Merge branch 'master' into fd_rw_atm_closure

51 files changed, 1226 insertions, 535 deletions

diff --git a/src/core/ext/client_channel/client_channel.c b/src/core/ext/client_channel/client_channel.c
index 06038bb5ba..62fb061bcf 100644
--- a/src/core/ext/client_channel/client_channel.c
+++ b/src/core/ext/client_channel/client_channel.c
@@ -51,6 +51,7 @@
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/connected_channel.h"
 #include "src/core/lib/channel/deadline_filter.h"
+#include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/iomgr.h"
 #include "src/core/lib/iomgr/polling_entity.h"
 #include "src/core/lib/profiling/timers.h"
@@ -160,13 +161,10 @@ typedef struct client_channel_channel_data {
   /** client channel factory */
   grpc_client_channel_factory *client_channel_factory;
 
-  /** mutex protecting all variables below in this data structure */
-  gpr_mu mu;
+  /** combiner protecting all variables below in this data structure */
+  grpc_combiner *combiner;
   /** currently active load balancer */
-  char *lb_policy_name;
   grpc_lb_policy *lb_policy;
-  /** service config in JSON form */
-  char *service_config_json;
   /** maps method names to method_parameters structs */
   grpc_slice_hash_table *method_params_table;
   /** incoming resolver result - set by resolver.next() */
@@ -183,6 +181,13 @@ typedef struct client_channel_channel_data {
   grpc_channel_stack *owning_stack;
   /** interested parties (owned) */
   grpc_pollset_set *interested_parties;
+
+  /* the following properties are guarded by a mutex since API's require them
+     to be instantaniously available */
+  gpr_mu info_mu;
+  char *info_lb_policy_name;
+  /** service config in JSON form */
+  char *info_service_config_json;
 } channel_data;
 
 /** We create one watcher for each new lb_policy that is returned from a
@@ -218,32 +223,23 @@ static void set_channel_connectivity_state_locked(grpc_exec_ctx *exec_ctx,
 }
 
 static void on_lb_policy_state_changed_locked(grpc_exec_ctx *exec_ctx,
-                                              lb_policy_connectivity_watcher *w,
-                                              grpc_error *error) {
+                                              void *arg, grpc_error *error) {
+  lb_policy_connectivity_watcher *w = arg;
   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;
-
-  if (publish_state == GRPC_CHANNEL_SHUTDOWN && 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;
-  }
-  set_channel_connectivity_state_locked(exec_ctx, w->chand, publish_state,
-                                        GRPC_ERROR_REF(error), "lb_changed");
-  if (w->state != GRPC_CHANNEL_SHUTDOWN) {
-    watch_lb_policy(exec_ctx, w->chand, w->lb_policy, w->state);
+  /* check if the notification is for the latest policy */
+  if (w->lb_policy == w->chand->lb_policy) {
+    if (publish_state == GRPC_CHANNEL_SHUTDOWN && 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;
+    }
+    set_channel_connectivity_state_locked(exec_ctx, w->chand, publish_state,
+                                          GRPC_ERROR_REF(error), "lb_changed");
+    if (w->state != GRPC_CHANNEL_SHUTDOWN) {
+      watch_lb_policy(exec_ctx, w->chand, w->lb_policy, w->state);
+    }
   }
-}
-
-static void on_lb_policy_state_changed(grpc_exec_ctx *exec_ctx, void *arg,
-                                       grpc_error *error) {
-  lb_policy_connectivity_watcher *w = arg;
-
-  gpr_mu_lock(&w->chand->mu);
-  on_lb_policy_state_changed_locked(exec_ctx, w, error);
-  gpr_mu_unlock(&w->chand->mu);
 
   GRPC_CHANNEL_STACK_UNREF(exec_ctx, w->chand->owning_stack, "watch_lb_policy");
   gpr_free(w);
@@ -256,16 +252,16 @@ static void watch_lb_policy(grpc_exec_ctx *exec_ctx, channel_data *chand,
   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,
-                    grpc_schedule_on_exec_ctx);
+  grpc_closure_init(&w->on_changed, on_lb_policy_state_changed_locked, w,
+                    grpc_combiner_scheduler(chand->combiner, false));
   w->state = current_state;
   w->lb_policy = lb_policy;
   grpc_lb_policy_notify_on_state_change(exec_ctx, lb_policy, &w->state,
                                         &w->on_changed);
 }
 
-static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
-                                       grpc_error *error) {
+static void on_resolver_result_changed_locked(grpc_exec_ctx *exec_ctx,
+                                              void *arg, grpc_error *error) {
   channel_data *chand = arg;
   char *lb_policy_name = NULL;
   grpc_lb_policy *lb_policy = NULL;
@@ -353,17 +349,18 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                      chand->interested_parties);
   }
 
-  gpr_mu_lock(&chand->mu);
+  gpr_mu_lock(&chand->info_mu);
   if (lb_policy_name != NULL) {
-    gpr_free(chand->lb_policy_name);
-    chand->lb_policy_name = lb_policy_name;
+    gpr_free(chand->info_lb_policy_name);
+    chand->info_lb_policy_name = lb_policy_name;
   }
   old_lb_policy = chand->lb_policy;
   chand->lb_policy = lb_policy;
   if (service_config_json != NULL) {
-    gpr_free(chand->service_config_json);
-    chand->service_config_json = service_config_json;
+    gpr_free(chand->info_service_config_json);
+    chand->info_service_config_json = service_config_json;
   }
+  gpr_mu_unlock(&chand->info_mu);
   if (chand->method_params_table != NULL) {
     grpc_slice_hash_table_unref(exec_ctx, chand->method_params_table);
   }
@@ -391,7 +388,6 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
     GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
     grpc_resolver_next(exec_ctx, chand->resolver, &chand->resolver_result,
                        &chand->on_resolver_result_changed);
-    gpr_mu_unlock(&chand->mu);
   } else {
     if (chand->resolver != NULL) {
       grpc_resolver_shutdown(exec_ctx, chand->resolver);
@@ -404,7 +400,6 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
         GRPC_ERROR_CREATE_REFERENCING("Got config after disconnection", refs,
                                       GPR_ARRAY_SIZE(refs)),
         "resolver_gone");
-    gpr_mu_unlock(&chand->mu);
   }
 
   if (exit_idle) {
@@ -426,20 +421,12 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
   GRPC_ERROR_UNREF(state_error);
 }
 
-static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
-                                  grpc_channel_element *elem,
-                                  grpc_transport_op *op) {
+static void start_transport_op_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                      grpc_error *error_ignored) {
+  grpc_transport_op *op = arg;
+  grpc_channel_element *elem = op->transport_private.args[0];
   channel_data *chand = elem->channel_data;
 
-  grpc_closure_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE);
-
-  GPR_ASSERT(op->set_accept_stream == false);
-  if (op->bind_pollset != NULL) {
-    grpc_pollset_set_add_pollset(exec_ctx, chand->interested_parties,
-                                 op->bind_pollset);
-  }
-
-  gpr_mu_lock(&chand->mu);
   if (op->on_connectivity_state_change != NULL) {
     grpc_connectivity_state_notify_on_state_change(
         exec_ctx, &chand->state_tracker, op->connectivity_state,
@@ -482,25 +469,48 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
     }
     GRPC_ERROR_UNREF(op->disconnect_with_error);
   }
-  gpr_mu_unlock(&chand->mu);
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, chand->owning_stack, "start_transport_op");
+
+  grpc_closure_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE);
+}
+
+static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
+                                  grpc_channel_element *elem,
+                                  grpc_transport_op *op) {
+  channel_data *chand = elem->channel_data;
+
+  GPR_ASSERT(op->set_accept_stream == false);
+  if (op->bind_pollset != NULL) {
+    grpc_pollset_set_add_pollset(exec_ctx, chand->interested_parties,
+                                 op->bind_pollset);
+  }
+
+  op->transport_private.args[0] = elem;
+  GRPC_CHANNEL_STACK_REF(chand->owning_stack, "start_transport_op");
+  grpc_closure_sched(
+      exec_ctx, grpc_closure_init(
+                    &op->transport_private.closure, start_transport_op_locked,
+                    op, grpc_combiner_scheduler(chand->combiner, false)),
+      GRPC_ERROR_NONE);
 }
 
 static void cc_get_channel_info(grpc_exec_ctx *exec_ctx,
                                 grpc_channel_element *elem,
                                 const grpc_channel_info *info) {
   channel_data *chand = elem->channel_data;
-  gpr_mu_lock(&chand->mu);
+  gpr_mu_lock(&chand->info_mu);
   if (info->lb_policy_name != NULL) {
-    *info->lb_policy_name = chand->lb_policy_name == NULL
+    *info->lb_policy_name = chand->info_lb_policy_name == NULL
                                 ? NULL
-                                : gpr_strdup(chand->lb_policy_name);
+                                : gpr_strdup(chand->info_lb_policy_name);
   }
   if (info->service_config_json != NULL) {
-    *info->service_config_json = chand->service_config_json == NULL
-                                     ? NULL
-                                     : gpr_strdup(chand->service_config_json);
+    *info->service_config_json =
+        chand->info_service_config_json == NULL
+            ? NULL
+            : gpr_strdup(chand->info_service_config_json);
   }
-  gpr_mu_unlock(&chand->mu);
+  gpr_mu_unlock(&chand->info_mu);
 }
 
 /* Constructor for channel_data */
@@ -512,11 +522,12 @@ static grpc_error *cc_init_channel_elem(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(args->is_last);
   GPR_ASSERT(elem->filter == &grpc_client_channel_filter);
   // Initialize data members.
-  gpr_mu_init(&chand->mu);
+  chand->combiner = grpc_combiner_create(NULL);
+  gpr_mu_init(&chand->info_mu);
   chand->owning_stack = args->channel_stack;
   grpc_closure_init(&chand->on_resolver_result_changed,
-                    on_resolver_result_changed, chand,
-                    grpc_schedule_on_exec_ctx);
+                    on_resolver_result_changed_locked, chand,
+                    grpc_combiner_scheduler(chand->combiner, false));
   chand->interested_parties = grpc_pollset_set_create();
   grpc_connectivity_state_init(&chand->state_tracker, GRPC_CHANNEL_IDLE,
                                "client_channel");
@@ -565,14 +576,15 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
                                      chand->interested_parties);
     GRPC_LB_POLICY_UNREF(exec_ctx, chand->lb_policy, "channel");
   }
-  gpr_free(chand->lb_policy_name);
-  gpr_free(chand->service_config_json);
+  gpr_free(chand->info_lb_policy_name);
+  gpr_free(chand->info_service_config_json);
   if (chand->method_params_table != NULL) {
     grpc_slice_hash_table_unref(exec_ctx, chand->method_params_table);
   }
   grpc_connectivity_state_destroy(exec_ctx, &chand->state_tracker);
-  grpc_pollset_set_destroy(chand->interested_parties);
-  gpr_mu_destroy(&chand->mu);
+  grpc_pollset_set_destroy(exec_ctx, chand->interested_parties);
+  GRPC_COMBINER_UNREF(exec_ctx, chand->combiner, "client_channel");
+  gpr_mu_destroy(&chand->info_mu);
 }
 
 /*************************************************************************
@@ -615,8 +627,6 @@ typedef struct client_channel_call_data {
       grpc_subchannel_call */
   gpr_atm subchannel_call;
 
-  gpr_mu mu;
-
   subchannel_creation_phase creation_phase;
   grpc_connected_subchannel *connected_subchannel;
   grpc_polling_entity *pollent;
@@ -661,52 +671,32 @@ static void fail_locked(grpc_exec_ctx *exec_ctx, call_data *calld,
   GRPC_ERROR_UNREF(error);
 }
 
-typedef struct {
-  grpc_transport_stream_op **ops;
-  size_t nops;
-  grpc_subchannel_call *call;
-} retry_ops_args;
-
-static void retry_ops(grpc_exec_ctx *exec_ctx, void *args, grpc_error *error) {
-  retry_ops_args *a = args;
-  size_t i;
-  for (i = 0; i < a->nops; i++) {
-    grpc_subchannel_call_process_op(exec_ctx, a->call, a->ops[i]);
-  }
-  GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, a->call, "retry_ops");
-  gpr_free(a->ops);
-  gpr_free(a);
-}
-
 static void retry_waiting_locked(grpc_exec_ctx *exec_ctx, call_data *calld) {
   if (calld->waiting_ops_count == 0) {
     return;
   }
 
-  retry_ops_args *a = gpr_malloc(sizeof(*a));
-  a->ops = calld->waiting_ops;
-  a->nops = calld->waiting_ops_count;
-  a->call = GET_CALL(calld);
-  if (a->call == CANCELLED_CALL) {
-    gpr_free(a);
+  grpc_subchannel_call *call = GET_CALL(calld);
+  grpc_transport_stream_op **ops = calld->waiting_ops;
+  size_t nops = calld->waiting_ops_count;
+  if (call == CANCELLED_CALL) {
     fail_locked(exec_ctx, calld, GRPC_ERROR_CANCELLED);
     return;
   }
   calld->waiting_ops = NULL;
   calld->waiting_ops_count = 0;
   calld->waiting_ops_capacity = 0;
-  GRPC_SUBCHANNEL_CALL_REF(a->call, "retry_ops");
-  grpc_closure_sched(
-      exec_ctx, grpc_closure_create(retry_ops, a, grpc_schedule_on_exec_ctx),
-      GRPC_ERROR_NONE);
+  for (size_t i = 0; i < nops; i++) {
+    grpc_subchannel_call_process_op(exec_ctx, call, ops[i]);
+  }
+  gpr_free(ops);
 }
 
-static void subchannel_ready(grpc_exec_ctx *exec_ctx, void *arg,
-                             grpc_error *error) {
+static void subchannel_ready_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                    grpc_error *error) {
   grpc_call_element *elem = arg;
   call_data *calld = elem->call_data;
   channel_data *chand = elem->channel_data;
-  gpr_mu_lock(&calld->mu);
   GPR_ASSERT(calld->creation_phase ==
              GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL);
   grpc_polling_entity_del_from_pollset_set(exec_ctx, calld->pollent,
@@ -742,7 +732,6 @@ static void subchannel_ready(grpc_exec_ctx *exec_ctx, void *arg,
                       (gpr_atm)(uintptr_t)subchannel_call);
     retry_waiting_locked(exec_ctx, calld);
   }
-  gpr_mu_unlock(&calld->mu);
   GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call, "pick_subchannel");
 }
 
@@ -768,37 +757,35 @@ typedef struct {
 /** Return true if subchannel is available immediately (in which case on_ready
     should not be called), or false otherwise (in which case on_ready should be
     called when the subchannel is available). */
-static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
-                            grpc_metadata_batch *initial_metadata,
-                            uint32_t initial_metadata_flags,
-                            grpc_connected_subchannel **connected_subchannel,
-                            grpc_closure *on_ready, grpc_error *error);
-
-static void continue_picking(grpc_exec_ctx *exec_ctx, void *arg,
-                             grpc_error *error) {
+static bool pick_subchannel_locked(
+    grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+    grpc_metadata_batch *initial_metadata, uint32_t initial_metadata_flags,
+    grpc_connected_subchannel **connected_subchannel, grpc_closure *on_ready,
+    grpc_error *error);
+
+static void continue_picking_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                    grpc_error *error) {
   continue_picking_args *cpa = arg;
   if (cpa->connected_subchannel == NULL) {
     /* cancelled, do nothing */
   } else if (error != GRPC_ERROR_NONE) {
     grpc_closure_sched(exec_ctx, cpa->on_ready, GRPC_ERROR_REF(error));
   } else {
-    call_data *calld = cpa->elem->call_data;
-    gpr_mu_lock(&calld->mu);
-    if (pick_subchannel(exec_ctx, cpa->elem, cpa->initial_metadata,
-                        cpa->initial_metadata_flags, cpa->connected_subchannel,
-                        cpa->on_ready, GRPC_ERROR_NONE)) {
+    if (pick_subchannel_locked(exec_ctx, cpa->elem, cpa->initial_metadata,
+                               cpa->initial_metadata_flags,
+                               cpa->connected_subchannel, cpa->on_ready,
+                               GRPC_ERROR_NONE)) {
       grpc_closure_sched(exec_ctx, cpa->on_ready, GRPC_ERROR_NONE);
     }
-    gpr_mu_unlock(&calld->mu);
   }
   gpr_free(cpa);
 }
 
