+ eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback-v2.patch added to -mm tree

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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




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