Avoid lock/unlock for common client channel pick.

2 files changed, 26 insertions, 13 deletions

diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index a2c521a20d..5e84dec0ca 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -335,18 +335,20 @@ static void start_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
 
 static void continue_creating_call(grpc_exec_ctx *exec_ctx, void *arg,
                                    int iomgr_success) {
+  grpc_subchannel_call_create_status call_creation_status;
   waiting_for_connect *w4c = arg;
   grpc_subchannel_del_interested_party(exec_ctx, w4c->subchannel, w4c->pollset);
-  grpc_subchannel_create_call(exec_ctx, w4c->subchannel, w4c->pollset,
-                              w4c->target, w4c->notify);
+  call_creation_status = grpc_subchannel_create_call(
+      exec_ctx, w4c->subchannel, w4c->pollset, w4c->target, w4c->notify);
+  GPR_ASSERT(call_creation_status == GRPC_SUBCHANNEL_CALL_CREATE_READY);
+  w4c->notify->cb(exec_ctx, w4c->notify->cb_arg, iomgr_success);
   GRPC_SUBCHANNEL_UNREF(exec_ctx, w4c->subchannel, "waiting_for_connect");
   gpr_free(w4c);
 }
 
-void grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
-                                 grpc_pollset *pollset,
-                                 grpc_subchannel_call **target,
-                                 grpc_closure *notify) {
+grpc_subchannel_call_create_status grpc_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *c, grpc_pollset *pollset,
+    grpc_subchannel_call **target, grpc_closure *notify) {
   connection *con;
   gpr_mu_lock(&c->mu);
   if (c->active != NULL) {
@@ -355,7 +357,7 @@ void grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
     gpr_mu_unlock(&c->mu);
 
     *target = create_call(exec_ctx, con);
-    notify->cb(exec_ctx, notify->cb_arg, 1);
+    return GRPC_SUBCHANNEL_CALL_CREATE_READY;
   } else {
     waiting_for_connect *w4c = gpr_malloc(sizeof(*w4c));
     w4c->next = c->waiting;
@@ -380,6 +382,7 @@ void grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx, grpc_subchannel *c,
     } else {
       gpr_mu_unlock(&c->mu);
     }
+    return GRPC_SUBCHANNEL_CALL_CREATE_PENDING;
   }
 }
 
diff --git a/src/core/client_config/subchannel.h b/src/core/client_config/subchannel.h
index 86b7fa5851..a26d08f02e 100644
--- a/src/core/client_config/subchannel.h
+++ b/src/core/client_config/subchannel.h
@@ -75,12 +75,22 @@ void grpc_subchannel_call_unref(grpc_exec_ctx *exec_ctx,
                                 grpc_subchannel_call *call
                                     GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 
-/** construct a call (possibly asynchronously) */
-void grpc_subchannel_create_call(grpc_exec_ctx *exec_ctx,
-                                 grpc_subchannel *subchannel,
-                                 grpc_pollset *pollset,
-                                 grpc_subchannel_call **target,
-                                 grpc_closure *notify);
+typedef enum {
+  GRPC_SUBCHANNEL_CALL_CREATE_READY,
+  GRPC_SUBCHANNEL_CALL_CREATE_PENDING
+} grpc_subchannel_call_create_status;
+
+/** construct a subchannel call (possibly asynchronously).
+ *
+ * If the returned status is \a GRPC_SUBCHANNEL_CALL_CREATE_READY, the call will
+ * return immediately and \a target will point to a connected \a subchannel_call
+ * instance. Note that \a notify will \em not be invoked in this case.
+ * Otherwise, if the returned status is GRPC_SUBCHANNEL_CALL_CREATE_PENDING, the
+ * subchannel call will be created asynchronously, invoking the \a notify
+ * callback upon completion. */
+grpc_subchannel_call_create_status grpc_subchannel_create_call(
+    grpc_exec_ctx *exec_ctx, grpc_subchannel *subchannel, grpc_pollset *pollset,
+    grpc_subchannel_call **target, grpc_closure *notify);
 
 /** process a transport level op */
 void grpc_subchannel_process_transport_op(grpc_exec_ctx *exec_ctx,