From c3e320b61581ef7919269ca242ff13951ccfc763 Mon Sep 17 00:00:00 2001 From: Roman Penyaev Date: Thu, 7 Mar 2019 16:28:49 -0800 Subject: [PATCH] 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@suse.de Signed-off-by: Roman Penyaev Cc: Davidlohr Bueso Cc: Jason Baron Cc: Al Viro Cc: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 60f6b2712f5e..53c3d4677dd4 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1162,14 +1162,7 @@ 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; } -- 2.30.2