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Date: Wed, 11 Feb 2009 10:27:45 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vegard Nossum <vegard.nossum@gmail.com>,
       Alexey Dobriyan <adobriyan@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>, Greg KH <gregkh@suse.de>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.29-rc3: BUG: scheduling while atomic: udevd/917/0x10000100
Message-ID: <20090211092745.GB14265@elte.hu>
References: <19f34abd0902110009g4cdb1754na1cbf0acb6a93cce@mail.gmail.com> <20090211083217.GC21105@elte.hu> <1234342189.23438.113.camel@twins>
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Wed, 2009-02-11 at 09:32 +0100, Ingo Molnar wrote:
> 
> > There's a fourth possibility:
> > 
> >  - Given that it's udevd that does it - maybe we leaked a softirq preempt
> >    count in some rare sysfs file, and it did not get discovered until the
> >    next innocent piece of kernel code preempted?
> > 
> > But i thought lockdep would already warn if we exited a syscall with locks
> > held or with a preempt count elevated - Peter?
> 
> From a quick look it only checks task->lockdep_depth, in lockdep_sys_exit().

That could be broadened then i guess - there's never a good excuse for exiting a 
syscall with an elevated preempt count.

	Ingo