* interacting with sessiond, else we cause a deadlock with live
* awaiting on metadata to be pushed out.
*
+ * The RCU read side lock must be held by the caller.
+ *
* Return 0 if new metadatda is available, EAGAIN if the metadata stream
* is empty or a negative value on error.
*/
int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
- struct lttng_consumer_stream *metadata)
+ struct lttng_consumer_stream *metadata_stream)
{
int ret;
int retry = 0;
+ struct lttng_consumer_channel *metadata_channel;
assert(ctx);
- assert(metadata);
+ assert(metadata_stream);
- pthread_mutex_unlock(&metadata->lock);
+ metadata_channel = metadata_stream->chan;
+ pthread_mutex_unlock(&metadata_stream->lock);
/*
* Request metadata from the sessiond, but don't wait for the flush
* because we locked the metadata thread.
*/
- ret = lttng_ustconsumer_request_metadata(ctx, metadata->chan, 0, 0);
- pthread_mutex_lock(&metadata->lock);
+ ret = lttng_ustconsumer_request_metadata(ctx, metadata_channel, 0, 0);
+ pthread_mutex_lock(&metadata_stream->lock);
if (ret < 0) {
goto end;
}
- ret = commit_one_metadata_packet(metadata);
+ /*
+ * The metadata stream and channel can be deleted while the
+ * metadata stream lock was released. The streamed is checked
+ * for deletion before we use it further.
+ *
+ * Note that it is safe to access a logically-deleted stream since its
+ * existence is still guaranteed by the RCU read side lock. However,
+ * it should no longer be used. The close/deletion of the metadata
+ * channel and stream already guarantees that all metadata has been
+ * consumed. Therefore, there is nothing left to do in this function.
+ */
+ if (consumer_stream_is_deleted(metadata_stream)) {
+ DBG("Metadata stream %" PRIu64 " was deleted during the metadata synchronization",
+ metadata_stream->key);
+ ret = 0;
+ goto end;
+ }
+
+ ret = commit_one_metadata_packet(metadata_stream);
if (ret <= 0) {
goto end;
} else if (ret > 0) {
retry = 1;
}
- ret = ustctl_snapshot(metadata->ustream);
+ ret = ustctl_snapshot(metadata_stream->ustream);
if (ret < 0) {
if (errno != EAGAIN) {
ERR("Sync metadata, taking UST snapshot");