-static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
-                            grpc_metadata_batch *initial_metadata,
-                            uint32_t initial_metadata_flags,
-                            grpc_connected_subchannel **connected_subchannel,
-                            grpc_closure *on_ready, grpc_error *error) {
+static bool pick_subchannel_locked(
+    grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+    grpc_metadata_batch *initial_metadata, uint32_t initial_metadata_flags,
+    grpc_connected_subchannel **connected_subchannel, grpc_closure *on_ready,
+    grpc_error *error) {
   GPR_TIMER_BEGIN("pick_subchannel", 0);
 
   channel_data *chand = elem->channel_data;
@@ -808,7 +795,6 @@ static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
 
   GPR_ASSERT(connected_subchannel);
 
-  gpr_mu_lock(&chand->mu);
   if (initial_metadata == NULL) {
     if (chand->lb_policy != NULL) {
       grpc_lb_policy_cancel_pick(exec_ctx, chand->lb_policy,
@@ -824,7 +810,6 @@ static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
             GRPC_ERROR_CREATE_REFERENCING("Pick cancelled", &error, 1));
       }
     }
-    gpr_mu_unlock(&chand->mu);
     GPR_TIMER_END("pick_subchannel", 0);
     GRPC_ERROR_UNREF(error);
     return true;
@@ -833,7 +818,6 @@ static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
   if (chand->lb_policy != NULL) {
     grpc_lb_policy *lb_policy = chand->lb_policy;
     GRPC_LB_POLICY_REF(lb_policy, "pick_subchannel");
-    gpr_mu_unlock(&chand->mu);
     // If the application explicitly set wait_for_ready, use that.
     // Otherwise, if the service config specified a value for this
     // method, use that.
@@ -872,88 +856,66 @@ static bool pick_subchannel(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
     cpa->connected_subchannel = connected_subchannel;
     cpa->on_ready = on_ready;
     cpa->elem = elem;
-    grpc_closure_init(&cpa->closure, continue_picking, cpa,
-                      grpc_schedule_on_exec_ctx);
+    grpc_closure_init(&cpa->closure, continue_picking_locked, cpa,
+                      grpc_combiner_scheduler(chand->combiner, true));
     grpc_closure_list_append(&chand->waiting_for_config_closures, &cpa->closure,
                              GRPC_ERROR_NONE);
   } else {
     grpc_closure_sched(exec_ctx, on_ready, GRPC_ERROR_CREATE("Disconnected"));
   }
-  gpr_mu_unlock(&chand->mu);
 
   GPR_TIMER_END("pick_subchannel", 0);
   return false;
 }
 
-// The logic here is fairly complicated, due to (a) the fact that we
-// need to handle the case where we receive the send op before the
-// initial metadata op, and (b) the need for efficiency, especially in
-// the streaming case.
-// TODO(ctiller): Explain this more thoroughly.
-static void cc_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
-                                         grpc_call_element *elem,
-                                         grpc_transport_stream_op *op) {
-  call_data *calld = elem->call_data;
+static void start_transport_stream_op_locked_inner(grpc_exec_ctx *exec_ctx,
+                                                   grpc_transport_stream_op *op,
+                                                   grpc_call_element *elem) {
   channel_data *chand = elem->channel_data;
-  GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
-  grpc_deadline_state_client_start_transport_stream_op(exec_ctx, elem, op);
-  /* try to (atomically) get the call */
-  grpc_subchannel_call *call = GET_CALL(calld);
-  GPR_TIMER_BEGIN("cc_start_transport_stream_op", 0);
-  if (call == CANCELLED_CALL) {
-    grpc_transport_stream_op_finish_with_failure(
-        exec_ctx, op, GRPC_ERROR_REF(calld->cancel_error));
-    GPR_TIMER_END("cc_start_transport_stream_op", 0);
-    return;
-  }
-  if (call != NULL) {
-    grpc_subchannel_call_process_op(exec_ctx, call, op);
-    GPR_TIMER_END("cc_start_transport_stream_op", 0);
-    return;
-  }
-  /* we failed; lock and figure out what to do */
-  gpr_mu_lock(&calld->mu);
-retry:
+  call_data *calld = elem->call_data;
+  grpc_subchannel_call *call;
+
   /* need to recheck that another thread hasn't set the call */
   call = GET_CALL(calld);
   if (call == CANCELLED_CALL) {
-    gpr_mu_unlock(&calld->mu);
     grpc_transport_stream_op_finish_with_failure(
         exec_ctx, op, GRPC_ERROR_REF(calld->cancel_error));
-    GPR_TIMER_END("cc_start_transport_stream_op", 0);
+    /* early out */
     return;
   }
   if (call != NULL) {
-    gpr_mu_unlock(&calld->mu);
     grpc_subchannel_call_process_op(exec_ctx, call, op);
-    GPR_TIMER_END("cc_start_transport_stream_op", 0);
+    /* early out */
     return;
   }
   /* if this is a cancellation, then we can raise our cancelled flag */
   if (op->cancel_error != GRPC_ERROR_NONE) {
     if (!gpr_atm_rel_cas(&calld->subchannel_call, 0,
                          (gpr_atm)(uintptr_t)CANCELLED_CALL)) {
-      goto retry;
+      /* recurse to retry */
+      start_transport_stream_op_locked_inner(exec_ctx, op, elem);
+      /* early out */
+      return;
     } else {
-      // Stash a copy of cancel_error in our call data, so that we can use
-      // it for subsequent operations.  This ensures that if the call is
-      // cancelled before any ops are passed down (e.g., if the deadline
-      // is in the past when the call starts), we can return the right
-      // error to the caller when the first op does get passed down.
+      /* Stash a copy of cancel_error in our call data, so that we can use
+         it for subsequent operations.  This ensures that if the call is
+         cancelled before any ops are passed down (e.g., if the deadline
+         is in the past when the call starts), we can return the right
+         error to the caller when the first op does get passed down. */
       calld->cancel_error = GRPC_ERROR_REF(op->cancel_error);
       switch (calld->creation_phase) {
         case GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING:
           fail_locked(exec_ctx, calld, GRPC_ERROR_REF(op->cancel_error));
           break;
         case GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL:
-          pick_subchannel(exec_ctx, elem, NULL, 0, &calld->connected_subchannel,
-                          NULL, GRPC_ERROR_REF(op->cancel_error));
+          pick_subchannel_locked(exec_ctx, elem, NULL, 0,
+                                 &calld->connected_subchannel, NULL,
+                                 GRPC_ERROR_REF(op->cancel_error));
           break;
       }
-      gpr_mu_unlock(&calld->mu);
       grpc_transport_stream_op_finish_with_failure(
           exec_ctx, op, GRPC_ERROR_REF(op->cancel_error));
-      GPR_TIMER_END("cc_start_transport_stream_op", 0);
+      /* early out */
       return;
     }
   }
@@ -962,16 +924,16 @@ retry:
       calld->connected_subchannel == NULL &&
       op->send_initial_metadata != NULL) {
     calld->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_PICKING_SUBCHANNEL;
-    grpc_closure_init(&calld->next_step, subchannel_ready, elem,
-                      grpc_schedule_on_exec_ctx);
+    grpc_closure_init(&calld->next_step, subchannel_ready_locked, elem,
+                      grpc_combiner_scheduler(chand->combiner, true));
     GRPC_CALL_STACK_REF(calld->owning_call, "pick_subchannel");
     /* If a subchannel is not available immediately, the polling entity from
        call_data should be provided to channel_data's interested_parties, so
        that IO of the lb_policy and resolver could be done under it. */
-    if (pick_subchannel(exec_ctx, elem, op->send_initial_metadata,
-                        op->send_initial_metadata_flags,
-                        &calld->connected_subchannel, &calld->next_step,
-                        GRPC_ERROR_NONE)) {
+    if (pick_subchannel_locked(exec_ctx, elem, op->send_initial_metadata,
+                               op->send_initial_metadata_flags,
+                               &calld->connected_subchannel, &calld->next_step,
+                               GRPC_ERROR_NONE)) {
       calld->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
       GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call, "pick_subchannel");
     } else {
@@ -994,31 +956,89 @@ retry:
     gpr_atm_rel_store(&calld->subchannel_call,
                       (gpr_atm)(uintptr_t)subchannel_call);
     retry_waiting_locked(exec_ctx, calld);
-    goto retry;
+    /* recurse to retry */
+    start_transport_stream_op_locked_inner(exec_ctx, op, elem);
+    /* early out */
+    return;
   }
   /* nothing to be done but wait */
   add_waiting_locked(calld, op);
-  gpr_mu_unlock(&calld->mu);
+}
+
+static void cc_start_transport_stream_op_locked(grpc_exec_ctx *exec_ctx,
+                                                void *arg,
+                                                grpc_error *error_ignored) {
+  GPR_TIMER_BEGIN("cc_start_transport_stream_op_locked", 0);
+
+  grpc_transport_stream_op *op = arg;
+  grpc_call_element *elem = op->handler_private.args[0];
+  call_data *calld = elem->call_data;
+
+  start_transport_stream_op_locked_inner(exec_ctx, op, elem);
+
+  GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call,
+                        "start_transport_stream_op");
+  GPR_TIMER_END("cc_start_transport_stream_op_locked", 0);
+}
+
+/* The logic here is fairly complicated, due to (a) the fact that we
+   need to handle the case where we receive the send op before the
+   initial metadata op, and (b) the need for efficiency, especially in
+   the streaming case.
+
+   We use double-checked locking to initially see if initialization has been
+   performed. If it has not, we acquire the combiner and perform initialization.
+   If it has, we proceed on the fast path. */
+static void cc_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
+                                         grpc_call_element *elem,
+                                         grpc_transport_stream_op *op) {
+  call_data *calld = elem->call_data;
+  channel_data *chand = elem->channel_data;
+  GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
+  grpc_deadline_state_client_start_transport_stream_op(exec_ctx, elem, op);
+  /* try to (atomically) get the call */
+  grpc_subchannel_call *call = GET_CALL(calld);
+  GPR_TIMER_BEGIN("cc_start_transport_stream_op", 0);
+  if (call == CANCELLED_CALL) {
+    grpc_transport_stream_op_finish_with_failure(
+        exec_ctx, op, GRPC_ERROR_REF(calld->cancel_error));
+    GPR_TIMER_END("cc_start_transport_stream_op", 0);
+    /* early out */
+    return;
+  }
+  if (call != NULL) {
+    grpc_subchannel_call_process_op(exec_ctx, call, op);
+    GPR_TIMER_END("cc_start_transport_stream_op", 0);
+    /* early out */
+    return;
+  }
+  /* we failed; lock and figure out what to do */
+  GRPC_CALL_STACK_REF(calld->owning_call, "start_transport_stream_op");
+  op->handler_private.args[0] = elem;
+  grpc_closure_sched(
+      exec_ctx,
+      grpc_closure_init(&op->handler_private.closure,
+                        cc_start_transport_stream_op_locked, op,
+                        grpc_combiner_scheduler(chand->combiner, false)),
+      GRPC_ERROR_NONE);
   GPR_TIMER_END("cc_start_transport_stream_op", 0);
 }
 
 // Gets data from the service config.  Invoked when the resolver returns
 // its initial result.
-static void read_service_config(grpc_exec_ctx *exec_ctx, void *arg,
-                                grpc_error *error) {
+static void read_service_config_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                       grpc_error *error) {
   grpc_call_element *elem = arg;
   channel_data *chand = elem->channel_data;
   call_data *calld = elem->call_data;
   // If this is an error, there's no point in looking at the service config.
   if (error == GRPC_ERROR_NONE) {
     // Get the method config table from channel data.
-    gpr_mu_lock(&chand->mu);
     grpc_slice_hash_table *method_params_table = NULL;
     if (chand->method_params_table != NULL) {
       method_params_table =
           grpc_slice_hash_table_ref(chand->method_params_table);
     }
-    gpr_mu_unlock(&chand->mu);
     // If the method config table was present, use it.
     if (method_params_table != NULL) {
       const method_parameters *method_params = grpc_method_config_table_get(
@@ -1028,7 +1048,6 @@ static void read_service_config(grpc_exec_ctx *exec_ctx, void *arg,
             gpr_time_cmp(method_params->timeout, gpr_time_0(GPR_TIMESPAN)) != 0;
         if (have_method_timeout ||
             method_params->wait_for_ready != WAIT_FOR_READY_UNSET) {
-          gpr_mu_lock(&calld->mu);
           if (have_method_timeout) {
             const gpr_timespec per_method_deadline =
                 gpr_time_add(calld->call_start_time, method_params->timeout);
@@ -1042,7 +1061,6 @@ static void read_service_config(grpc_exec_ctx *exec_ctx, void *arg,
             calld->wait_for_ready_from_service_config =
                 method_params->wait_for_ready;
           }
-          gpr_mu_unlock(&calld->mu);
         }
       }
       grpc_slice_hash_table_unref(exec_ctx, method_params_table);
@@ -1051,43 +1069,25 @@ static void read_service_config(grpc_exec_ctx *exec_ctx, void *arg,
   GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call, "read_service_config");
 }
 
-/* Constructor for call_data */
-static grpc_error *cc_init_call_elem(grpc_exec_ctx *exec_ctx,
-                                     grpc_call_element *elem,
-                                     grpc_call_element_args *args) {
+static void initial_read_service_config_locked(grpc_exec_ctx *exec_ctx,
+                                               void *arg,
+                                               grpc_error *error_ignored) {
+  grpc_call_element *elem = arg;
   channel_data *chand = elem->channel_data;
   call_data *calld = elem->call_data;
-  // Initialize data members.
-  grpc_deadline_state_init(exec_ctx, elem, args->call_stack);
-  calld->path = grpc_slice_ref_internal(args->path);
-  calld->call_start_time = args->start_time;
-  calld->deadline = gpr_convert_clock_type(args->deadline, GPR_CLOCK_MONOTONIC);
-  calld->wait_for_ready_from_service_config = WAIT_FOR_READY_UNSET;
-  calld->cancel_error = GRPC_ERROR_NONE;
-  gpr_atm_rel_store(&calld->subchannel_call, 0);
-  gpr_mu_init(&calld->mu);
-  calld->connected_subchannel = NULL;
-  calld->waiting_ops = NULL;
-  calld->waiting_ops_count = 0;
-  calld->waiting_ops_capacity = 0;
-  calld->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
-  calld->owning_call = args->call_stack;
-  calld->pollent = NULL;
   // If the resolver has already returned results, then we can access
   // the service config parameters immediately.  Otherwise, we need to
   // defer that work until the resolver returns an initial result.
   // TODO(roth): This code is almost but not quite identical to the code
   // in read_service_config() above.  It would be nice to find a way to
   // combine them, to avoid having to maintain it twice.
-  gpr_mu_lock(&chand->mu);
   if (chand->lb_policy != NULL) {
     // We already have a resolver result, so check for service config.
     if (chand->method_params_table != NULL) {
       grpc_slice_hash_table *method_params_table =
           grpc_slice_hash_table_ref(chand->method_params_table);
-      gpr_mu_unlock(&chand->mu);
       method_parameters *method_params = grpc_method_config_table_get(
-          exec_ctx, method_params_table, args->path);
+          exec_ctx, method_params_table, calld->path);
       if (method_params != NULL) {
         if (gpr_time_cmp(method_params->timeout,
                          gpr_time_0(GPR_CLOCK_MONOTONIC)) != 0) {
@@ -1101,24 +1101,53 @@ static grpc_error *cc_init_call_elem(grpc_exec_ctx *exec_ctx,
         }
       }
       grpc_slice_hash_table_unref(exec_ctx, method_params_table);
-    } else {
-      gpr_mu_unlock(&chand->mu);
     }
   } else {
     // We don't yet have a resolver result, so register a callback to
     // get the service config data once the resolver returns.
     // Take a reference to the call stack to be owned by the callback.
     GRPC_CALL_STACK_REF(calld->owning_call, "read_service_config");
-    grpc_closure_init(&calld->read_service_config, read_service_config, elem,
-                      grpc_schedule_on_exec_ctx);
+    grpc_closure_init(&calld->read_service_config, read_service_config_locked,
+                      elem, grpc_combiner_scheduler(chand->combiner, false));
     grpc_closure_list_append(&chand->waiting_for_config_closures,
                              &calld->read_service_config, GRPC_ERROR_NONE);
-    gpr_mu_unlock(&chand->mu);
   }
   // Start the deadline timer with the current deadline value.  If we
   // do not yet have service config data, then the timer may be reset
   // later.
   grpc_deadline_state_start(exec_ctx, elem, calld->deadline);
+  GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call,
+                        "initial_read_service_config");
+}
+
+/* Constructor for call_data */
+static grpc_error *cc_init_call_elem(grpc_exec_ctx *exec_ctx,
+                                     grpc_call_element *elem,
+                                     grpc_call_element_args *args) {
+  channel_data *chand = elem->channel_data;
+  call_data *calld = elem->call_data;
+  // Initialize data members.
+  grpc_deadline_state_init(exec_ctx, elem, args->call_stack);
+  calld->path = grpc_slice_ref_internal(args->path);
+  calld->call_start_time = args->start_time;
+  calld->deadline = gpr_convert_clock_type(args->deadline, GPR_CLOCK_MONOTONIC);
+  calld->wait_for_ready_from_service_config = WAIT_FOR_READY_UNSET;
+  calld->cancel_error = GRPC_ERROR_NONE;
+  gpr_atm_rel_store(&calld->subchannel_call, 0);
+  calld->connected_subchannel = NULL;
+  calld->waiting_ops = NULL;
+  calld->waiting_ops_count = 0;
+  calld->waiting_ops_capacity = 0;
+  calld->creation_phase = GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING;
+  calld->owning_call = args->call_stack;
+  calld->pollent = NULL;
+  GRPC_CALL_STACK_REF(calld->owning_call, "initial_read_service_config");
+  grpc_closure_sched(
+      exec_ctx,
+      grpc_closure_init(&calld->read_service_config,
+                        initial_read_service_config_locked, elem,
+                        grpc_combiner_scheduler(chand->combiner, false)),
+      GRPC_ERROR_NONE);
   return GRPC_ERROR_NONE;
 }
 
@@ -1136,7 +1165,6 @@ static void cc_destroy_call_elem(grpc_exec_ctx *exec_ctx,
     GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, call, "client_channel_destroy_call");
   }
   GPR_ASSERT(calld->creation_phase == GRPC_SUBCHANNEL_CALL_HOLDER_NOT_CREATING);
-  gpr_mu_destroy(&calld->mu);
   GPR_ASSERT(calld->waiting_ops_count == 0);
   if (calld->connected_subchannel != NULL) {
     GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, calld->connected_subchannel,
@@ -1172,26 +1200,36 @@ const grpc_channel_filter grpc_client_channel_filter = {
     "client-channel",
 };
 
+static void try_to_connect_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                  grpc_error *error_ignored) {
+  channel_data *chand = arg;
+  if (chand->lb_policy != NULL) {
+    grpc_lb_policy_exit_idle(exec_ctx, chand->lb_policy);
+  } else {
+    chand->exit_idle_when_lb_policy_arrives = true;
+    if (!chand->started_resolving && chand->resolver != NULL) {
+      GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
+      chand->started_resolving = true;
+      grpc_resolver_next(exec_ctx, chand->resolver, &chand->resolver_result,
+                         &chand->on_resolver_result_changed);
+    }
+  }
+  GRPC_CHANNEL_STACK_UNREF(exec_ctx, chand->owning_stack, "try_to_connect");
+}
+
 grpc_connectivity_state grpc_client_channel_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;
-  gpr_mu_lock(&chand->mu);
-  out = grpc_connectivity_state_check(&chand->state_tracker, NULL);
+  grpc_connectivity_state out =
+      grpc_connectivity_state_check(&chand->state_tracker);
   if (out == GRPC_CHANNEL_IDLE && try_to_connect) {
-    if (chand->lb_policy != NULL) {
-      grpc_lb_policy_exit_idle(exec_ctx, chand->lb_policy);
-    } else {
-      chand->exit_idle_when_lb_policy_arrives = true;
-      if (!chand->started_resolving && chand->resolver != NULL) {
-        GRPC_CHANNEL_STACK_REF(chand->owning_stack, "resolver");
-        chand->started_resolving = true;
-        grpc_resolver_next(exec_ctx, chand->resolver, &chand->resolver_result,
-                           &chand->on_resolver_result_changed);
-      }
-    }
+    GRPC_CHANNEL_STACK_REF(chand->owning_stack, "try_to_connect");
+    grpc_closure_sched(
+        exec_ctx,
+        grpc_closure_create(try_to_connect_locked, chand,
+                            grpc_combiner_scheduler(chand->combiner, false)),
+        GRPC_ERROR_NONE);
   }
-  gpr_mu_unlock(&chand->mu);
   return out;
 }
 
@@ -1199,6 +1237,7 @@ typedef struct {
   channel_data *chand;
   grpc_pollset *pollset;
   grpc_closure *on_complete;
+  grpc_connectivity_state *state;
   grpc_closure my_closure;
 } external_connectivity_watcher;
 
@@ -1211,7 +1250,16 @@ static void on_external_watch_complete(grpc_exec_ctx *exec_ctx, void *arg,
   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, error);
+  grpc_closure_run(exec_ctx, follow_up, GRPC_ERROR_REF(error));
+}
+
+static void watch_connectivity_state_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                            grpc_error *error_ignored) {
+  external_connectivity_watcher *w = arg;
+  grpc_closure_init(&w->my_closure, on_external_watch_complete, w,
+                    grpc_schedule_on_exec_ctx);
+  grpc_connectivity_state_notify_on_state_change(
+      exec_ctx, &w->chand->state_tracker, w->state, &w->my_closure);
 }
 
 void grpc_client_channel_watch_connectivity_state(
@@ -1222,13 +1270,13 @@ void grpc_client_channel_watch_connectivity_state(
   w->chand = chand;
   w->pollset = pollset;
   w->on_complete = on_complete;
+  w->state = state;
   grpc_pollset_set_add_pollset(exec_ctx, chand->interested_parties, pollset);
-  grpc_closure_init(&w->my_closure, on_external_watch_complete, w,
-                    grpc_schedule_on_exec_ctx);
   GRPC_CHANNEL_STACK_REF(w->chand->owning_stack,
                          "external_connectivity_watcher");
-  gpr_mu_lock(&chand->mu);
-  grpc_connectivity_state_notify_on_state_change(
-      exec_ctx, &chand->state_tracker, state, &w->my_closure);
-  gpr_mu_unlock(&chand->mu);
+  grpc_closure_sched(
+      exec_ctx,
+      grpc_closure_init(&w->my_closure, watch_connectivity_state_locked, w,
+                        grpc_combiner_scheduler(chand->combiner, true)),
+      GRPC_ERROR_NONE);
 }
diff --git a/src/core/ext/client_channel/lb_policy.c b/src/core/ext/client_channel/lb_policy.c
index 45ee72e2f0..90401b586f 100644
--- a/src/core/ext/client_channel/lb_policy.c
+++ b/src/core/ext/client_channel/lb_policy.c
@@ -94,7 +94,7 @@ void grpc_lb_policy_weak_unref(grpc_exec_ctx *exec_ctx,
   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);
+    grpc_pollset_set_destroy(exec_ctx, policy->interested_parties);
     policy->vtable->destroy(exec_ctx, policy);
   }
 }
diff --git a/src/core/ext/client_channel/subchannel.c b/src/core/ext/client_channel/subchannel.c
index aa036e883b..09c68a91dd 100644
--- a/src/core/ext/client_channel/subchannel.c
+++ b/src/core/ext/client_channel/subchannel.c
@@ -217,7 +217,7 @@ static void subchannel_destroy(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_slice_unref_internal(exec_ctx, 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);
+  grpc_pollset_set_destroy(exec_ctx, c->pollset_set);
   grpc_subchannel_key_destroy(exec_ctx, c->key);
   gpr_free(c);
 }
@@ -419,7 +419,7 @@ grpc_connectivity_state grpc_subchannel_check_connectivity(grpc_subchannel *c,
                                                            grpc_error **error) {
   grpc_connectivity_state state;
   gpr_mu_lock(&c->mu);
-  state = grpc_connectivity_state_check(&c->state_tracker, error);
+  state = grpc_connectivity_state_get(&c->state_tracker, error);
   gpr_mu_unlock(&c->mu);
   return state;
 }
diff --git a/src/core/ext/lb_policy/grpclb/grpclb.c b/src/core/ext/lb_policy/grpclb/grpclb.c
index ab62e5ed6a..8a2af48328 100644
--- a/src/core/ext/lb_policy/grpclb/grpclb.c
+++ b/src/core/ext/lb_policy/grpclb/grpclb.c
@@ -492,9 +492,8 @@ static grpc_lb_addresses *process_serverlist_locked(
 static bool update_lb_connectivity_status_locked(
     grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
     grpc_connectivity_state new_rr_state, grpc_error *new_rr_state_error) {
-  grpc_error *curr_state_error;
-  const grpc_connectivity_state curr_glb_state = grpc_connectivity_state_check(
-      &glb_policy->state_tracker, &curr_state_error);
+  const grpc_connectivity_state curr_glb_state =
+      grpc_connectivity_state_check(&glb_policy->state_tracker);
 
   /* The new connectivity status is a function of the previous one and the new
    * input coming from the status of the RR policy.
@@ -1098,8 +1097,8 @@ static grpc_connectivity_state glb_check_connectivity(
   glb_lb_policy *glb_policy = (glb_lb_policy *)pol;
   grpc_connectivity_state st;
   gpr_mu_lock(&glb_policy->mu);
-  st = grpc_connectivity_state_check(&glb_policy->state_tracker,
-                                     connectivity_error);
+  st = grpc_connectivity_state_get(&glb_policy->state_tracker,
+                                   connectivity_error);
   gpr_mu_unlock(&glb_policy->mu);
   return st;
 }
diff --git a/src/core/ext/lb_policy/pick_first/pick_first.c b/src/core/ext/lb_policy/pick_first/pick_first.c
index 9f2aa461be..1b965183f6 100644
--- a/src/core/ext/lb_policy/pick_first/pick_first.c
+++ b/src/core/ext/lb_policy/pick_first/pick_first.c
@@ -398,7 +398,7 @@ static grpc_connectivity_state pf_check_connectivity(grpc_exec_ctx *exec_ctx,
   pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
   grpc_connectivity_state st;
   gpr_mu_lock(&p->mu);
-  st = grpc_connectivity_state_check(&p->state_tracker, error);
+  st = grpc_connectivity_state_get(&p->state_tracker, error);
   gpr_mu_unlock(&p->mu);
   return st;
 }
diff --git a/src/core/ext/lb_policy/round_robin/round_robin.c b/src/core/ext/lb_policy/round_robin/round_robin.c
index 3e060d189a..63e3d033ad 100644
--- a/src/core/ext/lb_policy/round_robin/round_robin.c
+++ b/src/core/ext/lb_policy/round_robin/round_robin.c
@@ -655,7 +655,7 @@ static grpc_connectivity_state rr_check_connectivity(grpc_exec_ctx *exec_ctx,
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   grpc_connectivity_state st;
   gpr_mu_lock(&p->mu);
-  st = grpc_connectivity_state_check(&p->state_tracker, error);
+  st = grpc_connectivity_state_get(&p->state_tracker, error);
   gpr_mu_unlock(&p->mu);
   return st;
 }
diff --git a/src/core/ext/resolver/dns/native/dns_resolver.c b/src/core/ext/resolver/dns/native/dns_resolver.c
index 2c9623211b..c08b53ea04 100644
--- a/src/core/ext/resolver/dns/native/dns_resolver.c
+++ b/src/core/ext/resolver/dns/native/dns_resolver.c
@@ -244,7 +244,7 @@ static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   if (r->resolved_result != NULL) {
     grpc_channel_args_destroy(exec_ctx, r->resolved_result);
   }
-  grpc_pollset_set_destroy(r->interested_parties);
+  grpc_pollset_set_destroy(exec_ctx, r->interested_parties);
   gpr_free(r->name_to_resolve);
   gpr_free(r->default_port);
   grpc_channel_args_destroy(exec_ctx, r->channel_args);
diff --git a/src/core/ext/transport/chttp2/server/chttp2_server.c b/src/core/ext/transport/chttp2/server/chttp2_server.c
index ae2c3838ed..0fc180d52f 100644
--- a/src/core/ext/transport/chttp2/server/chttp2_server.c
+++ b/src/core/ext/transport/chttp2/server/chttp2_server.c
@@ -55,11 +55,6 @@
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/server.h"
 
-typedef struct pending_handshake_manager_node {
-  grpc_handshake_manager *handshake_mgr;
-  struct pending_handshake_manager_node *next;
-} pending_handshake_manager_node;
-
 typedef struct {
   grpc_server *server;
   grpc_tcp_server *tcp_server;
@@ -68,7 +63,7 @@ typedef struct {
   bool shutdown;
   grpc_closure tcp_server_shutdown_complete;
   grpc_closure *server_destroy_listener_done;
-  pending_handshake_manager_node *pending_handshake_mgrs;
+  grpc_handshake_manager *pending_handshake_mgrs;
 } server_state;
 
 typedef struct {
@@ -78,44 +73,6 @@ typedef struct {
   grpc_handshake_manager *handshake_mgr;
 } server_connection_state;
 
-static void pending_handshake_manager_add_locked(
-    server_state *state, grpc_handshake_manager *handshake_mgr) {
-  pending_handshake_manager_node *node = gpr_malloc(sizeof(*node));
-  node->handshake_mgr = handshake_mgr;
-  node->next = state->pending_handshake_mgrs;
-  state->pending_handshake_mgrs = node;
-}
-
-static void pending_handshake_manager_remove_locked(
-    server_state *state, grpc_handshake_manager *handshake_mgr) {
-  pending_handshake_manager_node **prev_node = &state->pending_handshake_mgrs;
-  for (pending_handshake_manager_node *node = state->pending_handshake_mgrs;
-       node != NULL; node = node->next) {
-    if (node->handshake_mgr == handshake_mgr) {
-      *prev_node = node->next;
-      gpr_free(node);
-      break;
-    }
-    prev_node = &node->next;
-  }
-}
-
-static void pending_handshake_manager_shutdown_locked(grpc_exec_ctx *exec_ctx,
-                                                      server_state *state,
-                                                      grpc_error *why) {
-  pending_handshake_manager_node *prev_node = NULL;
-  for (pending_handshake_manager_node *node = state->pending_handshake_mgrs;
-       node != NULL; node = node->next) {
-    grpc_handshake_manager_shutdown(exec_ctx, node->handshake_mgr,
-                                    GRPC_ERROR_REF(why));
-    gpr_free(prev_node);
-    prev_node = node;
-  }
-  gpr_free(prev_node);
-  state->pending_handshake_mgrs = NULL;
-  GRPC_ERROR_UNREF(why);
-}
-
 static void on_handshake_done(grpc_exec_ctx *exec_ctx, void *arg,
                               grpc_error *error) {
   grpc_handshaker_args *args = arg;
@@ -153,8 +110,9 @@ static void on_handshake_done(grpc_exec_ctx *exec_ctx, void *arg,
       grpc_channel_args_destroy(exec_ctx, args->args);
     }
   }
-  pending_handshake_manager_remove_locked(connection_state->server_state,
-                                          connection_state->handshake_mgr);
+  grpc_handshake_manager_pending_list_remove(
+      &connection_state->server_state->pending_handshake_mgrs,
+      connection_state->handshake_mgr);
   gpr_mu_unlock(&connection_state->server_state->mu);
   grpc_handshake_manager_destroy(exec_ctx, connection_state->handshake_mgr);
   grpc_tcp_server_unref(exec_ctx, connection_state->server_state->tcp_server);
@@ -174,7 +132,8 @@ static void on_accept(grpc_exec_ctx *exec_ctx, void *arg, grpc_endpoint *tcp,
     return;
   }
   grpc_handshake_manager *handshake_mgr = grpc_handshake_manager_create();
-  pending_handshake_manager_add_locked(state, handshake_mgr);
+  grpc_handshake_manager_pending_list_add(&state->pending_handshake_mgrs,
+                                          handshake_mgr);
   gpr_mu_unlock(&state->mu);
   grpc_tcp_server_ref(state->tcp_server);
   server_connection_state *connection_state =
@@ -213,8 +172,8 @@ static void tcp_server_shutdown_complete(grpc_exec_ctx *exec_ctx, void *arg,
   gpr_mu_lock(&state->mu);
   grpc_closure *destroy_done = state->server_destroy_listener_done;
   GPR_ASSERT(state->shutdown);
-  pending_handshake_manager_shutdown_locked(exec_ctx, state,
-                                            GRPC_ERROR_REF(error));
+  grpc_handshake_manager_pending_list_shutdown_all(
+      exec_ctx, state->pending_handshake_mgrs, GRPC_ERROR_REF(error));
   gpr_mu_unlock(&state->mu);
   // Flush queued work before destroying handshaker factory, since that
   // may do a synchronous unref.
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index ddbc656b96..d1fab25478 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -1041,8 +1041,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
   GPR_TIMER_BEGIN("perform_stream_op_locked", 0);
 
   grpc_transport_stream_op *op = stream_op;
-  grpc_chttp2_transport *t = op->transport_private.args[0];
-  grpc_chttp2_stream *s = op->transport_private.args[1];
+  grpc_chttp2_transport *t = op->handler_private.args[0];
+  grpc_chttp2_stream *s = op->handler_private.args[1];
 
   if (grpc_http_trace) {
     char *str = grpc_transport_stream_op_string(op);
@@ -1263,13 +1263,13 @@ static void perform_stream_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
     gpr_free(str);
   }
 
-  op->transport_private.args[0] = gt;
-  op->transport_private.args[1] = gs;
+  op->handler_private.args[0] = gt;
+  op->handler_private.args[1] = gs;
   GRPC_CHTTP2_STREAM_REF(s, "perform_stream_op");
   grpc_closure_sched(
       exec_ctx,
       grpc_closure_init(
-          &op->transport_private.closure, perform_stream_op_locked, op,
+          &op->handler_private.closure, perform_stream_op_locked, op,
           grpc_combiner_scheduler(t->combiner, op->covered_by_poller)),
       GRPC_ERROR_NONE);
   GPR_TIMER_END("perform_stream_op", 0);
diff --git a/src/core/lib/channel/handshaker.c b/src/core/lib/channel/handshaker.c
index 5bed2d041d..82c361c7ef 100644
--- a/src/core/lib/channel/handshaker.c
+++ b/src/core/lib/channel/handshaker.c
@@ -92,6 +92,10 @@ struct grpc_handshake_manager {
   void* user_data;
   // Handshaker args.
   grpc_handshaker_args args;
+  // Links to the previous and next managers in a list of all pending handshakes
+  // Used at server side only.
+  grpc_handshake_manager* prev;
+  grpc_handshake_manager* next;
 };
 
 grpc_handshake_manager* grpc_handshake_manager_create() {
@@ -102,6 +106,39 @@ grpc_handshake_manager* grpc_handshake_manager_create() {
   return mgr;
 }
 
+void grpc_handshake_manager_pending_list_add(grpc_handshake_manager** head,
+                                             grpc_handshake_manager* mgr) {
+  GPR_ASSERT(mgr->prev == NULL);
+  GPR_ASSERT(mgr->next == NULL);
+  mgr->next = *head;
+  if (*head) {
+    (*head)->prev = mgr;
+  }
+  *head = mgr;
+}
+
+void grpc_handshake_manager_pending_list_remove(grpc_handshake_manager** head,
+                                                grpc_handshake_manager* mgr) {
+  if (mgr->next != NULL) {
+    mgr->next->prev = mgr->prev;
+  }
+  if (mgr->prev != NULL) {
+    mgr->prev->next = mgr->next;
+  } else {
+    GPR_ASSERT(*head == mgr);
+    *head = mgr->next;
+  }
+}
+
+void grpc_handshake_manager_pending_list_shutdown_all(
+    grpc_exec_ctx* exec_ctx, grpc_handshake_manager* head, grpc_error* why) {
+  while (head != NULL) {
+    grpc_handshake_manager_shutdown(exec_ctx, head, GRPC_ERROR_REF(why));
+    head = head->next;
+  }
+  GRPC_ERROR_UNREF(why);
+}
+
 static bool is_power_of_2(size_t n) { return (n & (n - 1)) == 0; }
 
 void grpc_handshake_manager_add(grpc_handshake_manager* mgr,
diff --git a/src/core/lib/channel/handshaker.h b/src/core/lib/channel/handshaker.h
index a8e3692add..5f97c3fc73 100644
--- a/src/core/lib/channel/handshaker.h
+++ b/src/core/lib/channel/handshaker.h
@@ -163,4 +163,20 @@ void grpc_handshake_manager_do_handshake(
     gpr_timespec deadline, grpc_tcp_server_acceptor* acceptor,
     grpc_iomgr_cb_func on_handshake_done, void* user_data);
 
+/// Add \a mgr to the server side list of all pending handshake managers, the
+/// list starts with \a *head.
+// Not thread-safe. Caller needs to synchronize.
+void grpc_handshake_manager_pending_list_add(grpc_handshake_manager** head,
+                                             grpc_handshake_manager* mgr);
+
+/// Remove \a mgr from the server side list of all pending handshake managers.
+// Not thread-safe. Caller needs to synchronize.
+void grpc_handshake_manager_pending_list_remove(grpc_handshake_manager** head,
+                                                grpc_handshake_manager* mgr);
+
+/// Shutdown all pending handshake managers on the server side.
+// Not thread-safe. Caller needs to synchronize.
+void grpc_handshake_manager_pending_list_shutdown_all(
+    grpc_exec_ctx* exec_ctx, grpc_handshake_manager* head, grpc_error* why);
+
 #endif /* GRPC_CORE_LIB_CHANNEL_HANDSHAKER_H */
diff --git a/src/core/lib/http/httpcli.c b/src/core/lib/http/httpcli.c
index fb2108987b..6d7aa43b81 100644
--- a/src/core/lib/http/httpcli.c
+++ b/src/core/lib/http/httpcli.c
@@ -93,8 +93,9 @@ void grpc_httpcli_context_init(grpc_httpcli_context *context) {
   context->pollset_set = grpc_pollset_set_create();
 }
 
-void grpc_httpcli_context_destroy(grpc_httpcli_context *context) {
-  grpc_pollset_set_destroy(context->pollset_set);
+void grpc_httpcli_context_destroy(grpc_exec_ctx *exec_ctx,
+                                  grpc_httpcli_context *context) {
+  grpc_pollset_set_destroy(exec_ctx, context->pollset_set);
 }
 
 static void next_address(grpc_exec_ctx *exec_ctx, internal_request *req,
diff --git a/src/core/lib/http/httpcli.h b/src/core/lib/http/httpcli.h
index 11e03b44df..8ae03ee78f 100644
--- a/src/core/lib/http/httpcli.h
+++ b/src/core/lib/http/httpcli.h
@@ -83,7 +83,8 @@ typedef struct grpc_httpcli_request {
 typedef struct grpc_http_response grpc_httpcli_response;
 
 void grpc_httpcli_context_init(grpc_httpcli_context *context);
-void grpc_httpcli_context_destroy(grpc_httpcli_context *context);
+void grpc_httpcli_context_destroy(grpc_exec_ctx *exec_ctx,
+                                  grpc_httpcli_context *context);
 
 /* Asynchronously perform a HTTP GET.
    'context' specifies the http context under which to do the get
diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index 5c77eda006..31ef433229 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -1968,13 +1968,12 @@ static grpc_pollset_set *pollset_set_create(void) {
   return pss;
 }
 
-static void pollset_set_destroy(grpc_pollset_set *pss) {
+static void pollset_set_destroy(grpc_exec_ctx *exec_ctx,
+                                grpc_pollset_set *pss) {
   gpr_mu_destroy(&pss->po.mu);
 
   if (pss->po.pi != NULL) {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    PI_UNREF(&exec_ctx, pss->po.pi, "pss_destroy");
-    grpc_exec_ctx_finish(&exec_ctx);
+    PI_UNREF(exec_ctx, pss->po.pi, "pss_destroy");
   }
 
   gpr_free(pss);
diff --git a/src/core/lib/iomgr/ev_poll_posix.c b/src/core/lib/iomgr/ev_poll_posix.c
index 21eb62753e..c03fadaebb 100644
--- a/src/core/lib/iomgr/ev_poll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_posix.c
@@ -149,7 +149,7 @@ static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *rec,
 static bool fd_is_orphaned(grpc_fd *fd);
 
 /* Reference counting for fds */
-/*#define GRPC_FD_REF_COUNT_DEBUG*/
+//#define GRPC_FD_REF_COUNT_DEBUG
 #ifdef GRPC_FD_REF_COUNT_DEBUG
 static void fd_ref(grpc_fd *fd, const char *reason, const char *file, int line);
 static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
@@ -191,6 +191,7 @@ struct grpc_pollset {
   int kicked_without_pollers;
   grpc_closure *shutdown_done;
   grpc_closure_list idle_jobs;
+  int pollset_set_count;
   /* all polled fds */
   size_t fd_count;
   size_t fd_capacity;
@@ -228,7 +229,7 @@ static grpc_error *pollset_kick_ext(grpc_pollset *p,
 
 /* Return 1 if the pollset has active threads in pollset_work (pollset must
  * be locked) */
-static int pollset_has_workers(grpc_pollset *pollset);
+static bool pollset_has_workers(grpc_pollset *pollset);
 
 /*******************************************************************************
  * pollset_set definitions
@@ -282,8 +283,8 @@ cv_fd_table g_cvfds;
 static void ref_by(grpc_fd *fd, int n, const char *reason, const char *file,
                    int line) {
   gpr_log(GPR_DEBUG, "FD %d %p   ref %d %d -> %d [%s; %s:%d]", fd->fd, fd, n,
-          gpr_atm_no_barrier_load(&fd->refst),
-          gpr_atm_no_barrier_load(&fd->refst) + n, reason, file, line);
+          (int)gpr_atm_no_barrier_load(&fd->refst),
+          (int)gpr_atm_no_barrier_load(&fd->refst) + n, reason, file, line);
 #else
 #define REF_BY(fd, n, reason) ref_by(fd, n)
 #define UNREF_BY(fd, n, reason) unref_by(fd, n)
@@ -297,8 +298,8 @@ static void unref_by(grpc_fd *fd, int n, const char *reason, const char *file,
                      int line) {
   gpr_atm old;
   gpr_log(GPR_DEBUG, "FD %d %p unref %d %d -> %d [%s; %s:%d]", fd->fd, fd, n,
-          gpr_atm_no_barrier_load(&fd->refst),
-          gpr_atm_no_barrier_load(&fd->refst) - n, reason, file, line);
+          (int)gpr_atm_no_barrier_load(&fd->refst),
+          (int)gpr_atm_no_barrier_load(&fd->refst) - n, reason, file, line);
 #else
 static void unref_by(grpc_fd *fd, int n) {
   gpr_atm old;
@@ -658,10 +659,18 @@ static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
   worker->next->prev = worker->prev;
 }
 
-static int pollset_has_workers(grpc_pollset *p) {
+static bool pollset_has_workers(grpc_pollset *p) {
   return p->root_worker.next != &p->root_worker;
 }
 
+static bool pollset_in_pollset_sets(grpc_pollset *p) {
+  return p->pollset_set_count;
+}
+
+static bool pollset_has_observers(grpc_pollset *p) {
+  return pollset_has_workers(p) || pollset_in_pollset_sets(p);
+}
+
 static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
   if (pollset_has_workers(p)) {
     grpc_pollset_worker *w = p->root_worker.next;
@@ -800,6 +809,7 @@ static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
   pollset->fd_count = 0;
   pollset->fd_capacity = 0;
   pollset->fds = NULL;
+  pollset->pollset_set_count = 0;
 }
 
 static void pollset_destroy(grpc_pollset *pollset) {
@@ -1061,7 +1071,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   if (pollset->shutting_down) {
     if (pollset_has_workers(pollset)) {
       pollset_kick(pollset, NULL);
-    } else if (!pollset->called_shutdown) {
+    } else if (!pollset->called_shutdown && !pollset_has_observers(pollset)) {
       pollset->called_shutdown = 1;
       gpr_mu_unlock(&pollset->mu);
       finish_shutdown(exec_ctx, pollset);
@@ -1093,7 +1103,7 @@ static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   if (!pollset_has_workers(pollset)) {
     grpc_closure_list_sched(exec_ctx, &pollset->idle_jobs);
   }
-  if (!pollset->called_shutdown && !pollset_has_workers(pollset)) {
+  if (!pollset->called_shutdown && !pollset_has_observers(pollset)) {
     pollset->called_shutdown = 1;
     finish_shutdown(exec_ctx, pollset);
   }
@@ -1127,12 +1137,27 @@ static grpc_pollset_set *pollset_set_create(void) {
   return pollset_set;
 }
 
-static void pollset_set_destroy(grpc_pollset_set *pollset_set) {
+static void pollset_set_destroy(grpc_exec_ctx *exec_ctx,
+                                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_set");
   }
+  for (i = 0; i < pollset_set->pollset_count; i++) {
+    grpc_pollset *pollset = pollset_set->pollsets[i];
+    gpr_mu_lock(&pollset->mu);
+    pollset->pollset_set_count--;
+    /* check shutdown */
+    if (pollset->shutting_down && !pollset->called_shutdown &&
+        !pollset_has_observers(pollset)) {
+      pollset->called_shutdown = 1;
+      gpr_mu_unlock(&pollset->mu);
+      finish_shutdown(exec_ctx, pollset);
+    } else {
+      gpr_mu_unlock(&pollset->mu);
+    }
+  }
   gpr_free(pollset_set->pollsets);
   gpr_free(pollset_set->pollset_sets);
   gpr_free(pollset_set->fds);
@@ -1143,6 +1168,9 @@ static void pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
                                     grpc_pollset_set *pollset_set,
                                     grpc_pollset *pollset) {
   size_t i, j;
+  gpr_mu_lock(&pollset->mu);
+  pollset->pollset_set_count++;
+  gpr_mu_unlock(&pollset->mu);
   gpr_mu_lock(&pollset_set->mu);
   if (pollset_set->pollset_count == pollset_set->pollset_capacity) {
     pollset_set->pollset_capacity =
@@ -1178,6 +1206,17 @@ static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
     }
   }
   gpr_mu_unlock(&pollset_set->mu);
+  gpr_mu_lock(&pollset->mu);
+  pollset->pollset_set_count--;
+  /* check shutdown */
+  if (pollset->shutting_down && !pollset->called_shutdown &&
+      !pollset_has_observers(pollset)) {
+    pollset->called_shutdown = 1;
+    gpr_mu_unlock(&pollset->mu);
+    finish_shutdown(exec_ctx, pollset);
+  } else {
+    gpr_mu_unlock(&pollset->mu);
+  }
 }
 
 static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index 95b1d99d75..b5be5504b9 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -215,8 +215,9 @@ grpc_pollset_set *grpc_pollset_set_create(void) {
   return g_event_engine->pollset_set_create();
 }
 
-void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set) {
-  g_event_engine->pollset_set_destroy(pollset_set);
+void grpc_pollset_set_destroy(grpc_exec_ctx *exec_ctx,
+                              grpc_pollset_set *pollset_set) {
+  g_event_engine->pollset_set_destroy(exec_ctx, pollset_set);
 }
 
 void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
index 1aea7d61f3..1a9e5c115a 100644
--- a/src/core/lib/iomgr/ev_posix.h
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -74,7 +74,8 @@ typedef struct grpc_event_engine_vtable {
                          struct grpc_fd *fd);
 
   grpc_pollset_set *(*pollset_set_create)(void);
-  void (*pollset_set_destroy)(grpc_pollset_set *pollset_set);
+  void (*pollset_set_destroy)(grpc_exec_ctx *exec_ctx,
+                              grpc_pollset_set *pollset_set);
   void (*pollset_set_add_pollset)(grpc_exec_ctx *exec_ctx,
                                   grpc_pollset_set *pollset_set,
                                   grpc_pollset *pollset);
diff --git a/src/core/lib/iomgr/network_status_tracker.c b/src/core/lib/iomgr/network_status_tracker.c
index 1601a39002..4104bf927a 100644
--- a/src/core/lib/iomgr/network_status_tracker.c
+++ b/src/core/lib/iomgr/network_status_tracker.c
@@ -31,95 +31,18 @@
  *
  */
 
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
 #include "src/core/lib/iomgr/endpoint.h"
 
-typedef struct endpoint_ll_node {
-  grpc_endpoint *ep;
-  struct endpoint_ll_node *next;
-} endpoint_ll_node;
-
-static endpoint_ll_node *head = NULL;
-static gpr_mu g_endpoint_mutex;
-
-void grpc_network_status_shutdown(void) {
-  if (head != NULL) {
-    gpr_log(GPR_ERROR,
-            "Memory leaked as not all network endpoints were shut down");
-  }
-  gpr_mu_destroy(&g_endpoint_mutex);
-}
+void grpc_network_status_shutdown(void) {}
 
 void grpc_network_status_init(void) {
-  gpr_mu_init(&g_endpoint_mutex);
   // TODO(makarandd): Install callback with OS to monitor network status.
 }
 
-void grpc_destroy_network_status_monitor() {
-  for (endpoint_ll_node *curr = head; curr != NULL;) {
-    endpoint_ll_node *next = curr->next;
-    gpr_free(curr);
-    curr = next;
-  }
-  gpr_mu_destroy(&g_endpoint_mutex);
-}
-
-void grpc_network_status_register_endpoint(grpc_endpoint *ep) {
-  gpr_mu_lock(&g_endpoint_mutex);
-  if (head == NULL) {
-    head = (endpoint_ll_node *)gpr_malloc(sizeof(endpoint_ll_node));
-    head->ep = ep;
-    head->next = NULL;
-  } else {
-    endpoint_ll_node *prev_head = head;
-    head = (endpoint_ll_node *)gpr_malloc(sizeof(endpoint_ll_node));
-    head->ep = ep;
-    head->next = prev_head;
-  }
-  gpr_mu_unlock(&g_endpoint_mutex);
-}
+void grpc_destroy_network_status_monitor() {}
 
-void grpc_network_status_unregister_endpoint(grpc_endpoint *ep) {
-  gpr_mu_lock(&g_endpoint_mutex);
-  GPR_ASSERT(head);
-  bool found = false;
-  endpoint_ll_node *prev = head;
-  // if we're unregistering the head, just move head to the next
-  if (ep == head->ep) {
-    head = head->next;
-    gpr_free(prev);
-    found = true;
-  } else {
-    for (endpoint_ll_node *curr = head->next; curr != NULL; curr = curr->next) {
-      if (ep == curr->ep) {
-        prev->next = curr->next;
-        gpr_free(curr);
-        found = true;
-        break;
-      }
-      prev = curr;
-    }
-  }
-  gpr_mu_unlock(&g_endpoint_mutex);
-  GPR_ASSERT(found);
-}
+void grpc_network_status_register_endpoint(grpc_endpoint *ep) { (void)ep; }
 
-// Walk the linked-list from head and execute shutdown. It is possible that
-// other threads might be in the process of shutdown as well, but that has
-// no side effect since endpoint shutdown is idempotent.
-void grpc_network_status_shutdown_all_endpoints() {
-  gpr_mu_lock(&g_endpoint_mutex);
-  if (head == NULL) {
-    gpr_mu_unlock(&g_endpoint_mutex);
-    return;
-  }
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+void grpc_network_status_unregister_endpoint(grpc_endpoint *ep) { (void)ep; }
 
-  for (endpoint_ll_node *curr = head; curr != NULL; curr = curr->next) {
-    curr->ep->vtable->shutdown(&exec_ctx, curr->ep,
-                               GRPC_ERROR_CREATE("Network unavailable"));
-  }
-  gpr_mu_unlock(&g_endpoint_mutex);
-  grpc_exec_ctx_finish(&exec_ctx);
-}
+void grpc_network_status_shutdown_all_endpoints() {}
diff --git a/src/core/lib/iomgr/pollset_set.h b/src/core/lib/iomgr/pollset_set.h
index 34bb728c41..d11801d63b 100644
--- a/src/core/lib/iomgr/pollset_set.h
+++ b/src/core/lib/iomgr/pollset_set.h
@@ -44,7 +44,8 @@
 typedef struct grpc_pollset_set grpc_pollset_set;
 
 grpc_pollset_set *grpc_pollset_set_create(void);
-void grpc_pollset_set_destroy(grpc_pollset_set *pollset_set);
+void grpc_pollset_set_destroy(grpc_exec_ctx *exec_ctx,
+                              grpc_pollset_set *pollset_set);
 void grpc_pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
                                   grpc_pollset_set *pollset_set,
                                   grpc_pollset *pollset);
diff --git a/src/core/lib/iomgr/pollset_set_uv.c b/src/core/lib/iomgr/pollset_set_uv.c
index e5ef8b29e0..836cfee4ef 100644
--- a/src/core/lib/iomgr/pollset_set_uv.c
+++ b/src/core/lib/iomgr/pollset_set_uv.c
@@ -41,7 +41,8 @@ grpc_pollset_set* grpc_pollset_set_create(void) {
   return (grpc_pollset_set*)((intptr_t)0xdeafbeef);
 }
 
-void grpc_pollset_set_destroy(grpc_pollset_set* pollset_set) {}
+void grpc_pollset_set_destroy(grpc_exec_ctx* exec_ctx,
+                              grpc_pollset_set* pollset_set) {}
 
 void grpc_pollset_set_add_pollset(grpc_exec_ctx* exec_ctx,
                                   grpc_pollset_set* pollset_set,
diff --git a/src/core/lib/iomgr/pollset_set_windows.c b/src/core/lib/iomgr/pollset_set_windows.c
index 645650db9b..ae18c8a3ce 100644
--- a/src/core/lib/iomgr/pollset_set_windows.c
+++ b/src/core/lib/iomgr/pollset_set_windows.c
@@ -42,7 +42,8 @@ grpc_pollset_set* grpc_pollset_set_create(void) {
   return (grpc_pollset_set*)((intptr_t)0xdeafbeef);
 }
 
-void grpc_pollset_set_destroy(grpc_pollset_set* pollset_set) {}
+void grpc_pollset_set_destroy(grpc_exec_ctx* exec_ctx,
+                              grpc_pollset_set* pollset_set) {}
 
 void grpc_pollset_set_add_pollset(grpc_exec_ctx* exec_ctx,
                                   grpc_pollset_set* pollset_set,
diff --git a/src/core/lib/iomgr/timer_generic.c b/src/core/lib/iomgr/timer_generic.c
index 40c8351472..8a5617e7c1 100644
--- a/src/core/lib/iomgr/timer_generic.c
+++ b/src/core/lib/iomgr/timer_generic.c
@@ -121,12 +121,6 @@ void grpc_timer_list_shutdown(grpc_exec_ctx *exec_ctx) {
   g_initialized = false;
 }
 
-/* This is a cheap, but good enough, pointer hash for sharding the tasks: */
-static size_t shard_idx(const grpc_timer *info) {
-  size_t x = (size_t)info;
-  return ((x >> 4) ^ (x >> 9) ^ (x >> 14)) & (NUM_SHARDS - 1);
-}
-
 static double ts_to_dbl(gpr_timespec ts) {
   return (double)ts.tv_sec + 1e-9 * ts.tv_nsec;
 }
@@ -181,7 +175,7 @@ void grpc_timer_init(grpc_exec_ctx *exec_ctx, grpc_timer *timer,
                      gpr_timespec deadline, grpc_closure *closure,
                      gpr_timespec now) {
   int is_first_timer = 0;
-  shard_type *shard = &g_shards[shard_idx(timer)];
+  shard_type *shard = &g_shards[GPR_HASH_POINTER(timer, NUM_SHARDS)];
   GPR_ASSERT(deadline.clock_type == g_clock_type);
   GPR_ASSERT(now.clock_type == g_clock_type);
   timer->closure = closure;
@@ -247,7 +241,7 @@ void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer) {
     return;
   }
 
-  shard_type *shard = &g_shards[shard_idx(timer)];
+  shard_type *shard = &g_shards[GPR_HASH_POINTER(timer, NUM_SHARDS)];
   gpr_mu_lock(&shard->mu);
   if (!timer->triggered) {
     grpc_closure_sched(exec_ctx, timer->closure, GRPC_ERROR_CANCELLED);
diff --git a/src/core/lib/security/credentials/google_default/google_default_credentials.c b/src/core/lib/security/credentials/google_default/google_default_credentials.c
index a098741b70..ecd26de9fa 100644
--- a/src/core/lib/security/credentials/google_default/google_default_credentials.c
+++ b/src/core/lib/security/credentials/google_default/google_default_credentials.c
@@ -154,7 +154,7 @@ static int is_stack_running_on_compute_engine(grpc_exec_ctx *exec_ctx) {
   }
   gpr_mu_unlock(g_polling_mu);
 
-  grpc_httpcli_context_destroy(&context);
+  grpc_httpcli_context_destroy(exec_ctx, &context);
   grpc_closure_init(&destroy_closure, destroy_pollset,
                     grpc_polling_entity_pollset(&detector.pollent),
                     grpc_schedule_on_exec_ctx);
diff --git a/src/core/lib/security/credentials/jwt/jwt_verifier.c b/src/core/lib/security/credentials/jwt/jwt_verifier.c
index 2270be8f44..f128177e8c 100644
--- a/src/core/lib/security/credentials/jwt/jwt_verifier.c
+++ b/src/core/lib/security/credentials/jwt/jwt_verifier.c
@@ -898,10 +898,10 @@ grpc_jwt_verifier *grpc_jwt_verifier_create(
   return v;
 }
 
-void grpc_jwt_verifier_destroy(grpc_jwt_verifier *v) {
+void grpc_jwt_verifier_destroy(grpc_exec_ctx *exec_ctx, grpc_jwt_verifier *v) {
   size_t i;
   if (v == NULL) return;
-  grpc_httpcli_context_destroy(&v->http_ctx);
+  grpc_httpcli_context_destroy(exec_ctx, &v->http_ctx);
   if (v->mappings != NULL) {
     for (i = 0; i < v->num_mappings; i++) {
       gpr_free(v->mappings[i].email_domain);
diff --git a/src/core/lib/security/credentials/jwt/jwt_verifier.h b/src/core/lib/security/credentials/jwt/jwt_verifier.h
index 4fa320a415..5c3d2a7788 100644
--- a/src/core/lib/security/credentials/jwt/jwt_verifier.h
+++ b/src/core/lib/security/credentials/jwt/jwt_verifier.h
@@ -109,7 +109,8 @@ grpc_jwt_verifier *grpc_jwt_verifier_create(
     size_t num_mappings);
 
 /*The verifier must not be destroyed if there are still outstanding callbacks.*/
-void grpc_jwt_verifier_destroy(grpc_jwt_verifier *verifier);
+void grpc_jwt_verifier_destroy(grpc_exec_ctx *exec_ctx,
+                               grpc_jwt_verifier *verifier);
 
 /* User provided callback that will be called when the verification of the JWT
    is done (maybe in another thread).
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
index 1b0e43a1e4..c0f260f938 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
@@ -124,7 +124,7 @@ static void oauth2_token_fetcher_destruct(grpc_exec_ctx *exec_ctx,
       (grpc_oauth2_token_fetcher_credentials *)creds;
   grpc_credentials_md_store_unref(exec_ctx, c->access_token_md);
   gpr_mu_destroy(&c->mu);
-  grpc_httpcli_context_destroy(&c->httpcli_context);
+  grpc_httpcli_context_destroy(exec_ctx, &c->httpcli_context);
 }
 
 grpc_credentials_status
diff --git a/src/core/lib/support/cpu_posix.c b/src/core/lib/support/cpu_posix.c
index 667bde7cad..245f12f06d 100644
--- a/src/core/lib/support/cpu_posix.c
+++ b/src/core/lib/support/cpu_posix.c
@@ -41,6 +41,7 @@
 
 #include <grpc/support/log.h>
 #include <grpc/support/sync.h>
+#include <grpc/support/useful.h>
 
 static __thread char magic_thread_local;
 
@@ -60,18 +61,12 @@ unsigned gpr_cpu_num_cores(void) {
   return (unsigned)ncpus;
 }
 
-/* This is a cheap, but good enough, pointer hash for sharding things: */
-static size_t shard_ptr(const void *info) {
-  size_t x = (size_t)info;
-  return ((x >> 4) ^ (x >> 9) ^ (x >> 14)) % gpr_cpu_num_cores();
-}
-
 unsigned gpr_cpu_current_cpu(void) {
   /* NOTE: there's no way I know to return the actual cpu index portably...
      most code that's using this is using it to shard across work queues though,
      so here we use thread identity instead to achieve a similar though not
      identical effect */
-  return (unsigned)shard_ptr(&magic_thread_local);
+  return (unsigned)GPR_HASH_POINTER(&magic_thread_local, gpr_cpu_num_cores());
 }
 
 #endif /* GPR_CPU_POSIX */
diff --git a/src/core/lib/support/sync_posix.c b/src/core/lib/support/sync_posix.c
index de0f0484b5..16e7d6e12a 100644
--- a/src/core/lib/support/sync_posix.c
+++ b/src/core/lib/support/sync_posix.c
@@ -42,8 +42,10 @@
 #include <time.h>
 #include "src/core/lib/profiling/timers.h"
 
-#ifdef GPR_MU_COUNTERS
-gpr_atm grpc_mu_locks = 0;
+#ifdef GPR_LOW_LEVEL_COUNTERS
+gpr_atm gpr_mu_locks = 0;
+gpr_atm gpr_counter_atm_cas = 0;
+gpr_atm gpr_counter_atm_add = 0;
 #endif
 
 void gpr_mu_init(gpr_mu* mu) { GPR_ASSERT(pthread_mutex_init(mu, NULL) == 0); }
@@ -51,8 +53,8 @@ void gpr_mu_init(gpr_mu* mu) { GPR_ASSERT(pthread_mutex_init(mu, NULL) == 0); }
 void gpr_mu_destroy(gpr_mu* mu) { GPR_ASSERT(pthread_mutex_destroy(mu) == 0); }
 
 void gpr_mu_lock(gpr_mu* mu) {
-#ifdef GPR_MU_COUNTERS
-  gpr_atm_no_barrier_fetch_add(&grpc_mu_locks, 1);
+#ifdef GPR_LOW_LEVEL_COUNTERS
+  GPR_ATM_INC_COUNTER(gpr_mu_locks);
 #endif
   GPR_TIMER_BEGIN("gpr_mu_lock", 0);
   GPR_ASSERT(pthread_mutex_lock(mu) == 0);
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 3352e427cd..48a1e586e1 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -481,7 +481,10 @@ void grpc_call_destroy(grpc_call *c) {
   c->destroy_called = 1;
   cancel = !c->received_final_op;
   gpr_mu_unlock(&c->mu);
-  if (cancel) grpc_call_cancel(c, NULL);
+  if (cancel) {
+    cancel_with_error(&exec_ctx, c, STATUS_FROM_API_OVERRIDE,
+                      GRPC_ERROR_CANCELLED);
+  }
   GRPC_CALL_INTERNAL_UNREF(&exec_ctx, c, "destroy");
   grpc_exec_ctx_finish(&exec_ctx);
   GPR_TIMER_END("grpc_call_destroy", 0);
@@ -490,8 +493,11 @@ void grpc_call_destroy(grpc_call *c) {
 grpc_call_error grpc_call_cancel(grpc_call *call, void *reserved) {
   GRPC_API_TRACE("grpc_call_cancel(call=%p, reserved=%p)", 2, (call, reserved));
   GPR_ASSERT(!reserved);
-  return grpc_call_cancel_with_status(call, GRPC_STATUS_CANCELLED, "Cancelled",
-                                      NULL);
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  cancel_with_error(&exec_ctx, call, STATUS_FROM_API_OVERRIDE,
+                    GRPC_ERROR_CANCELLED);
+  grpc_exec_ctx_finish(&exec_ctx);
+  return GRPC_CALL_OK;
 }
 
 static void execute_op(grpc_exec_ctx *exec_ctx, grpc_call *call,
diff --git a/src/core/lib/transport/connectivity_state.c b/src/core/lib/transport/connectivity_state.c
index 8fc5bf3e9a..afe1f6164d 100644
--- a/src/core/lib/transport/connectivity_state.c
+++ b/src/core/lib/transport/connectivity_state.c
@@ -62,7 +62,7 @@ const char *grpc_connectivity_state_name(grpc_connectivity_state state) {
 void grpc_connectivity_state_init(grpc_connectivity_state_tracker *tracker,
                                   grpc_connectivity_state init_state,
                                   const char *name) {
-  tracker->current_state = init_state;
+  gpr_atm_no_barrier_store(&tracker->current_state_atm, init_state);
   tracker->current_error = GRPC_ERROR_NONE;
   tracker->watchers = NULL;
   tracker->name = gpr_strdup(name);
@@ -89,15 +89,30 @@ void grpc_connectivity_state_destroy(grpc_exec_ctx *exec_ctx,
 }
 
 grpc_connectivity_state grpc_connectivity_state_check(
+    grpc_connectivity_state_tracker *tracker) {
+  grpc_connectivity_state cur =
+      (grpc_connectivity_state)gpr_atm_no_barrier_load(
+          &tracker->current_state_atm);
+  if (grpc_connectivity_state_trace) {
+    gpr_log(GPR_DEBUG, "CONWATCH: %p %s: get %s", tracker, tracker->name,
+            grpc_connectivity_state_name(cur));
+  }
+  return cur;
+}
+
+grpc_connectivity_state grpc_connectivity_state_get(
     grpc_connectivity_state_tracker *tracker, grpc_error **error) {
+  grpc_connectivity_state cur =
+      (grpc_connectivity_state)gpr_atm_no_barrier_load(
+          &tracker->current_state_atm);
   if (grpc_connectivity_state_trace) {
     gpr_log(GPR_DEBUG, "CONWATCH: %p %s: get %s", tracker, tracker->name,
-            grpc_connectivity_state_name(tracker->current_state));
+            grpc_connectivity_state_name(cur));
   }
   if (error != NULL) {
     *error = GRPC_ERROR_REF(tracker->current_error);
   }
-  return tracker->current_state;
+  return cur;
 }
 
 bool grpc_connectivity_state_has_watchers(
@@ -108,6 +123,9 @@ bool grpc_connectivity_state_has_watchers(
 bool grpc_connectivity_state_notify_on_state_change(
     grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
     grpc_connectivity_state *current, grpc_closure *notify) {
+  grpc_connectivity_state cur =
+      (grpc_connectivity_state)gpr_atm_no_barrier_load(
+          &tracker->current_state_atm);
   if (grpc_connectivity_state_trace) {
     if (current == NULL) {
       gpr_log(GPR_DEBUG, "CONWATCH: %p %s: unsubscribe notify=%p", tracker,
@@ -115,7 +133,7 @@ bool grpc_connectivity_state_notify_on_state_change(
     } 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);
+              grpc_connectivity_state_name(cur), notify);
     }
   }
   if (current == NULL) {
@@ -138,8 +156,8 @@ bool grpc_connectivity_state_notify_on_state_change(
     }
     return false;
   } else {
-    if (tracker->current_state != *current) {
-      *current = tracker->current_state;
+    if (cur != *current) {
+      *current = cur;
       grpc_closure_sched(exec_ctx, notify,
                          GRPC_ERROR_REF(tracker->current_error));
     } else {
@@ -149,7 +167,7 @@ bool grpc_connectivity_state_notify_on_state_change(
       w->next = tracker->watchers;
       tracker->watchers = w;
     }
-    return tracker->current_state == GRPC_CHANNEL_IDLE;
+    return cur == GRPC_CHANNEL_IDLE;
   }
 }
 
@@ -157,11 +175,14 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
                                  grpc_connectivity_state_tracker *tracker,
                                  grpc_connectivity_state state,
                                  grpc_error *error, const char *reason) {
+  grpc_connectivity_state cur =
+      (grpc_connectivity_state)gpr_atm_no_barrier_load(
+          &tracker->current_state_atm);
   grpc_connectivity_state_watcher *w;
   if (grpc_connectivity_state_trace) {
     const char *error_string = grpc_error_string(error);
     gpr_log(GPR_DEBUG, "SET: %p %s: %s --> %s [%s] error=%p %s", tracker,
-            tracker->name, grpc_connectivity_state_name(tracker->current_state),
+            tracker->name, grpc_connectivity_state_name(cur),
             grpc_connectivity_state_name(state), reason, error, error_string);
   }
   switch (state) {
@@ -178,13 +199,13 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
   }
   GRPC_ERROR_UNREF(tracker->current_error);
   tracker->current_error = error;
-  if (tracker->current_state == state) {
+  if (cur == state) {
     return;
   }
-  GPR_ASSERT(tracker->current_state != GRPC_CHANNEL_SHUTDOWN);
-  tracker->current_state = state;
+  GPR_ASSERT(cur != GRPC_CHANNEL_SHUTDOWN);
+  gpr_atm_no_barrier_store(&tracker->current_state_atm, state);
   while ((w = tracker->watchers) != NULL) {
-    *w->current = tracker->current_state;
+    *w->current = state;
     tracker->watchers = w->next;
     if (grpc_connectivity_state_trace) {
       gpr_log(GPR_DEBUG, "NOTIFY: %p %s: %p", tracker, tracker->name,
diff --git a/src/core/lib/transport/connectivity_state.h b/src/core/lib/transport/connectivity_state.h
index 769c675b79..c9604c34dd 100644
--- a/src/core/lib/transport/connectivity_state.h
+++ b/src/core/lib/transport/connectivity_state.h
@@ -47,8 +47,8 @@ typedef struct grpc_connectivity_state_watcher {
 } grpc_connectivity_state_watcher;
 
 typedef struct {
-  /** current connectivity state */
-  grpc_connectivity_state current_state;
+  /** current grpc_connectivity_state */
+  gpr_atm current_state_atm;
   /** error associated with state */
   grpc_error *current_error;
   /** all our watchers */
@@ -59,6 +59,7 @@ typedef struct {
 
 extern int grpc_connectivity_state_trace;
 
+/** enum --> string conversion */
 const char *grpc_connectivity_state_name(grpc_connectivity_state state);
 
 void grpc_connectivity_state_init(grpc_connectivity_state_tracker *tracker,
@@ -68,22 +69,31 @@ void grpc_connectivity_state_destroy(grpc_exec_ctx *exec_ctx,
                                      grpc_connectivity_state_tracker *tracker);
 
 /** Set connectivity state; not thread safe; access must be serialized with an
- * external lock */
+ *  external lock */
 void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
                                  grpc_connectivity_state_tracker *tracker,
                                  grpc_connectivity_state state,
                                  grpc_error *associated_error,
                                  const char *reason);
 
+/** Return true if this connectivity state has watchers.
+    Access must be serialized with an external lock. */
 bool grpc_connectivity_state_has_watchers(
     grpc_connectivity_state_tracker *tracker);
 
+/** Return the last seen connectivity state. No need to synchronize access. */
 grpc_connectivity_state grpc_connectivity_state_check(
-    grpc_connectivity_state_tracker *tracker, grpc_error **current_error);
+    grpc_connectivity_state_tracker *tracker);
+
+/** Return the last seen connectivity state, and the associated error.
+    Access must be serialized with an external lock. */
+grpc_connectivity_state grpc_connectivity_state_get(
+    grpc_connectivity_state_tracker *tracker, grpc_error **error);
 
 /** 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) */
+    case).
+    Access must be serialized with an external lock. */
 bool grpc_connectivity_state_notify_on_state_change(
     grpc_exec_ctx *exec_ctx, grpc_connectivity_state_tracker *tracker,
     grpc_connectivity_state *current, grpc_closure *notify);
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 9a0abe1ca4..e56bf2780a 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -167,9 +167,9 @@ typedef struct grpc_transport_stream_op {
 
   /***************************************************************************
    * remaining fields are initialized and used at the discretion of the
-   * transport implementation */
+   * current handler of the op */
 
-  grpc_transport_private_op_data transport_private;
+  grpc_transport_private_op_data handler_private;
 } grpc_transport_stream_op;
 
 /** Transport op: a set of operations to perform on a transport as a whole */
diff --git a/src/cpp/server/health/default_health_check_service.cc b/src/cpp/server/health/default_health_check_service.cc
new file mode 100644
index 0000000000..46def70e8a
--- /dev/null
+++ b/src/cpp/server/health/default_health_check_service.cc
@@ -0,0 +1,166 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <memory>
+#include <mutex>
+
+#include <grpc++/impl/codegen/method_handler_impl.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/cpp/server/health/default_health_check_service.h"
+#include "src/cpp/server/health/health.pb.h"
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+namespace grpc {
+namespace {
+const char kHealthCheckMethodName[] = "/grpc.health.v1.Health/Check";
+}  // namespace
+
+DefaultHealthCheckService::HealthCheckServiceImpl::HealthCheckServiceImpl(
+    DefaultHealthCheckService* service)
+    : service_(service), method_(nullptr) {
+  MethodHandler* handler =
+      new RpcMethodHandler<HealthCheckServiceImpl, ByteBuffer, ByteBuffer>(
+          std::mem_fn(&HealthCheckServiceImpl::Check), this);
+  method_ = new RpcServiceMethod(kHealthCheckMethodName, RpcMethod::NORMAL_RPC,
+                                 handler);
+  AddMethod(method_);
+}
+
+Status DefaultHealthCheckService::HealthCheckServiceImpl::Check(
+    ServerContext* context, const ByteBuffer* request, ByteBuffer* response) {
+  // Decode request.
+  std::vector<Slice> slices;
+  request->Dump(&slices);
+  uint8_t* request_bytes = nullptr;
+  bool request_bytes_owned = false;
+  size_t request_size = 0;
+  grpc_health_v1_HealthCheckRequest request_struct;
+  if (slices.empty()) {
+    request_struct.has_service = false;
+  } else if (slices.size() == 1) {
+    request_bytes = const_cast<uint8_t*>(slices[0].begin());
+    request_size = slices[0].size();
+  } else {
+    request_bytes_owned = true;
+    request_bytes = static_cast<uint8_t*>(gpr_malloc(request->Length()));
+    uint8_t* copy_to = request_bytes;
+    for (size_t i = 0; i < slices.size(); i++) {
+      memcpy(copy_to, slices[i].begin(), slices[i].size());
+      copy_to += slices[i].size();
+    }
+  }
+
+  if (request_bytes != nullptr) {
+    pb_istream_t istream = pb_istream_from_buffer(request_bytes, request_size);
+    bool decode_status = pb_decode(
+        &istream, grpc_health_v1_HealthCheckRequest_fields, &request_struct);
+    if (request_bytes_owned) {
+      gpr_free(request_bytes);
+    }
+    if (!decode_status) {
+      return Status(StatusCode::INVALID_ARGUMENT, "");
+    }
+  }
+
+  // Check status from the associated default health checking service.
+  DefaultHealthCheckService::ServingStatus serving_status =
+      service_->GetServingStatus(
+          request_struct.has_service ? request_struct.service : "");
+  if (serving_status == DefaultHealthCheckService::NOT_FOUND) {
+    return Status(StatusCode::NOT_FOUND, "");
+  }
+
+  // Encode response
+  grpc_health_v1_HealthCheckResponse response_struct;
+  response_struct.has_status = true;
+  response_struct.status =
+      serving_status == DefaultHealthCheckService::SERVING
+          ? grpc_health_v1_HealthCheckResponse_ServingStatus_SERVING
+          : grpc_health_v1_HealthCheckResponse_ServingStatus_NOT_SERVING;
+  pb_ostream_t ostream;
+  memset(&ostream, 0, sizeof(ostream));
+  pb_encode(&ostream, grpc_health_v1_HealthCheckResponse_fields,
+            &response_struct);
+  grpc_slice response_slice = grpc_slice_malloc(ostream.bytes_written);
+  ostream = pb_ostream_from_buffer(GRPC_SLICE_START_PTR(response_slice),
+                                   GRPC_SLICE_LENGTH(response_slice));
+  bool encode_status = pb_encode(
+      &ostream, grpc_health_v1_HealthCheckResponse_fields, &response_struct);
+  if (!encode_status) {
+    return Status(StatusCode::INTERNAL, "Failed to encode response.");
+  }
+  Slice encoded_response(response_slice, Slice::STEAL_REF);
+  ByteBuffer response_buffer(&encoded_response, 1);
+  response->Swap(&response_buffer);
+  return Status::OK;
+}
+
+DefaultHealthCheckService::DefaultHealthCheckService() {
+  services_map_.emplace("", true);
+}
+
+void DefaultHealthCheckService::SetServingStatus(
+    const grpc::string& service_name, bool serving) {
+  std::lock_guard<std::mutex> lock(mu_);
+  services_map_[service_name] = serving;
+}
+
+void DefaultHealthCheckService::SetServingStatus(bool serving) {
+  std::lock_guard<std::mutex> lock(mu_);
+  for (auto iter = services_map_.begin(); iter != services_map_.end(); ++iter) {
+    iter->second = serving;
+  }
+}
+
+DefaultHealthCheckService::ServingStatus
+DefaultHealthCheckService::GetServingStatus(
+    const grpc::string& service_name) const {
+  std::lock_guard<std::mutex> lock(mu_);
+  const auto& iter = services_map_.find(service_name);
+  if (iter == services_map_.end()) {
+    return NOT_FOUND;
+  }
+  return iter->second ? SERVING : NOT_SERVING;
+}
+
+DefaultHealthCheckService::HealthCheckServiceImpl*
+DefaultHealthCheckService::GetHealthCheckService() {
+  GPR_ASSERT(impl_ == nullptr);
+  impl_.reset(new HealthCheckServiceImpl(this));
+  return impl_.get();
+}
+
+}  // namespace grpc
diff --git a/src/cpp/server/health/default_health_check_service.h b/src/cpp/server/health/default_health_check_service.h
new file mode 100644
index 0000000000..5c0e230342
--- /dev/null
+++ b/src/cpp/server/health/default_health_check_service.h
@@ -0,0 +1,78 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_INTERNAL_CPP_SERVER_DEFAULT_HEALTH_CHECK_SERVICE_H
+#define GRPC_INTERNAL_CPP_SERVER_DEFAULT_HEALTH_CHECK_SERVICE_H
+
+#include <mutex>
+
+#include <grpc++/health_check_service_interface.h>
+#include <grpc++/impl/codegen/service_type.h>
+#include <grpc++/support/byte_buffer.h>
+
+namespace grpc {
+
+// Default implementation of HealthCheckServiceInterface. Server will create and
+// own it.
+class DefaultHealthCheckService final : public HealthCheckServiceInterface {
+ public:
+  // The service impl to register with the server.
+  class HealthCheckServiceImpl : public Service {
+   public:
+    explicit HealthCheckServiceImpl(DefaultHealthCheckService* service);
+
+    Status Check(ServerContext* context, const ByteBuffer* request,
+                 ByteBuffer* response);
+
+   private:
+    const DefaultHealthCheckService* const service_;
+    RpcServiceMethod* method_;
+  };
+
+  DefaultHealthCheckService();
+  void SetServingStatus(const grpc::string& service_name,
+                        bool serving) override;
+  void SetServingStatus(bool serving) override;
+  enum ServingStatus { NOT_FOUND, SERVING, NOT_SERVING };
+  ServingStatus GetServingStatus(const grpc::string& service_name) const;
+  HealthCheckServiceImpl* GetHealthCheckService();
+
+ private:
+  mutable std::mutex mu_;
+  std::map<grpc::string, bool> services_map_;
+  std::unique_ptr<HealthCheckServiceImpl> impl_;
+};
+
+}  // namespace grpc
+
+#endif  // GRPC_INTERNAL_CPP_SERVER_DEFAULT_HEALTH_CHECK_SERVICE_H
diff --git a/src/cpp/server/health/health.pb.c b/src/cpp/server/health/health.pb.c
new file mode 100644
index 0000000000..09bd98a3d9
--- /dev/null
+++ b/src/cpp/server/health/health.pb.c
@@ -0,0 +1,24 @@
+/* Automatically generated nanopb constant definitions */
+/* Generated by nanopb-0.3.7-dev */
+
+#include "src/cpp/server/health/health.pb.h"
+
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+
+
+const pb_field_t grpc_health_v1_HealthCheckRequest_fields[2] = {
+    PB_FIELD(  1, STRING  , OPTIONAL, STATIC  , FIRST, grpc_health_v1_HealthCheckRequest, service, service, 0),
+    PB_LAST_FIELD
+};
+
+const pb_field_t grpc_health_v1_HealthCheckResponse_fields[2] = {
+    PB_FIELD(  1, UENUM   , OPTIONAL, STATIC  , FIRST, grpc_health_v1_HealthCheckResponse, status, status, 0),
+    PB_LAST_FIELD
+};
+
+
+/* @@protoc_insertion_point(eof) */
diff --git a/src/cpp/server/health/health.pb.h b/src/cpp/server/health/health.pb.h
new file mode 100644
index 0000000000..7051b3260a
--- /dev/null
+++ b/src/cpp/server/health/health.pb.h
@@ -0,0 +1,72 @@
+/* Automatically generated nanopb header */
+/* Generated by nanopb-0.3.7-dev */
+
+#ifndef PB_GRPC_HEALTH_V1_HEALTH_PB_H_INCLUDED
+#define PB_GRPC_HEALTH_V1_HEALTH_PB_H_INCLUDED
+#include "third_party/nanopb/pb.h"
+/* @@protoc_insertion_point(includes) */
+#if PB_PROTO_HEADER_VERSION != 30
+#error Regenerate this file with the current version of nanopb generator.
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Enum definitions */
+typedef enum _grpc_health_v1_HealthCheckResponse_ServingStatus {
+    grpc_health_v1_HealthCheckResponse_ServingStatus_UNKNOWN = 0,
+    grpc_health_v1_HealthCheckResponse_ServingStatus_SERVING = 1,
+    grpc_health_v1_HealthCheckResponse_ServingStatus_NOT_SERVING = 2
+} grpc_health_v1_HealthCheckResponse_ServingStatus;
+#define _grpc_health_v1_HealthCheckResponse_ServingStatus_MIN grpc_health_v1_HealthCheckResponse_ServingStatus_UNKNOWN
+#define _grpc_health_v1_HealthCheckResponse_ServingStatus_MAX grpc_health_v1_HealthCheckResponse_ServingStatus_NOT_SERVING
+#define _grpc_health_v1_HealthCheckResponse_ServingStatus_ARRAYSIZE ((grpc_health_v1_HealthCheckResponse_ServingStatus)(grpc_health_v1_HealthCheckResponse_ServingStatus_NOT_SERVING+1))
+
+/* Struct definitions */
+typedef struct _grpc_health_v1_HealthCheckRequest {
+    bool has_service;
+    char service[200];
+/* @@protoc_insertion_point(struct:grpc_health_v1_HealthCheckRequest) */
+} grpc_health_v1_HealthCheckRequest;
+
+typedef struct _grpc_health_v1_HealthCheckResponse {
+    bool has_status;
+    grpc_health_v1_HealthCheckResponse_ServingStatus status;
+/* @@protoc_insertion_point(struct:grpc_health_v1_HealthCheckResponse) */
+} grpc_health_v1_HealthCheckResponse;
+
+/* Default values for struct fields */
+
+/* Initializer values for message structs */
+#define grpc_health_v1_HealthCheckRequest_init_default {false, ""}
+#define grpc_health_v1_HealthCheckResponse_init_default {false, (grpc_health_v1_HealthCheckResponse_ServingStatus)0}
+#define grpc_health_v1_HealthCheckRequest_init_zero {false, ""}
+#define grpc_health_v1_HealthCheckResponse_init_zero {false, (grpc_health_v1_HealthCheckResponse_ServingStatus)0}
+
+/* Field tags (for use in manual encoding/decoding) */
+#define grpc_health_v1_HealthCheckRequest_service_tag 1
+#define grpc_health_v1_HealthCheckResponse_status_tag 1
+
+/* Struct field encoding specification for nanopb */
+extern const pb_field_t grpc_health_v1_HealthCheckRequest_fields[2];
+extern const pb_field_t grpc_health_v1_HealthCheckResponse_fields[2];
+
+/* Maximum encoded size of messages (where known) */
+#define grpc_health_v1_HealthCheckRequest_size   203
+#define grpc_health_v1_HealthCheckResponse_size  2
+
+/* Message IDs (where set with "msgid" option) */
+#ifdef PB_MSGID
+
+#define HEALTH_MESSAGES \
+
+
+#endif
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+/* @@protoc_insertion_point(eof) */
+
+#endif
diff --git a/src/cpp/server/health/health_check_service.cc b/src/cpp/server/health/health_check_service.cc
new file mode 100644
index 0000000000..cca68c5549
--- /dev/null
+++ b/src/cpp/server/health/health_check_service.cc
@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc++/health_check_service_interface.h>
+
+namespace grpc {
+namespace {
+bool g_grpc_default_health_check_service_enabled = false;
+}  // namesapce
+
+bool DefaultHealthCheckServiceEnabled() {
+  return g_grpc_default_health_check_service_enabled;
+}
+
+void EnableDefaultHealthCheckService(bool enable) {
+  g_grpc_default_health_check_service_enabled = enable;
+}
+
+}  // namespace grpc
diff --git a/src/cpp/server/health/health_check_service_server_builder_option.cc b/src/cpp/server/health/health_check_service_server_builder_option.cc
new file mode 100644
index 0000000000..24264204b3
--- /dev/null
+++ b/src/cpp/server/health/health_check_service_server_builder_option.cc
@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc++/ext/health_check_service_server_builder_option.h>
+
+namespace grpc {
+
+HealthCheckServiceServerBuilderOption::HealthCheckServiceServerBuilderOption(
+    std::unique_ptr<HealthCheckServiceInterface> hc)
+    : hc_(std::move(hc)) {}
+// Hand over hc_ to the server.
+void HealthCheckServiceServerBuilderOption::UpdateArguments(
+    ChannelArguments* args) {
+  args->SetPointer(kHealthCheckServiceInterfaceArg, hc_.release());
+}
+
+void HealthCheckServiceServerBuilderOption::UpdatePlugins(
+    std::vector<std::unique_ptr<ServerBuilderPlugin>>* plugins) {}
+
+}  // namespace grpc
diff --git a/src/cpp/server/server_cc.cc b/src/cpp/server/server_cc.cc
index 29898a4209..150c5a5faf 100644
--- a/src/cpp/server/server_cc.cc
+++ b/src/cpp/server/server_cc.cc
@@ -37,6 +37,7 @@
 
 #include <grpc++/completion_queue.h>
 #include <grpc++/generic/async_generic_service.h>
+#include <grpc++/impl/codegen/async_unary_call.h>
 #include <grpc++/impl/codegen/completion_queue_tag.h>
 #include <grpc++/impl/grpc_library.h>
 #include <grpc++/impl/method_handler_impl.h>
@@ -51,6 +52,7 @@
 #include <grpc/support/log.h>
 
 #include "src/core/lib/profiling/timers.h"
+#include "src/cpp/server/health/default_health_check_service.h"
 #include "src/cpp/thread_manager/thread_manager.h"
 
 namespace grpc {
@@ -186,7 +188,7 @@ class Server::SyncRequest final : public CompletionQueueTag {
    public:
     explicit CallData(Server* server, SyncRequest* mrd)
         : cq_(mrd->cq_),
-          call_(mrd->call_, server, &cq_),
+          call_(mrd->call_, server, &cq_, server->max_receive_message_size()),
           ctx_(mrd->deadline_, mrd->request_metadata_.metadata,
                mrd->request_metadata_.count),
           has_request_payload_(mrd->has_request_payload_),
@@ -342,6 +344,7 @@ class Server::SyncRequestThreadManager : public ThreadManager {
   int cq_timeout_msec_;
   std::vector<std::unique_ptr<SyncRequest>> sync_requests_;
   std::unique_ptr<RpcServiceMethod> unknown_method_;
+  std::unique_ptr<RpcServiceMethod> health_check_;
   std::shared_ptr<Server::GlobalCallbacks> global_callbacks_;
 };
 
@@ -358,7 +361,8 @@ Server::Server(
       shutdown_notified_(false),
       has_generic_service_(false),
       server_(nullptr),
-      server_initializer_(new ServerInitializer(this)) {
+      server_initializer_(new ServerInitializer(this)),
+      health_check_service_disabled_(false) {
   g_gli_initializer.summon();
   gpr_once_init(&g_once_init_callbacks, InitGlobalCallbacks);
   global_callbacks_ = g_callbacks;
@@ -374,6 +378,19 @@ Server::Server(
   grpc_channel_args channel_args;
   args->SetChannelArgs(&channel_args);
 
+  for (size_t i = 0; i < channel_args.num_args; i++) {
+    if (0 ==
+        strcmp(channel_args.args[i].key, kHealthCheckServiceInterfaceArg)) {
+      if (channel_args.args[i].value.pointer.p == nullptr) {
+        health_check_service_disabled_ = true;
+      } else {
+        health_check_service_.reset(static_cast<HealthCheckServiceInterface*>(
+            channel_args.args[i].value.pointer.p));
+      }
+      break;
+    }
+  }
+
   server_ = grpc_server_create(&channel_args, nullptr);
 }
 
@@ -480,6 +497,21 @@ bool Server::Start(ServerCompletionQueue** cqs, size_t num_cqs) {
   GPR_ASSERT(!started_);
   global_callbacks_->PreServerStart(this);
   started_ = true;
+
+  // Only create default health check service when user did not provide an
+  // explicit one.
+  if (health_check_service_ == nullptr && !health_check_service_disabled_ &&
+      DefaultHealthCheckServiceEnabled()) {
+    if (sync_server_cqs_->empty()) {
+      gpr_log(GPR_ERROR,
+              "Default health check service disabled at async-only server.");
+    } else {
+      auto* default_hc_service = new DefaultHealthCheckService;
+      health_check_service_.reset(default_hc_service);
+      RegisterService(nullptr, default_hc_service->GetHealthCheckService());
+    }
+  }
+
   grpc_server_start(server_);
 
   if (!has_generic_service_) {
@@ -590,7 +622,7 @@ bool ServerInterface::BaseAsyncRequest::FinalizeResult(void** tag,
   }
   context_->set_call(call_);
   context_->cq_ = call_cq_;
-  Call call(call_, server_, call_cq_);
+  Call call(call_, server_, call_cq_, server_->max_receive_message_size());
   if (*status && call_) {
     context_->BeginCompletionOp(&call);
   }
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
index 5ba83b143e..68a8f4879b 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropClient.cs
@@ -56,7 +56,7 @@ namespace Grpc.IntegrationTesting
     {
         private class ClientOptions
         {
-            [Option("server_host", Default = "127.0.0.1")]
+            [Option("server_host", Default = "localhost")]
             public string ServerHost { get; set; }
 
             [Option("server_host_override", Default = TestCredentials.DefaultHostOverride)]
diff --git a/src/objective-c/tests/CronetUnitTests/CronetUnitTests.m b/src/objective-c/tests/CronetUnitTests/CronetUnitTests.m
index 5e3c59f8b3..e97f3d2d1a 100644
--- a/src/objective-c/tests/CronetUnitTests/CronetUnitTests.m
+++ b/src/objective-c/tests/CronetUnitTests/CronetUnitTests.m
@@ -321,44 +321,8 @@ unsigned int parse_h2_length(const char *field) {
   grpc_metadata_array_init(&request_metadata_recv);
   grpc_call_details_init(&call_details);
 
-  memset(ops, 0, sizeof(ops));
-  op = ops;
-  op->op = GRPC_OP_SEND_INITIAL_METADATA;
-  op->data.send_initial_metadata.count = 2;
-  op->data.send_initial_metadata.metadata = meta_c;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  op->op = GRPC_OP_SEND_MESSAGE;
-  op->data.send_message.send_message = request_payload;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  op->op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  op->op = GRPC_OP_RECV_INITIAL_METADATA;
-  op->data.recv_initial_metadata.recv_initial_metadata = &initial_metadata_recv;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  op->op = GRPC_OP_RECV_MESSAGE;
-  op->data.recv_message.recv_message = &response_payload_recv;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
-  op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
-  op->data.recv_status_on_client.status = &status;
-  op->data.recv_status_on_client.status_details = &details;
-  op->flags = 0;
-  op->reserved = NULL;
-  op++;
-  error = grpc_call_start_batch(c, ops, (size_t)(op - ops), (void *)1, NULL);
-  GPR_ASSERT(GRPC_CALL_OK == error);
-
-  __weak XCTestExpectation *expectation = [self expectationWithDescription:@"Coalescing"];
+  __weak XCTestExpectation *expectation =
+      [self expectationWithDescription:@"Coalescing"];
 
   dispatch_async(
       dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
@@ -425,6 +389,46 @@ unsigned int parse_h2_length(const char *field) {
         [expectation fulfill];
       });
 
+  // Guarantees that server is listening to the port before client connects.
+  sleep(1);
+
+  memset(ops, 0, sizeof(ops));
+  op = ops;
+  op->op = GRPC_OP_SEND_INITIAL_METADATA;
+  op->data.send_initial_metadata.count = 2;
+  op->data.send_initial_metadata.metadata = meta_c;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  op->op = GRPC_OP_SEND_MESSAGE;
+  op->data.send_message.send_message = request_payload;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  op->op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  op->op = GRPC_OP_RECV_INITIAL_METADATA;
+  op->data.recv_initial_metadata.recv_initial_metadata = &initial_metadata_recv;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  op->op = GRPC_OP_RECV_MESSAGE;
+  op->data.recv_message.recv_message = &response_payload_recv;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
+  op->data.recv_status_on_client.trailing_metadata = &trailing_metadata_recv;
+  op->data.recv_status_on_client.status = &status;
+  op->data.recv_status_on_client.status_details = &details;
+  op->flags = 0;
+  op->reserved = NULL;
+  op++;
+  error = grpc_call_start_batch(c, ops, (size_t)(op - ops), (void *)1, NULL);
+  GPR_ASSERT(GRPC_CALL_OK == error);
+
   CQ_EXPECT_COMPLETION(cqv, (void *)1, 1);
   cq_verify(cqv);
 
