Do not hold the registry lock while communicating with the consumerd,
because doing so causes inter-process deadlocks between consumerd and
sessiond with the metadata request notification.
The deadlock involves both sessiond and consumerd:
* lttng-sessiond:
thread 11 - thread_application_management
close_metadata()
pthread_mutex_lock(®istry->lock);
consumer_close_metadata()
pthread_mutex_lock(socket->lock);
thread 15 - thread_consumer_management
ust_consumer_metadata_request()
pthread_mutex_lock(&ust_reg->lock);
thread 8 - thread_manage_clients
consumer_is_data_pending
pthread_mutex_lock(socket->lock);
consumer_socket_recv()
* lttng-consumerd:
thread 4 - consumer_timer_thread
sample_channel_positions()
pthread_mutex_lock(&stream->lock);
thread 8 - consumer_thread_sessiond_poll
consumer_data_pending
pthread_mutex_lock(&consumer_data.lock);
pthread_mutex_lock(&stream->lock);
thread 7 - consumer_thread_data_poll
lttng_consumer_read_subbuffer
pthread_mutex_lock(&stream->chan->lock);
pthread_mutex_lock(&stream->lock);
do_sync_metadata
pthread_mutex_lock(&metadata->lock);
lttng_ustconsumer_sync_metadata
pthread_mutex_unlock(&metadata_stream->lock);
lttng_ustconsumer_request_metadata()
pthread_mutex_lock(&ctx->metadata_socket_lock);
lttcomm_recv_unix_sock()
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
* nullified. The session lock MUST be held unless the application is
* in the destroy path.
*
* nullified. The session lock MUST be held unless the application is
* in the destroy path.
*
+ * Do not hold the registry lock while communicating with the consumerd, because
+ * doing so causes inter-process deadlocks between consumerd and sessiond with
+ * the metadata request notification.
+ *
* Return 0 on success else a negative value.
*/
static int close_metadata(struct ust_registry_session *registry,
* Return 0 on success else a negative value.
*/
static int close_metadata(struct ust_registry_session *registry,
{
int ret;
struct consumer_socket *socket;
{
int ret;
struct consumer_socket *socket;
+ uint64_t metadata_key;
+ bool registry_was_already_closed;
assert(registry);
assert(consumer);
assert(registry);
assert(consumer);
rcu_read_lock();
pthread_mutex_lock(®istry->lock);
rcu_read_lock();
pthread_mutex_lock(®istry->lock);
+ metadata_key = registry->metadata_key;
+ registry_was_already_closed = registry->metadata_closed;
+ if (metadata_key != 0) {
+ /*
+ * Metadata closed. Even on error this means that the consumer
+ * is not responding or not found so either way a second close
+ * should NOT be emit for this registry.
+ */
+ registry->metadata_closed = 1;
+ }
+ pthread_mutex_unlock(®istry->lock);
- if (!registry->metadata_key || registry->metadata_closed) {
+ if (metadata_key == 0 || registry_was_already_closed) {
consumer);
if (!socket) {
ret = -1;
consumer);
if (!socket) {
ret = -1;
- ret = consumer_close_metadata(socket, registry->metadata_key);
+ ret = consumer_close_metadata(socket, metadata_key);
-error:
- /*
- * Metadata closed. Even on error this means that the consumer is not
- * responding or not found so either way a second close should NOT be emit
- * for this registry.
- */
- registry->metadata_closed = 1;
- pthread_mutex_unlock(®istry->lock);
rcu_read_unlock();
return ret;
}
rcu_read_unlock();
return ret;
}