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

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

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 245f4ee46ee552eb60c75b7ca17156ed7ebd8d71..362cbd2dca61bde6f23a4375725b172b22f3bb70 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -139,7 +139,7 @@ error:
 /*
  * Take a snapshot of all the stream of a channel
  * RCU read-side lock must be held across this function to ensure existence of
- * channel. The channel lock must be held by the caller.
+ * channel.
  *
  * Returns 0 on success, < 0 on error
  */
@@ -154,6 +154,9 @@ static int lttng_kconsumer_snapshot_channel(
 
        DBG("Kernel consumer snapshot channel %" PRIu64, key);
 
+       /* Prevent channel modifications while we perform the snapshot.*/
+       pthread_mutex_lock(&channel->lock);
+
        rcu_read_lock();
 
        /* Splice is not supported yet for channel snapshot. */
@@ -347,13 +350,14 @@ end_unlock:
        pthread_mutex_unlock(&stream->lock);
 end:
        rcu_read_unlock();
+       pthread_mutex_unlock(&channel->lock);
        return ret;
 }
 
 /*
  * Read the whole metadata available for a snapshot.
  * RCU read-side lock must be held across this function to ensure existence of
- * metadata_channel. The channel lock must be held by the caller.
+ * metadata_channel.
  *
  * Returns 0 on success, < 0 on error
  */
@@ -376,7 +380,8 @@ static int lttng_kconsumer_snapshot_metadata(
        metadata_stream = metadata_channel->metadata_stream;
        assert(metadata_stream);
 
-       pthread_mutex_lock(&metadata_stream->lock);
+       /* Take all the appropriate locks hehehe.*/
+       metadata_stream->read_subbuffer_ops.lock(metadata_stream);
        assert(metadata_channel->trace_chunk);
        assert(metadata_stream->trace_chunk);
 
@@ -431,7 +436,7 @@ static int lttng_kconsumer_snapshot_metadata(
 
        ret = 0;
 error_snapshot:
-       pthread_mutex_unlock(&metadata_stream->lock);
+       metadata_stream->read_subbuffer_ops.unlock(metadata_stream);
        cds_list_del(&metadata_stream->send_node);
        consumer_stream_destroy(metadata_stream, NULL);
        metadata_channel->metadata_stream = NULL;
@@ -935,7 +940,6 @@ error_streams_sent_nosignal:
                        ERR("Channel %" PRIu64 " not found", key);
                        ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
-                       pthread_mutex_lock(&channel->lock);
                        if (msg.u.snapshot_channel.metadata == 1) {
                                ret = lttng_kconsumer_snapshot_metadata(channel, key,
                                                msg.u.snapshot_channel.pathname,
@@ -955,7 +959,6 @@ error_streams_sent_nosignal:
                                        ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
                                }
                        }
-                       pthread_mutex_unlock(&channel->lock);
                }
                health_code_update();