Merge branch 'slice_interning' into eliminate_mdstr

62 files changed, 797 insertions, 2408 deletions

diff --git a/src/core/ext/census/census_log.h b/src/core/ext/census/census_log.h
index 534ecc5705..1b185a53b9 100644
--- a/src/core/ext/census/census_log.h
+++ b/src/core/ext/census/census_log.h
@@ -84,7 +84,7 @@ const void *census_log_read_next(size_t *bytes_available);
 */
 size_t census_log_remaining_space(void);
 
-/* Returns the number of times gprc_stats_log_start_write() failed due to
+/* Returns the number of times grpc_stats_log_start_write() failed due to
    out-of-space. */
 int census_log_out_of_space_count(void);
 
diff --git a/src/core/ext/census/mlog.h b/src/core/ext/census/mlog.h
index a256426f91..18805ad994 100644
--- a/src/core/ext/census/mlog.h
+++ b/src/core/ext/census/mlog.h
@@ -88,7 +88,7 @@ const void* census_log_read_next(size_t* bytes_available);
 */
 size_t census_log_remaining_space(void);
 
-/* Returns the number of times gprc_stats_log_start_write() failed due to
+/* Returns the number of times grpc_stats_log_start_write() failed due to
    out-of-space. */
 int64_t census_log_out_of_space_count(void);
 
diff --git a/src/core/ext/client_channel/client_channel.c b/src/core/ext/client_channel/client_channel.c
index 94ca656b2a..011a8411aa 100644
--- a/src/core/ext/client_channel/client_channel.c
+++ b/src/core/ext/client_channel/client_channel.c
@@ -645,7 +645,7 @@ static void subchannel_ready(grpc_exec_ctx *exec_ctx, void *arg,
     grpc_subchannel_call *subchannel_call = NULL;
     grpc_error *new_error = grpc_connected_subchannel_create_call(
         exec_ctx, calld->connected_subchannel, calld->pollent, calld->path,
-        calld->deadline, &subchannel_call);
+        calld->call_start_time, calld->deadline, &subchannel_call);
     if (new_error != GRPC_ERROR_NONE) {
       new_error = grpc_error_add_child(new_error, error);
       subchannel_call = CANCELLED_CALL;
@@ -898,7 +898,7 @@ retry:
     grpc_subchannel_call *subchannel_call = NULL;
     grpc_error *error = grpc_connected_subchannel_create_call(
         exec_ctx, calld->connected_subchannel, calld->pollent, calld->path,
-        calld->deadline, &subchannel_call);
+        calld->call_start_time, calld->deadline, &subchannel_call);
     if (error != GRPC_ERROR_NONE) {
       subchannel_call = CANCELLED_CALL;
       fail_locked(exec_ctx, calld, GRPC_ERROR_REF(error));
diff --git a/src/core/ext/client_channel/subchannel.c b/src/core/ext/client_channel/subchannel.c
index 7b64a76f67..063b79cece 100644
--- a/src/core/ext/client_channel/subchannel.c
+++ b/src/core/ext/client_channel/subchannel.c
@@ -703,15 +703,15 @@ grpc_connected_subchannel *grpc_subchannel_get_connected_subchannel(
 
 grpc_error *grpc_connected_subchannel_create_call(
     grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *con,
-    grpc_polling_entity *pollent, grpc_slice path, gpr_timespec deadline,
-    grpc_subchannel_call **call) {
+    grpc_polling_entity *pollent, grpc_slice path, gpr_timespec start_time,
+    gpr_timespec deadline, grpc_subchannel_call **call) {
   grpc_channel_stack *chanstk = CHANNEL_STACK_FROM_CONNECTION(con);
   *call = gpr_malloc(sizeof(grpc_subchannel_call) + chanstk->call_stack_size);
   grpc_call_stack *callstk = SUBCHANNEL_CALL_TO_CALL_STACK(*call);
   (*call)->connection = con;  // Ref is added below.
   grpc_error *error =
       grpc_call_stack_init(exec_ctx, chanstk, 1, subchannel_call_destroy, *call,
-                           NULL, NULL, path, deadline, callstk);
+                           NULL, NULL, path, start_time, deadline, callstk);
   if (error != GRPC_ERROR_NONE) {
     const char *error_string = grpc_error_string(error);
     gpr_log(GPR_ERROR, "error: %s", error_string);
diff --git a/src/core/ext/client_channel/subchannel.h b/src/core/ext/client_channel/subchannel.h
index 17208cb853..e7a5bb4bbd 100644
--- a/src/core/ext/client_channel/subchannel.h
+++ b/src/core/ext/client_channel/subchannel.h
@@ -111,8 +111,8 @@ void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
 /** construct a subchannel call */
 grpc_error *grpc_connected_subchannel_create_call(
     grpc_exec_ctx *exec_ctx, grpc_connected_subchannel *connected_subchannel,
-    grpc_polling_entity *pollent, grpc_slice path, gpr_timespec deadline,
-    grpc_subchannel_call **subchannel_call);
+    grpc_polling_entity *pollent, grpc_slice path, gpr_timespec start_time,
+    gpr_timespec deadline, grpc_subchannel_call **subchannel_call);
 
 /** process a transport level op */
 void grpc_connected_subchannel_process_transport_op(
diff --git a/src/core/ext/lb_policy/grpclb/grpclb.c b/src/core/ext/lb_policy/grpclb/grpclb.c
index 37b232a0a4..3e5c039fdd 100644
--- a/src/core/ext/lb_policy/grpclb/grpclb.c
+++ b/src/core/ext/lb_policy/grpclb/grpclb.c
@@ -762,17 +762,24 @@ static void glb_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   if (glb_policy->rr_policy) {
     GRPC_LB_POLICY_UNREF(exec_ctx, glb_policy->rr_policy, "glb_shutdown");
   }
-  if (glb_policy->started_picking) {
-    if (glb_policy->lb_call != NULL) {
-      grpc_call_cancel(glb_policy->lb_call, NULL);
-      /* lb_on_server_status_received will pick up the cancel and clean up */
-    }
-  }
   grpc_connectivity_state_set(
       exec_ctx, &glb_policy->state_tracker, GRPC_CHANNEL_SHUTDOWN,
       GRPC_ERROR_CREATE("Channel Shutdown"), "glb_shutdown");
+  /* We need a copy of the lb_call pointer because we can't cancell the call
+   * while holding glb_policy->mu: lb_on_server_status_received, invoked due to
+   * the cancel, needs to acquire that same lock */
+  grpc_call *lb_call = glb_policy->lb_call;
+  glb_policy->lb_call = NULL;
   gpr_mu_unlock(&glb_policy->mu);
 
+  /* glb_policy->lb_call and this local lb_call must be consistent at this point
+   * because glb_policy->lb_call is only assigned in lb_call_init_locked as part
+   * of query_for_backends_locked, which can only be invoked while
+   * glb_policy->shutting_down is false. */
+  if (lb_call != NULL) {
+    grpc_call_cancel(lb_call, NULL);
+    /* lb_on_server_status_received will pick up the cancel and clean up */
+  }
   while (pp != NULL) {
     pending_pick *next = pp->next;
     *pp->target = NULL;
@@ -956,9 +963,11 @@ static void lb_on_server_status_received(grpc_exec_ctx *exec_ctx, void *arg,
                                          grpc_error *error);
 static void lb_on_response_received(grpc_exec_ctx *exec_ctx, void *arg,
                                     grpc_error *error);
-static void lb_call_init(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy) {
+static void lb_call_init_locked(grpc_exec_ctx *exec_ctx,
+                                glb_lb_policy *glb_policy) {
   GPR_ASSERT(glb_policy->server_name != NULL);
   GPR_ASSERT(glb_policy->server_name[0] != '\0');
+  GPR_ASSERT(!glb_policy->shutting_down);
 
   /* Note the following LB call progresses every time there's activity in \a
    * glb_policy->base.interested_parties, which is comprised of the polling
@@ -1011,7 +1020,9 @@ static void lb_call_destroy_locked(glb_lb_policy *glb_policy) {
 static void query_for_backends_locked(grpc_exec_ctx *exec_ctx,
                                       glb_lb_policy *glb_policy) {
   GPR_ASSERT(glb_policy->lb_channel != NULL);
-  lb_call_init(exec_ctx, glb_policy);
+  if (glb_policy->shutting_down) return;
+
+  lb_call_init_locked(exec_ctx, glb_policy);
 
   if (grpc_lb_glb_trace) {
     gpr_log(GPR_INFO, "Query for backends (grpclb: %p, lb_call: %p)",
@@ -1156,8 +1167,8 @@ static void lb_on_response_received(grpc_exec_ctx *exec_ctx, void *arg,
     }
     gpr_mu_unlock(&glb_policy->mu);
   } else { /* empty payload: call cancelled. */
-    /* dispose of the "lb_on_response_received" weak ref taken in
-     * query_for_backends_locked() and reused in every reception loop */
+           /* dispose of the "lb_on_response_received" weak ref taken in
+            * query_for_backends_locked() and reused in every reception loop */
     gpr_mu_unlock(&glb_policy->mu);
     GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &glb_policy->base,
                               "lb_on_response_received_empty_payload");
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 ac3c6a305a..c69f773e78 100644
--- a/src/core/ext/lb_policy/pick_first/pick_first.c
+++ b/src/core/ext/lb_policy/pick_first/pick_first.c
@@ -292,6 +292,8 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
   } else {
   loop:
     switch (p->checking_connectivity) {
+      case GRPC_CHANNEL_INIT:
+        GPR_UNREACHABLE_CODE(return );
       case GRPC_CHANNEL_READY:
         grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
                                     GRPC_CHANNEL_READY, GRPC_ERROR_NONE,
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 e101c0369c..f93dd078ce 100644
--- a/src/core/ext/lb_policy/round_robin/round_robin.c
+++ b/src/core/ext/lb_policy/round_robin/round_robin.c
@@ -116,8 +116,13 @@ typedef struct {
   grpc_closure connectivity_changed_closure;
   /** this subchannels current position in subchannel->ready_list */
   ready_list *ready_list_node;
-  /** last observed connectivity */
-  grpc_connectivity_state connectivity_state;
+  /** last observed connectivity. Not updated by
+   * \a grpc_subchannel_notify_on_state_change. Used to determine the previous
+   * state while processing the new state in \a rr_connectivity_changed */
+  grpc_connectivity_state prev_connectivity_state;
+  /** current connectivity state. Updated by \a
+   * grpc_subchannel_notify_on_state_change */
+  grpc_connectivity_state curr_connectivity_state;
   /** the subchannel's target user data */
   void *user_data;
   /** vtable to operate over \a user_data */
@@ -127,6 +132,7 @@ typedef struct {
 struct round_robin_lb_policy {
   /** base policy: must be first */
   grpc_lb_policy base;
+  gpr_mu mu;
 
   /** total number of addresses received at creation time */
   size_t num_addresses;
@@ -135,8 +141,11 @@ struct round_robin_lb_policy {
   size_t num_subchannels;
   subchannel_data **subchannels;
 
-  /** mutex protecting remaining members */
-  gpr_mu mu;
+  /** how many subchannels are in TRANSIENT_FAILURE */
+  size_t num_transient_failures;
+  /** how many subchannels are IDLE */
+  size_t num_idle;
+
   /** have we started picking? */
   int started_picking;
   /** are we shutting down? */
@@ -258,6 +267,10 @@ static void remove_disconnected_sc_locked(round_robin_lb_policy *p,
   gpr_free(node);
 }
 
+static bool is_ready_list_empty(round_robin_lb_policy *p) {
+  return p->ready_list.prev == NULL;
+}
+
 static void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
   round_robin_lb_policy *p = (round_robin_lb_policy *)pol;
   ready_list *elem;
@@ -268,7 +281,7 @@ static void rr_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
 
   for (size_t i = 0; i < p->num_subchannels; i++) {
     subchannel_data *sd = p->subchannels[i];
-    GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin_destroy");
+    GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "rr_destroy");
     if (sd->user_data != NULL) {
       GPR_ASSERT(sd->user_data_vtable != NULL);
       sd->user_data_vtable->destroy(exec_ctx, sd->user_data);
@@ -381,18 +394,18 @@ static void start_picking(grpc_exec_ctx *exec_ctx, round_robin_lb_policy *p) {
   size_t i;
   p->started_picking = 1;
 
-  if (grpc_lb_round_robin_trace) {
-    gpr_log(GPR_DEBUG, "LB_POLICY: p=%p num_subchannels=%" PRIuPTR, (void *)p,
-            p->num_subchannels);
-  }
-
   for (i = 0; i < p->num_subchannels; i++) {
     subchannel_data *sd = p->subchannels[i];
-    sd->connectivity_state = GRPC_CHANNEL_IDLE;
+    /* use some sentinel value outside of the range of grpc_connectivity_state
+     * to signal an undefined previous state. We won't be referring to this
+     * value again and it'll be overwritten after the first call to
+     * rr_connectivity_changed */
+    sd->prev_connectivity_state = GRPC_CHANNEL_INIT;
+    sd->curr_connectivity_state = GRPC_CHANNEL_IDLE;
+    GRPC_LB_POLICY_WEAK_REF(&p->base, "rr_connectivity");
     grpc_subchannel_notify_on_state_change(
         exec_ctx, sd->subchannel, p->base.interested_parties,
-        &sd->connectivity_state, &sd->connectivity_changed_closure);
-    GRPC_LB_POLICY_WEAK_REF(&p->base, "round_robin_connectivity");
+        &sd->curr_connectivity_state, &sd->connectivity_changed_closure);
   }
 }
 
@@ -422,7 +435,7 @@ static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     /* readily available, report right away */
     *target = GRPC_CONNECTED_SUBCHANNEL_REF(
         grpc_subchannel_get_connected_subchannel(selected->subchannel),
-        "picked");
+        "rr_picked");
 
     if (user_data != NULL) {
       *user_data = selected->user_data;
@@ -453,125 +466,184 @@ static int rr_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
   }
 }
 
+static void update_state_counters(subchannel_data *sd) {
+  round_robin_lb_policy *p = sd->policy;
+
+  /* update p->num_transient_failures (resp. p->num_idle): if the previous
+   * state was TRANSIENT_FAILURE (resp. IDLE), decrement
+   * p->num_transient_failures (resp. p->num_idle). */
+  if (sd->prev_connectivity_state == GRPC_CHANNEL_TRANSIENT_FAILURE) {
+    GPR_ASSERT(p->num_transient_failures > 0);
+    --p->num_transient_failures;
+  } else if (sd->prev_connectivity_state == GRPC_CHANNEL_IDLE) {
+    GPR_ASSERT(p->num_idle > 0);
+    --p->num_idle;
+  }
+}
+
+/* sd is the subchannel_data associted with the updated subchannel.
+ * shutdown_error will only be used upon policy transition to TRANSIENT_FAILURE
+ * or SHUTDOWN */
+static grpc_connectivity_state update_lb_connectivity_status(
+    grpc_exec_ctx *exec_ctx, subchannel_data *sd, grpc_error *error) {
+  /* In priority order. The first rule to match terminates the search (ie, if we
+   * are on rule n, all previous rules were unfulfilled).
+   *
+   * 1) RULE: ANY subchannel is READY => policy is READY.
+   *    CHECK: At least one subchannel is ready iff p->ready_list is NOT empty.
+   *
+   * 2) RULE: ANY subchannel is CONNECTING => policy is CONNECTING.
+   *    CHECK: sd->curr_connectivity_state == CONNECTING.
+   *
+   * 3) RULE: ALL subchannels are SHUTDOWN => policy is SHUTDOWN.
+   *    CHECK: p->num_subchannels = 0.
+   *
+   * 4) RULE: ALL subchannels are TRANSIENT_FAILURE => policy is
+   *    TRANSIENT_FAILURE.
+   *    CHECK: p->num_transient_failures == p->num_subchannels.
+   *
+   * 5) RULE: ALL subchannels are IDLE => policy is IDLE.
+   *    CHECK: p->num_idle == p->num_subchannels.
+   */
+  round_robin_lb_policy *p = sd->policy;
+  if (!is_ready_list_empty(p)) { /* 1) READY */
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker, GRPC_CHANNEL_READY,
+                                GRPC_ERROR_NONE, "rr_ready");
+    return GRPC_CHANNEL_READY;
+  } else if (sd->curr_connectivity_state ==
+             GRPC_CHANNEL_CONNECTING) { /* 2) CONNECTING */
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                GRPC_CHANNEL_CONNECTING, GRPC_ERROR_NONE,
+                                "rr_connecting");
+    return GRPC_CHANNEL_CONNECTING;
+  } else if (p->num_subchannels == 0) { /* 3) SHUTDOWN */
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                GRPC_CHANNEL_SHUTDOWN, GRPC_ERROR_REF(error),
+                                "rr_shutdown");
+    return GRPC_CHANNEL_SHUTDOWN;
+  } else if (p->num_transient_failures ==
+             p->num_subchannels) { /* 4) TRANSIENT_FAILURE */
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
+                                GRPC_CHANNEL_TRANSIENT_FAILURE,
+                                GRPC_ERROR_REF(error), "rr_transient_failure");
+    return GRPC_CHANNEL_TRANSIENT_FAILURE;
+  } else if (p->num_idle == p->num_subchannels) { /* 5) IDLE */
+    grpc_connectivity_state_set(exec_ctx, &p->state_tracker, GRPC_CHANNEL_IDLE,
+                                GRPC_ERROR_NONE, "rr_idle");
+    return GRPC_CHANNEL_IDLE;
+  }
+  /* no change */
+  return sd->curr_connectivity_state;
+}
+
 static void rr_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                     grpc_error *error) {
   subchannel_data *sd = arg;
   round_robin_lb_policy *p = sd->policy;
   pending_pick *pp;
 
-  int unref = 0;
-
   GRPC_ERROR_REF(error);
   gpr_mu_lock(&p->mu);
 
   if (p->shutdown) {
-    unref = 1;
-  } else {
-    switch (sd->connectivity_state) {
-      case GRPC_CHANNEL_READY:
-        grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
-                                    GRPC_CHANNEL_READY, GRPC_ERROR_REF(error),
-                                    "connecting_ready");
-        /* add the newly connected subchannel to the list of connected ones.
-         * Note that it goes to the "end of the line". */
-        sd->ready_list_node = add_connected_sc_locked(p, sd);
-        /* at this point we know there's at least one suitable subchannel. Go
-         * ahead and pick one and notify the pending suitors in
-         * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
-        ready_list *selected = peek_next_connected_locked(p);
-        GPR_ASSERT(selected != NULL);
-        if (p->pending_picks != NULL) {
-          /* if the selected subchannel is going to be used for the pending
-           * picks, update the last picked pointer */
-          advance_last_picked_locked(p);
+    gpr_mu_unlock(&p->mu);
+    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "rr_connectivity");
+    GRPC_ERROR_UNREF(error);
+    return;
+  }
+  switch (sd->curr_connectivity_state) {
+    case GRPC_CHANNEL_INIT:
+      GPR_UNREACHABLE_CODE(return );
+    case GRPC_CHANNEL_READY:
+      /* add the newly connected subchannel to the list of connected ones.
+       * Note that it goes to the "end of the line". */
+      sd->ready_list_node = add_connected_sc_locked(p, sd);
+      /* at this point we know there's at least one suitable subchannel. Go
+       * ahead and pick one and notify the pending suitors in
+       * p->pending_picks. This preemtively replicates rr_pick()'s actions. */
+      ready_list *selected = peek_next_connected_locked(p);
+      GPR_ASSERT(selected != NULL);
+      if (p->pending_picks != NULL) {
+        /* if the selected subchannel is going to be used for the pending
+         * picks, update the last picked pointer */
+        advance_last_picked_locked(p);
+      }
+      while ((pp = p->pending_picks)) {
+        p->pending_picks = pp->next;
+        *pp->target = GRPC_CONNECTED_SUBCHANNEL_REF(
+            grpc_subchannel_get_connected_subchannel(selected->subchannel),
+            "rr_picked");
+        if (pp->user_data != NULL) {
+          *pp->user_data = selected->user_data;
         }
-
+        if (grpc_lb_round_robin_trace) {
+          gpr_log(GPR_DEBUG,
+                  "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
+                  (void *)selected->subchannel, (void *)selected);
+        }
+        grpc_exec_ctx_sched(exec_ctx, pp->on_complete, GRPC_ERROR_NONE, NULL);
+        gpr_free(pp);
+      }
+      update_lb_connectivity_status(exec_ctx, sd, error);
+      sd->prev_connectivity_state = sd->curr_connectivity_state;
+      /* renew notification: reuses the "rr_connectivity" weak ref */
+      grpc_subchannel_notify_on_state_change(
+          exec_ctx, sd->subchannel, p->base.interested_parties,
+          &sd->curr_connectivity_state, &sd->connectivity_changed_closure);
+      break;
+    case GRPC_CHANNEL_IDLE:
+      ++p->num_idle;
+    /* fallthrough */
+    case GRPC_CHANNEL_CONNECTING:
+      update_state_counters(sd);
+      update_lb_connectivity_status(exec_ctx, sd, error);
+      sd->prev_connectivity_state = sd->curr_connectivity_state;
+      /* renew notification: reuses the "rr_connectivity" weak ref */
+      grpc_subchannel_notify_on_state_change(
+          exec_ctx, sd->subchannel, p->base.interested_parties,
+          &sd->curr_connectivity_state, &sd->connectivity_changed_closure);
+      break;
+    case GRPC_CHANNEL_TRANSIENT_FAILURE:
+      ++p->num_transient_failures;
+      /* remove from ready list if still present */
+      if (sd->ready_list_node != NULL) {
+        remove_disconnected_sc_locked(p, sd->ready_list_node);
+        sd->ready_list_node = NULL;
+      }
+      update_lb_connectivity_status(exec_ctx, sd, error);
+      sd->prev_connectivity_state = sd->curr_connectivity_state;
+      /* renew notification: reuses the "rr_connectivity" weak ref */
+      grpc_subchannel_notify_on_state_change(
+          exec_ctx, sd->subchannel, p->base.interested_parties,
+          &sd->curr_connectivity_state, &sd->connectivity_changed_closure);
+      break;
+    case GRPC_CHANNEL_SHUTDOWN:
+      update_state_counters(sd);
+      if (sd->ready_list_node != NULL) {
+        remove_disconnected_sc_locked(p, sd->ready_list_node);
+        sd->ready_list_node = NULL;
+      }
+      --p->num_subchannels;
+      GPR_SWAP(subchannel_data *, p->subchannels[sd->index],
+               p->subchannels[p->num_subchannels]);
+      GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "rr_subchannel_shutdown");
+      p->subchannels[sd->index]->index = sd->index;
+      if (update_lb_connectivity_status(exec_ctx, sd, error) ==
+          GRPC_CHANNEL_SHUTDOWN) {
+        /* the policy is shutting down. Flush all the pending picks... */
         while ((pp = p->pending_picks)) {
           p->pending_picks = pp->next;
-
-          *pp->target = GRPC_CONNECTED_SUBCHANNEL_REF(
-              grpc_subchannel_get_connected_subchannel(selected->subchannel),
-              "picked");
-          if (pp->user_data != NULL) {
-            *pp->user_data = selected->user_data;
-          }
-          if (grpc_lb_round_robin_trace) {
-            gpr_log(GPR_DEBUG,
-                    "[RR CONN CHANGED] TARGET <-- SUBCHANNEL %p (NODE %p)",
-                    (void *)selected->subchannel, (void *)selected);
-          }
+          *pp->target = NULL;
           grpc_exec_ctx_sched(exec_ctx, pp->on_complete, GRPC_ERROR_NONE, NULL);
           gpr_free(pp);
         }
-        grpc_subchannel_notify_on_state_change(
-            exec_ctx, sd->subchannel, p->base.interested_parties,
-            &sd->connectivity_state, &sd->connectivity_changed_closure);
-        break;
-      case GRPC_CHANNEL_CONNECTING:
-      case GRPC_CHANNEL_IDLE:
-        grpc_connectivity_state_set(
-            exec_ctx, &p->state_tracker, sd->connectivity_state,
-            GRPC_ERROR_REF(error), "connecting_changed");
-        grpc_subchannel_notify_on_state_change(
-            exec_ctx, sd->subchannel, p->base.interested_parties,
-            &sd->connectivity_state, &sd->connectivity_changed_closure);
-        break;
-      case GRPC_CHANNEL_TRANSIENT_FAILURE:
-        /* renew state notification */
-        grpc_subchannel_notify_on_state_change(
-            exec_ctx, sd->subchannel, p->base.interested_parties,
-            &sd->connectivity_state, &sd->connectivity_changed_closure);
-
-        /* remove from ready list if still present */
-        if (sd->ready_list_node != NULL) {
-          remove_disconnected_sc_locked(p, sd->ready_list_node);
-          sd->ready_list_node = NULL;
-        }
-        grpc_connectivity_state_set(
-            exec_ctx, &p->state_tracker, GRPC_CHANNEL_TRANSIENT_FAILURE,
-            GRPC_ERROR_REF(error), "connecting_transient_failure");
-        break;
-      case GRPC_CHANNEL_SHUTDOWN:
-        if (sd->ready_list_node != NULL) {
-          remove_disconnected_sc_locked(p, sd->ready_list_node);
-          sd->ready_list_node = NULL;
-        }
-
-        p->num_subchannels--;
-        GPR_SWAP(subchannel_data *, p->subchannels[sd->index],
-                 p->subchannels[p->num_subchannels]);
-        GRPC_SUBCHANNEL_UNREF(exec_ctx, sd->subchannel, "round_robin");
-        p->subchannels[sd->index]->index = sd->index;
-        gpr_free(sd);
-
-        unref = 1;
-        if (p->num_subchannels == 0) {
-          grpc_connectivity_state_set(
-              exec_ctx, &p->state_tracker, GRPC_CHANNEL_SHUTDOWN,
-              GRPC_ERROR_CREATE_REFERENCING("Round Robin Channels Exhausted",
-                                            &error, 1),
-              "no_more_channels");
-          while ((pp = p->pending_picks)) {
-            p->pending_picks = pp->next;
-            *pp->target = NULL;
-            grpc_exec_ctx_sched(exec_ctx, pp->on_complete, GRPC_ERROR_NONE,
-                                NULL);
-            gpr_free(pp);
-          }
-        } else {
-          grpc_connectivity_state_set(
-              exec_ctx, &p->state_tracker, GRPC_CHANNEL_TRANSIENT_FAILURE,
-              GRPC_ERROR_REF(error), "subchannel_failed");
-        }
-    } /* switch */
-  }   /* !unref */
-
-  gpr_mu_unlock(&p->mu);
-
-  if (unref) {
-    GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "round_robin_connectivity");
+      }
+      gpr_free(sd);
+      /* unref the "rr_connectivity" weak ref from start_picking */
+      GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "rr_connectivity");
+      break;
   }
-
+  gpr_mu_unlock(&p->mu);
   GRPC_ERROR_UNREF(error);
 }
 
