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.

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  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: a16ceb1 ("epoll: autoremove wakers even more aggressively")
Signed-off-by: Ben Segall <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Benjamin Segall

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;
 }