[lttng-dev] [PATCH lttng-tools 04/10] Fix: ust-consumer: flush empty packets on snapshot channel

[Mathieu Desnoyers]

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 at efficios.com>
---
 src/common/ust-consumer/ust-consumer.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 91ffdce..c631904 100644
--- 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) {
-- 
2.1.4