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Subject[PATCH v2 3/4] epoll: unify awaking of wakeup source on ep_poll_callback() path
Original comment "Activate ep->ws since epi->ws may get deactivated
at any time" indeed sounds loud, but it is incorrect, because the path
where we check epi->ws is a path where insert to ovflist happens, i.e.
ep_scan_ready_list() has taken ep->mtx and waits for this callback
to finish, thus ep_modify() (which unregisters wakeup source) waits
for ep_scan_ready_list().

Here in this patch I simply call ep_pm_stay_awake_rcu(), which is
a bit extra for this path (indirectly protected by main ep->mtx, so
even rcu is not needed), but I do not want to create another naked
__ep_pm_stay_awake() variant only for this particular case, so rcu
variant is just better for all the cases.

Signed-off-by: Roman Penyaev <>
Cc: Davidlohr Bueso <>
Cc: Jason Baron <>
Cc: Al Viro <>
Cc: Andrew Morton <>
Cc: Linus Torvalds <>
fs/eventpoll.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 3c373a510f65..0122b9147542 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1167,14 +1167,7 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v
if (epi->next == EP_UNACTIVE_PTR) {
epi->next = READ_ONCE(ep->ovflist);
WRITE_ONCE(ep->ovflist, epi);
- if (epi->ws) {
- /*
- * Activate ep->ws since epi->ws may get
- * deactivated at any time.
- */
- __pm_stay_awake(ep->ws);
- }
+ ep_pm_stay_awake_rcu(epi);
goto out_unlock;
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