4 files changed, 22 insertions, 11 deletions

diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index d91dd116b8..ec9e47a6dd 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -505,7 +505,8 @@ void grpc_connected_subchannel_ping(grpc_exec_ctx *exec_ctx,
   elem->filter->start_transport_op(exec_ctx, elem, &op);
 }
 
-static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
+static void publish_transport_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_subchannel *c) {
   size_t channel_stack_size;
   grpc_connected_subchannel *con;
   grpc_channel_stack *stk;
@@ -541,8 +542,6 @@ static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   grpc_closure_init(&sw_subchannel->closure, subchannel_on_child_state_changed,
                     sw_subchannel);
 
-  gpr_mu_lock(&c->mu);
-
   if (c->disconnected) {
     gpr_mu_unlock(&c->mu);
     gpr_free(sw_subchannel);
@@ -575,7 +574,6 @@ static void publish_transport(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   grpc_connectivity_state_set(exec_ctx, &c->state_tracker, GRPC_CHANNEL_READY,
                               "connected");
 
-  gpr_mu_unlock(&c->mu);
   gpr_free((void *)filters);
 }
 
@@ -644,21 +642,23 @@ static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *arg,
                                  bool iomgr_success) {
   grpc_subchannel *c = arg;
 
+  GRPC_SUBCHANNEL_WEAK_REF(c, "connected");
+  gpr_mu_lock(&c->mu);
   if (c->connecting_result.transport != NULL) {
-    publish_transport(exec_ctx, c);
+    publish_transport_locked(exec_ctx, c);
   } else if (c->disconnected) {
     GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
   } else {
     gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
-    gpr_mu_lock(&c->mu);
     GPR_ASSERT(!c->have_alarm);
     c->have_alarm = 1;
     grpc_connectivity_state_set(exec_ctx, &c->state_tracker,
                                 GRPC_CHANNEL_TRANSIENT_FAILURE,
                                 "connect_failed");
     grpc_timer_init(exec_ctx, &c->alarm, c->next_attempt, on_alarm, c, now);
-    gpr_mu_unlock(&c->mu);
   }
+  gpr_mu_unlock(&c->mu);
+  GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
 }
 
 static gpr_timespec compute_connect_deadline(grpc_subchannel *c) {
diff --git a/src/core/iomgr/timer.c b/src/core/iomgr/timer.c
index 8379fffad0..f444643428 100644
--- a/src/core/iomgr/timer.c
+++ b/src/core/iomgr/timer.c
@@ -33,11 +33,11 @@
 
 #include "src/core/iomgr/timer.h"
 
-#include "src/core/iomgr/timer_heap.h"
-#include "src/core/iomgr/time_averaged_stats.h"
 #include <grpc/support/log.h>
 #include <grpc/support/sync.h>
 #include <grpc/support/useful.h>
+#include "src/core/iomgr/time_averaged_stats.h"
+#include "src/core/iomgr/timer_heap.h"
 
 #define INVALID_HEAP_INDEX 0xffffffffu
 
@@ -330,6 +330,18 @@ static int run_some_expired_timers(grpc_exec_ctx *exec_ctx, gpr_timespec now,
 
     gpr_mu_unlock(&g_mu);
     gpr_mu_unlock(&g_checker_mu);
+  } else if (next != NULL) {
+    /* TODO(ctiller): this forces calling code to do an short poll, and
+       then retry the timer check (because this time through the timer list was
+       contended).
+
+       We could reduce the cost here dramatically by keeping a count of how many
+       currently active pollers got through the uncontended case above
+       successfully, and waking up other pollers IFF that count drops to zero.
+
+       Once that count is in place, this entire else branch could disappear. */
+    *next = gpr_time_min(
+        *next, gpr_time_add(now, gpr_time_from_millis(1, GPR_TIMESPAN)));
   }
 
   return (int)n;
diff --git a/src/core/iomgr/timer.h b/src/core/iomgr/timer.h
index 9ad1e92f42..e239e884e7 100644
--- a/src/core/iomgr/timer.h
+++ b/src/core/iomgr/timer.h
@@ -96,7 +96,6 @@ void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer);
    *next is never guaranteed to be updated on any given execution; however,
    with high probability at least one thread in the system will see an update
    at any time slice. */
-
 bool grpc_timer_check(grpc_exec_ctx *exec_ctx, gpr_timespec now,
                       gpr_timespec *next);
 void grpc_timer_list_init(gpr_timespec now);
diff --git a/src/core/surface/completion_queue.c b/src/core/surface/completion_queue.c
index f6a95ebbd3..b22818ea87 100644
--- a/src/core/surface/completion_queue.c
+++ b/src/core/surface/completion_queue.c
@@ -86,7 +86,7 @@ struct grpc_completion_queue {
 #define POLLSET_FROM_CQ(cq) ((grpc_pollset *)(cq + 1))
 
 static gpr_mu g_freelist_mu;
-grpc_completion_queue *g_freelist;
+static grpc_completion_queue *g_freelist;
 
 static void on_pollset_shutdown_done(grpc_exec_ctx *exec_ctx, void *cc,
                                      bool success);