@@ -607,9 +679,9 @@ static void rr_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
     gpr_mu_unlock(&p->mu);
     target = GRPC_CONNECTED_SUBCHANNEL_REF(
         grpc_subchannel_get_connected_subchannel(selected->subchannel),
-        "picked");
+        "rr_picked");
     grpc_connected_subchannel_ping(exec_ctx, target, closure);
-    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, target, "picked");
+    GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, target, "rr_picked");
   } else {
     gpr_mu_unlock(&p->mu);
     grpc_exec_ctx_sched(exec_ctx, closure,
@@ -705,6 +777,11 @@ static grpc_lb_policy *round_robin_create(grpc_exec_ctx *exec_ctx,
   grpc_lb_policy_init(&p->base, &round_robin_lb_policy_vtable);
   grpc_connectivity_state_init(&p->state_tracker, GRPC_CHANNEL_IDLE,
                                "round_robin");
+
+  if (grpc_lb_round_robin_trace) {
+    gpr_log(GPR_DEBUG, "Created RR policy at %p with %lu subchannels",
+            (void *)p, (unsigned long)p->num_subchannels);
+  }
   gpr_mu_init(&p->mu);
   return &p->base;
 }
diff --git a/src/core/ext/load_reporting/load_reporting_filter.c b/src/core/ext/load_reporting/load_reporting_filter.c
index 2b08c4efec..f50e6520cd 100644
--- a/src/core/ext/load_reporting/load_reporting_filter.c
+++ b/src/core/ext/load_reporting/load_reporting_filter.c
@@ -68,7 +68,8 @@ typedef struct {
   grpc_exec_ctx *exec_ctx;
 } recv_md_filter_args;
 
-static grpc_mdelem *recv_md_filter(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *recv_md_filter(grpc_exec_ctx *exec_ctx, void *user_data,
+                                   grpc_mdelem *md) {
   recv_md_filter_args *a = user_data;
   grpc_call_element *elem = a->elem;
   call_data *calld = elem->call_data;
@@ -189,7 +190,8 @@ static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
   */
 }
 
-static grpc_mdelem *lr_trailing_md_filter(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *lr_trailing_md_filter(grpc_exec_ctx *exec_ctx,
+                                          void *user_data, grpc_mdelem *md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
 
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index 21838167e9..fac9a08584 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -1040,7 +1040,7 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
                                       "op.send_initial_metadata");
         }
       } else {
-        s->send_trailing_metadata = NULL;
+        s->send_initial_metadata = NULL;
         grpc_chttp2_complete_closure_step(
             exec_ctx, t, s, &s->send_initial_metadata_finished,
             GRPC_ERROR_CREATE(
@@ -1525,13 +1525,17 @@ static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
                                 grpc_error *error) {
   error =
       removal_error(error, s, "Pending writes failed due to stream closure");
-  s->fetching_send_message = NULL;
+  s->send_initial_metadata = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->send_initial_metadata_finished, GRPC_ERROR_REF(error),
       "send_initial_metadata_finished");
+
+  s->send_trailing_metadata = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->send_trailing_metadata_finished,
       GRPC_ERROR_REF(error), "send_trailing_metadata_finished");
+
+  s->fetching_send_message = NULL;
   grpc_chttp2_complete_closure_step(
       exec_ctx, t, s, &s->fetching_send_message_finished, GRPC_ERROR_REF(error),
       "fetching_send_message_finished");
@@ -2296,6 +2300,14 @@ static char *chttp2_get_peer(grpc_exec_ctx *exec_ctx, grpc_transport *t) {
   return gpr_strdup(((grpc_chttp2_transport *)t)->peer_string);
 }
 
+/*******************************************************************************
+ * MONITORING
+ */
+static grpc_endpoint *chttp2_get_endpoint(grpc_exec_ctx *exec_ctx,
+                                          grpc_transport *t) {
+  return ((grpc_chttp2_transport *)t)->ep;
+}
+
 static const grpc_transport_vtable vtable = {sizeof(grpc_chttp2_stream),
                                              "chttp2",
                                              init_stream,
@@ -2305,7 +2317,8 @@ static const grpc_transport_vtable vtable = {sizeof(grpc_chttp2_stream),
                                              perform_transport_op,
                                              destroy_stream,
                                              destroy_transport,
-                                             chttp2_get_peer};
+                                             chttp2_get_peer,
+                                             chttp2_get_endpoint};
 
 grpc_transport *grpc_create_chttp2_transport(
     grpc_exec_ctx *exec_ctx, const grpc_channel_args *channel_args,
diff --git a/src/core/ext/transport/chttp2/transport/parsing.c b/src/core/ext/transport/chttp2/transport/parsing.c
index 35609f08e4..b8ab987104 100644
--- a/src/core/ext/transport/chttp2/transport/parsing.c
+++ b/src/core/ext/transport/chttp2/transport/parsing.c
@@ -471,7 +471,8 @@ static void on_initial_header(grpc_exec_ctx *exec_ctx, void *tp,
                 grpc_mdstr_as_c_string(md->value));
         *cached_timeout = gpr_inf_future(GPR_TIMESPAN);
       }
-      grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
+      cached_timeout =
+          grpc_mdelem_set_user_data(md, free_timeout, cached_timeout);
     }
     grpc_chttp2_incoming_metadata_buffer_set_deadline(
         &s->metadata_buffer[0],
diff --git a/src/core/ext/transport/cronet/transport/cronet_transport.c b/src/core/ext/transport/cronet/transport/cronet_transport.c
index 2ab9a8c19d..a4c110101e 100644
--- a/src/core/ext/transport/cronet/transport/cronet_transport.c
+++ b/src/core/ext/transport/cronet/transport/cronet_transport.c
@@ -42,6 +42,7 @@
 #include <grpc/support/useful.h>
 
 #include "src/core/ext/transport/chttp2/transport/incoming_metadata.h"
+#include "src/core/lib/iomgr/endpoint.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/surface/channel.h"
@@ -1095,6 +1096,11 @@ static char *get_peer(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
   return NULL;
 }
 
+static grpc_endpoint *get_endpoint(grpc_exec_ctx *exec_ctx,
+                                   grpc_transport *gt) {
+  return NULL;
+}
+
 static void perform_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                        grpc_transport_op *op) {}
 
@@ -1107,4 +1113,5 @@ const grpc_transport_vtable grpc_cronet_vtable = {sizeof(stream_obj),
                                                   perform_op,
                                                   destroy_stream,
                                                   destroy_transport,
-                                                  get_peer};
+                                                  get_peer,
+                                                  get_endpoint};
diff --git a/src/core/lib/channel/channel_args.c b/src/core/lib/channel/channel_args.c
index c956b0febc..1a099ac437 100644
--- a/src/core/lib/channel/channel_args.c
+++ b/src/core/lib/channel/channel_args.c
@@ -300,6 +300,12 @@ uint32_t grpc_channel_args_compression_algorithm_get_states(
   }
 }
 
+grpc_channel_args *grpc_channel_args_set_socket_mutator(
+    grpc_channel_args *a, grpc_socket_mutator *mutator) {
+  grpc_arg tmp = grpc_socket_mutator_to_arg(mutator);
+  return grpc_channel_args_copy_and_add(a, &tmp, 1);
+}
+
 int grpc_channel_args_compare(const grpc_channel_args *a,
                               const grpc_channel_args *b) {
   int c = GPR_ICMP(a->num_args, b->num_args);
diff --git a/src/core/lib/channel/channel_args.h b/src/core/lib/channel/channel_args.h
index 5933133413..5c7d31f8bb 100644
--- a/src/core/lib/channel/channel_args.h
+++ b/src/core/lib/channel/channel_args.h
@@ -36,6 +36,7 @@
 
 #include <grpc/compression.h>
 #include <grpc/grpc.h>
+#include "src/core/lib/iomgr/socket_mutator.h"
 
 // Channel args are intentionally immutable, to avoid the need for locking.
 
@@ -101,6 +102,13 @@ uint32_t grpc_channel_args_compression_algorithm_get_states(
 int grpc_channel_args_compare(const grpc_channel_args *a,
                               const grpc_channel_args *b);
 
+/** Returns a channel arg instance with socket mutator added. The socket mutator
+ * will perform its mutate_fd method on all file descriptors used by the
+ * channel.
+ * If \a a is non-MULL, its args are copied. */
+grpc_channel_args *grpc_channel_args_set_socket_mutator(
+    grpc_channel_args *a, grpc_socket_mutator *mutator);
+
 /** Returns the value of argument \a name from \a args, or NULL if not found. */
 const grpc_arg *grpc_channel_args_find(const grpc_channel_args *args,
                                        const char *name);
diff --git a/src/core/lib/channel/channel_stack.c b/src/core/lib/channel/channel_stack.c
index 30e7d65d9c..0f3957d5ac 100644
--- a/src/core/lib/channel/channel_stack.c
+++ b/src/core/lib/channel/channel_stack.c
@@ -162,7 +162,8 @@ grpc_error *grpc_call_stack_init(
     grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
     int initial_refs, grpc_iomgr_cb_func destroy, void *destroy_arg,
     grpc_call_context_element *context, const void *transport_server_data,
-    grpc_slice path, gpr_timespec deadline, grpc_call_stack *call_stack) {
+    grpc_slice path, gpr_timespec start_time, gpr_timespec deadline,
+    grpc_call_stack *call_stack) {
   grpc_channel_element *channel_elems = CHANNEL_ELEMS_FROM_STACK(channel_stack);
   grpc_call_element_args args;
   size_t count = channel_stack->count;
@@ -179,7 +180,7 @@ grpc_error *grpc_call_stack_init(
 
   /* init per-filter data */
   grpc_error *first_error = GRPC_ERROR_NONE;
-  args.start_time = gpr_now(GPR_CLOCK_MONOTONIC);
+  args.start_time = start_time;
   for (i = 0; i < count; i++) {
     args.call_stack = call_stack;
     args.server_transport_data = transport_server_data;
diff --git a/src/core/lib/channel/channel_stack.h b/src/core/lib/channel/channel_stack.h
index 17ec027305..376756533b 100644
--- a/src/core/lib/channel/channel_stack.h
+++ b/src/core/lib/channel/channel_stack.h
@@ -231,7 +231,8 @@ grpc_error *grpc_call_stack_init(
     grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
     int initial_refs, grpc_iomgr_cb_func destroy, void *destroy_arg,
     grpc_call_context_element *context, const void *transport_server_data,
-    grpc_slice path, gpr_timespec deadline, grpc_call_stack *call_stack);
+    grpc_slice path, gpr_timespec start_time, gpr_timespec deadline,
+    grpc_call_stack *call_stack);
 /* Set a pollset or a pollset_set for a call stack: must occur before the first
  * op is started */
 void grpc_call_stack_set_pollset_or_pollset_set(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/channel/compress_filter.c b/src/core/lib/channel/compress_filter.c
index f58ab42d53..96564757b4 100644
--- a/src/core/lib/channel/compress_filter.c
+++ b/src/core/lib/channel/compress_filter.c
@@ -84,7 +84,8 @@ typedef struct channel_data {
 /** For each \a md element from the incoming metadata, filter out the entry for
  * "grpc-encoding", using its value to populate the call data's
  * compression_algorithm field. */
-static grpc_mdelem *compression_md_filter(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *compression_md_filter(grpc_exec_ctx *exec_ctx,
+                                          void *user_data, grpc_mdelem *md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
   channel_data *channeld = elem->channel_data;
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index 2ef066c5b2..4b62a35750 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -36,6 +36,7 @@
 #include <grpc/support/string_util.h>
 #include <string.h>
 #include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/slice/percent_encoding.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
 #include "src/core/lib/support/string.h"
@@ -58,6 +59,7 @@ typedef struct call_data {
   grpc_linked_mdelem payload_bin;
 
   grpc_metadata_batch *recv_initial_metadata;
+  grpc_metadata_batch *recv_trailing_metadata;
   uint8_t *payload_bytes;
 
   /* Vars to read data off of send_message */
@@ -71,14 +73,16 @@ typedef struct call_data {
   bool send_message_blocked;
 
   /** Closure to call when finished with the hc_on_recv hook */
-  grpc_closure *on_done_recv;
+  grpc_closure *on_done_recv_initial_metadata;
+  grpc_closure *on_done_recv_trailing_metadata;
   grpc_closure *on_complete;
   grpc_closure *post_send;
 
   /** Receive closures are chained: we inject this closure as the on_done_recv
       up-call on transport_op, and remember to call our on_done_recv member
       after handling it. */
-  grpc_closure hc_on_recv;
+  grpc_closure hc_on_recv_initial_metadata;
+  grpc_closure hc_on_recv_trailing_metadata;
   grpc_closure hc_on_complete;
   grpc_closure got_slice;
   grpc_closure send_done;
@@ -90,13 +94,9 @@ typedef struct channel_data {
   size_t max_payload_size_for_get;
 } channel_data;
 
-typedef struct {
-  grpc_call_element *elem;
-  grpc_exec_ctx *exec_ctx;
-} client_recv_filter_args;
-
-static grpc_mdelem *client_recv_filter(void *user_data, grpc_mdelem *md) {
-  client_recv_filter_args *a = user_data;
+static grpc_mdelem *client_recv_filter(grpc_exec_ctx *exec_ctx, void *user_data,
+                                       grpc_mdelem *md) {
+  grpc_call_element *elem = user_data;
   if (md == GRPC_MDELEM_STATUS_200) {
     return NULL;
   } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_STATUS) == 0) {
@@ -106,9 +106,19 @@ static grpc_mdelem *client_recv_filter(void *user_data, grpc_mdelem *md) {
     grpc_slice message = grpc_slice_from_copied_string(message_string);
     gpr_free(message_string);
     gpr_free(val);
-    grpc_call_element_send_close_with_message(a->exec_ctx, a->elem,
+    grpc_call_element_send_close_with_message(exec_ctx, elem,
                                               GRPC_STATUS_CANCELLED, &message);
     return NULL;
+  } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_GRPC_MESSAGE) == 0) {
+    grpc_slice pct_decoded_msg =
+        grpc_permissive_percent_decode_slice(md->value);
+    if (grpc_slice_is_equivalent(pct_decoded_msg, md->value)) {
+      grpc_slice_unref(pct_decoded_msg);
+      return md;
+    } else {
+      return grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_GRPC_MESSAGE,
+                                     pct_decoded_msg);
+    }
   } else if (md == GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC) {
     return NULL;
   } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_CONTENT_TYPE) == 0) {
@@ -134,16 +144,24 @@ static grpc_mdelem *client_recv_filter(void *user_data, grpc_mdelem *md) {
   return md;
 }
 
-static void hc_on_recv(grpc_exec_ctx *exec_ctx, void *user_data,
-                       grpc_error *error) {
+static void hc_on_recv_initial_metadata(grpc_exec_ctx *exec_ctx,
+                                        void *user_data, grpc_error *error) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
-  client_recv_filter_args a;
-  a.elem = elem;
-  a.exec_ctx = exec_ctx;
   grpc_metadata_batch_filter(exec_ctx, calld->recv_initial_metadata,
-                             client_recv_filter, &a);
-  calld->on_done_recv->cb(exec_ctx, calld->on_done_recv->cb_arg, error);
+                             client_recv_filter, elem);
+  grpc_closure_run(exec_ctx, calld->on_done_recv_initial_metadata,
+                   GRPC_ERROR_REF(error));
+}
+
+static void hc_on_recv_trailing_metadata(grpc_exec_ctx *exec_ctx,
+                                         void *user_data, grpc_error *error) {
+  grpc_call_element *elem = user_data;
+  call_data *calld = elem->call_data;
+  grpc_metadata_batch_filter(exec_ctx, calld->recv_trailing_metadata,
+                             client_recv_filter, elem);
+  grpc_closure_run(exec_ctx, calld->on_done_recv_trailing_metadata,
+                   GRPC_ERROR_REF(error));
 }
 
 static void hc_on_complete(grpc_exec_ctx *exec_ctx, void *user_data,
@@ -164,7 +182,8 @@ static void send_done(grpc_exec_ctx *exec_ctx, void *elemp, grpc_error *error) {
   calld->post_send->cb(exec_ctx, calld->post_send->cb_arg, error);
 }
 
-static grpc_mdelem *client_strip_filter(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *client_strip_filter(grpc_exec_ctx *exec_ctx,
+                                        void *user_data, grpc_mdelem *md) {
   /* eat the things we'd like to set ourselves */
   if (grpc_slice_cmp(md->key, GRPC_MDSTR_METHOD) == 0) return NULL;
   if (grpc_slice_cmp(md->key, GRPC_MDSTR_SCHEME) == 0) return NULL;
@@ -286,8 +305,15 @@ static void hc_mutate_op(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
   if (op->recv_initial_metadata != NULL) {
     /* substitute our callback for the higher callback */
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv = op->recv_initial_metadata_ready;
-    op->recv_initial_metadata_ready = &calld->hc_on_recv;
+    calld->on_done_recv_initial_metadata = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->hc_on_recv_initial_metadata;
+  }
+
+  if (op->recv_trailing_metadata != NULL) {
+    /* substitute our callback for the higher callback */
+    calld->recv_trailing_metadata = op->recv_trailing_metadata;
+    calld->on_done_recv_trailing_metadata = op->on_complete;
+    op->on_complete = &calld->hc_on_recv_trailing_metadata;
   }
 }
 
@@ -313,11 +339,15 @@ static grpc_error *init_call_elem(grpc_exec_ctx *exec_ctx,
                                   grpc_call_element *elem,
                                   grpc_call_element_args *args) {
   call_data *calld = elem->call_data;
-  calld->on_done_recv = NULL;
+  calld->on_done_recv_initial_metadata = NULL;
+  calld->on_done_recv_trailing_metadata = NULL;
   calld->on_complete = NULL;
   calld->payload_bytes = NULL;
   grpc_slice_buffer_init(&calld->slices);
-  grpc_closure_init(&calld->hc_on_recv, hc_on_recv, elem);
+  grpc_closure_init(&calld->hc_on_recv_initial_metadata,
+                    hc_on_recv_initial_metadata, elem);
+  grpc_closure_init(&calld->hc_on_recv_trailing_metadata,
+                    hc_on_recv_trailing_metadata, elem);
   grpc_closure_init(&calld->hc_on_complete, hc_on_complete, elem);
   grpc_closure_init(&calld->got_slice, got_slice, elem);
   grpc_closure_init(&calld->send_done, send_done, elem);
diff --git a/src/core/lib/channel/http_server_filter.c b/src/core/lib/channel/http_server_filter.c
index 23f1a60002..d8393337cd 100644
--- a/src/core/lib/channel/http_server_filter.c
+++ b/src/core/lib/channel/http_server_filter.c
@@ -37,6 +37,7 @@
 #include <grpc/support/log.h>
 #include <string.h>
 #include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/slice/percent_encoding.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
 #include "src/core/lib/transport/static_metadata.h"
@@ -83,14 +84,27 @@ typedef struct call_data {
 
 typedef struct channel_data { uint8_t unused; } channel_data;
 
-typedef struct {
-  grpc_call_element *elem;
-  grpc_exec_ctx *exec_ctx;
-} server_filter_args;
+static grpc_mdelem *server_filter_outgoing_metadata(grpc_exec_ctx *exec_ctx,
+                                                    void *user_data,
+                                                    grpc_mdelem *md) {
+  if (grpc_slice_cmp(md->key, GRPC_MDSTR_GRPC_MESSAGE) == 0) {
+    grpc_slice pct_encoded_msg = grpc_percent_encode_slice(
+        md->value, grpc_compatible_percent_encoding_unreserved_bytes);
+    if (grpc_slice_is_equivalent(pct_encoded_msg, md->value)) {
+      grpc_slice_unref_internal(exec_ctx, pct_encoded_msg);
+      return md;
+    } else {
+      return grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_GRPC_MESSAGE,
+                                     pct_encoded_msg);
+    }
+  } else {
+    return md;
+  }
+}
 
