epoll: lock ep->mtx in ep_free to silence lockdep
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]>
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a3acf93..5744a7f 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -745,11 +745,15 @@
* 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);
