thread: return int from spdk_thread_seng_msg

This at least allows the caller to know there was a
problem, and that the messages wasn't actually sent.

SPDK by default creates huge rings so this problem
should never occur, but out-of-tree use cases may
send messages much more often and require at least
a notification when it fails.

While here, change the thread check to an assert.
There's no need to work around someone calling
this function with a null thread parameter.

Fixes issue #811.

Signed-off-by: Jim Harris <james.r.harris@intel.com>

Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/472438 (master)

(cherry picked from commit 4036f95bf8)
Change-Id: Ie6d432d616be45c7a4232aff1548cef198702bc0
Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/478442
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## v19.10.1: (Upcoming Release)
+
+### thread
+
+`spdk_thread_send_msg` now returns int indicating if the message was successfully
+sent.
+
 ## v19.10:
 
 ### rpc

include/spdk/thread.h

@@ -373,8 +373,12 @@ int spdk_thread_get_stats(struct spdk_thread_stats *stats);
  * \param thread The target thread.
  * \param fn This function will be called on the given thread.
  * \param ctx This context will be passed to fn when called.
+ *
+ * \return 0 on success
+ * \return -ENOMEM if the message could not be allocated
+ * \return -EIO if the message could not be sent to the destination thread
  */
-void spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx);
+int spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx);
 
 /**
  * Send a message to each thread, serially.

lib/thread/thread.c

@@ -648,17 +648,14 @@ spdk_thread_get_stats(struct spdk_thread_stats *stats)
 	return 0;
 }
 
-void
+int
 spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx)
 {
 	struct spdk_thread *local_thread;
 	struct spdk_msg *msg;
 	int rc;
 
-	if (!thread) {
-		assert(false);
-		return;
-	}
+	assert(thread != NULL);
 
 	local_thread = _get_thread();
 
@@ -675,8 +672,8 @@ spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx
 	if (msg == NULL) {
 		msg = spdk_mempool_get(g_spdk_msg_mempool);
 		if (!msg) {
-			assert(false);
-			return;
+			SPDK_ERRLOG("msg could not be allocated\n");
+			return -ENOMEM;
 		}
 	}
 
@@ -685,10 +682,12 @@ spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx
 
 	rc = spdk_ring_enqueue(thread->messages, (void **)&msg, 1, NULL);
 	if (rc != 1) {
-		assert(false);
+		SPDK_ERRLOG("msg could not be enqueued\n");
 		spdk_mempool_put(g_spdk_msg_mempool, msg);
-		return;
+		return -EIO;
 	}
+
+	return 0;
 }
 
 struct spdk_poller *
@@ -1200,6 +1199,7 @@ spdk_for_each_channel(void *io_device, spdk_channel_msg fn, void *ctx,
 	struct spdk_thread *thread;
 	struct spdk_io_channel *ch;
 	struct spdk_io_channel_iter *i;
+	int rc;
 
 	i = calloc(1, sizeof(*i));
 	if (!i) {
@@ -1223,7 +1223,8 @@ spdk_for_each_channel(void *io_device, spdk_channel_msg fn, void *ctx,
 				i->cur_thread = thread;
 				i->ch = ch;
 				pthread_mutex_unlock(&g_devlist_mutex);
-				spdk_thread_send_msg(thread, _call_channel, i);
+				rc = spdk_thread_send_msg(thread, _call_channel, i);
+				assert(rc == 0);
 				return;
 			}
 		}
@@ -1231,7 +1232,8 @@ spdk_for_each_channel(void *io_device, spdk_channel_msg fn, void *ctx,
 
 	pthread_mutex_unlock(&g_devlist_mutex);
 
-	spdk_thread_send_msg(i->orig_thread, _call_completion, i);
+	rc = spdk_thread_send_msg(i->orig_thread, _call_completion, i);
+	assert(rc == 0);
 }
 
 void

test/unit/lib/blobfs/blobfs_bdev.c/blobfs_bdev_ut.c

@@ -145,10 +145,11 @@ spdk_bdev_close(struct spdk_bdev_desc *desc)
 {
 }
 
-void
+int
 spdk_thread_send_msg(const struct spdk_thread *thread, spdk_msg_fn fn, void *ctx)
 {
 	fn(ctx);
+	return 0;
 }
 
 struct spdk_thread *