Fix: ust-consumer: segfault on snapshot after regenerate metadata

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

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 2948fda5043ad7b8aa4dd177e0beb04b25d38d48..bfecf09e2a6ae36bf578052f91b2b4c95855ebff 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -1005,7 +1005,7 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        metadata_stream = metadata_channel->metadata_stream;
        assert(metadata_stream);
 
-       pthread_mutex_lock(&metadata_stream->lock);
+       metadata_stream->read_subbuffer_ops.lock(metadata_stream);
        if (relayd_id != (uint64_t) -1ULL) {
                metadata_stream->net_seq_idx = relayd_id;
                ret = consumer_send_relayd_stream(metadata_stream, path);
@@ -1013,14 +1013,12 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
                ret = consumer_stream_create_output_files(metadata_stream,
                                false);
        }
-       pthread_mutex_unlock(&metadata_stream->lock);
        if (ret < 0) {
                goto error_stream;
        }
 
        do {
                health_code_update();
-
                ret = lttng_consumer_read_subbuffer(metadata_stream, ctx, true);
                if (ret < 0) {
                        goto error_stream;
@@ -1028,9 +1026,10 @@ static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
        } while (ret > 0);
 
 error_stream:
+       metadata_stream->read_subbuffer_ops.unlock(metadata_stream);
        /*
-        * Clean up the stream completly because the next snapshot will use a new
-        * metadata stream.
+        * Clean up the stream completely because the next snapshot will use a
+        * new metadata stream.
         */
        consumer_stream_destroy(metadata_stream, NULL);
        cds_list_del(&metadata_stream->send_node);
@@ -1324,10 +1323,21 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
                 * metadata position to ensure the metadata poll thread consumes
                 * the whole cache.
                 */
-               pthread_mutex_lock(&channel->metadata_stream->lock);
-               metadata_stream_reset_cache_consumed_position(
-                               channel->metadata_stream);
-               pthread_mutex_unlock(&channel->metadata_stream->lock);
+
+               /*
+                * channel::metadata_stream can be null when the metadata
+                * channel is under a snapshot session type. No need to update
+                * the stream position in that scenario.
+                */
+               if (channel->metadata_stream != NULL) {
+                       pthread_mutex_lock(&channel->metadata_stream->lock);
+                       metadata_stream_reset_cache_consumed_position(
+                                       channel->metadata_stream);
+                       pthread_mutex_unlock(&channel->metadata_stream->lock);
+               } else {
+                       /* Validate we are in snapshot mode. */
+                       assert(!channel->monitor);
+               }
                /* Fall-through. */
        case CONSUMER_METADATA_CACHE_WRITE_STATUS_APPENDED_CONTENT:
                /*