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Date: Wed, 21 Mar 2007 22:28:02 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Jarek Poplawski <jarkao2@o2.pl>
Cc: Oleg Nesterov <oleg@tv-sign.ru>, Neil Brown <neilb@suse.de>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Folkert van Heusden <folkert@vanheusden.com>,
       linux-kernel@vger.kernel.org, "J\. Bruce Fields" <bfields@fieldses.org>,
       Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] lockdep: lockdep_depth vs. debug_locks Re: [2.6.20]
 BUG: workqueue leaked lock
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On Thu, 22 Mar 2007 07:11:19 +0100 Jarek Poplawski <jarkao2@o2.pl> wrote:

> 
> Here is some joke:
> 
> [PATCH] lockdep: lockdep_depth vs. debug_locks
> 
> lockdep really shouldn't be used when debug_locks == 0!
> 

This isn't a very good changelog.

> 
> Reported-by: Folkert van Heusden <folkert@vanheusden.com>
> Inspired-by: Oleg Nesterov <oleg@tv-sign.ru>
> Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
> 
> ---
> 
> diff -Nurp 2.6.21-rc4-git4-/include/linux/lockdep.h 2.6.21-rc4-git4/include/linux/lockdep.h
> --- 2.6.21-rc4-git4-/include/linux/lockdep.h	2007-03-20 20:24:17.000000000 +0100
> +++ 2.6.21-rc4-git4/include/linux/lockdep.h	2007-03-21 22:32:41.000000000 +0100
> @@ -245,7 +245,7 @@ extern void lock_release(struct lockdep_
>  
>  # define INIT_LOCKDEP				.lockdep_recursion = 0,
>  
> -#define lockdep_depth(tsk)	((tsk)->lockdep_depth)
> +#define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
>  
>  #else /* !LOCKDEP */
>  

What problem does this solve, and how does it solve it?

I assume that some codepath is incrementing ->lockdep_depth even when
debug_locks==0.  Isn't that wrong of it?