-static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
-  server_filter_args *a = user_data;
-  grpc_call_element *elem = a->elem;
+static grpc_mdelem *server_filter(grpc_exec_ctx *exec_ctx, void *user_data,
+                                  grpc_mdelem *md) {
+  grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
 
   /* Check if it is one of the headers we care about. */
@@ -145,9 +159,9 @@ static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
     /* swallow it and error everything out. */
     /* TODO(klempner): We ought to generate more descriptive error messages
        on the wire here. */
-    grpc_call_element_send_cancel(a->exec_ctx, elem);
     gpr_free(key);
     gpr_free(value);
+    grpc_call_element_send_cancel(exec_ctx, elem);
     return NULL;
   } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_PATH) == 0) {
     if (calld->seen_path) {
@@ -163,7 +177,7 @@ static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
     /* translate host to :authority since :authority may be
        omitted */
     grpc_mdelem *authority = grpc_mdelem_from_slices(
-        a->exec_ctx, GRPC_MDSTR_AUTHORITY, grpc_slice_ref(md->value));
+        exec_ctx, GRPC_MDSTR_AUTHORITY, grpc_slice_ref(md->value));
     calld->seen_authority = 1;
     return authority;
   } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_GRPC_PAYLOAD_BIN) == 0) {
@@ -185,11 +199,8 @@ static void hs_on_recv(grpc_exec_ctx *exec_ctx, void *user_data,
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
   if (err == GRPC_ERROR_NONE) {
-    server_filter_args a;
-    a.elem = elem;
-    a.exec_ctx = exec_ctx;
     grpc_metadata_batch_filter(exec_ctx, calld->recv_initial_metadata,
-                               server_filter, &a);
+                               server_filter, elem);
     /* Have we seen the required http2 transport headers?
        (:method, :scheme, content-type, with :path and :authority covered
        at the channel level right now) */
@@ -263,7 +274,7 @@ static void hs_recv_message_ready(grpc_exec_ctx *exec_ctx, void *user_data,
   }
 }
 
-static void hs_mutate_op(grpc_call_element *elem,
+static void hs_mutate_op(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                          grpc_transport_stream_op *op) {
   /* grab pointers to our data from the call element */
   call_data *calld = elem->call_data;
@@ -299,6 +310,11 @@ static void hs_mutate_op(grpc_call_element *elem,
       op->on_complete = &calld->hs_on_complete;
     }
   }
+
+  if (op->send_trailing_metadata) {
+    grpc_metadata_batch_filter(exec_ctx, op->send_trailing_metadata,
+                               server_filter_outgoing_metadata, elem);
+  }
 }
 
 static void hs_start_transport_op(grpc_exec_ctx *exec_ctx,
@@ -306,7 +322,7 @@ static void hs_start_transport_op(grpc_exec_ctx *exec_ctx,
                                   grpc_transport_stream_op *op) {
   GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
   GPR_TIMER_BEGIN("hs_start_transport_op", 0);
-  hs_mutate_op(elem, op);
+  hs_mutate_op(exec_ctx, elem, op);
   grpc_call_next_op(exec_ctx, elem, op);
   GPR_TIMER_END("hs_start_transport_op", 0);
 }
diff --git a/src/core/lib/iomgr/endpoint.c b/src/core/lib/iomgr/endpoint.c
index a4b6668276..2d300f4560 100644
--- a/src/core/lib/iomgr/endpoint.c
+++ b/src/core/lib/iomgr/endpoint.c
@@ -66,6 +66,8 @@ char* grpc_endpoint_get_peer(grpc_endpoint* ep) {
   return ep->vtable->get_peer(ep);
 }
 
+int grpc_endpoint_get_fd(grpc_endpoint* ep) { return ep->vtable->get_fd(ep); }
+
 grpc_workqueue* grpc_endpoint_get_workqueue(grpc_endpoint* ep) {
   return ep->vtable->get_workqueue(ep);
 }
diff --git a/src/core/lib/iomgr/endpoint.h b/src/core/lib/iomgr/endpoint.h
index bf211ca16a..1609b64f2b 100644
--- a/src/core/lib/iomgr/endpoint.h
+++ b/src/core/lib/iomgr/endpoint.h
@@ -61,6 +61,7 @@ struct grpc_endpoint_vtable {
   void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep);
   grpc_resource_user *(*get_resource_user)(grpc_endpoint *ep);
   char *(*get_peer)(grpc_endpoint *ep);
+  int (*get_fd)(grpc_endpoint *ep);
 };
 
 /* When data is available on the connection, calls the callback with slices.
@@ -73,6 +74,10 @@ void grpc_endpoint_read(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
 
 char *grpc_endpoint_get_peer(grpc_endpoint *ep);
 
+/* Get the file descriptor used by \a ep. Return -1 if \a ep is not using an fd.
+   */
+int grpc_endpoint_get_fd(grpc_endpoint *ep);
+
 /* Retrieve a reference to the workqueue associated with this endpoint */
 grpc_workqueue *grpc_endpoint_get_workqueue(grpc_endpoint *ep);
 
diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index db51ec4939..86674ca8c6 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -31,7 +31,6 @@
  *
  */
 
-#include <grpc/grpc_posix.h>
 #include "src/core/lib/iomgr/port.h"
 
 /* This polling engine is only relevant on linux kernels supporting epoll() */
@@ -163,7 +162,7 @@ static void fd_global_shutdown(void);
 #define PI_ADD_REF(p, r) pi_add_ref((p))
 #define PI_UNREF(exec_ctx, p, r) pi_unref((exec_ctx), (p))
 
-#endif /* !defined(GPRC_PI_REF_COUNT_DEBUG) */
+#endif /* !defined(GRPC_PI_REF_COUNT_DEBUG) */
 
