linux-kernel - Re: WARNING: at kernel/lockdep.c:690 __lock

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Date:	Sun, 16 Oct 2011 08:09:20 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Borislav Petkov <bp@...en8.de>, Tejun Heo <tj@...nel.org>,
	Tejun Heo <htejun@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: WARNING: at kernel/lockdep.c:690 __lock_acquire+0x168/0x164b()

On (10/15/11 15:32), David Rientjes wrote:
> > > I think this is a problem with lockdep itself, could you try reverting 
> > > f59de8992aa6 ("lockdep: Clear whole lockdep_map on initialization") if 
> > > this reliably happens everytime you reboot (lockdep will only emit this 
> > > once and then will suppress future warnings until the next boot)?
> > > 
> > > I think the new memset() is inadvertently clearing the name for 
> > > double_unlock_balance().
> > 
> > Great,
> > 
> > so I'm not the only one seeing the above:
> > http://marc.info/?l=linux-kernel&m=131468805610527
> > 
> > Due to it being very hard to reproduce, we dismissed it then as a
> > possible hw corruption.
> > 
> > But yeah, it looks like I have triggered it on -rc9 too, just the
> > other day. Oh, and I see -rc6 and -rc8 warnings in the logs too. Ok,
> > correction, not that hard to trigger.
> > 
> 
> Could you try to revert f59de8992aa6 ("lockdep: Clear whole lockdep_map on 
> initialization") with this patch and see if it helps?  Thanks.


Sure, I'd love to and will do, it's just I'm not sure I can easily reproduce it.



> ---
> 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();
> 
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