  chand->master = args->master;
 }
 
 static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/surface/secure_channel_create.c b/src/core/surface/secure_channel_create.c
index c9a54d9237..863c905ea3 100644
--- a/src/core/surface/secure_channel_create.c
+++ b/src/core/surface/secure_channel_create.c
@@ -228,7 +228,6 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   gpr_mu_init(&c->mu);
   gpr_ref_init(&c->refs, 1);
   args->args = final_args;
-  args->master = f->master;
   s = grpc_subchannel_create(&c->base, args);
   grpc_connector_unref(exec_ctx, &c->base);
   grpc_channel_args_destroy(final_args);
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 3e88f69abf..6ba9db8348 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -910,7 +910,7 @@ static void perform_transport_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
 
   grpc_exec_ctx_enqueue(exec_ctx, op->on_consumed, 1);
 
-  if (op->on_connectivity_state_change) {
+  if (op->on_connectivity_state_change != NULL) {
     grpc_connectivity_state_notify_on_state_change(
         exec_ctx, &t->channel_callback.state_tracker, op->connectivity_state,
         op->on_connectivity_state_change);
diff --git a/src/core/transport/connectivity_state.c b/src/core/transport/connectivity_state.c
index b001af7e35..3c3fd4671d 100644
--- a/src/core/transport/connectivity_state.c
+++ b/src/core/transport/connectivity_state.c
@@ -87,7 +87,7 @@ void grpc_connectivity_state_destroy(grpc_exec_ctx *exec_ctx,
 grpc_connectivity_state grpc_connectivity_state_check(
     grpc_connectivity_state_tracker *tracker) {
   if (grpc_connectivity_state_trace) {
-    gpr_log(GPR_DEBUG, "CONWATCH: %s: get %s", tracker->name,
+    gpr_log(GPR_DEBUG, "CONWATCH: %p %s: get %s", tracker, tracker->name,
             grpc_connectivity_state_name(tracker->current_state));
   }
   return tracker->current_state;
@@ -97,42 +97,47 @@ int grpc_connectivity_state_notify_on_state_change(
     grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
     grpc_connectivity_state *current, grpc_closure *notify) {
   if (grpc_connectivity_state_trace) {
-    gpr_log(GPR_DEBUG, "CONWATCH: %s: from %s [cur=%s] notify=%p",
-            tracker->name, grpc_connectivity_state_name(*current),
-            grpc_connectivity_state_name(tracker->current_state), notify);
+    if (current == NULL) {
+      gpr_log(GPR_DEBUG, "CONWATCH: %p %s: unsubscribe notify=%p", tracker,
+              tracker->name, notify);
+    } else {
+      gpr_log(GPR_DEBUG, "CONWATCH: %p %s: from %s [cur=%s] notify=%p", tracker,
+              tracker->name, grpc_connectivity_state_name(*current),
+              grpc_connectivity_state_name(tracker->current_state), notify);
+    }
   }
-  if (tracker->current_state != *current) {
-    *current = tracker->current_state;
-    grpc_exec_ctx_enqueue(exec_ctx, notify, 1);
+  if (current == NULL) {
+    grpc_connectivity_state_watcher *w = tracker->watchers;
+    if (w != NULL && w->notify == notify) {
+      grpc_exec_ctx_enqueue(exec_ctx, notify, 0);
+      tracker->watchers = w->next;
+      gpr_free(w);
+      return 0;
+    }
+    while (w != NULL) {
+      grpc_connectivity_state_watcher *rm_candidate = w->next;
+      if (rm_candidate != NULL && rm_candidate->notify == notify) {
+        grpc_exec_ctx_enqueue(exec_ctx, notify, 0);
+        w->next = w->next->next;
+        gpr_free(rm_candidate);
+        return 0;
+      }
+      w = w->next;
+    }
+    return 0;
   } else {
-    grpc_connectivity_state_watcher *w = gpr_malloc(sizeof(*w));
-    w->current = current;
-    w->notify = notify;
-    w->next = tracker->watchers;
-    tracker->watchers = w;
-  }
-  return tracker->current_state == GRPC_CHANNEL_IDLE;
-}
-
-int grpc_connectivity_state_change_unsubscribe(
-    grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
-    grpc_closure *subscribed_notify) {
-  grpc_connectivity_state_watcher *w = tracker->watchers;
-  if (w != NULL && w->notify == subscribed_notify) {
-    tracker->watchers = w->next;
-    gpr_free(w);
-    return 1;
-  }
-  while (w != NULL) {
-    grpc_connectivity_state_watcher *rm_candidate = w->next;
-    if (rm_candidate != NULL && rm_candidate->notify == subscribed_notify) {
-      w->next = w->next->next;
-      gpr_free(rm_candidate);
-      return 1;
+    if (tracker->current_state != *current) {
+      *current = tracker->current_state;
+      grpc_exec_ctx_enqueue(exec_ctx, notify, 1);
+    } else {
+      grpc_connectivity_state_watcher *w = gpr_malloc(sizeof(*w));
+      w->current = current;
+      w->notify = notify;
+      w->next = tracker->watchers;
+      tracker->watchers = w;
     }
-    w = w->next;
+    return tracker->current_state == GRPC_CHANNEL_IDLE;
   }
-  return 0;
 }
 
