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Message-Id: <20110203141548.039540914@chello.nl>
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Date: Thu, 03 Feb 2011 15:09:41 +0100
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Thomas Gleixner <tglx@linutronix.de>, Tejun Heo <tj@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>, Faisal Latif <faisal.latif@intel.com>,
        Roland Dreier <roland@kernel.org>, Sean Hefty <sean.hefty@intel.com>,
        Hal Rosenstock <hal.rosenstock@gmail.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Alessandro Rubini <rubini@cvml.unipv.it>,
        Trond Myklebust <Trond.Myklebust@netapp.com>,
        Mark Fasheh <mfasheh@suse.com>, Joel Becker <jlbec@evilplan.org>,
        "David S. Miller" <davem@davemloft.net>,
        "John W. Linville" <linville@tuxdriver.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Yong Zhang <yong.zhang0@gmail.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [PATCH 1/4] lockdep, timer: Fix del_timer_sync() annotation
References: <20110203140940.072679794@chello.nl>
Content-Disposition: inline; filename=timer-del_timer_sync.patch
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
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Content-Length: 1410
Lines: 42

Calling local_bh_enable() will want to actually start processing
softirqs, which isn't a good idea since this can get called with IRQs
disabled.

Cure this by using _local_bh_enable() which doesn't start processing
softirqs, and use raw_local_irq_save() to avoid any softirqs from
happending without letting lockdep think IRQs are in fact disabled.

Reported-by: Nick Bowler <nbowler@elliptictech.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
---
 kernel/timer.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/timer.c
===================================================================
--- linux-2.6.orig/kernel/timer.c
+++ linux-2.6/kernel/timer.c
@@ -969,10 +969,14 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
 int del_timer_sync(struct timer_list *timer)
 {
 #ifdef CONFIG_LOCKDEP
+	unsigned long flags;
+
+	raw_local_irq_save(flags);
 	local_bh_disable();
 	lock_map_acquire(&timer->lockdep_map);
 	lock_map_release(&timer->lockdep_map);
-	local_bh_enable();
+	_local_bh_enable();
+	raw_local_irq_restore(flags);
 #endif
 	/*
 	 * don't use it in hardirq context, because it


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