 /* This is also used as grpc_workqueue (by directly casing it) */
 typedef struct polling_island {
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c b/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
deleted file mode 100644
index bf51404203..0000000000
--- a/src/core/lib/iomgr/ev_poll_and_epoll_posix.c
+++ /dev/null
@@ -1,2076 +0,0 @@
-/*
- *
- * Copyright 2015, 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.
- *
- */
-
-/* This file will be removed shortly: it's here to keep refactoring
- * steps simple and auditable.
- * It's the combination of the old files:
- *  - fd_posix.{h,c}
- *  - pollset_posix.{h,c}
- *  - pullset_multipoller_with_{poll,epoll}.{h,c}
- * The new version will be split into:
- *  - ev_poll_posix.{h,c}
- *  - ev_epoll_posix.{h,c}
- */
-
-#include "src/core/lib/iomgr/port.h"
-
-#ifdef GRPC_POSIX_SOCKET
-
-#include "src/core/lib/iomgr/ev_poll_and_epoll_posix.h"
-
-#include <assert.h>
-#include <errno.h>
-#include <poll.h>
-#include <string.h>
-#include <sys/socket.h>
-#include <unistd.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/string_util.h>
-#include <grpc/support/tls.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/lib/iomgr/iomgr_internal.h"
-#include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/profiling/timers.h"
-#include "src/core/lib/support/block_annotate.h"
-
-/*******************************************************************************
- * FD declarations
- */
-
-typedef struct grpc_fd_watcher {
-  struct grpc_fd_watcher *next;
-  struct grpc_fd_watcher *prev;
-  grpc_pollset *pollset;
-  grpc_pollset_worker *worker;
-  grpc_fd *fd;
-} grpc_fd_watcher;
-
-struct grpc_fd {
-  int fd;
-  /* refst format:
-     bit0:   1=active/0=orphaned
-     bit1-n: refcount
-     meaning that mostly we ref by two to avoid altering the orphaned bit,
-     and just unref by 1 when we're ready to flag the object as orphaned */
-  gpr_atm refst;
-
-  gpr_mu mu;
-  int shutdown;
-  int closed;
-  int released;
-
-  /* The watcher list.
-
-     The following watcher related fields are protected by watcher_mu.
-
-     An fd_watcher is an ephemeral object created when an fd wants to
-     begin polling, and destroyed after the poll.
-
-     It denotes the fd's interest in whether to read poll or write poll
-     or both or neither on this fd.
-
-     If a watcher is asked to poll for reads or writes, the read_watcher
-     or write_watcher fields are set respectively. A watcher may be asked
-     to poll for both, in which case both fields will be set.
-
-     read_watcher and write_watcher may be NULL if no watcher has been
-     asked to poll for reads or writes.
-
-     If an fd_watcher is not asked to poll for reads or writes, it's added
-     to a linked list of inactive watchers, rooted at inactive_watcher_root.
-     If at a later time there becomes need of a poller to poll, one of
-     the inactive pollers may be kicked out of their poll loops to take
-     that responsibility. */
-  grpc_fd_watcher inactive_watcher_root;
-  grpc_fd_watcher *read_watcher;
-  grpc_fd_watcher *write_watcher;
-
-  grpc_closure *read_closure;
-  grpc_closure *write_closure;
-
-  struct grpc_fd *freelist_next;
-
-  grpc_closure *on_done_closure;
-
-  grpc_iomgr_object iomgr_object;
-
-  /* The pollset that last noticed and notified that the fd is readable */
-  grpc_pollset *read_notifier_pollset;
-};
-
-/* Begin polling on an fd.
-   Registers that the given pollset is interested in this fd - so that if read
-   or writability interest changes, the pollset can be kicked to pick up that
-   new interest.
-   Return value is:
-     (fd_needs_read? read_mask : 0) | (fd_needs_write? write_mask : 0)
-   i.e. a combination of read_mask and write_mask determined by the fd's current
-   interest in said events.
-   Polling strategies that do not need to alter their behavior depending on the
-   fd's current interest (such as epoll) do not need to call this function.
-   MUST NOT be called with a pollset lock taken */
-static uint32_t fd_begin_poll(grpc_fd *fd, grpc_pollset *pollset,
-                              grpc_pollset_worker *worker, uint32_t read_mask,
-                              uint32_t write_mask, grpc_fd_watcher *rec);
-/* Complete polling previously started with fd_begin_poll
-   MUST NOT be called with a pollset lock taken
-   if got_read or got_write are 1, also does the become_{readable,writable} as
-   appropriate. */
-static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *rec,
-                        int got_read, int got_write,
-                        grpc_pollset *read_notifier_pollset);
-
-/* Return 1 if this fd is orphaned, 0 otherwise */
-static bool fd_is_orphaned(grpc_fd *fd);
-
-/* Reference counting for fds */
-/*#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,
-                     int line);
-#define GRPC_FD_REF(fd, reason) fd_ref(fd, reason, __FILE__, __LINE__)
-#define GRPC_FD_UNREF(fd, reason) fd_unref(fd, reason, __FILE__, __LINE__)
-#else
-static void fd_ref(grpc_fd *fd);
-static void fd_unref(grpc_fd *fd);
-#define GRPC_FD_REF(fd, reason) fd_ref(fd)
-#define GRPC_FD_UNREF(fd, reason) fd_unref(fd)
-#endif
-
-static void fd_global_init(void);
-static void fd_global_shutdown(void);
-
-#define CLOSURE_NOT_READY ((grpc_closure *)0)
-#define CLOSURE_READY ((grpc_closure *)1)
-
-/*******************************************************************************
- * pollset declarations
- */
-
-typedef struct grpc_pollset_vtable grpc_pollset_vtable;
-
-typedef struct grpc_cached_wakeup_fd {
-  grpc_wakeup_fd fd;
-  struct grpc_cached_wakeup_fd *next;
-} grpc_cached_wakeup_fd;
-
-struct grpc_pollset_worker {
-  grpc_cached_wakeup_fd *wakeup_fd;
-  int reevaluate_polling_on_wakeup;
-  int kicked_specifically;
-  struct grpc_pollset_worker *next;
-  struct grpc_pollset_worker *prev;
-};
-
-struct grpc_pollset {
-  /* pollsets under posix can mutate representation as fds are added and
-     removed.
-     For example, we may choose a poll() based implementation on linux for
-     few fds, and an epoll() based implementation for many fds */
-  const grpc_pollset_vtable *vtable;
-  gpr_mu mu;
-  grpc_pollset_worker root_worker;
-  int in_flight_cbs;
-  int shutting_down;
-  int called_shutdown;
-  int kicked_without_pollers;
-  grpc_closure *shutdown_done;
-  grpc_closure_list idle_jobs;
-  union {
-    int fd;
-    void *ptr;
-  } data;
-  /* Local cache of eventfds for workers */
-  grpc_cached_wakeup_fd *local_wakeup_cache;
-};
-
-struct grpc_pollset_vtable {
-  void (*add_fd)(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                 struct grpc_fd *fd, int and_unlock_pollset);
-  grpc_error *(*maybe_work_and_unlock)(grpc_exec_ctx *exec_ctx,
-                                       grpc_pollset *pollset,
-                                       grpc_pollset_worker *worker,
-                                       gpr_timespec deadline, gpr_timespec now);
-  void (*finish_shutdown)(grpc_pollset *pollset);
-  void (*destroy)(grpc_pollset *pollset);
-};
-
-/* Add an fd to a pollset */
-static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           struct grpc_fd *fd);
-
-static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
-                               grpc_pollset_set *pollset_set, grpc_fd *fd);
-
-/* Convert a timespec to milliseconds:
-   - very small or negative poll times are clamped to zero to do a
-     non-blocking poll (which becomes spin polling)
-   - other small values are rounded up to one millisecond
-   - longer than a millisecond polls are rounded up to the next nearest
-     millisecond to avoid spinning
-   - infinite timeouts are converted to -1 */
-static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
-                                           gpr_timespec now);
-
-/* Allow kick to wakeup the currently polling worker */
-#define GRPC_POLLSET_CAN_KICK_SELF 1
-/* Force the wakee to repoll when awoken */
-#define GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP 2
-/* As per pollset_kick, with an extended set of flags (defined above)
-   -- mostly for fd_posix's use. */
-static grpc_error *pollset_kick_ext(grpc_pollset *p,
-                                    grpc_pollset_worker *specific_worker,
-                                    uint32_t flags) GRPC_MUST_USE_RESULT;
-
-/* turn a pollset into a multipoller: platform specific */
-typedef void (*platform_become_multipoller_type)(grpc_exec_ctx *exec_ctx,
-                                                 grpc_pollset *pollset,
-                                                 struct grpc_fd **fds,
-                                                 size_t fd_count);
-static platform_become_multipoller_type platform_become_multipoller;
-
-/* Return 1 if the pollset has active threads in pollset_work (pollset must
- * be locked) */
-static int pollset_has_workers(grpc_pollset *pollset);
-
-static void remove_fd_from_all_epoll_sets(int fd);
-
-/*******************************************************************************
- * pollset_set definitions
- */
-
-struct grpc_pollset_set {
-  gpr_mu mu;
-
-  size_t pollset_count;
-  size_t pollset_capacity;
-  grpc_pollset **pollsets;
-
-  size_t pollset_set_count;
-  size_t pollset_set_capacity;
-  struct grpc_pollset_set **pollset_sets;
-
-  size_t fd_count;
-  size_t fd_capacity;
-  grpc_fd **fds;
-};
-
-/*******************************************************************************
- * fd_posix.c
- */
-
-/* We need to keep a freelist not because of any concerns of malloc performance
- * but instead so that implementations with multiple threads in (for example)
- * epoll_wait deal with the race between pollset removal and incoming poll
- * notifications.
- *
- * The problem is that the poller ultimately holds a reference to this
- * object, so it is very difficult to know when is safe to free it, at least
- * without some expensive synchronization.
- *
- * If we keep the object freelisted, in the worst case losing this race just
- * becomes a spurious read notification on a reused fd.
- */
-/* TODO(klempner): We could use some form of polling generation count to know
- * when these are safe to free. */
-/* TODO(klempner): Consider disabling freelisting if we don't have multiple
- * threads in poll on the same fd */
-/* TODO(klempner): Batch these allocations to reduce fragmentation */
-static grpc_fd *fd_freelist = NULL;
-static gpr_mu fd_freelist_mu;
-
-static void freelist_fd(grpc_fd *fd) {
-  gpr_mu_lock(&fd_freelist_mu);
-  fd->freelist_next = fd_freelist;
-  fd_freelist = fd;
-  grpc_iomgr_unregister_object(&fd->iomgr_object);
-  gpr_mu_unlock(&fd_freelist_mu);
-}
-
-static grpc_fd *alloc_fd(int fd) {
-  grpc_fd *r = NULL;
-  gpr_mu_lock(&fd_freelist_mu);
-  if (fd_freelist != NULL) {
-    r = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-  }
-  gpr_mu_unlock(&fd_freelist_mu);
-  if (r == NULL) {
-    r = gpr_malloc(sizeof(grpc_fd));
-    gpr_mu_init(&r->mu);
-  }
-
-  gpr_mu_lock(&r->mu);
-  gpr_atm_rel_store(&r->refst, 1);
-  r->shutdown = 0;
-  r->read_closure = CLOSURE_NOT_READY;
-  r->write_closure = CLOSURE_NOT_READY;
-  r->fd = fd;
-  r->inactive_watcher_root.next = r->inactive_watcher_root.prev =
-      &r->inactive_watcher_root;
-  r->freelist_next = NULL;
-  r->read_watcher = r->write_watcher = NULL;
-  r->on_done_closure = NULL;
-  r->closed = 0;
-  r->released = 0;
-  r->read_notifier_pollset = NULL;
-  gpr_mu_unlock(&r->mu);
-  return r;
-}
-
-static void destroy(grpc_fd *fd) {
-  gpr_mu_destroy(&fd->mu);
-  gpr_free(fd);
-}
-
-#ifdef GRPC_FD_REF_COUNT_DEBUG
-#define REF_BY(fd, n, reason) ref_by(fd, n, reason, __FILE__, __LINE__)
-#define UNREF_BY(fd, n, reason) unref_by(fd, n, reason, __FILE__, __LINE__)
-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);
-#else
-#define REF_BY(fd, n, reason) ref_by(fd, n)
-#define UNREF_BY(fd, n, reason) unref_by(fd, n)
-static void ref_by(grpc_fd *fd, int n) {
-#endif
-  GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&fd->refst, n) > 0);
-}
-
-#ifdef GRPC_FD_REF_COUNT_DEBUG
-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);
-#else
-static void unref_by(grpc_fd *fd, int n) {
-  gpr_atm old;
-#endif
-  old = gpr_atm_full_fetch_add(&fd->refst, -n);
-  if (old == n) {
-    freelist_fd(fd);
-  } else {
-    GPR_ASSERT(old > n);
-  }
-}
-
-static void fd_global_init(void) { gpr_mu_init(&fd_freelist_mu); }
-
-static void fd_global_shutdown(void) {
-  gpr_mu_lock(&fd_freelist_mu);
-  gpr_mu_unlock(&fd_freelist_mu);
-  while (fd_freelist != NULL) {
-    grpc_fd *fd = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-    destroy(fd);
-  }
-  gpr_mu_destroy(&fd_freelist_mu);
-}
-
-static grpc_fd *fd_create(int fd, const char *name) {
-  grpc_fd *r = alloc_fd(fd);
-  char *name2;
-  gpr_asprintf(&name2, "%s fd=%d", name, fd);
-  grpc_iomgr_register_object(&r->iomgr_object, name2);
-  gpr_free(name2);
-#ifdef GRPC_FD_REF_COUNT_DEBUG
-  gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, r, name);
-#endif
-  return r;
-}
-
-static bool fd_is_orphaned(grpc_fd *fd) {
-  return (gpr_atm_acq_load(&fd->refst) & 1) == 0;
-}
-
-static grpc_error *pollset_kick_locked(grpc_fd_watcher *watcher) {
-  gpr_mu_lock(&watcher->pollset->mu);
-  GPR_ASSERT(watcher->worker);
-  grpc_error *err = pollset_kick_ext(watcher->pollset, watcher->worker,
-                                     GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP);
-  gpr_mu_unlock(&watcher->pollset->mu);
-  return err;
-}
-
-static void maybe_wake_one_watcher_locked(grpc_fd *fd) {
-  if (fd->inactive_watcher_root.next != &fd->inactive_watcher_root) {
-    pollset_kick_locked(fd->inactive_watcher_root.next);
-  } else if (fd->read_watcher) {
-    pollset_kick_locked(fd->read_watcher);
-  } else if (fd->write_watcher) {
-    pollset_kick_locked(fd->write_watcher);
-  }
-}
-
-static void wake_all_watchers_locked(grpc_fd *fd) {
-  grpc_fd_watcher *watcher;
-  for (watcher = fd->inactive_watcher_root.next;
-       watcher != &fd->inactive_watcher_root; watcher = watcher->next) {
-    pollset_kick_locked(watcher);
-  }
-  if (fd->read_watcher) {
-    pollset_kick_locked(fd->read_watcher);
-  }
-  if (fd->write_watcher && fd->write_watcher != fd->read_watcher) {
-    pollset_kick_locked(fd->write_watcher);
-  }
-}
-
-static int has_watchers(grpc_fd *fd) {
-  return fd->read_watcher != NULL || fd->write_watcher != NULL ||
-         fd->inactive_watcher_root.next != &fd->inactive_watcher_root;
-}
-
-static void close_fd_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  fd->closed = 1;
-  if (!fd->released) {
-    close(fd->fd);
-  } else {
-    remove_fd_from_all_epoll_sets(fd->fd);
-  }
-  grpc_exec_ctx_sched(exec_ctx, fd->on_done_closure, GRPC_ERROR_NONE, NULL);
-}
-
-static int fd_wrapped_fd(grpc_fd *fd) {
-  if (fd->released || fd->closed) {
-    return -1;
-  } else {
-    return fd->fd;
-  }
-}
-
-static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                      grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
-  fd->on_done_closure = on_done;
-  fd->released = release_fd != NULL;
-  if (!fd->released) {
-    shutdown(fd->fd, SHUT_RDWR);
-  } else {
-    *release_fd = fd->fd;
-  }
-  gpr_mu_lock(&fd->mu);
-  REF_BY(fd, 1, reason); /* remove active status, but keep referenced */
-  if (!has_watchers(fd)) {
-    close_fd_locked(exec_ctx, fd);
-  } else {
-    wake_all_watchers_locked(fd);
-  }
-  gpr_mu_unlock(&fd->mu);
-  UNREF_BY(fd, 2, reason); /* drop the reference */
-}
-
-/* increment refcount by two to avoid changing the orphan bit */
-#ifdef GRPC_FD_REF_COUNT_DEBUG
-static void fd_ref(grpc_fd *fd, const char *reason, const char *file,
-                   int line) {
-  ref_by(fd, 2, reason, file, line);
-}
-
-static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
-                     int line) {
-  unref_by(fd, 2, reason, file, line);
-}
-#else
-static void fd_ref(grpc_fd *fd) { ref_by(fd, 2); }
-
-static void fd_unref(grpc_fd *fd) { unref_by(fd, 2); }
-#endif
-
-static grpc_error *fd_shutdown_error(bool shutdown) {
-  if (!shutdown) {
-    return GRPC_ERROR_NONE;
-  } else {
-    return GRPC_ERROR_CREATE("FD shutdown");
-  }
-}
-
-static void notify_on_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                             grpc_closure **st, grpc_closure *closure) {
-  if (fd->shutdown) {
-    grpc_exec_ctx_sched(exec_ctx, closure, GRPC_ERROR_CREATE("FD shutdown"),
-                        NULL);
-  } else if (*st == CLOSURE_NOT_READY) {
-    /* not ready ==> switch to a waiting state by setting the closure */
-    *st = closure;
-  } else if (*st == CLOSURE_READY) {
-    /* already ready ==> queue the closure to run immediately */
-    *st = CLOSURE_NOT_READY;
-    grpc_exec_ctx_sched(exec_ctx, closure, fd_shutdown_error(fd->shutdown),
-                        NULL);
-    maybe_wake_one_watcher_locked(fd);
-  } else {
-    /* upcallptr was set to a different closure.  This is an error! */
-    gpr_log(GPR_ERROR,
-            "User called a notify_on function with a previous callback still "
-            "pending");
-    abort();
-  }
-}
-
-/* returns 1 if state becomes not ready */
-static int set_ready_locked(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                            grpc_closure **st) {
-  if (*st == CLOSURE_READY) {
-    /* duplicate ready ==> ignore */
-    return 0;
-  } else if (*st == CLOSURE_NOT_READY) {
-    /* not ready, and not waiting ==> flag ready */
-    *st = CLOSURE_READY;
-    return 0;
-  } else {
-    /* waiting ==> queue closure */
-    grpc_exec_ctx_sched(exec_ctx, *st, fd_shutdown_error(fd->shutdown), NULL);
-    *st = CLOSURE_NOT_READY;
-    return 1;
-  }
-}
-
-static void set_read_notifier_pollset_locked(
-    grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_pollset *read_notifier_pollset) {
-  fd->read_notifier_pollset = read_notifier_pollset;
-}
-
-static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  gpr_mu_lock(&fd->mu);
-  /* only shutdown once */
-  if (!fd->shutdown) {
-    fd->shutdown = 1;
-    /* signal read/write closed to OS so that future operations fail */
-    shutdown(fd->fd, SHUT_RDWR);
-    set_ready_locked(exec_ctx, fd, &fd->read_closure);
-    set_ready_locked(exec_ctx, fd, &fd->write_closure);
-  }
-  gpr_mu_unlock(&fd->mu);
-}
-
-static bool fd_is_shutdown(grpc_fd *fd) {
-  gpr_mu_lock(&fd->mu);
-  bool r = fd->shutdown;
-  gpr_mu_unlock(&fd->mu);
-  return r;
-}
-
-static void fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                              grpc_closure *closure) {
-  gpr_mu_lock(&fd->mu);
-  notify_on_locked(exec_ctx, fd, &fd->read_closure, closure);
-  gpr_mu_unlock(&fd->mu);
-}
-
-static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                               grpc_closure *closure) {
-  gpr_mu_lock(&fd->mu);
-  notify_on_locked(exec_ctx, fd, &fd->write_closure, closure);
-  gpr_mu_unlock(&fd->mu);
-}
-
-/* Return the read-notifier pollset */
-static grpc_pollset *fd_get_read_notifier_pollset(grpc_exec_ctx *exec_ctx,
-                                                  grpc_fd *fd) {
-  grpc_pollset *notifier = NULL;
-
-  gpr_mu_lock(&fd->mu);
-  notifier = fd->read_notifier_pollset;
-  gpr_mu_unlock(&fd->mu);
-
-  return notifier;
-}
-
-static uint32_t fd_begin_poll(grpc_fd *fd, grpc_pollset *pollset,
-                              grpc_pollset_worker *worker, uint32_t read_mask,
-                              uint32_t write_mask, grpc_fd_watcher *watcher) {
-  uint32_t mask = 0;
-  grpc_closure *cur;
-  int requested;
-  /* keep track of pollers that have requested our events, in case they change
-   */
-  GRPC_FD_REF(fd, "poll");
-
-  gpr_mu_lock(&fd->mu);
-
-  /* if we are shutdown, then don't add to the watcher set */
-  if (fd->shutdown) {
-    watcher->fd = NULL;
-    watcher->pollset = NULL;
-    watcher->worker = NULL;
-    gpr_mu_unlock(&fd->mu);
-    GRPC_FD_UNREF(fd, "poll");
-    return 0;
-  }
-
-  /* if there is nobody polling for read, but we need to, then start doing so */
-  cur = fd->read_closure;
-  requested = cur != CLOSURE_READY;
-  if (read_mask && fd->read_watcher == NULL && requested) {
-    fd->read_watcher = watcher;
-    mask |= read_mask;
-  }
-  /* if there is nobody polling for write, but we need to, then start doing so
-   */
-  cur = fd->write_closure;
-  requested = cur != CLOSURE_READY;
-  if (write_mask && fd->write_watcher == NULL && requested) {
-    fd->write_watcher = watcher;
-    mask |= write_mask;
-  }
-  /* if not polling, remember this watcher in case we need someone to later */
-  if (mask == 0 && worker != NULL) {
-    watcher->next = &fd->inactive_watcher_root;
-    watcher->prev = watcher->next->prev;
-    watcher->next->prev = watcher->prev->next = watcher;
-  }
-  watcher->pollset = pollset;
-  watcher->worker = worker;
-  watcher->fd = fd;
-  gpr_mu_unlock(&fd->mu);
-
-  return mask;
-}
-
-static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *watcher,
-                        int got_read, int got_write,
-                        grpc_pollset *read_notifier_pollset) {
-  int was_polling = 0;
-  int kick = 0;
-  grpc_fd *fd = watcher->fd;
-
-  if (fd == NULL) {
-    return;
-  }
-
-  gpr_mu_lock(&fd->mu);
-
-  if (watcher == fd->read_watcher) {
-    /* remove read watcher, kick if we still need a read */
-    was_polling = 1;
-    if (!got_read) {
-      kick = 1;
-    }
-    fd->read_watcher = NULL;
-  }
-  if (watcher == fd->write_watcher) {
-    /* remove write watcher, kick if we still need a write */
-    was_polling = 1;
-    if (!got_write) {
-      kick = 1;
-    }
-    fd->write_watcher = NULL;
-  }
-  if (!was_polling && watcher->worker != NULL) {
-    /* remove from inactive list */
-    watcher->next->prev = watcher->prev;
-    watcher->prev->next = watcher->next;
-  }
-  if (got_read) {
-    if (set_ready_locked(exec_ctx, fd, &fd->read_closure)) {
-      kick = 1;
-    }
-
-    if (read_notifier_pollset != NULL) {
-      set_read_notifier_pollset_locked(exec_ctx, fd, read_notifier_pollset);
-    }
-  }
-  if (got_write) {
-    if (set_ready_locked(exec_ctx, fd, &fd->write_closure)) {
-      kick = 1;
-    }
-  }
-  if (kick) {
-    maybe_wake_one_watcher_locked(fd);
-  }
-  if (fd_is_orphaned(fd) && !has_watchers(fd) && !fd->closed) {
-    close_fd_locked(exec_ctx, fd);
-  }
-  gpr_mu_unlock(&fd->mu);
-
-  GRPC_FD_UNREF(fd, "poll");
-}
-
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) { return NULL; }
-
-/*******************************************************************************
- * pollset_posix.c
- */
-
-GPR_TLS_DECL(g_current_thread_poller);
-GPR_TLS_DECL(g_current_thread_worker);
-
-/** The alarm system needs to be able to wakeup 'some poller' sometimes
- *  (specifically when a new alarm needs to be triggered earlier than the next
- *  alarm 'epoch').
- *  This wakeup_fd gives us something to alert on when such a case occurs. */
-grpc_wakeup_fd grpc_global_wakeup_fd;
-
-static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev->next = worker->next;
-  worker->next->prev = worker->prev;
-}
-
-static int pollset_has_workers(grpc_pollset *p) {
-  return p->root_worker.next != &p->root_worker;
-}
-
-static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
-  if (pollset_has_workers(p)) {
-    grpc_pollset_worker *w = p->root_worker.next;
-    remove_worker(p, w);
-    return w;
-  } else {
-    return NULL;
-  }
-}
-
-static void push_back_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->next = &p->root_worker;
-  worker->prev = worker->next->prev;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev = &p->root_worker;
-  worker->next = worker->prev->next;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-static void kick_append_error(grpc_error **composite, grpc_error *error) {
-  if (error == GRPC_ERROR_NONE) return;
-  if (*composite == GRPC_ERROR_NONE) {
-    *composite = GRPC_ERROR_CREATE("Kick Failure");
-  }
-  *composite = grpc_error_add_child(*composite, error);
-}
-
-static grpc_error *pollset_kick_ext(grpc_pollset *p,
-                                    grpc_pollset_worker *specific_worker,
-                                    uint32_t flags) {
-  GPR_TIMER_BEGIN("pollset_kick_ext", 0);
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  /* pollset->mu already held */
-  if (specific_worker != NULL) {
-    if (specific_worker == GRPC_POLLSET_KICK_BROADCAST) {
-      GPR_TIMER_BEGIN("pollset_kick_ext.broadcast", 0);
-      GPR_ASSERT((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) == 0);
-      for (specific_worker = p->root_worker.next;
-           specific_worker != &p->root_worker;
-           specific_worker = specific_worker->next) {
-        kick_append_error(
-            &error, grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd));
-      }
-      p->kicked_without_pollers = true;
-      GPR_TIMER_END("pollset_kick_ext.broadcast", 0);
-    } else if (gpr_tls_get(&g_current_thread_worker) !=
-               (intptr_t)specific_worker) {
-      GPR_TIMER_MARK("different_thread_worker", 0);
-      if ((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) != 0) {
-        specific_worker->reevaluate_polling_on_wakeup = true;
-      }
-      specific_worker->kicked_specifically = true;
-      kick_append_error(&error,
-                        grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd));
-    } else if ((flags & GRPC_POLLSET_CAN_KICK_SELF) != 0) {
-      GPR_TIMER_MARK("kick_yoself", 0);
-      if ((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) != 0) {
-        specific_worker->reevaluate_polling_on_wakeup = true;
-      }
-      specific_worker->kicked_specifically = true;
-      kick_append_error(&error,
-                        grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd));
-    }
-  } else if (gpr_tls_get(&g_current_thread_poller) != (intptr_t)p) {
-    GPR_ASSERT((flags & GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) == 0);
-    GPR_TIMER_MARK("kick_anonymous", 0);
-    specific_worker = pop_front_worker(p);
-    if (specific_worker != NULL) {
-      if (gpr_tls_get(&g_current_thread_worker) == (intptr_t)specific_worker) {
-        GPR_TIMER_MARK("kick_anonymous_not_self", 0);
-        push_back_worker(p, specific_worker);
-        specific_worker = pop_front_worker(p);
-        if ((flags & GRPC_POLLSET_CAN_KICK_SELF) == 0 &&
-            gpr_tls_get(&g_current_thread_worker) ==
-                (intptr_t)specific_worker) {
-          push_back_worker(p, specific_worker);
-          specific_worker = NULL;
-        }
-      }
-      if (specific_worker != NULL) {
-        GPR_TIMER_MARK("finally_kick", 0);
-        push_back_worker(p, specific_worker);
-        kick_append_error(
-            &error, grpc_wakeup_fd_wakeup(&specific_worker->wakeup_fd->fd));
-      }
-    } else {
-      GPR_TIMER_MARK("kicked_no_pollers", 0);
-      p->kicked_without_pollers = true;
-    }
-  }
-
-  GPR_TIMER_END("pollset_kick_ext", 0);
-  return error;
-}
-
-static grpc_error *pollset_kick(grpc_pollset *p,
-                                grpc_pollset_worker *specific_worker) {
-  return pollset_kick_ext(p, specific_worker, 0);
-}
-
-/* global state management */
-
-static grpc_error *pollset_global_init(void) {
-  gpr_tls_init(&g_current_thread_poller);
-  gpr_tls_init(&g_current_thread_worker);
-  return grpc_wakeup_fd_init(&grpc_global_wakeup_fd);
-}
-
-static void pollset_global_shutdown(void) {
-  grpc_wakeup_fd_destroy(&grpc_global_wakeup_fd);
-  gpr_tls_destroy(&g_current_thread_poller);
-  gpr_tls_destroy(&g_current_thread_worker);
-}
-
-static grpc_error *kick_poller(void) {
-  return grpc_wakeup_fd_wakeup(&grpc_global_wakeup_fd);
-}
-
-/* main interface */
-
-static void become_basic_pollset(grpc_pollset *pollset, grpc_fd *fd_or_null);
-
-static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
-  gpr_mu_init(&pollset->mu);
-  *mu = &pollset->mu;
-  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
-  pollset->in_flight_cbs = 0;
-  pollset->shutting_down = 0;
-  pollset->called_shutdown = 0;
-  pollset->kicked_without_pollers = 0;
-  pollset->idle_jobs.head = pollset->idle_jobs.tail = NULL;
-  pollset->local_wakeup_cache = NULL;
-  pollset->kicked_without_pollers = 0;
-  become_basic_pollset(pollset, NULL);
-}
-
-static void pollset_destroy(grpc_pollset *pollset) {
-  GPR_ASSERT(pollset->in_flight_cbs == 0);
-  GPR_ASSERT(!pollset_has_workers(pollset));
-  GPR_ASSERT(pollset->idle_jobs.head == pollset->idle_jobs.tail);
-  pollset->vtable->destroy(pollset);
-  while (pollset->local_wakeup_cache) {
-    grpc_cached_wakeup_fd *next = pollset->local_wakeup_cache->next;
-    grpc_wakeup_fd_destroy(&pollset->local_wakeup_cache->fd);
-    gpr_free(pollset->local_wakeup_cache);
-    pollset->local_wakeup_cache = next;
-  }
-  gpr_mu_destroy(&pollset->mu);
-}
-
-static void pollset_reset(grpc_pollset *pollset) {
-  GPR_ASSERT(pollset->shutting_down);
-  GPR_ASSERT(pollset->in_flight_cbs == 0);
-  GPR_ASSERT(!pollset_has_workers(pollset));
-  GPR_ASSERT(pollset->idle_jobs.head == pollset->idle_jobs.tail);
-  pollset->vtable->destroy(pollset);
-  pollset->shutting_down = 0;
-  pollset->called_shutdown = 0;
-  pollset->kicked_without_pollers = 0;
-  become_basic_pollset(pollset, NULL);
-}
-
-static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           grpc_fd *fd) {
-  gpr_mu_lock(&pollset->mu);
-  pollset->vtable->add_fd(exec_ctx, pollset, fd, 1);
-/* the following (enabled only in debug) will reacquire and then release
-   our lock - meaning that if the unlocking flag passed to add_fd above is
-   not respected, the code will deadlock (in a way that we have a chance of
-   debugging) */
-#ifndef NDEBUG
-  gpr_mu_lock(&pollset->mu);
-  gpr_mu_unlock(&pollset->mu);
-#endif
-}
-
-static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
-  GPR_ASSERT(grpc_closure_list_empty(pollset->idle_jobs));
-  pollset->vtable->finish_shutdown(pollset);
-  grpc_exec_ctx_sched(exec_ctx, pollset->shutdown_done, GRPC_ERROR_NONE, NULL);
-}
-
-static void work_combine_error(grpc_error **composite, grpc_error *error) {
-  if (error == GRPC_ERROR_NONE) return;
-  if (*composite == GRPC_ERROR_NONE) {
-    *composite = GRPC_ERROR_CREATE("pollset_work");
-  }
-  *composite = grpc_error_add_child(*composite, error);
-}
-
-static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                                grpc_pollset_worker **worker_hdl,
-                                gpr_timespec now, gpr_timespec deadline) {
-  grpc_pollset_worker worker;
-  *worker_hdl = &worker;
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  /* pollset->mu already held */
-  int added_worker = 0;
-  int locked = 1;
-  int queued_work = 0;
-  int keep_polling = 0;
-  GPR_TIMER_BEGIN("pollset_work", 0);
-  /* this must happen before we (potentially) drop pollset->mu */
-  worker.next = worker.prev = NULL;
-  worker.reevaluate_polling_on_wakeup = 0;
-  if (pollset->local_wakeup_cache != NULL) {
-    worker.wakeup_fd = pollset->local_wakeup_cache;
-    pollset->local_wakeup_cache = worker.wakeup_fd->next;
-  } else {
-    worker.wakeup_fd = gpr_malloc(sizeof(*worker.wakeup_fd));
-    error = grpc_wakeup_fd_init(&worker.wakeup_fd->fd);
-    if (error != GRPC_ERROR_NONE) {
-      return error;
-    }
-  }
-  worker.kicked_specifically = 0;
-  /* If there's work waiting for the pollset to be idle, and the
-     pollset is idle, then do that work */
-  if (!pollset_has_workers(pollset) &&
-      !grpc_closure_list_empty(pollset->idle_jobs)) {
-    GPR_TIMER_MARK("pollset_work.idle_jobs", 0);
-    grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
-    goto done;
-  }
-  /* If we're shutting down then we don't execute any extended work */
-  if (pollset->shutting_down) {
-    GPR_TIMER_MARK("pollset_work.shutting_down", 0);
-    goto done;
-  }
-  /* Give do_promote priority so we don't starve it out */
-  if (pollset->in_flight_cbs) {
-    GPR_TIMER_MARK("pollset_work.in_flight_cbs", 0);
-    gpr_mu_unlock(&pollset->mu);
-    locked = 0;
-    goto done;
-  }
-  /* Start polling, and keep doing so while we're being asked to
-     re-evaluate our pollers (this allows poll() based pollers to
-     ensure they don't miss wakeups) */
-  keep_polling = 1;
-  while (keep_polling) {
-    keep_polling = 0;
-    if (!pollset->kicked_without_pollers) {
-      if (!added_worker) {
-        push_front_worker(pollset, &worker);
-        added_worker = 1;
-        gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
-      }
-      gpr_tls_set(&g_current_thread_poller, (intptr_t)pollset);
-      GPR_TIMER_BEGIN("maybe_work_and_unlock", 0);
-      work_combine_error(&error,
-                         pollset->vtable->maybe_work_and_unlock(
-                             exec_ctx, pollset, &worker, deadline, now));
-      GPR_TIMER_END("maybe_work_and_unlock", 0);
-      locked = 0;
-      gpr_tls_set(&g_current_thread_poller, 0);
-    } else {
-      GPR_TIMER_MARK("pollset_work.kicked_without_pollers", 0);
-      pollset->kicked_without_pollers = 0;
-    }
-  /* Finished execution - start cleaning up.
-     Note that we may arrive here from outside the enclosing while() loop.
-     In that case we won't loop though as we haven't added worker to the
-     worker list, which means nobody could ask us to re-evaluate polling). */
-  done:
-    if (!locked) {
-      queued_work |= grpc_exec_ctx_flush(exec_ctx);
-      gpr_mu_lock(&pollset->mu);
-      locked = 1;
-    }
-    /* If we're forced to re-evaluate polling (via pollset_kick with
-       GRPC_POLLSET_REEVALUATE_POLLING_ON_WAKEUP) then we land here and force
-       a loop */
-    if (worker.reevaluate_polling_on_wakeup) {
-      worker.reevaluate_polling_on_wakeup = 0;
-      pollset->kicked_without_pollers = 0;
-      if (queued_work || worker.kicked_specifically) {
-        /* If there's queued work on the list, then set the deadline to be
-           immediate so we get back out of the polling loop quickly */
-        deadline = gpr_inf_past(GPR_CLOCK_MONOTONIC);
-      }
-      keep_polling = 1;
-    }
-  }
-  if (added_worker) {
-    remove_worker(pollset, &worker);
-    gpr_tls_set(&g_current_thread_worker, 0);
-  }
-  /* release wakeup fd to the local pool */
-  worker.wakeup_fd->next = pollset->local_wakeup_cache;
-  pollset->local_wakeup_cache = worker.wakeup_fd;
-  /* check shutdown conditions */
-  if (pollset->shutting_down) {
-    if (pollset_has_workers(pollset)) {
-      pollset_kick(pollset, NULL);
-    } else if (!pollset->called_shutdown && pollset->in_flight_cbs == 0) {
-      pollset->called_shutdown = 1;
