Merge github.com:grpc/grpc into grpc_millis

2 files changed, 17 insertions, 10 deletions

diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index b2146cf211..2b78016b2d 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -1512,7 +1512,7 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
     } else if (grpc_compression_options_is_stream_compression_algorithm_enabled(
                    &compression_options, algo) == 0) {
       /* check if algorithm is supported by current channel config */
-      char *algo_name = NULL;
+      const char *algo_name = NULL;
       grpc_stream_compression_algorithm_name(algo, &algo_name);
       gpr_asprintf(&error_msg, "Stream compression algorithm '%s' is disabled.",
                    algo_name);
@@ -1526,7 +1526,7 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
     if (!GPR_BITGET(call->stream_encodings_accepted_by_peer,
                     call->incoming_stream_compression_algorithm)) {
       if (GRPC_TRACER_ON(grpc_compression_trace)) {
-        char *algo_name = NULL;
+        const char *algo_name = NULL;
         grpc_stream_compression_algorithm_name(
             call->incoming_stream_compression_algorithm, &algo_name);
         gpr_log(
@@ -1553,7 +1553,7 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
     } else if (grpc_compression_options_is_algorithm_enabled(
                    &compression_options, algo) == 0) {
       /* check if algorithm is supported by current channel config */
-      char *algo_name = NULL;
+      const char *algo_name = NULL;
       grpc_compression_algorithm_name(algo, &algo_name);
       gpr_asprintf(&error_msg, "Compression algorithm '%s' is disabled.",
                    algo_name);
@@ -1569,7 +1569,7 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
     if (!GPR_BITGET(call->encodings_accepted_by_peer,
                     call->incoming_compression_algorithm)) {
       if (GRPC_TRACER_ON(grpc_compression_trace)) {
-        char *algo_name = NULL;
+        const char *algo_name = NULL;
         grpc_compression_algorithm_name(call->incoming_compression_algorithm,
                                         &algo_name);
         gpr_log(GPR_ERROR,
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index 5335cf111e..e403a2db06 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -566,13 +566,13 @@ static void cq_check_tag(grpc_completion_queue *cq, void *tag, bool lock_cq) {}
  * true if the increment was successful; false if the counter is zero */
 static bool atm_inc_if_nonzero(gpr_atm *counter) {
   while (true) {
-    gpr_atm count = gpr_atm_no_barrier_load(counter);
+    gpr_atm count = gpr_atm_acq_load(counter);
     /* If zero, we are done. If not, we must to a CAS (instead of an atomic
      * increment) to maintain the contract: do not increment the counter if it
      * is zero. */
     if (count == 0) {
       return false;
-    } else if (gpr_atm_no_barrier_cas(counter, count, count + 1)) {
+    } else if (gpr_atm_full_cas(counter, count, count + 1)) {
       break;
     }
   }
@@ -644,8 +644,12 @@ static void cq_end_op_for_next(grpc_exec_ctx *exec_ctx,
   /* Add the completion to the queue */
   bool is_first = cq_event_queue_push(&cqd->queue, storage);
   gpr_atm_no_barrier_fetch_add(&cqd->things_queued_ever, 1);
-  bool will_definitely_shutdown =
-      gpr_atm_no_barrier_load(&cqd->pending_events) == 1;
+
+  /* Since we do not hold the cq lock here, it is important to do an 'acquire'
+     load here (instead of a 'no_barrier' load) to match with the release store
+     (done via gpr_atm_full_fetch_add(pending_events, -1)) in cq_shutdown_next
+     */
+  bool will_definitely_shutdown = gpr_atm_acq_load(&cqd->pending_events) == 1;
 
   if (!will_definitely_shutdown) {
     /* Only kick if this is the first item queued */
@@ -885,7 +889,7 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
       }
     }
 
-    if (gpr_atm_no_barrier_load(&cqd->pending_events) == 0) {
+    if (gpr_atm_acq_load(&cqd->pending_events) == 0) {
       /* Before returning, check if the queue has any items left over (since
          gpr_mpscq_pop() can sometimes return NULL even if the queue is not
          empty. If so, keep retrying but do not return GRPC_QUEUE_SHUTDOWN */
@@ -931,7 +935,7 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
   }
 
   if (cq_event_queue_num_items(&cqd->queue) > 0 &&
-      gpr_atm_no_barrier_load(&cqd->pending_events) > 0) {
+      gpr_atm_acq_load(&cqd->pending_events) > 0) {
     gpr_mu_lock(cq->mu);
     cq->poller_vtable->kick(POLLSET_FROM_CQ(cq), NULL);
     gpr_mu_unlock(cq->mu);
@@ -982,6 +986,9 @@ static void cq_shutdown_next(grpc_exec_ctx *exec_ctx,
     return;
   }
   cqd->shutdown_called = true;
+  /* Doing a full_fetch_add (i.e acq/release) here to match with
+   * cq_begin_op_for_next and and cq_end_op_for_next functions which read/write
+   * on this counter without necessarily holding a lock on cq */
   if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
     cq_finish_shutdown_next(exec_ctx, cq);
   }