Fix: ust-consumer: metadata cache lock not taken when sampling max offset

Found by inspecting the code while searching for an unrelated problem.
The 'max_offset' field is probably only accessed by the sessiond
poll thread, but this isn't a documented (nor reasonably maintainable)
guarantee.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I1d2b29e9a483aa8e49c2db589284b853cce65491

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 209931f5644a3d74dc27ed1a8f7dbb3d3863d387..e522de750275e08ff366b27ab31d64407b62b1c2 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -3054,7 +3054,9 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                uint64_t contiguous, pushed;
 
                /* Ease our life a bit. */
+               pthread_mutex_lock(&stream->chan->metadata_cache->lock);
                contiguous = stream->chan->metadata_cache->max_offset;
+               pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
                pushed = stream->ust_metadata_pushed;
 
                /*