-      gpr_mu_unlock(&pollset->mu);
-      finish_shutdown(exec_ctx, pollset);
-      grpc_exec_ctx_flush(exec_ctx);
-      /* Continuing to access pollset here is safe -- it is the caller's
-       * responsibility to not destroy when it has outstanding calls to
-       * pollset_work.
-       * TODO(dklempner): Can we refactor the shutdown logic to avoid this? */
-      gpr_mu_lock(&pollset->mu);
-    } else if (!grpc_closure_list_empty(pollset->idle_jobs)) {
-      grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
-      gpr_mu_unlock(&pollset->mu);
-      grpc_exec_ctx_flush(exec_ctx);
-      gpr_mu_lock(&pollset->mu);
-    }
-  }
-  *worker_hdl = NULL;
-  GPR_TIMER_END("pollset_work", 0);
-  return error;
-}
-
-static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                             grpc_closure *closure) {
-  GPR_ASSERT(!pollset->shutting_down);
-  pollset->shutting_down = 1;
-  pollset->shutdown_done = closure;
-  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
-  if (!pollset_has_workers(pollset)) {
-    grpc_exec_ctx_enqueue_list(exec_ctx, &pollset->idle_jobs, NULL);
-  }
-  if (!pollset->called_shutdown && pollset->in_flight_cbs == 0 &&
-      !pollset_has_workers(pollset)) {
-    pollset->called_shutdown = 1;
-    finish_shutdown(exec_ctx, pollset);
-  }
-}
-
-static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
-                                           gpr_timespec now) {
-  gpr_timespec timeout;
-  static const int64_t max_spin_polling_us = 10;
-  if (gpr_time_cmp(deadline, gpr_inf_future(deadline.clock_type)) == 0) {
-    return -1;
-  }
-  if (gpr_time_cmp(deadline, gpr_time_add(now, gpr_time_from_micros(
-                                                   max_spin_polling_us,
-                                                   GPR_TIMESPAN))) <= 0) {
-    return 0;
-  }
-  timeout = gpr_time_sub(deadline, now);
-  return gpr_time_to_millis(gpr_time_add(
-      timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
-}
-
-/*
- * basic_pollset - a vtable that provides polling for zero or one file
- *                 descriptor via poll()
- */
-
-typedef struct grpc_unary_promote_args {
-  const grpc_pollset_vtable *original_vtable;
-  grpc_pollset *pollset;
-  grpc_fd *fd;
-  grpc_closure promotion_closure;
-} grpc_unary_promote_args;
-
-static void basic_do_promote(grpc_exec_ctx *exec_ctx, void *args,
-                             grpc_error *error) {
-  grpc_unary_promote_args *up_args = args;
-  const grpc_pollset_vtable *original_vtable = up_args->original_vtable;
-  grpc_pollset *pollset = up_args->pollset;
-  grpc_fd *fd = up_args->fd;
-
-  /*
-   * This is quite tricky. There are a number of cases to keep in mind here:
-   * 1. fd may have been orphaned
-   * 2. The pollset may no longer be a unary poller (and we can't let case #1
-   * leak to other pollset types!)
-   * 3. pollset's fd (which may have changed) may have been orphaned
-   * 4. The pollset may be shutting down.
-   */
-
-  gpr_mu_lock(&pollset->mu);
-  /* First we need to ensure that nobody is polling concurrently */
-  GPR_ASSERT(!pollset_has_workers(pollset));
-
-  gpr_free(up_args);
-  /* At this point the pollset may no longer be a unary poller. In that case
-   * we should just call the right add function and be done. */
-  /* TODO(klempner): If we're not careful this could cause infinite recursion.
-   * That's not a problem for now because empty_pollset has a trivial poller
-   * and we don't have any mechanism to unbecome multipoller. */
-  pollset->in_flight_cbs--;
-  if (pollset->shutting_down) {
-    /* We don't care about this pollset anymore. */
-    if (pollset->in_flight_cbs == 0 && !pollset->called_shutdown) {
-      pollset->called_shutdown = 1;
-      finish_shutdown(exec_ctx, pollset);
-    }
-  } else if (fd_is_orphaned(fd)) {
-    /* Don't try to add it to anything, we'll drop our ref on it below */
-  } else if (pollset->vtable != original_vtable) {
-    pollset->vtable->add_fd(exec_ctx, pollset, fd, 0);
-  } else if (fd != pollset->data.ptr) {
-    grpc_fd *fds[2];
-    fds[0] = pollset->data.ptr;
-    fds[1] = fd;
-
-    if (fds[0] && !fd_is_orphaned(fds[0])) {
-      platform_become_multipoller(exec_ctx, pollset, fds, GPR_ARRAY_SIZE(fds));
-      GRPC_FD_UNREF(fds[0], "basicpoll");
-    } else {
-      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
-       * unary poller */
-      /* Note that it is possible that fds[1] is also orphaned at this point.
-       * That's okay, we'll correct it at the next add or poll. */
-      if (fds[0]) GRPC_FD_UNREF(fds[0], "basicpoll");
-      pollset->data.ptr = fd;
-      GRPC_FD_REF(fd, "basicpoll");
-    }
-  }
-
-  gpr_mu_unlock(&pollset->mu);
-
-  /* Matching ref in basic_pollset_add_fd */
-  GRPC_FD_UNREF(fd, "basicpoll_add");
-}
-
-static void basic_pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                                 grpc_fd *fd, int and_unlock_pollset) {
-  grpc_unary_promote_args *up_args;
-  GPR_ASSERT(fd);
-  if (fd == pollset->data.ptr) goto exit;
-
-  if (!pollset_has_workers(pollset)) {
-    /* Fast path -- no in flight cbs */
-    /* TODO(klempner): Comment this out and fix any test failures or establish
-     * they are due to timing issues */
-    grpc_fd *fds[2];
-    fds[0] = pollset->data.ptr;
-    fds[1] = fd;
-
-    if (fds[0] == NULL) {
-      pollset->data.ptr = fd;
-      GRPC_FD_REF(fd, "basicpoll");
-    } else if (!fd_is_orphaned(fds[0])) {
-      platform_become_multipoller(exec_ctx, pollset, fds, GPR_ARRAY_SIZE(fds));
-      GRPC_FD_UNREF(fds[0], "basicpoll");
-    } else {
-      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
-       * unary poller */
-      GRPC_FD_UNREF(fds[0], "basicpoll");
-      pollset->data.ptr = fd;
-      GRPC_FD_REF(fd, "basicpoll");
-    }
-    goto exit;
-  }
-
-  /* Now we need to promote. This needs to happen when we're not polling. Since
-   * this may be called from poll, the wait needs to happen asynchronously. */
-  GRPC_FD_REF(fd, "basicpoll_add");
-  pollset->in_flight_cbs++;
-  up_args = gpr_malloc(sizeof(*up_args));
-  up_args->fd = fd;
-  up_args->original_vtable = pollset->vtable;
-  up_args->pollset = pollset;
-  up_args->promotion_closure.cb = basic_do_promote;
-  up_args->promotion_closure.cb_arg = up_args;
-
-  grpc_closure_list_append(&pollset->idle_jobs, &up_args->promotion_closure,
-                           GRPC_ERROR_NONE);
-  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
-
-exit:
-  if (and_unlock_pollset) {
-    gpr_mu_unlock(&pollset->mu);
-  }
-}
-
-static grpc_error *basic_pollset_maybe_work_and_unlock(
-    grpc_exec_ctx *exec_ctx, grpc_pollset *pollset, grpc_pollset_worker *worker,
-    gpr_timespec deadline, gpr_timespec now) {
-#define POLLOUT_CHECK (POLLOUT | POLLHUP | POLLERR)
-#define POLLIN_CHECK (POLLIN | POLLHUP | POLLERR)
-
-  struct pollfd pfd[3];
-  grpc_fd *fd;
-  grpc_fd_watcher fd_watcher;
-  int timeout;
-  int r;
-  nfds_t nfds;
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  fd = pollset->data.ptr;
-  if (fd && fd_is_orphaned(fd)) {
-    GRPC_FD_UNREF(fd, "basicpoll");
-    fd = pollset->data.ptr = NULL;
-  }
-  timeout = poll_deadline_to_millis_timeout(deadline, now);
-  pfd[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd);
-  pfd[0].events = POLLIN;
-  pfd[0].revents = 0;
-  pfd[1].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
-  pfd[1].events = POLLIN;
-  pfd[1].revents = 0;
-  nfds = 2;
-  if (fd) {
-    pfd[2].fd = fd->fd;
-    pfd[2].revents = 0;
-    GRPC_FD_REF(fd, "basicpoll_begin");
-    gpr_mu_unlock(&pollset->mu);
-    pfd[2].events =
-        (short)fd_begin_poll(fd, pollset, worker, POLLIN, POLLOUT, &fd_watcher);
-    if (pfd[2].events != 0) {
-      nfds++;
-    }
-  } else {
-    gpr_mu_unlock(&pollset->mu);
-  }
-
-  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
-     even going into the blocking annotation if possible */
-  /* poll fd count (argument 2) is shortened by one if we have no events
-     to poll on - such that it only includes the kicker */
-  GPR_TIMER_BEGIN("poll", 0);
-  GRPC_SCHEDULING_START_BLOCKING_REGION;
-  r = grpc_poll_function(pfd, nfds, timeout);
-  GRPC_SCHEDULING_END_BLOCKING_REGION;
-  GPR_TIMER_END("poll", 0);
-
-  if (r < 0) {
-    if (errno != EINTR) {
-      work_combine_error(&error, GRPC_OS_ERROR(errno, "poll"));
-    }
-    if (fd) {
-      fd_end_poll(exec_ctx, &fd_watcher, 0, 0, NULL);
-    }
-  } else if (r == 0) {
-    if (fd) {
-      fd_end_poll(exec_ctx, &fd_watcher, 0, 0, NULL);
-    }
-  } else {
-    if (pfd[0].revents & POLLIN_CHECK) {
-      work_combine_error(&error,
-                         grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd));
-    }
-    if (pfd[1].revents & POLLIN_CHECK) {
-      work_combine_error(&error,
-                         grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd));
-    }
-    if (nfds > 2) {
-      fd_end_poll(exec_ctx, &fd_watcher, pfd[2].revents & POLLIN_CHECK,
-                  pfd[2].revents & POLLOUT_CHECK, pollset);
-    } else if (fd) {
-      fd_end_poll(exec_ctx, &fd_watcher, 0, 0, NULL);
-    }
-  }
-
-  if (fd) {
-    GRPC_FD_UNREF(fd, "basicpoll_begin");
-  }
-
-  return error;
-}
-
-static void basic_pollset_destroy(grpc_pollset *pollset) {
-  if (pollset->data.ptr != NULL) {
-    GRPC_FD_UNREF(pollset->data.ptr, "basicpoll");
-    pollset->data.ptr = NULL;
-  }
-}
-
-static const grpc_pollset_vtable basic_pollset = {
-    basic_pollset_add_fd, basic_pollset_maybe_work_and_unlock,
-    basic_pollset_destroy, basic_pollset_destroy};
-
-static void become_basic_pollset(grpc_pollset *pollset, grpc_fd *fd_or_null) {
-  pollset->vtable = &basic_pollset;
-  pollset->data.ptr = fd_or_null;
-  if (fd_or_null != NULL) {
-    GRPC_FD_REF(fd_or_null, "basicpoll");
-  }
-}
-
-/*******************************************************************************
- * pollset_multipoller_with_poll_posix.c
- */
-
-#ifndef GRPC_LINUX_MULTIPOLL_WITH_EPOLL
-
-typedef struct {
-  /* all polled fds */
-  size_t fd_count;
-  size_t fd_capacity;
-  grpc_fd **fds;
-  /* fds that have been removed from the pollset explicitly */
-  size_t del_count;
-  size_t del_capacity;
-  grpc_fd **dels;
-} poll_hdr;
-
-static void multipoll_with_poll_pollset_add_fd(grpc_exec_ctx *exec_ctx,
-                                               grpc_pollset *pollset,
-                                               grpc_fd *fd,
-                                               int and_unlock_pollset) {
-  size_t i;
-  poll_hdr *h = pollset->data.ptr;
-  /* TODO(ctiller): this is O(num_fds^2); maybe switch to a hash set here */
-  for (i = 0; i < h->fd_count; i++) {
-    if (h->fds[i] == fd) goto exit;
-  }
-  if (h->fd_count == h->fd_capacity) {
-    h->fd_capacity = GPR_MAX(h->fd_capacity + 8, h->fd_count * 3 / 2);
-    h->fds = gpr_realloc(h->fds, sizeof(grpc_fd *) * h->fd_capacity);
-  }
-  h->fds[h->fd_count++] = fd;
-  GRPC_FD_REF(fd, "multipoller");
-exit:
-  if (and_unlock_pollset) {
-    gpr_mu_unlock(&pollset->mu);
-  }
-}
-
-static grpc_error *multipoll_with_poll_pollset_maybe_work_and_unlock(
-    grpc_exec_ctx *exec_ctx, grpc_pollset *pollset, grpc_pollset_worker *worker,
-    gpr_timespec deadline, gpr_timespec now) {
-#define POLLOUT_CHECK (POLLOUT | POLLHUP | POLLERR)
-#define POLLIN_CHECK (POLLIN | POLLHUP | POLLERR)
-
-  int timeout;
-  int r;
-  size_t i, j, fd_count;
-  nfds_t pfd_count;
-  poll_hdr *h;
-  /* TODO(ctiller): inline some elements to avoid an allocation */
-  grpc_fd_watcher *watchers;
-  struct pollfd *pfds;
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  h = pollset->data.ptr;
-  timeout = poll_deadline_to_millis_timeout(deadline, now);
-  /* TODO(ctiller): perform just one malloc here if we exceed the inline case */
-  pfds = gpr_malloc(sizeof(*pfds) * (h->fd_count + 2));
-  watchers = gpr_malloc(sizeof(*watchers) * (h->fd_count + 2));
-  fd_count = 0;
-  pfd_count = 2;
-  pfds[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd);
-  pfds[0].events = POLLIN;
-  pfds[0].revents = 0;
-  pfds[1].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
-  pfds[1].events = POLLIN;
-  pfds[1].revents = 0;
-  for (i = 0; i < h->fd_count; i++) {
-    int remove = fd_is_orphaned(h->fds[i]);
-    for (j = 0; !remove && j < h->del_count; j++) {
-      if (h->fds[i] == h->dels[j]) remove = 1;
-    }
-    if (remove) {
-      GRPC_FD_UNREF(h->fds[i], "multipoller");
-    } else {
-      h->fds[fd_count++] = h->fds[i];
-      watchers[pfd_count].fd = h->fds[i];
-      GRPC_FD_REF(watchers[pfd_count].fd, "multipoller_start");
-      pfds[pfd_count].fd = h->fds[i]->fd;
-      pfds[pfd_count].revents = 0;
-      pfd_count++;
-    }
-  }
-  for (j = 0; j < h->del_count; j++) {
-    GRPC_FD_UNREF(h->dels[j], "multipoller_del");
-  }
-  h->del_count = 0;
-  h->fd_count = fd_count;
-  gpr_mu_unlock(&pollset->mu);
-
-  for (i = 2; i < pfd_count; i++) {
-    grpc_fd *fd = watchers[i].fd;
-    pfds[i].events = (short)fd_begin_poll(fd, pollset, worker, POLLIN, POLLOUT,
-                                          &watchers[i]);
-    GRPC_FD_UNREF(fd, "multipoller_start");
-  }
-
-  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
-     even going into the blocking annotation if possible */
-  GRPC_SCHEDULING_START_BLOCKING_REGION;
-  r = grpc_poll_function(pfds, pfd_count, timeout);
-  GRPC_SCHEDULING_END_BLOCKING_REGION;
-
-  if (r < 0) {
-    if (errno != EINTR) {
-      work_combine_error(&error, GRPC_OS_ERROR(errno, "poll"));
-    }
-    for (i = 2; i < pfd_count; i++) {
-      fd_end_poll(exec_ctx, &watchers[i], 0, 0, NULL);
-    }
-  } else if (r == 0) {
-    for (i = 2; i < pfd_count; i++) {
-      fd_end_poll(exec_ctx, &watchers[i], 0, 0, NULL);
-    }
-  } else {
-    if (pfds[0].revents & POLLIN_CHECK) {
-      work_combine_error(&error,
-                         grpc_wakeup_fd_consume_wakeup(&grpc_global_wakeup_fd));
-    }
-    if (pfds[1].revents & POLLIN_CHECK) {
-      work_combine_error(&error,
-                         grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd));
-    }
-    for (i = 2; i < pfd_count; i++) {
-      if (watchers[i].fd == NULL) {
-        fd_end_poll(exec_ctx, &watchers[i], 0, 0, NULL);
-        continue;
-      }
-      fd_end_poll(exec_ctx, &watchers[i], pfds[i].revents & POLLIN_CHECK,
-                  pfds[i].revents & POLLOUT_CHECK, pollset);
-    }
-  }
-
-  gpr_free(pfds);
-  gpr_free(watchers);
-
-  return error;
-}
-
-static void multipoll_with_poll_pollset_finish_shutdown(grpc_pollset *pollset) {
-  size_t i;
-  poll_hdr *h = pollset->data.ptr;
-  for (i = 0; i < h->fd_count; i++) {
-    GRPC_FD_UNREF(h->fds[i], "multipoller");
-  }
-  for (i = 0; i < h->del_count; i++) {
-    GRPC_FD_UNREF(h->dels[i], "multipoller_del");
-  }
-  h->fd_count = 0;
-  h->del_count = 0;
-}
-
-static void multipoll_with_poll_pollset_destroy(grpc_pollset *pollset) {
-  poll_hdr *h = pollset->data.ptr;
-  multipoll_with_poll_pollset_finish_shutdown(pollset);
-  gpr_free(h->fds);
-  gpr_free(h->dels);
-  gpr_free(h);
-}
-
-static const grpc_pollset_vtable multipoll_with_poll_pollset = {
-    multipoll_with_poll_pollset_add_fd,
-    multipoll_with_poll_pollset_maybe_work_and_unlock,
-    multipoll_with_poll_pollset_finish_shutdown,
-    multipoll_with_poll_pollset_destroy};
-
-static void poll_become_multipoller(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset *pollset, grpc_fd **fds,
-                                    size_t nfds) {
-  size_t i;
-  poll_hdr *h = gpr_malloc(sizeof(poll_hdr));
-  pollset->vtable = &multipoll_with_poll_pollset;
-  pollset->data.ptr = h;
-  h->fd_count = nfds;
-  h->fd_capacity = nfds;
-  h->fds = gpr_malloc(nfds * sizeof(grpc_fd *));
-  h->del_count = 0;
-  h->del_capacity = 0;
-  h->dels = NULL;
-  for (i = 0; i < nfds; i++) {
-    h->fds[i] = fds[i];
-    GRPC_FD_REF(fds[i], "multipoller");
-  }
-}
-
-#endif /* !GRPC_LINUX_MULTIPOLL_WITH_EPOLL */
-
-/*******************************************************************************
- * pollset_multipoller_with_epoll_posix.c
- */
-
-#ifdef GRPC_LINUX_MULTIPOLL_WITH_EPOLL
-
-#include <errno.h>
-#include <poll.h>
-#include <string.h>
-#include <sys/epoll.h>
-#include <unistd.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/profiling/timers.h"
-#include "src/core/lib/support/block_annotate.h"
-
-static void set_ready(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure **st,
-                      grpc_pollset *read_notifier_pollset) {
-  /* only one set_ready can be active at once (but there may be a racing
-     notify_on) */
-  gpr_mu_lock(&fd->mu);
-  set_ready_locked(exec_ctx, fd, st);
-
-  /* A non-NULL read_notifier_pollset means that the fd is readable. */
-  if (read_notifier_pollset != NULL) {
-    /* Note: Since the fd might be a part of multiple pollsets, this might be
-     * called multiple times (for each time the fd becomes readable) and it is
-     * okay to set the fd's read-notifier pollset to anyone of these pollsets */
-    set_read_notifier_pollset_locked(exec_ctx, fd, read_notifier_pollset);
-  }
-
-  gpr_mu_unlock(&fd->mu);
-}
-
-static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                               grpc_pollset *notifier_pollset) {
-  set_ready(exec_ctx, fd, &fd->read_closure, notifier_pollset);
-}
-
-static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  set_ready(exec_ctx, fd, &fd->write_closure, NULL);
-}
-
-struct epoll_fd_list {
-  int *epoll_fds;
-  size_t count;
-  size_t capacity;
-};
-
-static struct epoll_fd_list epoll_fd_global_list;
-static gpr_once init_epoll_fd_list_mu = GPR_ONCE_INIT;
-static gpr_mu epoll_fd_list_mu;
-
-static void init_mu(void) { gpr_mu_init(&epoll_fd_list_mu); }
-
-static void add_epoll_fd_to_global_list(int epoll_fd) {
-  gpr_once_init(&init_epoll_fd_list_mu, init_mu);
-
-  gpr_mu_lock(&epoll_fd_list_mu);
-  if (epoll_fd_global_list.count == epoll_fd_global_list.capacity) {
-    epoll_fd_global_list.capacity =
-        GPR_MAX((size_t)8, epoll_fd_global_list.capacity * 2);
-    epoll_fd_global_list.epoll_fds =
-        gpr_realloc(epoll_fd_global_list.epoll_fds,
-                    epoll_fd_global_list.capacity * sizeof(int));
-  }
-  epoll_fd_global_list.epoll_fds[epoll_fd_global_list.count++] = epoll_fd;
-  gpr_mu_unlock(&epoll_fd_list_mu);
-}
-
-static void remove_epoll_fd_from_global_list(int epoll_fd) {
-  gpr_mu_lock(&epoll_fd_list_mu);
-  GPR_ASSERT(epoll_fd_global_list.count > 0);
-  for (size_t i = 0; i < epoll_fd_global_list.count; i++) {
-    if (epoll_fd == epoll_fd_global_list.epoll_fds[i]) {
-      epoll_fd_global_list.epoll_fds[i] =
-          epoll_fd_global_list.epoll_fds[--(epoll_fd_global_list.count)];
-      break;
-    }
-  }
-  gpr_mu_unlock(&epoll_fd_list_mu);
-}
-
-static void remove_fd_from_all_epoll_sets(int fd) {
-  int err;
-  gpr_once_init(&init_epoll_fd_list_mu, init_mu);
-  gpr_mu_lock(&epoll_fd_list_mu);
-  if (epoll_fd_global_list.count == 0) {
-    gpr_mu_unlock(&epoll_fd_list_mu);
-    return;
-  }
-  for (size_t i = 0; i < epoll_fd_global_list.count; i++) {
-    err = epoll_ctl(epoll_fd_global_list.epoll_fds[i], EPOLL_CTL_DEL, fd, NULL);
-    if (err < 0 && errno != ENOENT) {
-      gpr_log(GPR_ERROR, "epoll_ctl del for %d failed: %s", fd,
-              strerror(errno));
-    }
-  }
-  gpr_mu_unlock(&epoll_fd_list_mu);
-}
-
-typedef struct {
-  grpc_pollset *pollset;
-  grpc_fd *fd;
-  grpc_closure closure;
-} delayed_add;
-
-typedef struct { int epoll_fd; } epoll_hdr;
-
-static void finally_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           grpc_fd *fd) {
-  epoll_hdr *h = pollset->data.ptr;
-  struct epoll_event ev;
-  int err;
-  grpc_fd_watcher watcher;
-
-  /* We pretend to be polling whilst adding an fd to keep the fd from being
-     closed during the add. This may result in a spurious wakeup being assigned
-     to this pollset whilst adding, but that should be benign. */
-  GPR_ASSERT(fd_begin_poll(fd, pollset, NULL, 0, 0, &watcher) == 0);
-  if (watcher.fd != NULL) {
-    ev.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET);
-    ev.data.ptr = fd;
-    err = epoll_ctl(h->epoll_fd, EPOLL_CTL_ADD, fd->fd, &ev);
-    if (err < 0) {
-      /* FDs may be added to a pollset multiple times, so EEXIST is normal. */
-      if (errno != EEXIST) {
-        gpr_log(GPR_ERROR, "epoll_ctl add for %d failed: %s", fd->fd,
-                strerror(errno));
-      }
-    }
-  }
-  fd_end_poll(exec_ctx, &watcher, 0, 0, NULL);
-}
-
-static void perform_delayed_add(grpc_exec_ctx *exec_ctx, void *arg,
-                                grpc_error *error) {
-  delayed_add *da = arg;
-
-  if (!fd_is_orphaned(da->fd)) {
-    finally_add_fd(exec_ctx, da->pollset, da->fd);
-  }
-
-  gpr_mu_lock(&da->pollset->mu);
-  da->pollset->in_flight_cbs--;
-  if (da->pollset->shutting_down) {
-    /* We don't care about this pollset anymore. */
-    if (da->pollset->in_flight_cbs == 0 && !da->pollset->called_shutdown) {
-      da->pollset->called_shutdown = 1;
-      grpc_exec_ctx_sched(exec_ctx, da->pollset->shutdown_done, GRPC_ERROR_NONE,
-                          NULL);
-    }
-  }
-  gpr_mu_unlock(&da->pollset->mu);
-
-  GRPC_FD_UNREF(da->fd, "delayed_add");
-
-  gpr_free(da);
-}
-
-static void multipoll_with_epoll_pollset_add_fd(grpc_exec_ctx *exec_ctx,
-                                                grpc_pollset *pollset,
-                                                grpc_fd *fd,
-                                                int and_unlock_pollset) {
-  if (and_unlock_pollset) {
-    gpr_mu_unlock(&pollset->mu);
-    finally_add_fd(exec_ctx, pollset, fd);
-  } else {
-    delayed_add *da = gpr_malloc(sizeof(*da));
-    da->pollset = pollset;
-    da->fd = fd;
-    GRPC_FD_REF(fd, "delayed_add");
-    grpc_closure_init(&da->closure, perform_delayed_add, da);
-    pollset->in_flight_cbs++;
-    grpc_exec_ctx_sched(exec_ctx, &da->closure, GRPC_ERROR_NONE, NULL);
-  }
-}
-
-/* TODO(klempner): We probably want to turn this down a bit */
-#define GRPC_EPOLL_MAX_EVENTS 1000
-
-static grpc_error *multipoll_with_epoll_pollset_maybe_work_and_unlock(
-    grpc_exec_ctx *exec_ctx, grpc_pollset *pollset, grpc_pollset_worker *worker,
-    gpr_timespec deadline, gpr_timespec now) {
-  struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS];
-  int ep_rv;
-  int poll_rv;
-  epoll_hdr *h = pollset->data.ptr;
-  int timeout_ms;
-  struct pollfd pfds[2];
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  /* If you want to ignore epoll's ability to sanely handle parallel pollers,
-   * for a more apples-to-apples performance comparison with poll, add a
-   * if (pollset->counter != 0) { return 0; }
-   * here.
-   */
-
-  gpr_mu_unlock(&pollset->mu);
-
-  timeout_ms = poll_deadline_to_millis_timeout(deadline, now);
-
-  pfds[0].fd = GRPC_WAKEUP_FD_GET_READ_FD(&worker->wakeup_fd->fd);
-  pfds[0].events = POLLIN;
-  pfds[0].revents = 0;
-  pfds[1].fd = h->epoll_fd;
-  pfds[1].events = POLLIN;
-  pfds[1].revents = 0;
-
-  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
-     even going into the blocking annotation if possible */
-  GPR_TIMER_BEGIN("poll", 0);
-  GRPC_SCHEDULING_START_BLOCKING_REGION;
-  poll_rv = grpc_poll_function(pfds, 2, timeout_ms);
-  GRPC_SCHEDULING_END_BLOCKING_REGION;
-  GPR_TIMER_END("poll", 0);
-
-  if (poll_rv < 0) {
-    if (errno != EINTR) {
-      work_combine_error(&error, GRPC_OS_ERROR(errno, "poll"));
-    }
-  } else if (poll_rv == 0) {
-    /* do nothing */
-  } else {
-    if (pfds[0].revents) {
-      work_combine_error(&error,
-                         grpc_wakeup_fd_consume_wakeup(&worker->wakeup_fd->fd));
-    }
-    if (pfds[1].revents) {
-      do {
-        /* The following epoll_wait never blocks; it has a timeout of 0 */
-        ep_rv = epoll_wait(h->epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, 0);
-        if (ep_rv < 0) {
-          if (errno != EINTR) {
-            work_combine_error(&error, GRPC_OS_ERROR(errno, "epoll_wait"));
-          }
-        } else {
-          int i;
-          for (i = 0; i < ep_rv; ++i) {
-            grpc_fd *fd = ep_ev[i].data.ptr;
-            /* TODO(klempner): We might want to consider making err and pri
-             * separate events */
-            int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
-            int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
-            int write_ev = ep_ev[i].events & EPOLLOUT;
-            if (fd == NULL) {
-              work_combine_error(&error, grpc_wakeup_fd_consume_wakeup(
-                                             &grpc_global_wakeup_fd));
-            } else {
-              if (read_ev || cancel) {
-                fd_become_readable(exec_ctx, fd, pollset);
-              }
-              if (write_ev || cancel) {
-                fd_become_writable(exec_ctx, fd);
-              }
-            }
-          }
-        }
-      } while (ep_rv == GRPC_EPOLL_MAX_EVENTS);
-    }
-  }
-  return error;
-}
-
-static void multipoll_with_epoll_pollset_finish_shutdown(
-    grpc_pollset *pollset) {}
-
-static void multipoll_with_epoll_pollset_destroy(grpc_pollset *pollset) {
-  epoll_hdr *h = pollset->data.ptr;
-  close(h->epoll_fd);
-  remove_epoll_fd_from_global_list(h->epoll_fd);
-  gpr_free(h);
-}
-
-static const grpc_pollset_vtable multipoll_with_epoll_pollset = {
-    multipoll_with_epoll_pollset_add_fd,
-    multipoll_with_epoll_pollset_maybe_work_and_unlock,
-    multipoll_with_epoll_pollset_finish_shutdown,
-    multipoll_with_epoll_pollset_destroy};
-
-static void epoll_become_multipoller(grpc_exec_ctx *exec_ctx,
-                                     grpc_pollset *pollset, grpc_fd **fds,
-                                     size_t nfds) {
-  size_t i;
-  epoll_hdr *h = gpr_malloc(sizeof(epoll_hdr));
-  struct epoll_event ev;
-  int err;
-
-  pollset->vtable = &multipoll_with_epoll_pollset;
-  pollset->data.ptr = h;
-  h->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
-  if (h->epoll_fd < 0) {
-    /* TODO(klempner): Fall back to poll here, especially on ENOSYS */
-    gpr_log(GPR_ERROR, "epoll_create1 failed: %s", strerror(errno));
-    abort();
-  }
-  add_epoll_fd_to_global_list(h->epoll_fd);
-
-  ev.events = (uint32_t)(EPOLLIN | EPOLLET);
-  ev.data.ptr = NULL;
-  err = epoll_ctl(h->epoll_fd, EPOLL_CTL_ADD,
-                  GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd), &ev);
-  if (err < 0) {
-    gpr_log(GPR_ERROR, "epoll_ctl add for %d failed: %s",
-            GRPC_WAKEUP_FD_GET_READ_FD(&grpc_global_wakeup_fd),
-            strerror(errno));
-  }
-
-  for (i = 0; i < nfds; i++) {
-    multipoll_with_epoll_pollset_add_fd(exec_ctx, pollset, fds[i], 0);
-  }
-}
-
-#else /* GRPC_LINUX_MULTIPOLL_WITH_EPOLL */
-
-static void remove_fd_from_all_epoll_sets(int fd) {}
-
-#endif /* GRPC_LINUX_MULTIPOLL_WITH_EPOLL */
-
-/*******************************************************************************
- * pollset_set_posix.c
- */
-
-static grpc_pollset_set *pollset_set_create(void) {
-  grpc_pollset_set *pollset_set = gpr_malloc(sizeof(*pollset_set));
-  memset(pollset_set, 0, sizeof(*pollset_set));
-  gpr_mu_init(&pollset_set->mu);
-  return pollset_set;
-}
-
-static void pollset_set_destroy(grpc_pollset_set *pollset_set) {
-  size_t i;
-  gpr_mu_destroy(&pollset_set->mu);
-  for (i = 0; i < pollset_set->fd_count; i++) {
-    GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
-  }
-  gpr_free(pollset_set->pollsets);
-  gpr_free(pollset_set->pollset_sets);
-  gpr_free(pollset_set->fds);
-  gpr_free(pollset_set);
-}
-
-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_set->mu);
-  if (pollset_set->pollset_count == pollset_set->pollset_capacity) {
-    pollset_set->pollset_capacity =
-        GPR_MAX(8, 2 * pollset_set->pollset_capacity);
-    pollset_set->pollsets =
-        gpr_realloc(pollset_set->pollsets, pollset_set->pollset_capacity *
-                                               sizeof(*pollset_set->pollsets));
-  }
-  pollset_set->pollsets[pollset_set->pollset_count++] = pollset;
-  for (i = 0, j = 0; i < pollset_set->fd_count; i++) {
-    if (fd_is_orphaned(pollset_set->fds[i])) {
-      GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
-    } else {
-      pollset_add_fd(exec_ctx, pollset, pollset_set->fds[i]);
-      pollset_set->fds[j++] = pollset_set->fds[i];
-    }
-  }
-  pollset_set->fd_count = j;
-  gpr_mu_unlock(&pollset_set->mu);
-}
-
-static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pollset_set,
-                                    grpc_pollset *pollset) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  for (i = 0; i < pollset_set->pollset_count; i++) {
-    if (pollset_set->pollsets[i] == pollset) {
-      pollset_set->pollset_count--;
-      GPR_SWAP(grpc_pollset *, pollset_set->pollsets[i],
-               pollset_set->pollsets[pollset_set->pollset_count]);
-      break;
-    }
-  }
-  gpr_mu_unlock(&pollset_set->mu);
-}
-
-static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  size_t i, j;
-  gpr_mu_lock(&bag->mu);
-  if (bag->pollset_set_count == bag->pollset_set_capacity) {
-    bag->pollset_set_capacity = GPR_MAX(8, 2 * bag->pollset_set_capacity);
-    bag->pollset_sets =
-        gpr_realloc(bag->pollset_sets,
-                    bag->pollset_set_capacity * sizeof(*bag->pollset_sets));
-  }
-  bag->pollset_sets[bag->pollset_set_count++] = item;
-  for (i = 0, j = 0; i < bag->fd_count; i++) {
-    if (fd_is_orphaned(bag->fds[i])) {
-      GRPC_FD_UNREF(bag->fds[i], "pollset_set");
-    } else {
-      pollset_set_add_fd(exec_ctx, item, bag->fds[i]);
-      bag->fds[j++] = bag->fds[i];
-    }
-  }
-  bag->fd_count = j;
-  gpr_mu_unlock(&bag->mu);
-}
-
-static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  size_t i;
-  gpr_mu_lock(&bag->mu);
-  for (i = 0; i < bag->pollset_set_count; i++) {
-    if (bag->pollset_sets[i] == item) {
-      bag->pollset_set_count--;
-      GPR_SWAP(grpc_pollset_set *, bag->pollset_sets[i],
-               bag->pollset_sets[bag->pollset_set_count]);
-      break;
-    }
-  }
-  gpr_mu_unlock(&bag->mu);
-}
-
-static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
-                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  if (pollset_set->fd_count == pollset_set->fd_capacity) {
-    pollset_set->fd_capacity = GPR_MAX(8, 2 * pollset_set->fd_capacity);
-    pollset_set->fds = gpr_realloc(
-        pollset_set->fds, pollset_set->fd_capacity * sizeof(*pollset_set->fds));
-  }
-  GRPC_FD_REF(fd, "pollset_set");
-  pollset_set->fds[pollset_set->fd_count++] = fd;
-  for (i = 0; i < pollset_set->pollset_count; i++) {
-    pollset_add_fd(exec_ctx, pollset_set->pollsets[i], fd);
-  }
-  for (i = 0; i < pollset_set->pollset_set_count; i++) {
-    pollset_set_add_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
-  }
-  gpr_mu_unlock(&pollset_set->mu);
-}
-
-static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
-                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  for (i = 0; i < pollset_set->fd_count; i++) {
-    if (pollset_set->fds[i] == fd) {
-      pollset_set->fd_count--;
-      GPR_SWAP(grpc_fd *, pollset_set->fds[i],
-               pollset_set->fds[pollset_set->fd_count]);
-      GRPC_FD_UNREF(fd, "pollset_set");
-      break;
-    }
-  }
-  for (i = 0; i < pollset_set->pollset_set_count; i++) {
-    pollset_set_del_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
-  }
-  gpr_mu_unlock(&pollset_set->mu);
-}
-
-/*******************************************************************************
- * workqueue stubs
- */
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  return workqueue;
-}
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  return workqueue;
-}
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {}
-#endif
-
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx,
-                              grpc_workqueue *workqueue, grpc_closure *closure,
-                              grpc_error *error) {
-  grpc_exec_ctx_sched(exec_ctx, closure, error, NULL);
-}
-
-/*******************************************************************************
- * event engine binding
- */
-
-static void shutdown_engine(void) {
-  fd_global_shutdown();
-  pollset_global_shutdown();
-}
-
-static const grpc_event_engine_vtable vtable = {
-    .pollset_size = sizeof(grpc_pollset),
-
-    .fd_create = fd_create,
-    .fd_wrapped_fd = fd_wrapped_fd,
-    .fd_orphan = fd_orphan,
-    .fd_shutdown = fd_shutdown,
-    .fd_is_shutdown = fd_is_shutdown,
-    .fd_notify_on_read = fd_notify_on_read,
-    .fd_notify_on_write = fd_notify_on_write,
-    .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
-
-    .pollset_init = pollset_init,
-    .pollset_shutdown = pollset_shutdown,
-    .pollset_reset = pollset_reset,
-    .pollset_destroy = pollset_destroy,
-    .pollset_work = pollset_work,
-    .pollset_kick = pollset_kick,
-    .pollset_add_fd = pollset_add_fd,
-
-    .pollset_set_create = pollset_set_create,
-    .pollset_set_destroy = pollset_set_destroy,
-    .pollset_set_add_pollset = pollset_set_add_pollset,
-    .pollset_set_del_pollset = pollset_set_del_pollset,
-    .pollset_set_add_pollset_set = pollset_set_add_pollset_set,
-    .pollset_set_del_pollset_set = pollset_set_del_pollset_set,
-    .pollset_set_add_fd = pollset_set_add_fd,
-    .pollset_set_del_fd = pollset_set_del_fd,
-
-    .kick_poller = kick_poller,
-
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_enqueue = workqueue_enqueue,
-
-    .shutdown_engine = shutdown_engine,
-};
-
-const grpc_event_engine_vtable *grpc_init_poll_and_epoll_posix(void) {
-#ifdef GRPC_LINUX_MULTIPOLL_WITH_EPOLL
-  platform_become_multipoller = epoll_become_multipoller;
-#else
-  platform_become_multipoller = poll_become_multipoller;
-#endif
-  fd_global_init();
-  pollset_global_init();
-  return &vtable;
-}
-
-#endif
diff --git a/src/core/lib/iomgr/ev_poll_and_epoll_posix.h b/src/core/lib/iomgr/ev_poll_and_epoll_posix.h
deleted file mode 100644
index 06d6dbf29d..0000000000
--- a/src/core/lib/iomgr/ev_poll_and_epoll_posix.h
+++ /dev/null
@@ -1,41 +0,0 @@
-/*
- *
- * Copyright 2015, 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_CORE_LIB_IOMGR_EV_POLL_AND_EPOLL_POSIX_H
-#define GRPC_CORE_LIB_IOMGR_EV_POLL_AND_EPOLL_POSIX_H
-
-#include "src/core/lib/iomgr/ev_posix.h"
-
-const grpc_event_engine_vtable *grpc_init_poll_and_epoll_posix(void);
-
-#endif /* GRPC_CORE_LIB_IOMGR_EV_POLL_AND_EPOLL_POSIX_H */
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index ef36ba89b2..ab139895fd 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -45,7 +45,6 @@
 #include <grpc/support/useful.h>
 
