The patch titled
Subject: epoll: unify awaking of wakeup source on ep_poll_callback() path
has been added to the -mm tree. Its filename is
epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path.patch
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From: Roman Penyaev <rpenyaev@xxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20190103150104.17128-4-rpenyaev@xxxxxxx
Signed-off-by: Roman Penyaev <rpenyaev@xxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
--- a/fs/eventpoll.c~epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path
+++ a/fs/eventpoll.c
@@ -1167,14 +1167,7 @@ static int ep_poll_callback(wait_queue_e
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;
}
_
Patches currently in -mm which might be from rpenyaev@xxxxxxx are
epoll-make-sure-all-elements-in-ready-list-are-in-fifo-order.patch
epoll-loosen-irq-safety-in-ep_poll_callback.patch
epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path.patch
epoll-use-rwlock-in-order-to-reduce-ep_poll_callback-contention.patch
