Fix deadlock: don't take channel lock in timer

[lttng-tools.git] / src / common / consumer-metadata-cache.c

diff --git a/src/common/consumer-metadata-cache.c b/src/common/consumer-metadata-cache.c
index 5967a8eb296a51041f754622f65bb0b706ffe393..d597e64e37883c91182bcaf9c54327cd9cc0d54f 100644 (file)
--- a/src/common/consumer-metadata-cache.c
+++ b/src/common/consumer-metadata-cache.c
@@ -190,7 +190,7 @@ void consumer_metadata_cache_destroy(struct lttng_consumer_channel *channel)
  * Return 0 if everything has been flushed, 1 if there is data not flushed.
  */
 int consumer_metadata_cache_flushed(struct lttng_consumer_channel *channel,
-               uint64_t offset)
+               uint64_t offset, int timer)
 {
        int ret = 0;
        struct lttng_consumer_stream *metadata_stream;
@@ -199,12 +199,15 @@ int consumer_metadata_cache_flushed(struct lttng_consumer_channel *channel,
        assert(channel->metadata_cache);
 
        /*
-        * XXX This consumer_data.lock should eventually be replaced by
-        * a channel lock. It protects metadata_stream read and endpoint
-        * status check.
+        * If not called from a timer handler, we have to take the
+        * channel lock to be mutually exclusive with channel teardown.
+        * Timer handler does not need to take this lock because it is
+        * already synchronized by timer stop (and, more importantly,
+        * taking this lock in a timer handler would cause a deadlock).
         */
-       pthread_mutex_lock(&consumer_data.lock);
-       pthread_mutex_lock(&channel->lock);
+       if (!timer) {
+               pthread_mutex_lock(&channel->lock);
+       }
        pthread_mutex_lock(&channel->timer_lock);
        pthread_mutex_lock(&channel->metadata_cache->lock);
 
@@ -229,8 +232,9 @@ int consumer_metadata_cache_flushed(struct lttng_consumer_channel *channel,
 
        pthread_mutex_unlock(&channel->metadata_cache->lock);
        pthread_mutex_unlock(&channel->timer_lock);
-       pthread_mutex_unlock(&channel->lock);
-       pthread_mutex_unlock(&consumer_data.lock);
+       if (!timer) {
+               pthread_mutex_unlock(&channel->lock);
+       }
 
        return ret;
 }