The patch titled
Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback
has been added to the -mm tree. Its filename is
eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2.patch
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------------------------------------------------------
From: Khazhismel Kumykov <khazhy@xxxxxxxxxx>
Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback
use if/elif instead of goto + cleanup suggested by Roman
Link: http://lkml.kernel.org/r/20200424190039.192373-1-khazhy@xxxxxxxxxx
Fixes: 339ddb53d373 ("fs/epoll: remove unnecessary wakeups of nested epoll")
Signed-off-by: Khazhismel Kumykov <khazhy@xxxxxxxxxx>
Reviewed-by: Roman Penyaev <rpenyaev@xxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Heiher <r@xxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
--- a/fs/eventpoll.c~eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2
+++ a/fs/eventpoll.c
@@ -1171,6 +1171,10 @@ static inline bool chain_epi_lockless(st
{
struct eventpoll *ep = epi->ep;
+ /* Fast preliminary check */
+ if (epi->next != EP_UNACTIVE_PTR)
+ return false;
+
/* Check that the same epi has not been just chained from another CPU */
if (cmpxchg(&epi->next, EP_UNACTIVE_PTR, NULL) != EP_UNACTIVE_PTR)
return false;
@@ -1237,19 +1241,14 @@ static int ep_poll_callback(wait_queue_e
* chained in ep->ovflist and requeued later on.
*/
if (READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR) {
- if (epi->next == EP_UNACTIVE_PTR &&
- chain_epi_lockless(epi))
+ if (chain_epi_lockless(epi))
+ ep_pm_stay_awake_rcu(epi);
+ } else if (!ep_is_linked(epi)) {
+ /* In the usual case, add event to ready list. */
+ if (list_add_tail_lockless(&epi->rdllink, &ep->rdllist))
ep_pm_stay_awake_rcu(epi);
- goto out_wakeup_unlock;
- }
-
- /* If this file is already in the ready list we exit soon */
- if (!ep_is_linked(epi) &&
- list_add_tail_lockless(&epi->rdllink, &ep->rdllist)) {
- ep_pm_stay_awake_rcu(epi);
}
-out_wakeup_unlock:
/*
* Wake up ( if active ) both the eventpoll wait list and the ->poll()
* wait list.
_
Patches currently in -mm which might be from khazhy@xxxxxxxxxx are
eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch
eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2.patch