 #include "src/core/lib/iomgr/ev_epoll_linux.h"
-#include "src/core/lib/iomgr/ev_poll_and_epoll_posix.h"
 #include "src/core/lib/iomgr/ev_poll_posix.h"
 #include "src/core/lib/support/env.h"
 
@@ -67,7 +66,6 @@ static const event_engine_factory g_factories[] = {
     {"epoll", grpc_init_epoll_linux},
     {"poll", grpc_init_poll_posix},
     {"poll-cv", grpc_init_poll_cv_posix},
-    {"legacy", grpc_init_poll_and_epoll_posix},
 };
 
 static void add(const char *beg, const char *end, char ***ss, size_t *ns) {
diff --git a/src/core/lib/iomgr/executor.c b/src/core/lib/iomgr/executor.c
index 8d7535d6fe..4e78b619fb 100644
--- a/src/core/lib/iomgr/executor.c
+++ b/src/core/lib/iomgr/executor.c
@@ -121,9 +121,8 @@ void grpc_executor_push(grpc_closure *closure, grpc_error *error) {
   gpr_mu_unlock(&g_executor.mu);
 }
 
-void grpc_executor_shutdown() {
+void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx) {
   int pending_join;
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
   gpr_mu_lock(&g_executor.mu);
   pending_join = g_executor.pending_join;
@@ -133,8 +132,7 @@ void grpc_executor_shutdown() {
    * list below because we aren't accepting new work */
 
   /* Execute pending callbacks, some may be performing cleanups */
-  grpc_exec_ctx_enqueue_list(&exec_ctx, &g_executor.closures, NULL);
-  grpc_exec_ctx_finish(&exec_ctx);
+  grpc_exec_ctx_enqueue_list(exec_ctx, &g_executor.closures, NULL);
   GPR_ASSERT(grpc_closure_list_empty(g_executor.closures));
   if (pending_join) {
     gpr_thd_join(g_executor.tid);
diff --git a/src/core/lib/iomgr/executor.h b/src/core/lib/iomgr/executor.h
index da9dcd07d0..7bf8f21940 100644
--- a/src/core/lib/iomgr/executor.h
+++ b/src/core/lib/iomgr/executor.h
@@ -48,6 +48,6 @@ void grpc_executor_init();
 void grpc_executor_push(grpc_closure *closure, grpc_error *error);
 
 /** Shutdown the executor, running all pending work as part of the call */
-void grpc_executor_shutdown();
+void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx);
 
 #endif /* GRPC_CORE_LIB_IOMGR_EXECUTOR_H */
diff --git a/src/core/lib/iomgr/iomgr.c b/src/core/lib/iomgr/iomgr.c
index 4fd83e0b22..8a233d0ba8 100644
--- a/src/core/lib/iomgr/iomgr.c
+++ b/src/core/lib/iomgr/iomgr.c
@@ -83,11 +83,10 @@ static void dump_objects(const char *kind) {
   }
 }
 
-void grpc_iomgr_shutdown(void) {
+void grpc_iomgr_shutdown(grpc_exec_ctx *exec_ctx) {
   gpr_timespec shutdown_deadline = gpr_time_add(
       gpr_now(GPR_CLOCK_REALTIME), gpr_time_from_seconds(10, GPR_TIMESPAN));
   gpr_timespec last_warning_time = gpr_now(GPR_CLOCK_REALTIME);
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
   grpc_iomgr_platform_flush();
 
@@ -104,10 +103,9 @@ void grpc_iomgr_shutdown(void) {
       }
       last_warning_time = gpr_now(GPR_CLOCK_REALTIME);
     }
-    if (grpc_timer_check(&exec_ctx, gpr_inf_future(GPR_CLOCK_MONOTONIC),
-                         NULL)) {
+    if (grpc_timer_check(exec_ctx, gpr_inf_future(GPR_CLOCK_MONOTONIC), NULL)) {
       gpr_mu_unlock(&g_mu);
-      grpc_exec_ctx_flush(&exec_ctx);
+      grpc_exec_ctx_flush(exec_ctx);
       gpr_mu_lock(&g_mu);
       continue;
     }
@@ -138,8 +136,8 @@ void grpc_iomgr_shutdown(void) {
   }
   gpr_mu_unlock(&g_mu);
 
-  grpc_timer_list_shutdown(&exec_ctx);
-  grpc_exec_ctx_finish(&exec_ctx);
+  grpc_timer_list_shutdown(exec_ctx);
+  grpc_exec_ctx_flush(exec_ctx);
 
   /* ensure all threads have left g_mu */
   gpr_mu_lock(&g_mu);
diff --git a/src/core/lib/iomgr/iomgr.h b/src/core/lib/iomgr/iomgr.h
index c1cfaf302e..245a1e08aa 100644
--- a/src/core/lib/iomgr/iomgr.h
+++ b/src/core/lib/iomgr/iomgr.h
@@ -34,12 +34,14 @@
 #ifndef GRPC_CORE_LIB_IOMGR_IOMGR_H
 #define GRPC_CORE_LIB_IOMGR_IOMGR_H
 
+#include <grpc/impl/codegen/exec_ctx_fwd.h>
 #include "src/core/lib/iomgr/port.h"
 
 /** Initializes the iomgr. */
 void grpc_iomgr_init(void);
 
-/** Signals the intention to shutdown the iomgr. */
-void grpc_iomgr_shutdown(void);
+/** Signals the intention to shutdown the iomgr. Expects to be able to flush
+ * exec_ctx. */
+void grpc_iomgr_shutdown(grpc_exec_ctx *exec_ctx);
 
 #endif /* GRPC_CORE_LIB_IOMGR_IOMGR_H */
diff --git a/src/core/lib/iomgr/socket_mutator.c b/src/core/lib/iomgr/socket_mutator.c
new file mode 100644
index 0000000000..34b61dcfe5
--- /dev/null
+++ b/src/core/lib/iomgr/socket_mutator.c
@@ -0,0 +1,98 @@
+/*
+ *
+ * Copyright 2015, 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 "src/core/lib/iomgr/socket_mutator.h"
+
+#include <grpc/impl/codegen/grpc_types.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/useful.h>
+
+void grpc_socket_mutator_init(grpc_socket_mutator *mutator,
+                              const grpc_socket_mutator_vtable *vtable) {
+  mutator->vtable = vtable;
+  gpr_ref_init(&mutator->refcount, 1);
+}
+
+grpc_socket_mutator *grpc_socket_mutator_ref(grpc_socket_mutator *mutator) {
+  gpr_ref(&mutator->refcount);
+  return mutator;
+}
+
+bool grpc_socket_mutator_mutate_fd(grpc_socket_mutator *mutator, int fd) {
+  return mutator->vtable->mutate_fd(fd, mutator);
+}
+
+int grpc_socket_mutator_compare(grpc_socket_mutator *a,
+                                grpc_socket_mutator *b) {
+  int c = GPR_ICMP(a, b);
+  if (c != 0) {
+    grpc_socket_mutator *sma = a;
+    grpc_socket_mutator *smb = b;
+    c = GPR_ICMP(sma->vtable, smb->vtable);
+    if (c == 0) {
+      c = sma->vtable->compare(sma, smb);
+    }
+  }
+  return c;
+}
+
+void grpc_socket_mutator_unref(grpc_socket_mutator *mutator) {
+  if (gpr_unref(&mutator->refcount)) {
+    mutator->vtable->destory(mutator);
+  }
+}
+
+static void *socket_mutator_arg_copy(void *p) {
+  return grpc_socket_mutator_ref(p);
+}
+
+static void socket_mutator_arg_destroy(grpc_exec_ctx *exec_ctx, void *p) {
+  grpc_socket_mutator_unref(p);
+}
+
+static int socket_mutator_cmp(void *a, void *b) {
+  return grpc_socket_mutator_compare((grpc_socket_mutator *)a,
+                                     (grpc_socket_mutator *)b);
+}
+
+static const grpc_arg_pointer_vtable socket_mutator_arg_vtable = {
+    socket_mutator_arg_copy, socket_mutator_arg_destroy, socket_mutator_cmp};
+
+grpc_arg grpc_socket_mutator_to_arg(grpc_socket_mutator *mutator) {
+  grpc_arg arg;
+  arg.type = GRPC_ARG_POINTER;
+  arg.key = GRPC_ARG_SOCKET_MUTATOR;
+  arg.value.pointer.vtable = &socket_mutator_arg_vtable;
+  arg.value.pointer.p = mutator;
+  return arg;
+}
diff --git a/src/core/lib/iomgr/socket_mutator.h b/src/core/lib/iomgr/socket_mutator.h
new file mode 100644
index 0000000000..2f5b6c248e
--- /dev/null
+++ b/src/core/lib/iomgr/socket_mutator.h
@@ -0,0 +1,80 @@
+/*
+ *
+ * Copyright 2015, 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_CORE_LIB_IOMGR_SOCKET_MUTATOR_H
+#define GRPC_CORE_LIB_IOMGR_SOCKET_MUTATOR_H
+
+#include <grpc/impl/codegen/grpc_types.h>
+#include <grpc/support/sync.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** The virtual table of grpc_socket_mutator */
+typedef struct {
+  /** Mutates the socket opitons of \a fd */
+  bool (*mutate_fd)(int fd, grpc_socket_mutator *mutator);
+  /** Compare socket mutator \a a and \a b */
+  int (*compare)(grpc_socket_mutator *a, grpc_socket_mutator *b);
+  /** Destroys the socket mutator instance */
+  void (*destory)(grpc_socket_mutator *mutator);
+} grpc_socket_mutator_vtable;
+
+/** The Socket Mutator interface allows changes on socket options */
+struct grpc_socket_mutator {
+  const grpc_socket_mutator_vtable *vtable;
+  gpr_refcount refcount;
+};
+
+/** called by concrete implementations to initialize the base struct */
+void grpc_socket_mutator_init(grpc_socket_mutator *mutator,
+                              const grpc_socket_mutator_vtable *vtable);
+
+/** Wrap \a mutator as a grpc_arg */
+grpc_arg grpc_socket_mutator_to_arg(grpc_socket_mutator *mutator);
+
+/** Perform the file descriptor mutation operation of \a mutator on \a fd */
+bool grpc_socket_mutator_mutate_fd(grpc_socket_mutator *mutator, int fd);
+
+/** Compare if \a a and \a b are the same mutator or have same settings */
+int grpc_socket_mutator_compare(grpc_socket_mutator *a, grpc_socket_mutator *b);
+
+grpc_socket_mutator *grpc_socket_mutator_ref(grpc_socket_mutator *mutator);
+void grpc_socket_mutator_unref(grpc_socket_mutator *mutator);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GRPC_CORE_LIB_IOMGR_SOCKET_MUTATOR_H */
diff --git a/src/core/lib/iomgr/socket_utils_common_posix.c b/src/core/lib/iomgr/socket_utils_common_posix.c
index bc28bbe316..88e9ade253 100644
--- a/src/core/lib/iomgr/socket_utils_common_posix.c
+++ b/src/core/lib/iomgr/socket_utils_common_posix.c
@@ -209,6 +209,15 @@ grpc_error *grpc_set_socket_low_latency(int fd, int low_latency) {
   return GRPC_ERROR_NONE;
 }
 
+/* set a socket using a grpc_socket_mutator */
+grpc_error *grpc_set_socket_with_mutator(int fd, grpc_socket_mutator *mutator) {
+  GPR_ASSERT(mutator);
+  if (!grpc_socket_mutator_mutate_fd(mutator, fd)) {
+    return GRPC_ERROR_CREATE("grpc_socket_mutator failed.");
+  }
+  return GRPC_ERROR_NONE;
+}
+
 static gpr_once g_probe_ipv6_once = GPR_ONCE_INIT;
 static int g_ipv6_loopback_available;
 
diff --git a/src/core/lib/iomgr/socket_utils_posix.h b/src/core/lib/iomgr/socket_utils_posix.h
index 175fb2b717..e84d3781a1 100644
--- a/src/core/lib/iomgr/socket_utils_posix.h
+++ b/src/core/lib/iomgr/socket_utils_posix.h
@@ -39,7 +39,9 @@
 #include <sys/socket.h>
 #include <unistd.h>
 
+#include <grpc/impl/codegen/grpc_types.h>
 #include "src/core/lib/iomgr/error.h"
+#include "src/core/lib/iomgr/socket_mutator.h"
 
 /* a wrapper for accept or accept4 */
 int grpc_accept4(int sockfd, grpc_resolved_address *resolved_addr, int nonblock,
@@ -88,6 +90,9 @@ grpc_error *grpc_set_socket_sndbuf(int fd, int buffer_size_bytes);
 /* Tries to set the socket's receive buffer to given size. */
 grpc_error *grpc_set_socket_rcvbuf(int fd, int buffer_size_bytes);
 
+/* Tries to set the socket using a grpc_socket_mutator */
+grpc_error *grpc_set_socket_with_mutator(int fd, grpc_socket_mutator *mutator);
+
 /* An enum to keep track of IPv4/IPv6 socket modes.
 