 void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
@@ -141,7 +146,7 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
                                  const char *reason) {
   grpc_connectivity_state_watcher *w;
   if (grpc_connectivity_state_trace) {
-    gpr_log(GPR_DEBUG, "SET: %s: %s --> %s [%s]", tracker->name,
+    gpr_log(GPR_DEBUG, "SET: %p %s: %s --> %s [%s]", tracker, tracker->name,
             grpc_connectivity_state_name(tracker->current_state),
             grpc_connectivity_state_name(state), reason);
   }
diff --git a/src/core/transport/connectivity_state.h b/src/core/transport/connectivity_state.h
index af2734c016..a4eb6652e5 100644
--- a/src/core/transport/connectivity_state.h
+++ b/src/core/transport/connectivity_state.h
@@ -75,16 +75,11 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
 grpc_connectivity_state grpc_connectivity_state_check(
     grpc_connectivity_state_tracker *tracker);
 
-/** Return 1 if the channel should start connecting, 0 otherwise */
+/** Return 1 if the channel should start connecting, 0 otherwise.
+    If current==NULL cancel notify if it is already queued (success==0 in that
+    case) */
 int grpc_connectivity_state_notify_on_state_change(
     grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
     grpc_connectivity_state *current, grpc_closure *notify);
 
-/** Remove \a subscribed_notify from the list of closures to be called on a
- * state change if present, returning 1. Otherwise, nothing is done and return
- * 0. */
-int grpc_connectivity_state_change_unsubscribe(
-    grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
-    grpc_closure *subscribed_notify);
-
 #endif /* GRPC_INTERNAL_CORE_TRANSPORT_CONNECTIVITY_STATE_H */
diff --git a/src/core/transport/static_metadata.c b/src/core/transport/static_metadata.c
index e7aff325c2..c2bfef0397 100644
--- a/src/core/transport/static_metadata.c
+++ b/src/core/transport/static_metadata.c
@@ -65,92 +65,23 @@ const gpr_uint8
         80, 81, 82, 33, 83, 33, 84, 33, 85, 33, 86, 33};
 
