Date: Mon, 7 Jul 2008 08:35:19 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-next@vger.kernel.org, linux-mm@kvack.org
Subject: Re: next-0704: WARNING: at kernel/sched.c:4254 add_preempt_count;
	PANIC
Message-ID: <20080707063519.GE23583@elte.hu>
References: <487159DA.708@gmail.com>
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* Alexander Beregalov <a.beregalov@gmail.com> wrote:

> Hi
> 
> WARNING: at kernel/sched.c:4254 add_preempt_count+0x61/0x63()
> Modules linked in: i2c_nforce2
> Pid: 3620, comm: rtorrent Not tainted 2.6.26-rc8-next-20080704 #5

this warning is what triggers:

 #ifdef CONFIG_DEBUG_PREEMPT
         /*
          * Underflow?
          */
         if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
                 return;

i.e. preempt counter underflow. That can happen either due to unbalanced 
preempt_disable()/preempt_enable() pairs, or can happen due to stack 
overflow/corruption.

	Ingo
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