@@ -445,7 +449,7 @@ unsigned int parse_h2_length(const char *field) {
   grpc_completion_queue_shutdown(cq);
   drain_cq(cq);
   grpc_completion_queue_destroy(cq);
-  
+
   [self waitForExpectationsWithTimeout:4 handler:nil];
 }
 
diff --git a/src/php/ext/grpc/call.c b/src/php/ext/grpc/call.c
index be071903d0..48a374fa08 100644
--- a/src/php/ext/grpc/call.c
+++ b/src/php/ext/grpc/call.c
@@ -104,7 +104,8 @@ zval *grpc_parse_metadata_array(grpc_metadata_array
     str_key = ecalloc(key_len + 1, sizeof(char));
     memcpy(str_key, GRPC_SLICE_START_PTR(elem->key), key_len);
     str_val = ecalloc(GRPC_SLICE_LENGTH(elem->value) + 1, sizeof(char));
-    memcpy(str_val, GRPC_SLICE_START_PTR(elem->value), GRPC_SLICE_LENGTH(elem->value));
+    memcpy(str_val, GRPC_SLICE_START_PTR(elem->value),
+           GRPC_SLICE_LENGTH(elem->value));
     if (php_grpc_zend_hash_find(array_hash, str_key, key_len, (void **)&data)
         == SUCCESS) {
       if (Z_TYPE_P(data) != IS_ARRAY) {
@@ -115,7 +116,8 @@ zval *grpc_parse_metadata_array(grpc_metadata_array
         efree(str_val);
         return NULL;
       }
-      php_grpc_add_next_index_stringl(data, str_val, GRPC_SLICE_LENGTH(elem->value),
+      php_grpc_add_next_index_stringl(data, str_val,
+                                      GRPC_SLICE_LENGTH(elem->value),
                                       false);
     } else {
       PHP_GRPC_MAKE_STD_ZVAL(inner_array);
@@ -172,8 +174,10 @@ bool create_metadata_array(zval *array, grpc_metadata_array *metadata) {
       if (Z_TYPE_P(value) != IS_STRING) {
         return false;
       }
-      metadata->metadata[metadata->count].key = grpc_slice_from_copied_string(key1);
-      metadata->metadata[metadata->count].value = grpc_slice_from_copied_buffer(Z_STRVAL_P(value), Z_STRLEN_P(value));
+      metadata->metadata[metadata->count].key =
+        grpc_slice_from_copied_string(key1);
+      metadata->metadata[metadata->count].value =
+        grpc_slice_from_copied_buffer(Z_STRVAL_P(value), Z_STRLEN_P(value));
       metadata->count += 1;
     PHP_GRPC_HASH_FOREACH_END()
   PHP_GRPC_HASH_FOREACH_END()
@@ -233,7 +237,8 @@ PHP_METHOD(Call, __construct) {
       grpc_slice_from_copied_string(host_override) : grpc_empty_slice();
   call->wrapped =
     grpc_channel_create_call(channel->wrapped, NULL, GRPC_PROPAGATE_DEFAULTS,
-                             completion_queue, method_slice, host_override != NULL ? &host_slice : NULL,
+                             completion_queue, method_slice,
+                             host_override != NULL ? &host_slice : NULL,
                              deadline->wrapped, NULL);
   grpc_slice_unref(method_slice);
   grpc_slice_unref(host_slice);
@@ -384,8 +389,10 @@ PHP_METHOD(Call, startBatch) {
                                1 TSRMLS_CC);
           goto cleanup;
         }
-        send_status_details = grpc_slice_from_copied_string(Z_STRVAL_P(inner_value));
-        ops[op_num].data.send_status_from_server.status_details = &send_status_details;
+        send_status_details = grpc_slice_from_copied_string(
+          Z_STRVAL_P(inner_value));
+        ops[op_num].data.send_status_from_server.status_details =
+          &send_status_details;
       } else {
         zend_throw_exception(spl_ce_InvalidArgumentException,
                              "String status details is required",
@@ -557,12 +564,33 @@ PHP_METHOD(Call, setCredentials) {
   RETURN_LONG(error);
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_construct, 0, 0, 3)
+  ZEND_ARG_INFO(0, channel)
+  ZEND_ARG_INFO(0, method)
+  ZEND_ARG_INFO(0, deadline)
+  ZEND_ARG_INFO(0, host_override)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_startBatch, 0, 0, 1)
+  ZEND_ARG_INFO(0, ops)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_getPeer, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_cancel, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_setCredentials, 0, 0, 1)
+  ZEND_ARG_INFO(0, credentials)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry call_methods[] = {
-  PHP_ME(Call, __construct, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
-  PHP_ME(Call, startBatch, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Call, getPeer, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Call, cancel, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Call, setCredentials, NULL, ZEND_ACC_PUBLIC)
+  PHP_ME(Call, __construct, arginfo_construct, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
+  PHP_ME(Call, startBatch, arginfo_startBatch, ZEND_ACC_PUBLIC)
+  PHP_ME(Call, getPeer, arginfo_getPeer, ZEND_ACC_PUBLIC)
+  PHP_ME(Call, cancel, arginfo_cancel, ZEND_ACC_PUBLIC)
+  PHP_ME(Call, setCredentials, arginfo_setCredentials, ZEND_ACC_PUBLIC)
   PHP_FE_END
 };
 
diff --git a/src/php/ext/grpc/call_credentials.c b/src/php/ext/grpc/call_credentials.c
index 043817facd..625c0c62ae 100644
--- a/src/php/ext/grpc/call_credentials.c
+++ b/src/php/ext/grpc/call_credentials.c
@@ -212,10 +212,19 @@ void plugin_destroy_state(void *ptr) {
   efree(state);
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createComposite, 0, 0, 2)
+  ZEND_ARG_INFO(0, creds1)
+  ZEND_ARG_INFO(0, creds2)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createFromPlugin, 0, 0, 1)
+  ZEND_ARG_INFO(0, callback)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry call_credentials_methods[] = {
-  PHP_ME(CallCredentials, createComposite, NULL,
+  PHP_ME(CallCredentials, createComposite, arginfo_createComposite,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(CallCredentials, createFromPlugin, NULL,
+  PHP_ME(CallCredentials, createFromPlugin, arginfo_createFromPlugin,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
   PHP_FE_END
 };
diff --git a/src/php/ext/grpc/channel.c b/src/php/ext/grpc/channel.c
index 4ce4f307b0..c26fe4a6fb 100644
--- a/src/php/ext/grpc/channel.c
+++ b/src/php/ext/grpc/channel.c
@@ -243,12 +243,37 @@ PHP_METHOD(Channel, close) {
   }
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_construct, 0, 0, 2)
+  ZEND_ARG_INFO(0, target)
+  ZEND_ARG_INFO(0, args)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_getTarget, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_getConnectivityState, 0, 0, 0)
+  ZEND_ARG_INFO(0, try_to_connect)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_watchConnectivityState, 0, 0, 2)
+  ZEND_ARG_INFO(0, last_state)
+  ZEND_ARG_INFO(0, deadline)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_close, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry channel_methods[] = {
-  PHP_ME(Channel, __construct, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
-  PHP_ME(Channel, getTarget, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Channel, getConnectivityState, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Channel, watchConnectivityState, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Channel, close, NULL, ZEND_ACC_PUBLIC)
+  PHP_ME(Channel, __construct, arginfo_construct,
+         ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
+  PHP_ME(Channel, getTarget, arginfo_getTarget,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Channel, getConnectivityState, arginfo_getConnectivityState,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Channel, watchConnectivityState, arginfo_watchConnectivityState,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Channel, close, arginfo_close,
+         ZEND_ACC_PUBLIC)
   PHP_FE_END
 };
 
diff --git a/src/php/ext/grpc/channel_credentials.c b/src/php/ext/grpc/channel_credentials.c
index 36a8223b88..2160a548c3 100644
--- a/src/php/ext/grpc/channel_credentials.c
+++ b/src/php/ext/grpc/channel_credentials.c
@@ -199,16 +199,37 @@ PHP_METHOD(ChannelCredentials, createInsecure) {
   RETURN_NULL();
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_setDefaultRootsPem, 0, 0, 1)
+  ZEND_ARG_INFO(0, pem_roots)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createDefault, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createSsl, 0, 0, 0)
+  ZEND_ARG_INFO(0, pem_root_certs)
+  ZEND_ARG_INFO(0, pem_private_key)
+  ZEND_ARG_INFO(0, pem_cert_chain)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createComposite, 0, 0, 2)
+  ZEND_ARG_INFO(0, channel_creds)
+  ZEND_ARG_INFO(0, call_creds)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createInsecure, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry channel_credentials_methods[] = {
-  PHP_ME(ChannelCredentials, setDefaultRootsPem, NULL,
+  PHP_ME(ChannelCredentials, setDefaultRootsPem, arginfo_setDefaultRootsPem,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(ChannelCredentials, createDefault, NULL,
+  PHP_ME(ChannelCredentials, createDefault, arginfo_createDefault,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(ChannelCredentials, createSsl, NULL,
+  PHP_ME(ChannelCredentials, createSsl, arginfo_createSsl,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(ChannelCredentials, createComposite, NULL,
+  PHP_ME(ChannelCredentials, createComposite, arginfo_createComposite,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(ChannelCredentials, createInsecure, NULL,
+  PHP_ME(ChannelCredentials, createInsecure, arginfo_createInsecure,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
   PHP_FE_END
 };
diff --git a/src/php/ext/grpc/server.c b/src/php/ext/grpc/server.c
index 9ac5d2a3c3..87780e997e 100644
--- a/src/php/ext/grpc/server.c
+++ b/src/php/ext/grpc/server.c
@@ -116,8 +116,6 @@ PHP_METHOD(Server, __construct) {
 
 /**
  * Request a call on a server. Creates a single GRPC_SERVER_RPC_NEW event.
- * @param long $tag_new The tag to associate with the new request
- * @param long $tag_cancel The tag to use if the call is cancelled
  * @return void
  */
 PHP_METHOD(Server, requestCall) {
@@ -239,12 +237,36 @@ PHP_METHOD(Server, start) {
   grpc_server_start(server->wrapped);
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_construct, 0, 0, 0)
+  ZEND_ARG_INFO(0, args)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_requestCall, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_addHttp2Port, 0, 0, 1)
+  ZEND_ARG_INFO(0, addr)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_addSecureHttp2Port, 0, 0, 2)
+  ZEND_ARG_INFO(0, addr)
+  ZEND_ARG_INFO(0, server_creds)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_start, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry server_methods[] = {
-  PHP_ME(Server, __construct, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
-  PHP_ME(Server, requestCall, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Server, addHttp2Port, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Server, addSecureHttp2Port, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Server, start, NULL, ZEND_ACC_PUBLIC)
+  PHP_ME(Server, __construct, arginfo_construct,
+         ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
+  PHP_ME(Server, requestCall, arginfo_requestCall,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Server, addHttp2Port, arginfo_addHttp2Port,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Server, addSecureHttp2Port, arginfo_addSecureHttp2Port,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Server, start, arginfo_start,
+         ZEND_ACC_PUBLIC)
   PHP_FE_END
 };
 
diff --git a/src/php/ext/grpc/server_credentials.c b/src/php/ext/grpc/server_credentials.c
index 3e39fee246..ec29dfdc7c 100644
--- a/src/php/ext/grpc/server_credentials.c
+++ b/src/php/ext/grpc/server_credentials.c
@@ -117,8 +117,14 @@ PHP_METHOD(ServerCredentials, createSsl) {
   RETURN_DESTROY_ZVAL(creds_object);
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_createSsl, 0, 0, 3)
+  ZEND_ARG_INFO(0, pem_root_certs)
+  ZEND_ARG_INFO(0, pem_private_key)
+  ZEND_ARG_INFO(0, pem_cert_chain)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry server_credentials_methods[] = {
-  PHP_ME(ServerCredentials, createSsl, NULL,
+  PHP_ME(ServerCredentials, createSsl, arginfo_createSsl,
          ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
   PHP_FE_END
  };
diff --git a/src/php/ext/grpc/timeval.c b/src/php/ext/grpc/timeval.c
index 7ada915aad..78c29e385b 100644
--- a/src/php/ext/grpc/timeval.c
+++ b/src/php/ext/grpc/timeval.c
@@ -245,17 +245,65 @@ PHP_METHOD(Timeval, sleepUntil) {
   gpr_sleep_until(this->wrapped);
 }
 
+ZEND_BEGIN_ARG_INFO_EX(arginfo_construct, 0, 0, 1)
+  ZEND_ARG_INFO(0, microseconds)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_add, 0, 0, 1)
+  ZEND_ARG_INFO(0, timeval)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_compare, 0, 0, 2)
+  ZEND_ARG_INFO(0, a_timeval)
+  ZEND_ARG_INFO(0, b_timeval)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_infFuture, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_infPast, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_now, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_similar, 0, 0, 3)
+  ZEND_ARG_INFO(0, a_timeval)
+  ZEND_ARG_INFO(0, b_timeval)
+  ZEND_ARG_INFO(0, threshold_timeval)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_sleepUntil, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_subtract, 0, 0, 1)
+  ZEND_ARG_INFO(0, timeval)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_INFO_EX(arginfo_zero, 0, 0, 0)
+ZEND_END_ARG_INFO()
+
 static zend_function_entry timeval_methods[] = {
-  PHP_ME(Timeval, __construct, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
-  PHP_ME(Timeval, add, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Timeval, compare, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(Timeval, infFuture, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(Timeval, infPast, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(Timeval, now, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(Timeval, similar, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
-  PHP_ME(Timeval, sleepUntil, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Timeval, subtract, NULL, ZEND_ACC_PUBLIC)
-  PHP_ME(Timeval, zero, NULL, ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, __construct, arginfo_construct,
+         ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
+  PHP_ME(Timeval, add, arginfo_add,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Timeval, compare, arginfo_compare,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, infFuture, arginfo_infFuture,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, infPast, arginfo_infPast,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, now, arginfo_now,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, similar, arginfo_similar,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
+  PHP_ME(Timeval, sleepUntil, arginfo_sleepUntil,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Timeval, subtract, arginfo_subtract,
+         ZEND_ACC_PUBLIC)
+  PHP_ME(Timeval, zero, arginfo_zero,
+         ZEND_ACC_PUBLIC | ZEND_ACC_STATIC)
   PHP_FE_END
 };
 
diff --git a/src/proto/grpc/health/v1/health.options b/src/proto/grpc/health/v1/health.options
new file mode 100644
index 0000000000..240b498b58
--- /dev/null
+++ b/src/proto/grpc/health/v1/health.options
@@ -0,0 +1 @@
+grpc.health.v1.HealthCheckRequest.service max_size:200
diff --git a/src/python/grpcio_tests/tests/interop/client.py b/src/python/grpcio_tests/tests/interop/client.py
index 833818e662..97f6843d3c 100644
--- a/src/python/grpcio_tests/tests/interop/client.py
+++ b/src/python/grpcio_tests/tests/interop/client.py
@@ -45,7 +45,7 @@ def _args():
         '--server_host',
         help='the host to which to connect',
         type=str,
-        default="127.0.0.1")
+        default="localhost")
     parser.add_argument(
         '--server_port', help='the port to which to connect', type=int)
     parser.add_argument(
diff --git a/src/ruby/lib/grpc/generic/client_stub.rb b/src/ruby/lib/grpc/generic/client_stub.rb
index 6934257cbc..d8de0beefb 100644
--- a/src/ruby/lib/grpc/generic/client_stub.rb
+++ b/src/ruby/lib/grpc/generic/client_stub.rb
@@ -84,7 +84,7 @@ module GRPC
     # channel:
     #
     # - :channel_override
-    # when present, this must be a pre-created GRPC::Channel.  If it's
+    # when present, this must be a pre-created GRPC::Core::Channel.  If it's
     # present the host and arbitrary keyword arg areignored, and the RPC
     # connection uses this channel.
     #