 const char *const grpc_static_metadata_strings[GRPC_STATIC_MDSTR_COUNT] = {
-    "0",
-    "1",
-    "2",
-    "200",
-    "204",
-    "206",
-    "304",
-    "400",
-    "404",
-    "500",
-    "accept",
-    "accept-charset",
-    "accept-encoding",
-    "accept-language",
-    "accept-ranges",
-    "access-control-allow-origin",
-    "age",
-    "allow",
-    "application/grpc",
-    ":authority",
-    "authorization",
-    "cache-control",
-    "content-disposition",
-    "content-encoding",
-    "content-language",
-    "content-length",
-    "content-location",
-    "content-range",
-    "content-type",
-    "cookie",
-    "date",
-    "deflate",
-    "deflate,gzip",
-    "",
-    "etag",
-    "expect",
-    "expires",
-    "from",
-    "GET",
-    "grpc",
-    "grpc-accept-encoding",
-    "grpc-encoding",
-    "grpc-internal-encoding-request",
-    "grpc-message",
-    "grpc-status",
-    "grpc-timeout",
-    "gzip",
-    "gzip, deflate",
-    "host",
-    "http",
-    "https",
-    "identity",
-    "identity,deflate",
-    "identity,deflate,gzip",
-    "identity,gzip",
-    "if-match",
-    "if-modified-since",
-    "if-none-match",
-    "if-range",
-    "if-unmodified-since",
-    "last-modified",
-    "link",
-    "location",
-    "max-forwards",
-    ":method",
-    ":path",
-    "POST",
-    "proxy-authenticate",
-    "proxy-authorization",
-    "range",
-    "referer",
-    "refresh",
-    "retry-after",
-    ":scheme",
-    "server",
-    "set-cookie",
-    "/",
-    "/index.html",
-    ":status",
-    "strict-transport-security",
-    "te",
-    "trailers",
-    "transfer-encoding",
-    "user-agent",
-    "vary",
-    "via",
+    "0", "1", "2", "200", "204", "206", "304", "400", "404", "500", "accept",
+    "accept-charset", "accept-encoding", "accept-language", "accept-ranges",
+    "access-control-allow-origin", "age", "allow", "application/grpc",
+    ":authority", "authorization", "cache-control", "content-disposition",
+    "content-encoding", "content-language", "content-length",
+    "content-location", "content-range", "content-type", "cookie", "date",
+    "deflate", "deflate,gzip", "", "etag", "expect", "expires", "from", "GET",
+    "grpc", "grpc-accept-encoding", "grpc-encoding",
+    "grpc-internal-encoding-request", "grpc-message", "grpc-status",
+    "grpc-timeout", "gzip", "gzip, deflate", "host", "http", "https",
+    "identity", "identity,deflate", "identity,deflate,gzip", "identity,gzip",
+    "if-match", "if-modified-since", "if-none-match", "if-range",
+    "if-unmodified-since", "last-modified", "link", "location", "max-forwards",
+    ":method", ":path", "POST", "proxy-authenticate", "proxy-authorization",
+    "range", "referer", "refresh", "retry-after", ":scheme", "server",
+    "set-cookie", "/", "/index.html", ":status", "strict-transport-security",
+    "te", "trailers", "transfer-encoding", "user-agent", "vary", "via",
     "www-authenticate"};
 
 const gpr_uint8 grpc_static_accept_encoding_metadata[8] = {0,  29, 26, 30,
diff --git a/src/core/transport/transport.c b/src/core/transport/transport.c
index f2bebc62f3..2ab978be46 100644
--- a/src/core/transport/transport.c
+++ b/src/core/transport/transport.c
@@ -40,8 +40,8 @@
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
 void grpc_stream_ref(grpc_stream_refcount *refcount, const char *reason) {
   gpr_atm val = gpr_atm_no_barrier_load(&refcount->refs.count);
-  gpr_log(GPR_DEBUG, "STREAM %p:%p   REF %d->%d %s", refcount,
-          refcount->destroy.cb_arg, val, val + 1, reason);
+  gpr_log(GPR_DEBUG, "%s %p:%p   REF %d->%d %s", refcount->object_type,
+          refcount, refcount->destroy.cb_arg, val, val + 1, reason);
 #else
 void grpc_stream_ref(grpc_stream_refcount *refcount) {
 #endif
@@ -52,8 +52,8 @@ void grpc_stream_ref(grpc_stream_refcount *refcount) {
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx, grpc_stream_refcount *refcount,
                        const char *reason) {
   gpr_atm val = gpr_atm_no_barrier_load(&refcount->refs.count);
-  gpr_log(GPR_DEBUG, "STREAM %p:%p UNREF %d->%d %s", refcount,
-          refcount->destroy.cb_arg, val, val - 1, reason);
+  gpr_log(GPR_DEBUG, "%s %p:%p UNREF %d->%d %s", refcount->object_type,
+          refcount, refcount->destroy.cb_arg, val, val - 1, reason);
 #else
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx,
                        grpc_stream_refcount *refcount) {
@@ -63,6 +63,19 @@ void grpc_stream_unref(grpc_exec_ctx *exec_ctx,
   }
 }
 
