Fix: only lock the metadata_cache in userspace consumers

The kernel consumer, which re-uses the consumer_del_metadata_stream
function, has no metadata cache. Therefore, it can't be used to
protect the metadata stream (see 5feafd41).

However, only the userspace consumers invoke
consumer_metadata_cache_write() which the previous fix seeked to
protect against. It is therefore safe to omit this lock in the
kernel consumer case.

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

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 21adb00b4d945eaf0255c0f9b2bf100ae1793c2c..19d705c93c1b674e67a42975b0ce4cc84d577a73 100644 (file)
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -2052,7 +2052,10 @@ 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->metadata_cache->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);
 
@@ -2080,7 +2083,9 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
 
        pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&stream->chan->lock);
-       pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
+       if (stream->chan->metadata_cache) {
+               pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
+       }
        pthread_mutex_unlock(&consumer_data.lock);
 
        if (free_chan) {