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epoll: lock ep->mtx in ep_free to silence lockdep

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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 <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Arve Hjønnevåg <[email protected]>
Cc: Davide Libenzi <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: NeilBrown <[email protected]>,
Cc: Rafael J. Wysocki <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Eric Wong 2013-04-30 15:27:40 -07:00 • committed by Linus Torvalds
commit ddf676c38b
1 changed files with 4 additions and 0 deletions
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4
fs/eventpoll.c
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@ -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);