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+void grpc_stream_ref_init(grpc_stream_refcount *refcount, int initial_refs,
+                          grpc_iomgr_cb_func cb, void *cb_arg,
+                          const char *object_type) {
+  refcount->object_type = object_type;
+#else
+void grpc_stream_ref_init(grpc_stream_refcount *refcount, int initial_refs,
+                          grpc_iomgr_cb_func cb, void *cb_arg) {
+#endif
+  gpr_ref_init(&refcount->refs, initial_refs);
+  grpc_closure_init(&refcount->destroy, cb, cb_arg);
+}
+
 size_t grpc_transport_stream_size(grpc_transport *transport) {
   return transport->vtable->sizeof_stream;
 }
diff --git a/src/core/transport/transport.h b/src/core/transport/transport.h
index f296ce8251..f94f0ae76e 100644
--- a/src/core/transport/transport.h
+++ b/src/core/transport/transport.h
@@ -50,19 +50,32 @@ typedef struct grpc_transport grpc_transport;
    for a stream. */
 typedef struct grpc_stream grpc_stream;
 
+/*#define GRPC_STREAM_REFCOUNT_DEBUG*/
+
 typedef struct grpc_stream_refcount {
   gpr_refcount refs;
   grpc_closure destroy;
+#ifdef GRPC_STREAM_REFCOUNT_DEBUG
+  const char *object_type;
+#endif
 } grpc_stream_refcount;
 
-/*#define GRPC_STREAM_REFCOUNT_DEBUG*/
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
+void grpc_stream_ref_init(grpc_stream_refcount *refcount, int initial_refs,
+                          grpc_iomgr_cb_func cb, void *cb_arg,
+                          const char *object_type);
 void grpc_stream_ref(grpc_stream_refcount *refcount, const char *reason);
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx, grpc_stream_refcount *refcount,
                        const char *reason);
+#define GRPC_STREAM_REF_INIT(rc, ir, cb, cb_arg, objtype) \
+  grpc_stream_ref_init(rc, ir, cb, cb_arg, objtype)
 #else
+void grpc_stream_ref_init(grpc_stream_refcount *refcount, int initial_refs,
+                          grpc_iomgr_cb_func cb, void *cb_arg);
 void grpc_stream_ref(grpc_stream_refcount *refcount);
 void grpc_stream_unref(grpc_exec_ctx *exec_ctx, grpc_stream_refcount *refcount);
+#define GRPC_STREAM_REF_INIT(rc, ir, cb, cb_arg, objtype) \
+  grpc_stream_ref_init(rc, ir, cb, cb_arg)
 #endif
 
 /* Transport stream op: a set of operations to perform on a transport
@@ -96,7 +109,7 @@ typedef struct grpc_transport_stream_op {
 typedef struct grpc_transport_op {
   /** called when processing of this op is done */
   grpc_closure *on_consumed;
-  /** connectivity monitoring */
+  /** connectivity monitoring - set connectivity_state to NULL to unsubscribe */
   grpc_closure *on_connectivity_state_change;
   grpc_connectivity_state *connectivity_state;
   /** should the transport be disconnected */
diff --git a/src/php/bin/run_tests.sh b/src/php/bin/run_tests.sh
index 2a7335e20a..235d161ca7 100755
--- a/src/php/bin/run_tests.sh
+++ b/src/php/bin/run_tests.sh
@@ -30,7 +30,7 @@
 
 # Loads the local shared library, and runs all of the test cases in tests/
 # against it
-set -e
+set -ex
 cd $(dirname $0)/../../..
 root=$(pwd)
 cd src/php/bin