linux-kernel - [PATCH 2/2] sched/wait: assert the wait_queue_head lock is held in __wake_up

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Message-Id: <20171206235230.19425-3-hch@lst.de>
Date:   Wed,  6 Dec 2017 15:52:30 -0800
From:   Christoph Hellwig <hch@....de>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jason Baron <jbaron@...mai.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] sched/wait: assert the wait_queue_head lock is held in __wake_up_common

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@....de>
---
 kernel/sched/wait.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 98feab7933c7..347c06c8222e 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