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Date: Thu, 20 Oct 2011 22:07:02 +0300
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Borislav Petkov <bp@alien8.de>, David Rientjes <rientjes@google.com>,
        Tejun Heo <tj@kernel.org>, Tejun Heo <htejun@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b()
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On (10/20/11 21:53), Sergey Senozhatsky wrote:
> Date: Thu, 20 Oct 2011 21:53:29 +0300
> From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> To: Borislav Petkov <bp@alien8.de>, David Rientjes <rientjes@google.com>,
>  Tejun Heo <tj@kernel.org>, Tejun Heo <htejun@gmail.com>, Peter Zijlstra
>  <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
>  linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>
> Subject: Re: WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b()
> User-Agent: Mutt/1.5.21 (2010-09-15)
> 
> On (10/20/11 20:39), Borislav Petkov wrote:
> > On Sat, Oct 15, 2011 at 03:32:32PM -0700, David Rientjes wrote:
> > > Could you try to revert f59de8992aa6 ("lockdep: Clear whole lockdep_map on 
> > > initialization") with this patch and see if it helps?  Thanks.
> > > ---
> > > diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> > > --- a/kernel/lockdep.c
> > > +++ b/kernel/lockdep.c
> > > @@ -2874,7 +2874,10 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
> > >  void lockdep_init_map(struct lockdep_map *lock, const char *name,
> > >  		      struct lock_class_key *key, int subclass)
> > >  {
> > > -	memset(lock, 0, sizeof(*lock));
> > > +	int i;
> > > +
> > > +	for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
> > > +		lock->class_cache[i] = NULL;
> > >  
> > >  #ifdef CONFIG_LOCK_STAT
> > >  	lock->cpu = raw_smp_processor_id();
> > 
> > FWIW,
> > 
> > the box has been running here with f59de8992aa6 reverted for a couple of
> > days now and no sign of the warning. I'll keep watching it but it looks
> > ok so far, so David, you could've nailed it.
> > 
> 
> Hello,
> Well, the same with me. My laptop has been running with reverted f59de8992aa6 without any
> problems so far. Yet, I'm not sure I understand how memset() and loop could
> produce different results.
> 

Oh, well, nevermind I think I get it. 

Reverting opens https://bugzilla.kernel.org/show_bug.cgi?id=35532 again.  


> commit in question (f59de8992aa6dc85e81aadc26b0f69e17809721d) has been merge on
> Jul 14 15:19:09 2011 +0200, so, Borislav, you probably should have seen it
> not only on 3.1-rc5, 3.1-rc6,..., but even on 3.0.
> 
> 


	Sergey