Fix: ust-consumer: flush empty packets on snapshot channel

Snapshot operation on a non-stopped stream should use a "final" flush to
ensure empty packets are flushed, so we gather timestamps at the moment
where the snapshot is taken. This is important for streams that have a
low amount of activity, which might be on an empty packet when the
snapshot is triggered.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index a66f305cd02e433f41bf31d0591c0e545d524a1a..89109b919a85231615fdb7f86a3c98518a9d422a 100644 (file)
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -1111,7 +1111,13 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                        }
                }
 
-               ustctl_flush_buffer(stream->ustream, 1);
+               /*
+                * If tracing is active, we want to perform a "full" buffer flush.
+                * Else, if quiescent, it has already been done by the prior stop.
+                */
+               if (!stream->quiescent) {
+                       ustctl_flush_buffer(stream->ustream, 0);
+               }
 
                ret = lttng_ustconsumer_take_snapshot(stream);
                if (ret < 0) {