[PATCH] tracing/ftrace: add missing unlock in register_stat_tracer()

[Li Zefan <lizf@cn.fujitsu.com>]

We should unlock all_stat_sessions_mutex before returning failure.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---

I noticed Ingo tend to delete the impact line from my changelog
if it added nothing new to the title, so no impact line for this
patch. :)

---
 kernel/trace/trace_stat.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index cb29282..8669f3c 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -73,8 +73,10 @@ int register_stat_tracer(struct tracer_stat *trace)
 	/* Already registered? */
 	mutex_lock(&all_stat_sessions_mutex);
 	list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
-		if (node->ts == trace)
+		if (node->ts == trace) {
+			mutex_unlock(all_stat_sessions_mutex);
 			return -EINVAL;
+		}
 	}
 	mutex_unlock(&all_stat_sessions_mutex);
 
-- 
1.5.4.rc3