linux-kernel - [PATCH] epoll: add a reschedule point in ep

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Message-ID: <1376751997.21329.8.camel@edumazet-glaptop>
Date:	Sat, 17 Aug 2013 08:06:37 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...IV.linux.org.uk>, edumazet@...gle.com,
	Theodore Ts'o <tytso@....edu>
Subject: [PATCH] epoll: add a reschedule point in ep_free()

From: Eric Dumazet <edumazet@...gle.com>

ep_free() might iterate on a huge set of epitems and hold
cpu too long. Add two cond_resched() in order to yield cpu
to other tasks. This is safe as we only hold mutexes in
this function.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
Cc: Theodore Ts'o <tytso@....edu>
---
Google-Bug-Id: 8940884

 fs/eventpoll.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9ad17b15..4ff595d 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -740,6 +740,7 @@ static void ep_free(struct eventpoll *ep)
 		epi = rb_entry(rbp, struct epitem, rbn);
 
 		ep_unregister_pollwait(ep, epi);
+		cond_resched();
 	}
 
 	/*
@@ -754,6 +755,7 @@ static void ep_free(struct eventpoll *ep)
 	while ((rbp = rb_first(&ep->rbr)) != NULL) {
 		epi = rb_entry(rbp, struct epitem, rbn);
 		ep_remove(ep, epi);
+		cond_resched();
 	}
 	mutex_unlock(&ep->mtx);
 



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