linux-kernel - [PATCH 2/2] workqueue: convert BUG_ON()s in __queue_delayed_work() to WARN_ON

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Date:	Tue, 4 Dec 2012 07:55:06 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Xiaotian Feng <dannyfeng@...cent.com>,
	Neela Syam Kolli <megaraidlinux@....com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	linux-scsi@...r.kernel.org
Subject: [PATCH 2/2] workqueue: convert BUG_ON()s in __queue_delayed_work()
 to WARN_ON_ONCE()s

>From 87aa1e796ff6d491b5ed4e5663e5a4e449ac513b Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@...nel.org>
Date: Tue, 4 Dec 2012 07:40:39 -0800

8852aac25e ("workqueue: mod_delayed_work_on() shouldn't queue timer on
0 delay") unexpectedly uncovered a very nasty abuse of delayed_work in
megaraid - it allocated work_struct, used container_of() to cast it to
delayed_work and then pass that into queue_delayed_work().

Previously, this was okay because 0 @delay short-circuited to
queue_work() before doing anything with delayed_work.  8852aac25e
moved 0 @delay test into __queue_delayed_work() after sanity check on
delayed_work making megaraid trigger BUG_ON().

Although megaraid is already fixed by c1d390d8e6 ("megaraid: fix
BUG_ON() from incorrect use of delayed work"), this patch converts
BUG_ON()s in __queue_delayed_work() to WARN_ON_ONCE()s so that such
abusers, if there are more, trigger warning but don't crash the
machine.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Xiaotian Feng <xtfeng@...il.com>
---
 kernel/workqueue.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 084aa47..1dae900 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1361,8 +1361,8 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,

 	WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
 		     timer->data != (unsigned long)dwork);
-	BUG_ON(timer_pending(timer));
-	BUG_ON(!list_empty(&work->entry));
+	WARN_ON_ONCE(timer_pending(timer));
+	WARN_ON_ONCE(!list_empty(&work->entry));

 	/*
 	 * If @delay is 0, queue @dwork->work immediately.  This is for
-- 
1.7.11.7

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