From ddf676c38b56a8641c8eb9fb856fa304018ff390 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Tue, 30 Apr 2013 15:27:40 -0700 Subject: [PATCH] epoll: lock ep->mtx in ep_free to silence lockdep MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Technically we do not need to hold ep->mtx during ep_free since we are certain there are no other users of ep at that point. However, lockdep complains with a "suspicious rcu_dereference_check() usage!" message; so lock the mutex before ep_remove to silence the warning. Signed-off-by: Eric Wong Cc: Al Viro Cc: Arve Hjønnevåg Cc: Davide Libenzi Cc: Eric Dumazet Cc: NeilBrown , Cc: Rafael J. Wysocki Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index a3acf936c72a..5744a7f01875 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -745,11 +745,15 @@ static void ep_free(struct eventpoll *ep) * point we are sure no poll callbacks will be lingering around, and also by * holding "epmutex" we can be sure that no file cleanup code will hit * us during this operation. So we can avoid the lock on "ep->lock". + * We do not need to lock ep->mtx, either, we only do it to prevent + * a lockdep warning. */ + mutex_lock(&ep->mtx); while ((rbp = rb_first(&ep->rbr)) != NULL) { epi = rb_entry(rbp, struct epitem, rbn); ep_remove(ep, epi); } + mutex_unlock(&ep->mtx); mutex_unlock(&epmutex); mutex_destroy(&ep->mtx);