    Currently, this information is only used when a socket is first created, but
diff --git a/src/core/lib/iomgr/tcp_client.h b/src/core/lib/iomgr/tcp_client.h
index 18e6e60ebc..0485661316 100644
--- a/src/core/lib/iomgr/tcp_client.h
+++ b/src/core/lib/iomgr/tcp_client.h
@@ -34,6 +34,7 @@
 #ifndef GRPC_CORE_LIB_IOMGR_TCP_CLIENT_H
 #define GRPC_CORE_LIB_IOMGR_TCP_CLIENT_H
 
+#include <grpc/impl/codegen/grpc_types.h>
 #include <grpc/support/time.h>
 #include "src/core/lib/iomgr/endpoint.h"
 #include "src/core/lib/iomgr/pollset_set.h"
diff --git a/src/core/lib/iomgr/tcp_client_posix.c b/src/core/lib/iomgr/tcp_client_posix.c
index 3b0fe3bc15..7e49d89aa8 100644
--- a/src/core/lib/iomgr/tcp_client_posix.c
+++ b/src/core/lib/iomgr/tcp_client_posix.c
@@ -51,6 +51,7 @@
 #include "src/core/lib/iomgr/ev_posix.h"
 #include "src/core/lib/iomgr/iomgr_posix.h"
 #include "src/core/lib/iomgr/sockaddr_utils.h"
+#include "src/core/lib/iomgr/socket_mutator.h"
 #include "src/core/lib/iomgr/socket_utils_posix.h"
 #include "src/core/lib/iomgr/tcp_posix.h"
 #include "src/core/lib/iomgr/timer.h"
@@ -73,7 +74,8 @@ typedef struct {
   grpc_channel_args *channel_args;
 } async_connect;
 
-static grpc_error *prepare_socket(const grpc_resolved_address *addr, int fd) {
+static grpc_error *prepare_socket(const grpc_resolved_address *addr, int fd,
+                                  const grpc_channel_args *channel_args) {
   grpc_error *err = GRPC_ERROR_NONE;
 
   GPR_ASSERT(fd >= 0);
@@ -88,6 +90,16 @@ static grpc_error *prepare_socket(const grpc_resolved_address *addr, int fd) {
   }
   err = grpc_set_socket_no_sigpipe_if_possible(fd);
   if (err != GRPC_ERROR_NONE) goto error;
+  if (channel_args) {
+    for (size_t i = 0; i < channel_args->num_args; i++) {
+      if (0 == strcmp(channel_args->args[i].key, GRPC_ARG_SOCKET_MUTATOR)) {
+        GPR_ASSERT(channel_args->args[i].type == GRPC_ARG_POINTER);
+        grpc_socket_mutator *mutator = channel_args->args[i].value.pointer.p;
+        err = grpc_set_socket_with_mutator(fd, mutator);
+        if (err != GRPC_ERROR_NONE) goto error;
+      }
+    }
+  }
   goto done;
 
 error:
@@ -287,7 +299,7 @@ static void tcp_client_connect_impl(grpc_exec_ctx *exec_ctx,
     GPR_ASSERT(grpc_sockaddr_is_v4mapped(addr, &addr4_copy));
     addr = &addr4_copy;
   }
-  if ((error = prepare_socket(addr, fd)) != GRPC_ERROR_NONE) {
+  if ((error = prepare_socket(addr, fd, channel_args)) != GRPC_ERROR_NONE) {
     grpc_exec_ctx_sched(exec_ctx, closure, error, NULL);
     return;
   }
diff --git a/src/core/lib/iomgr/tcp_posix.c b/src/core/lib/iomgr/tcp_posix.c
index e27a762f20..ba288c768e 100644
--- a/src/core/lib/iomgr/tcp_posix.c
+++ b/src/core/lib/iomgr/tcp_posix.c
@@ -497,6 +497,11 @@ static char *tcp_get_peer(grpc_endpoint *ep) {
   return gpr_strdup(tcp->peer_string);
 }
 
+static int tcp_get_fd(grpc_endpoint *ep) {
+  grpc_tcp *tcp = (grpc_tcp *)ep;
+  return tcp->fd;
+}
+
 static grpc_workqueue *tcp_get_workqueue(grpc_endpoint *ep) {
   grpc_tcp *tcp = (grpc_tcp *)ep;
   return grpc_fd_get_workqueue(tcp->em_fd);
@@ -515,7 +520,8 @@ static const grpc_endpoint_vtable vtable = {tcp_read,
                                             tcp_shutdown,
                                             tcp_destroy,
                                             tcp_get_resource_user,
-                                            tcp_get_peer};
+                                            tcp_get_peer,
+                                            tcp_get_fd};
 
 grpc_endpoint *grpc_tcp_create(grpc_fd *em_fd,
                                grpc_resource_quota *resource_quota,
diff --git a/src/core/lib/iomgr/tcp_uv.c b/src/core/lib/iomgr/tcp_uv.c
index e690b18f20..6e2ad1dbe9 100644
--- a/src/core/lib/iomgr/tcp_uv.c
+++ b/src/core/lib/iomgr/tcp_uv.c
@@ -87,10 +87,12 @@ static void tcp_free(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
 
 /*#define GRPC_TCP_REFCOUNT_DEBUG*/
 #ifdef GRPC_TCP_REFCOUNT_DEBUG
-#define TCP_UNREF(exec_ctx, tcp, reason) tcp_unref((exec_ctx), (tcp), (reason), __FILE__, __LINE__)
-#define TCP_REF(tcp, reason) tcp_ref((exec_ctx), (tcp), (reason), __FILE__, __LINE__)
-static void tcp_unref(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp, const char *reason, const char *file,
-                      int line) {
+#define TCP_UNREF(exec_ctx, tcp, reason) \
+  tcp_unref((exec_ctx), (tcp), (reason), __FILE__, __LINE__)
+#define TCP_REF(tcp, reason) \
+  tcp_ref((exec_ctx), (tcp), (reason), __FILE__, __LINE__)
+static void tcp_unref(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp,
+                      const char *reason, const char *file, int line) {
   gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, "TCP unref %p : %s %d -> %d", tcp,
           reason, tcp->refcount.count, tcp->refcount.count - 1);
   if (gpr_unref(&tcp->refcount)) {
@@ -157,7 +159,7 @@ static void read_callback(uv_stream_t *stream, ssize_t nread,
       grpc_error_free_string(str);
       for (i = 0; i < tcp->read_slices->count; i++) {
         char *dump = grpc_dump_slice(tcp->read_slices->slices[i],
-                                    GPR_DUMP_HEX | GPR_DUMP_ASCII);
+                                     GPR_DUMP_HEX | GPR_DUMP_ASCII);
         gpr_log(GPR_DEBUG, "READ %p (peer=%s): %s", tcp, tcp->peer_string,
                 dump);
         gpr_free(dump);
@@ -234,7 +236,7 @@ static void uv_endpoint_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
 
     for (j = 0; j < write_slices->count; j++) {
       char *data = grpc_dump_slice(write_slices->slices[j],
-                                  GPR_DUMP_HEX | GPR_DUMP_ASCII);
+                                   GPR_DUMP_HEX | GPR_DUMP_ASCII);
       gpr_log(GPR_DEBUG, "WRITE %p (peer=%s): %s", tcp, tcp->peer_string, data);
       gpr_free(data);
     }
@@ -323,10 +325,13 @@ static grpc_resource_user *uv_get_resource_user(grpc_endpoint *ep) {
 
 static grpc_workqueue *uv_get_workqueue(grpc_endpoint *ep) { return NULL; }
 
+static int uv_get_fd(grpc_endpoint *ep) { return -1; }
+
 static grpc_endpoint_vtable vtable = {
     uv_endpoint_read,  uv_endpoint_write,     uv_get_workqueue,
     uv_add_to_pollset, uv_add_to_pollset_set, uv_endpoint_shutdown,
-    uv_destroy,        uv_get_resource_user,  uv_get_peer};
+    uv_destroy,        uv_get_resource_user,  uv_get_peer,
+    uv_get_fd};
 
 grpc_endpoint *grpc_tcp_create(uv_tcp_t *handle,
                                grpc_resource_quota *resource_quota,
diff --git a/src/core/lib/iomgr/tcp_windows.c b/src/core/lib/iomgr/tcp_windows.c
index e5fa360094..34afe51df0 100644
--- a/src/core/lib/iomgr/tcp_windows.c
+++ b/src/core/lib/iomgr/tcp_windows.c
@@ -402,6 +402,8 @@ static grpc_resource_user *win_get_resource_user(grpc_endpoint *ep) {
   return tcp->resource_user;
 }
 
+static int win_get_fd(grpc_endpoint *ep) { return -1; }
+
 static grpc_endpoint_vtable vtable = {win_read,
                                       win_write,
                                       win_get_workqueue,
@@ -410,7 +412,8 @@ static grpc_endpoint_vtable vtable = {win_read,
                                       win_shutdown,
                                       win_destroy,
                                       win_get_resource_user,
-                                      win_get_peer};
+                                      win_get_peer,
+                                      win_get_fd};
 
 grpc_endpoint *grpc_tcp_create(grpc_winsocket *socket,
                                grpc_resource_quota *resource_quota,
diff --git a/src/core/lib/security/credentials/jwt/jwt_credentials.c b/src/core/lib/security/credentials/jwt/jwt_credentials.c
index 4ce5675fba..616be64a54 100644
--- a/src/core/lib/security/credentials/jwt/jwt_credentials.c
+++ b/src/core/lib/security/credentials/jwt/jwt_credentials.c
@@ -147,17 +147,44 @@ grpc_service_account_jwt_access_credentials_create_from_auth_json_key(
   return &c->base;
 }
 
+static char *redact_private_key(const char *json_key) {
+  char *json_copy = gpr_strdup(json_key);
+  grpc_json *json = grpc_json_parse_string(json_copy);
+  if (!json) {
+    gpr_free(json_copy);
+    return gpr_strdup("<Json failed to parse.>");
+  }
+  const char *redacted = "<redacted>";
+  grpc_json *current = json->child;
+  while (current) {
+    if (current->type == GRPC_JSON_STRING &&
+        strcmp(current->key, "private_key") == 0) {
+      current->value = (char *)redacted;
+      break;
+    }
+    current = current->next;
+  }
+  char *clean_json = grpc_json_dump_to_string(json, 2);
+  gpr_free(json_copy);
+  grpc_json_destroy(json);
+  return clean_json;
+}
+
 grpc_call_credentials *grpc_service_account_jwt_access_credentials_create(
     const char *json_key, gpr_timespec token_lifetime, void *reserved) {
-  GRPC_API_TRACE(
-      "grpc_service_account_jwt_access_credentials_create("
-      "json_key=%s, "
-      "token_lifetime="
-      "gpr_timespec { tv_sec: %" PRId64
-      ", tv_nsec: %d, clock_type: %d }, "
-      "reserved=%p)",
-      5, (json_key, token_lifetime.tv_sec, token_lifetime.tv_nsec,
-          (int)token_lifetime.clock_type, reserved));
+  if (grpc_api_trace) {
+    char *clean_json = redact_private_key(json_key);
+    gpr_log(GPR_INFO,
+            "grpc_service_account_jwt_access_credentials_create("
+            "json_key=%s, "
+            "token_lifetime="
+            "gpr_timespec { tv_sec: %" PRId64
+            ", tv_nsec: %d, clock_type: %d }, "
+            "reserved=%p)",
+            clean_json, token_lifetime.tv_sec, token_lifetime.tv_nsec,
+            (int)token_lifetime.clock_type, reserved);
+    gpr_free(clean_json);
+  }
   GPR_ASSERT(reserved == NULL);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_call_credentials *creds =
diff --git a/src/core/lib/security/credentials/jwt/jwt_verifier.c b/src/core/lib/security/credentials/jwt/jwt_verifier.c
index 0281db385b..71febc248a 100644
--- a/src/core/lib/security/credentials/jwt/jwt_verifier.c
+++ b/src/core/lib/security/credentials/jwt/jwt_verifier.c
@@ -629,7 +629,7 @@ static void on_keys_retrieved(grpc_exec_ctx *exec_ctx, void *user_data,
 end:
   if (json != NULL) grpc_json_destroy(json);
   if (verification_key != NULL) EVP_PKEY_free(verification_key);
-  ctx->user_cb(ctx->user_data, status, claims);
+  ctx->user_cb(exec_ctx, ctx->user_data, status, claims);
   verifier_cb_ctx_destroy(exec_ctx, ctx);
 }
 
@@ -682,7 +682,8 @@ static void on_openid_config_retrieved(grpc_exec_ctx *exec_ctx, void *user_data,
 
 error:
   if (json != NULL) grpc_json_destroy(json);
-  ctx->user_cb(ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR, NULL);
+  ctx->user_cb(exec_ctx, ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR,
+               NULL);
   verifier_cb_ctx_destroy(exec_ctx, ctx);
 }
 
@@ -793,7 +794,8 @@ static void retrieve_key_and_verify(grpc_exec_ctx *exec_ctx,
   return;
 
 error:
-  ctx->user_cb(ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR, NULL);
+  ctx->user_cb(exec_ctx, ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR,
+               NULL);
   verifier_cb_ctx_destroy(exec_ctx, ctx);
 }
 
@@ -844,7 +846,7 @@ void grpc_jwt_verifier_verify(grpc_exec_ctx *exec_ctx,
 error:
   if (header != NULL) jose_header_destroy(exec_ctx, header);
   if (claims != NULL) grpc_jwt_claims_destroy(exec_ctx, claims);
-  cb(user_data, GRPC_JWT_VERIFIER_BAD_FORMAT, NULL);
+  cb(exec_ctx, user_data, GRPC_JWT_VERIFIER_BAD_FORMAT, NULL);
 }
 
 grpc_jwt_verifier *grpc_jwt_verifier_create(
diff --git a/src/core/lib/security/credentials/jwt/jwt_verifier.h b/src/core/lib/security/credentials/jwt/jwt_verifier.h
index c084575bcf..b79f411903 100644
--- a/src/core/lib/security/credentials/jwt/jwt_verifier.h
+++ b/src/core/lib/security/credentials/jwt/jwt_verifier.h
@@ -115,7 +115,8 @@ void grpc_jwt_verifier_destroy(grpc_jwt_verifier *verifier);
    is done (maybe in another thread).
    It is the responsibility of the callee to call grpc_jwt_claims_destroy on
    the claims. */
-typedef void (*grpc_jwt_verification_done_cb)(void *user_data,
+typedef void (*grpc_jwt_verification_done_cb)(grpc_exec_ctx *exec_ctx,
+                                              void *user_data,
                                               grpc_jwt_verifier_status status,
                                               grpc_jwt_claims *claims);
 
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
index b7bdc53a35..cbcd74958c 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
@@ -394,15 +394,32 @@ grpc_refresh_token_credentials_create_from_auth_refresh_token(
   return &c->base.base;
 }
 
+static char *create_loggable_refresh_token(grpc_auth_refresh_token *token) {
+  if (strcmp(token->type, GRPC_AUTH_JSON_TYPE_INVALID) == 0) {
+    return gpr_strdup("<Invalid json token>");
+  }
+  char *loggable_token = NULL;
+  gpr_asprintf(&loggable_token,
+               "{\n type: %s\n client_id: %s\n client_secret: "
+               "<redacted>\n refresh_token: <redacted>\n}",
+               token->type, token->client_id);
+  return loggable_token;
+}
+
 grpc_call_credentials *grpc_google_refresh_token_credentials_create(
     const char *json_refresh_token, void *reserved) {
-  GRPC_API_TRACE(
-      "grpc_refresh_token_credentials_create(json_refresh_token=%s, "
-      "reserved=%p)",
-      2, (json_refresh_token, reserved));
+  grpc_auth_refresh_token token =
+      grpc_auth_refresh_token_create_from_string(json_refresh_token);
+  if (grpc_api_trace) {
+    char *loggable_token = create_loggable_refresh_token(&token);
+    gpr_log(GPR_INFO,
+            "grpc_refresh_token_credentials_create(json_refresh_token=%s, "
+            "reserved=%p)",
+            loggable_token, reserved);
+    gpr_free(loggable_token);
+  }
   GPR_ASSERT(reserved == NULL);
-  return grpc_refresh_token_credentials_create_from_auth_refresh_token(
-      grpc_auth_refresh_token_create_from_string(json_refresh_token));
+  return grpc_refresh_token_credentials_create_from_auth_refresh_token(token);
 }
 
 //
@@ -433,9 +450,9 @@ grpc_call_credentials *grpc_access_token_credentials_create(
       gpr_malloc(sizeof(grpc_access_token_credentials));
   char *token_md_value;
   GRPC_API_TRACE(
-      "grpc_access_token_credentials_create(access_token=%s, "
+      "grpc_access_token_credentials_create(access_token=<redacted>, "
       "reserved=%p)",
-      2, (access_token, reserved));
+      1, (reserved));
   GPR_ASSERT(reserved == NULL);
   memset(c, 0, sizeof(grpc_access_token_credentials));
   c->base.type = GRPC_CALL_CREDENTIALS_TYPE_OAUTH2;
diff --git a/src/core/lib/security/credentials/plugin/plugin_credentials.c b/src/core/lib/security/credentials/plugin/plugin_credentials.c
index 29f28024f6..f90d7dce83 100644
--- a/src/core/lib/security/credentials/plugin/plugin_credentials.c
+++ b/src/core/lib/security/credentials/plugin/plugin_credentials.c
@@ -106,6 +106,8 @@ static void plugin_md_request_metadata_ready(void *request,
         grpc_slice_unref_internal(&exec_ctx, md_array[i].value);
       }
       gpr_free(md_array);
+    } else if (num_md == 0) {
+      r->cb(&exec_ctx, r->user_data, NULL, 0, GRPC_CREDENTIALS_OK, NULL);
     }
   }
   gpr_free(r);
diff --git a/src/core/lib/security/transport/handshake.c b/src/core/lib/security/transport/handshake.c
index 26e63a71e9..16d758d7a1 100644
--- a/src/core/lib/security/transport/handshake.c
+++ b/src/core/lib/security/transport/handshake.c
@@ -127,7 +127,7 @@ static void security_handshake_done(grpc_exec_ctx *exec_ctx,
           h->auth_context);
   } else {
     const char *msg = grpc_error_string(error);
-    gpr_log(GPR_INFO, "Security handshake failed: %s", msg);
+    gpr_log(GPR_DEBUG, "Security handshake failed: %s", msg);
     grpc_error_free_string(msg);
 
     if (h->secure_endpoint != NULL) {
diff --git a/src/core/lib/security/transport/secure_endpoint.c b/src/core/lib/security/transport/secure_endpoint.c
index 594aa6161d..0e9a392c60 100644
--- a/src/core/lib/security/transport/secure_endpoint.c
+++ b/src/core/lib/security/transport/secure_endpoint.c
@@ -31,7 +31,12 @@
  *
  */
 
-#include "src/core/lib/security/transport/secure_endpoint.h"
+/* With the addition of a libuv endpoint, sockaddr.h now includes uv.h when
+   using that endpoint. Because of various transitive includes in uv.h,
+   including windows.h on Windows, uv.h must be included before other system
+   headers. Therefore, sockaddr.h must always be included first */
+#include "src/core/lib/iomgr/sockaddr.h"
+
 #include <grpc/slice.h>
 #include <grpc/slice_buffer.h>
 #include <grpc/support/alloc.h>
@@ -39,6 +44,7 @@
 #include <grpc/support/sync.h>
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/security/transport/secure_endpoint.h"
 #include "src/core/lib/security/transport/tsi_error.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
@@ -367,6 +373,8 @@ static char *endpoint_get_peer(grpc_endpoint *secure_ep) {
   return grpc_endpoint_get_peer(ep->wrapped_ep);
 }
 
