[patch 41/85] epoll: unify awaking of wakeup source on ep_poll_callback() path

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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>
---


--- a/fs/eventpoll.c~epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path
+++ a/fs/eventpoll.c
@@ -1162,14 +1162,7 @@ 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;
 	}
_



[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux