[PATCH 3/3] sched/wait: assert the wait_queue_head lock is held in __wake_up_common

[Christoph Hellwig]

Better ensure we actually hold the lock using lockdep than just commenting
on it.  Due to the various exported _locked interfaces it is far too easy
to get the locking wrong.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/wait.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 929ecb7d6b78..d09c4de4865c 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -76,6 +76,8 @@ static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode,
 	wait_queue_entry_t *curr, *next;
 	int cnt = 0;
 
+	lockdep_assert_held(&wq_head->lock);
+
 	if (bookmark && (bookmark->flags & WQ_FLAG_BOOKMARK)) {
 		curr = list_next_entry(bookmark, entry);
 
-- 
2.14.2