From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Sun, 8 Jan 2017 19:29:09 +0000 (-0500)
Subject: Fix: reverse channel and metadata cache lock nesting order
X-Git-Tag: v2.8.6~5
X-Git-Url: https://git.liburcu.org/?p=lttng-tools.git;a=commitdiff_plain;h=69018d12995a4fb76285cd77e9ad013ac81c0b27

Fix: reverse channel and metadata cache lock nesting order

CID 1368319:  Program hangs  (ORDER_REVERSAL)

The lttng_consumer_channel lock must be nested outside of the
metadata cache lock, as indicated in the structure's comments.

Reported-by: Coverity Scan
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 19d705c93..bfec997ee 100644
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -2052,11 +2052,11 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
 	DBG3("Consumer delete metadata stream %d", stream->wait_fd);
 
 	pthread_mutex_lock(&consumer_data.lock);
+	pthread_mutex_lock(&stream->chan->lock);
 	if (stream->chan->metadata_cache) {
 		/* Only applicable to userspace consumers. */
 		pthread_mutex_lock(&stream->chan->metadata_cache->lock);
 	}
-	pthread_mutex_lock(&stream->chan->lock);
 	pthread_mutex_lock(&stream->lock);
 
 	/* Remove any reference to that stream. */
@@ -2082,10 +2082,10 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
 	stream->chan->metadata_stream = NULL;
 
 	pthread_mutex_unlock(&stream->lock);
-	pthread_mutex_unlock(&stream->chan->lock);
 	if (stream->chan->metadata_cache) {
 		pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
 	}
+	pthread_mutex_unlock(&stream->chan->lock);
 	pthread_mutex_unlock(&consumer_data.lock);
 
 	if (free_chan) {