From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 18 May 2016 18:04:12 +0000 (-0400)
Subject: Fix: kernel tracing: flush after stop
X-Git-Tag: v2.9.0-rc1~175
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=566d897083dccb8d1fcec3f4727aee56facd4f25;hp=0dd01979d6f26886199ef746377640b57260421c

Fix: kernel tracing: flush after stop

We should flush the last packet after stop, not before. Otherwise, we
may end up with events written immediately after the flush, which
defeats the purpose of flushing.

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

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index 21422a57d..cc26e6dae 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -2447,7 +2447,15 @@ int cmd_stop_trace(struct ltt_session *session)
 	if (ksession && ksession->active) {
 		DBG("Stop kernel tracing");
 
-		/* Flush metadata if exist */
+		ret = kernel_stop_session(ksession);
+		if (ret < 0) {
+			ret = LTTNG_ERR_KERN_STOP_FAIL;
+			goto error;
+		}
+
+		kernel_wait_quiescent(kernel_tracer_fd);
+
+		/* Flush metadata after stopping (if exists) */
 		if (ksession->metadata_stream_fd >= 0) {
 			ret = kernel_metadata_flush_buffer(ksession->metadata_stream_fd);
 			if (ret < 0) {
@@ -2455,7 +2463,7 @@ int cmd_stop_trace(struct ltt_session *session)
 			}
 		}
 
-		/* Flush all buffers before stopping */
+		/* Flush all buffers after stopping */
 		cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
 			ret = kernel_flush_buffer(kchan);
 			if (ret < 0) {
@@ -2463,14 +2471,6 @@ int cmd_stop_trace(struct ltt_session *session)
 			}
 		}
 
-		ret = kernel_stop_session(ksession);
-		if (ret < 0) {
-			ret = LTTNG_ERR_KERN_STOP_FAIL;
-			goto error;
-		}
-
-		kernel_wait_quiescent(kernel_tracer_fd);
-
 		ksession->active = 0;
 	}