epoll: ep_autoremove_wake_function should use list_del_init_careful

autoremove_wake_function uses list_del_init_careful, so should epoll's
more aggressive variant.  It only doesn't because it was copied from an
older wait.c rather than the most recent.

[bsegall@google.com: add comment]
Link: https://lkml.kernel.org/r/xm26bki0ulsr.fsf_-_@google.com
Link: https://lkml.kernel.org/r/xm26pm6hvfer.fsf@google.com
Fixes: a16ceb139610 ("epoll: autoremove wakers even more aggressively")
Signed-off-by: Ben Segall <bsegall@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 980483455cc0974f55195f34fc30ef8423784151..266d45c7685b446de7893a1cc533b4e2c3166081 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1805,7 +1805,11 @@ static int ep_autoremove_wake_function(struct wait_queue_entry *wq_entry,
 {
        int ret = default_wake_function(wq_entry, mode, sync, key);
 
-       list_del_init(&wq_entry->entry);
+       /*
+        * Pairs with list_empty_careful in ep_poll, and ensures future loop
+        * iterations see the cause of this wakeup.
+        */
+       list_del_init_careful(&wq_entry->entry);
        return ret;
 }