+static int endpoint_get_fd(grpc_endpoint *secure_ep) { return -1; }
+
 static grpc_workqueue *endpoint_get_workqueue(grpc_endpoint *secure_ep) {
   secure_endpoint *ep = (secure_endpoint *)secure_ep;
   return grpc_endpoint_get_workqueue(ep->wrapped_ep);
@@ -386,7 +394,8 @@ static const grpc_endpoint_vtable vtable = {endpoint_read,
                                             endpoint_shutdown,
                                             endpoint_destroy,
                                             endpoint_get_resource_user,
-                                            endpoint_get_peer};
+                                            endpoint_get_peer,
+                                            endpoint_get_fd};
 
 grpc_endpoint *grpc_secure_endpoint_create(
     struct tsi_frame_protector *protector, grpc_endpoint *transport,
diff --git a/src/core/lib/security/transport/server_auth_filter.c b/src/core/lib/security/transport/server_auth_filter.c
index 1b43bdd4ba..db0d0d6907 100644
--- a/src/core/lib/security/transport/server_auth_filter.c
+++ b/src/core/lib/security/transport/server_auth_filter.c
@@ -83,7 +83,8 @@ static grpc_metadata_array metadata_batch_to_md_array(
   return result;
 }
 
-static grpc_mdelem *remove_consumed_md(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *remove_consumed_md(grpc_exec_ctx *exec_ctx, void *user_data,
+                                       grpc_mdelem *md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
   size_t i;
diff --git a/src/core/lib/slice/slice.c b/src/core/lib/slice/slice.c
index d1f045bd6f..dc3e6fd93d 100644
--- a/src/core/lib/slice/slice.c
+++ b/src/core/lib/slice/slice.c
@@ -368,3 +368,11 @@ int grpc_slice_str_cmp(grpc_slice a, const char *b) {
   if (d != 0) return d;
   return memcmp(GRPC_SLICE_START_PTR(a), b, b_length);
 }
+
+int grpc_slice_is_equivalent(grpc_slice a, grpc_slice b) {
+  if (a.refcount == NULL || b.refcount == NULL) {
+    return grpc_slice_cmp(a, b) == 0;
+  }
+  return a.data.refcounted.length == b.data.refcounted.length &&
+         a.data.refcounted.bytes == b.data.refcounted.bytes;
+}
diff --git a/src/core/lib/slice/slice_buffer.c b/src/core/lib/slice/slice_buffer.c
index 872bd10a09..08eaf4963a 100644
--- a/src/core/lib/slice/slice_buffer.c
+++ b/src/core/lib/slice/slice_buffer.c
@@ -75,10 +75,7 @@ void grpc_slice_buffer_destroy_internal(grpc_exec_ctx *exec_ctx,
 
 void grpc_slice_buffer_destroy(grpc_slice_buffer *sb) {
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_slice_buffer_reset_and_unref_internal(&exec_ctx, sb);
-  if (sb->slices != sb->inlined) {
-    gpr_free(sb->slices);
-  }
+  grpc_slice_buffer_destroy_internal(&exec_ctx, sb);
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
diff --git a/src/core/lib/slice/slice_internal.h b/src/core/lib/slice/slice_internal.h
index a027a3979b..8bfe066fdb 100644
--- a/src/core/lib/slice/slice_internal.h
+++ b/src/core/lib/slice/slice_internal.h
@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_SUPPORT_SLICE_INTERNAL_H
-#define GRPC_CORE_LIB_SUPPORT_SLICE_INTERNAL_H
+#ifndef GRPC_CORE_LIB_SLICE_SLICE_INTERNAL_H
+#define GRPC_CORE_LIB_SLICE_SLICE_INTERNAL_H
 
 #include <grpc/slice.h>
 #include <grpc/slice_buffer.h>
@@ -50,4 +50,4 @@ void grpc_slice_intern_init(void);
 void grpc_slice_intern_shutdown(void);
 void grpc_test_only_set_slice_interning_hash_seed(uint32_t key);
 
-#endif
+#endif /* GRPC_CORE_LIB_SLICE_SLICE_INTERNAL_H */
diff --git a/src/core/lib/support/string.c b/src/core/lib/support/string.c
index cafeb4364d..85b915f118 100644
--- a/src/core/lib/support/string.c
+++ b/src/core/lib/support/string.c
@@ -267,5 +267,28 @@ int gpr_stricmp(const char *a, const char *b) {
   return ca - cb;
 }
 
+static void add_string_to_split(const char *beg, const char *end, char ***strs,
+                                size_t *nstrs, size_t *capstrs) {
+  char *out = gpr_malloc((size_t)(end - beg) + 1);
+  memcpy(out, beg, (size_t)(end - beg));
+  out[end - beg] = 0;
+  if (*nstrs == *capstrs) {
+    *capstrs = GPR_MAX(8, 2 * *capstrs);
+    *strs = gpr_realloc(*strs, sizeof(*strs) * *capstrs);
+  }
+  (*strs)[*nstrs] = out;
+  ++*nstrs;
+}
+
 void gpr_string_split(const char *input, const char *sep, char ***strs,
-                      size_t *nstrs) {}
+                      size_t *nstrs) {
+  char *next;
+  *strs = NULL;
+  *nstrs = 0;
+  size_t capstrs = 0;
+  while ((next = strstr(input, sep))) {
+    add_string_to_split(input, next, strs, nstrs, &capstrs);
+    input = next + strlen(sep);
+  }
+  add_string_to_split(input, input + strlen(input), strs, nstrs, &capstrs);
+}
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 37548697fa..38aa99372e 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -125,6 +125,7 @@ struct grpc_call {
   grpc_channel *channel;
   grpc_call *parent;
   grpc_call *first_child;
+  gpr_timespec start_time;
   /* TODO(ctiller): share with cq if possible? */
   gpr_mu mu;
 
@@ -241,6 +242,7 @@ grpc_error *grpc_call_create(grpc_exec_ctx *exec_ctx,
   call->channel = args->channel;
   call->cq = args->cq;
   call->parent = args->parent_call;
+  call->start_time = gpr_now(GPR_CLOCK_MONOTONIC);
   /* Always support no compression */
   GPR_BITSET(&call->encodings_accepted_by_peer, GRPC_COMPRESS_NONE);
   call->is_client = args->server_transport_data == NULL;
@@ -314,10 +316,10 @@ grpc_error *grpc_call_create(grpc_exec_ctx *exec_ctx,
 
   GRPC_CHANNEL_INTERNAL_REF(args->channel, "call");
   /* initial refcount dropped by grpc_call_destroy */
-  grpc_error *error =
-      grpc_call_stack_init(exec_ctx, channel_stack, 1, destroy_call, call,
-                           call->context, args->server_transport_data, path,
-                           send_deadline, CALL_STACK_FROM_CALL(call));
+  grpc_error *error = grpc_call_stack_init(
+      exec_ctx, channel_stack, 1, destroy_call, call, call->context,
+      args->server_transport_data, path, call->start_time, send_deadline,
+      CALL_STACK_FROM_CALL(call));
   if (error != GRPC_ERROR_NONE) {
     grpc_status_code status;
     const char *error_str;
@@ -429,6 +431,8 @@ static void destroy_call(grpc_exec_ctx *exec_ctx, void *call,
 
   get_final_status(call, set_status_value_directly,
                    &c->final_info.final_status);
+  c->final_info.stats.latency =
+      gpr_time_sub(gpr_now(GPR_CLOCK_MONOTONIC), c->start_time);
 
   grpc_call_stack_destroy(exec_ctx, CALL_STACK_FROM_CALL(c), &c->final_info, c);
   GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel, "call");
@@ -618,9 +622,6 @@ static int prepare_application_metadata(
     if (call->send_extra_metadata_count == 0) {
       prepend_extra_metadata = 0;
     } else {
-      for (i = 0; i < call->send_extra_metadata_count; i++) {
-        GRPC_MDELEM_REF(call->send_extra_metadata[i].md);
-      }
       for (i = 1; i < call->send_extra_metadata_count; i++) {
         call->send_extra_metadata[i].prev = &call->send_extra_metadata[i - 1];
       }
@@ -666,6 +667,7 @@ static int prepare_application_metadata(
           &call->send_extra_metadata[call->send_extra_metadata_count - 1];
       batch->list.head->prev = NULL;
       batch->list.tail->next = NULL;
+      call->send_extra_metadata_count = 0;
       break;
     case 3: {
       /* prepend AND md */
@@ -681,6 +683,7 @@ static int prepare_application_metadata(
       batch->list.tail = linked_from_md(last_md);
       batch->list.head->prev = NULL;
       batch->list.tail->next = NULL;
+      call->send_extra_metadata_count = 0;
       break;
     }
     default:
@@ -945,38 +948,35 @@ static grpc_mdelem *publish_app_metadata(grpc_call *call, grpc_mdelem *elem,
   return elem;
 }
 
-typedef struct {
-  grpc_exec_ctx *exec_ctx;
-  grpc_call *call;
-} recv_filter_args;
-
-static grpc_mdelem *recv_initial_filter(void *args, grpc_mdelem *elem) {
-  recv_filter_args *a = args;
-  elem = recv_common_filter(a->exec_ctx, a->call, elem);
+static grpc_mdelem *recv_initial_filter(grpc_exec_ctx *exec_ctx, void *args,
+                                        grpc_mdelem *elem) {
+  grpc_call *call = args;
+  elem = recv_common_filter(exec_ctx, call, elem);
   if (elem == NULL) {
     return NULL;
   } else if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_ENCODING) == 0) {
     GPR_TIMER_BEGIN("incoming_compression_algorithm", 0);
-    set_incoming_compression_algorithm(a->call, decode_compression(elem));
+    set_incoming_compression_algorithm(call, decode_compression(elem));
     GPR_TIMER_END("incoming_compression_algorithm", 0);
     return NULL;
   } else if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_ACCEPT_ENCODING) == 0) {
     GPR_TIMER_BEGIN("encodings_accepted_by_peer", 0);
-    set_encodings_accepted_by_peer(a->exec_ctx, a->call, elem);
+    set_encodings_accepted_by_peer(exec_ctx, call, elem);
     GPR_TIMER_END("encodings_accepted_by_peer", 0);
     return NULL;
   } else {
-    return publish_app_metadata(a->call, elem, 0);
+    return publish_app_metadata(call, elem, 0);
   }
 }
 
-static grpc_mdelem *recv_trailing_filter(void *args, grpc_mdelem *elem) {
-  recv_filter_args *a = args;
-  elem = recv_common_filter(a->exec_ctx, a->call, elem);
+static grpc_mdelem *recv_trailing_filter(grpc_exec_ctx *exec_ctx, void *args,
+                                         grpc_mdelem *elem) {
+  grpc_call *call = args;
+  elem = recv_common_filter(exec_ctx, call, elem);
   if (elem == NULL) {
     return NULL;
   } else {
-    return publish_app_metadata(a->call, elem, 1);
+    return publish_app_metadata(call, elem, 1);
   }
 }
 
@@ -1222,8 +1222,7 @@ static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
   if (error == GRPC_ERROR_NONE) {
     grpc_metadata_batch *md =
         &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
-    recv_filter_args args = {exec_ctx, call};
-    grpc_metadata_batch_filter(exec_ctx, md, recv_initial_filter, &args);
+    grpc_metadata_batch_filter(exec_ctx, md, recv_initial_filter, call);
 
     GPR_TIMER_BEGIN("validate_filtered_metadata", 0);
     validate_filtered_metadata(exec_ctx, bctl);
@@ -1289,8 +1288,7 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp,
   if (bctl->recv_final_op) {
     grpc_metadata_batch *md =
         &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-    recv_filter_args args = {exec_ctx, call};
-    grpc_metadata_batch_filter(exec_ctx, md, recv_trailing_filter, &args);
+    grpc_metadata_batch_filter(exec_ctx, md, recv_trailing_filter, call);
 
     call->received_final_op = true;
     /* propagate cancellation to any interested children */
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index 5a8c77f046..91b8f2b068 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -229,9 +229,9 @@ void grpc_shutdown(void) {
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   gpr_mu_lock(&g_init_mu);
   if (--g_initializations == 0) {
-    grpc_executor_shutdown();
+    grpc_executor_shutdown(&exec_ctx);
     grpc_cq_global_shutdown();
-    grpc_iomgr_shutdown();
+    grpc_iomgr_shutdown(&exec_ctx);
     gpr_timers_global_destroy();
     grpc_tracer_shutdown();
     for (i = g_number_of_plugins; i >= 0; i--) {
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 74411f3aab..3973630c85 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -199,6 +199,7 @@ struct grpc_server {
   grpc_completion_queue **cqs;
   grpc_pollset **pollsets;
   size_t cq_count;
+  size_t pollset_count;
   bool started;
 
   /* The two following mutexes control access to server-state
@@ -734,7 +735,8 @@ static void maybe_finish_shutdown(grpc_exec_ctx *exec_ctx,
   }
 }
 
-static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
+static grpc_mdelem *server_filter(grpc_exec_ctx *exec_ctx, void *user_data,
+                                  grpc_mdelem *md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
   if (grpc_slice_cmp(md->key, GRPC_MDSTR_PATH) == 0) {
@@ -1079,7 +1081,7 @@ void grpc_server_start(grpc_server *server) {
   GRPC_API_TRACE("grpc_server_start(server=%p)", 1, (server));
 
   server->started = true;
-  size_t pollset_count = 0;
+  server->pollset_count = 0;
   server->pollsets = gpr_malloc(sizeof(grpc_pollset *) * server->cq_count);
   server->request_freelist_per_cq =
       gpr_malloc(sizeof(*server->request_freelist_per_cq) * server->cq_count);
@@ -1087,7 +1089,8 @@ void grpc_server_start(grpc_server *server) {
       gpr_malloc(sizeof(*server->requested_calls_per_cq) * server->cq_count);
   for (i = 0; i < server->cq_count; i++) {
     if (!grpc_cq_is_non_listening_server_cq(server->cqs[i])) {
-      server->pollsets[pollset_count++] = grpc_cq_pollset(server->cqs[i]);
+      server->pollsets[server->pollset_count++] =
+          grpc_cq_pollset(server->cqs[i]);
     }
     server->request_freelist_per_cq[i] =
         gpr_stack_lockfree_create((size_t)server->max_requested_calls_per_cq);
@@ -1106,7 +1109,8 @@ void grpc_server_start(grpc_server *server) {
   }
 
   for (l = server->listeners; l; l = l->next) {
-    l->start(&exec_ctx, server, l->arg, server->pollsets, pollset_count);
+    l->start(&exec_ctx, server, l->arg, server->pollsets,
+             server->pollset_count);
   }
 
   grpc_exec_ctx_finish(&exec_ctx);
@@ -1114,7 +1118,7 @@ void grpc_server_start(grpc_server *server) {
 
 void grpc_server_get_pollsets(grpc_server *server, grpc_pollset ***pollsets,
                               size_t *pollset_count) {
-  *pollset_count = server->cq_count;
+  *pollset_count = server->pollset_count;
   *pollsets = server->pollsets;
 }
 
diff --git a/src/core/lib/transport/connectivity_state.c b/src/core/lib/transport/connectivity_state.c
index fdb5307814..89072879d9 100644
--- a/src/core/lib/transport/connectivity_state.c
+++ b/src/core/lib/transport/connectivity_state.c
@@ -43,6 +43,8 @@ int grpc_connectivity_state_trace = 0;
 
 const char *grpc_connectivity_state_name(grpc_connectivity_state state) {
   switch (state) {
+    case GRPC_CHANNEL_INIT:
+      return "INIT";
     case GRPC_CHANNEL_IDLE:
       return "IDLE";
     case GRPC_CHANNEL_CONNECTING:
@@ -159,6 +161,7 @@ void grpc_connectivity_state_set(grpc_exec_ctx *exec_ctx,
     grpc_error_free_string(error_string);
   }
   switch (state) {
+    case GRPC_CHANNEL_INIT:
     case GRPC_CHANNEL_CONNECTING:
     case GRPC_CHANNEL_IDLE:
     case GRPC_CHANNEL_READY:
diff --git a/src/core/lib/transport/metadata.c b/src/core/lib/transport/metadata.c
index fd6c52c4c1..cedf9170b7 100644
--- a/src/core/lib/transport/metadata.c
+++ b/src/core/lib/transport/metadata.c
@@ -441,8 +441,8 @@ void *grpc_mdelem_get_user_data(grpc_mdelem *md, void (*destroy_func)(void *)) {
   return result;
 }
 
-void grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
-                               void *user_data) {
+void *grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
+                                void *user_data) {
   internal_metadata *im = (internal_metadata *)md;
   GPR_ASSERT(!is_mdelem_static(md));
   GPR_ASSERT((user_data == NULL) == (destroy_func == NULL));
@@ -453,9 +453,10 @@ void grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
     if (destroy_func != NULL) {
       destroy_func(user_data);
     }
-    return;
+    return (void *)gpr_atm_no_barrier_load(&im->user_data);
   }
   gpr_atm_no_barrier_store(&im->user_data, (gpr_atm)user_data);
   gpr_atm_rel_store(&im->destroy_user_data, (gpr_atm)destroy_func);
   gpr_mu_unlock(&im->mu_user_data);
+  return user_data;
 }
diff --git a/src/core/lib/transport/metadata.h b/src/core/lib/transport/metadata.h
index fcd1c9222f..50c8e1fa91 100644
--- a/src/core/lib/transport/metadata.h
+++ b/src/core/lib/transport/metadata.h
@@ -94,8 +94,8 @@ size_t grpc_mdelem_get_size_in_hpack_table(grpc_mdelem *elem);
    is used as a type tag and is checked during user_data fetch. */
 void *grpc_mdelem_get_user_data(grpc_mdelem *md,
                                 void (*if_destroy_func)(void *));
-void grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
-                               void *user_data);
+void *grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
+                                void *user_data);
 
 /* Reference counting */
 //#define GRPC_METADATA_REFCOUNT_DEBUG
diff --git a/src/core/lib/transport/metadata_batch.c b/src/core/lib/transport/metadata_batch.c
index 4430224e70..b62ecc3aa6 100644
--- a/src/core/lib/transport/metadata_batch.c
+++ b/src/core/lib/transport/metadata_batch.c
@@ -143,7 +143,8 @@ void grpc_metadata_batch_move(grpc_metadata_batch *dst,
 
 void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
                                 grpc_metadata_batch *batch,
-                                grpc_mdelem *(*filter)(void *user_data,
+                                grpc_mdelem *(*filter)(grpc_exec_ctx *exec_ctx,
+                                                       void *user_data,
                                                        grpc_mdelem *elem),
                                 void *user_data) {
   grpc_linked_mdelem *l;
@@ -154,7 +155,7 @@ void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
   assert_valid_list(&batch->list);
   for (l = batch->list.head; l; l = next) {
     grpc_mdelem *orig = l->md;
-    grpc_mdelem *filt = filter(user_data, orig);
+    grpc_mdelem *filt = filter(exec_ctx, user_data, orig);
     next = l->next;
     if (filt == NULL) {
       if (l->prev) {
@@ -181,7 +182,8 @@ void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
   GPR_TIMER_END("grpc_metadata_batch_filter", 0);
 }
 
-static grpc_mdelem *no_metadata_for_you(void *user_data, grpc_mdelem *elem) {
+static grpc_mdelem *no_metadata_for_you(grpc_exec_ctx *exec_ctx,
+                                        void *user_data, grpc_mdelem *elem) {
   return NULL;
 }
 
diff --git a/src/core/lib/transport/metadata_batch.h b/src/core/lib/transport/metadata_batch.h
index 862c21b45b..c0bd5174ab 100644
--- a/src/core/lib/transport/metadata_batch.h
+++ b/src/core/lib/transport/metadata_batch.h
@@ -122,7 +122,8 @@ void grpc_metadata_batch_add_tail(grpc_metadata_batch *batch,
     the element will be moved to the garbage list. */
 void grpc_metadata_batch_filter(grpc_exec_ctx *exec_ctx,
                                 grpc_metadata_batch *batch,
-                                grpc_mdelem *(*filter)(void *user_data,
+                                grpc_mdelem *(*filter)(grpc_exec_ctx *exec_ctx,
+                                                       void *user_data,
                                                        grpc_mdelem *elem),
                                 void *user_data);
 
diff --git a/src/core/lib/transport/pid_controller.h b/src/core/lib/transport/pid_controller.h
index 059b5b0834..83c82d6471 100644
--- a/src/core/lib/transport/pid_controller.h
+++ b/src/core/lib/transport/pid_controller.h
@@ -61,4 +61,4 @@ void grpc_pid_controller_reset(grpc_pid_controller *pid_controller);
 double grpc_pid_controller_update(grpc_pid_controller *pid_controller,
                                   double error, double dt);
 
-#endif
+#endif /* GRPC_CORE_LIB_TRANSPORT_PID_CONTROLLER_H */
diff --git a/src/core/lib/transport/transport.c b/src/core/lib/transport/transport.c
index 1b79520e68..9bc278c133 100644
--- a/src/core/lib/transport/transport.c
+++ b/src/core/lib/transport/transport.c
@@ -161,6 +161,11 @@ char *grpc_transport_get_peer(grpc_exec_ctx *exec_ctx,
   return transport->vtable->get_peer(exec_ctx, transport);
 }
 
+grpc_endpoint *grpc_transport_get_endpoint(grpc_exec_ctx *exec_ctx,
+                                           grpc_transport *transport) {
+  return transport->vtable->get_endpoint(exec_ctx, transport);
+}
+
 void grpc_transport_stream_op_finish_with_failure(grpc_exec_ctx *exec_ctx,
                                                   grpc_transport_stream_op *op,
                                                   grpc_error *error) {
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 3e38d98f28..d1281830aa 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -37,6 +37,7 @@
 #include <stddef.h>
 
 #include "src/core/lib/channel/context.h"
+#include "src/core/lib/iomgr/endpoint.h"
 #include "src/core/lib/iomgr/polling_entity.h"
 #include "src/core/lib/iomgr/pollset.h"
 #include "src/core/lib/iomgr/pollset_set.h"
@@ -296,6 +297,10 @@ void grpc_transport_destroy(grpc_exec_ctx *exec_ctx, grpc_transport *transport);
 char *grpc_transport_get_peer(grpc_exec_ctx *exec_ctx,
                               grpc_transport *transport);
 
+/* Get the endpoint used by \a transport */
+grpc_endpoint *grpc_transport_get_endpoint(grpc_exec_ctx *exec_ctx,
+                                           grpc_transport *transport);
+
 /* Allocate a grpc_transport_op, and preconfigure the on_consumed closure to
    \a on_consumed and then delete the returned transport op */
 grpc_transport_op *grpc_make_transport_op(grpc_closure *on_consumed);
diff --git a/src/core/lib/transport/transport_impl.h b/src/core/lib/transport/transport_impl.h
index fc7140671b..8553148c35 100644
--- a/src/core/lib/transport/transport_impl.h
+++ b/src/core/lib/transport/transport_impl.h
@@ -74,6 +74,9 @@ typedef struct grpc_transport_vtable {
 
   /* implementation of grpc_transport_get_peer */
   char *(*get_peer)(grpc_exec_ctx *exec_ctx, grpc_transport *self);
+
+  /* implementation of grpc_transport_get_endpoint */
+  grpc_endpoint *(*get_endpoint)(grpc_exec_ctx *exec_ctx, grpc_transport *self);
 } grpc_transport_vtable;
 
 /* an instance of a grpc transport */