linux-kernel - Re: [PATCH] lockdep: lockdep_depth vs. debug_locks Re: [2.6.20] BUG: workqueue leaked lock

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Date:	Wed, 21 Mar 2007 22:28:02 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jarek Poplawski <jarkao2@...pl>
Cc:	Oleg Nesterov <oleg@...sign.ru>, Neil Brown <neilb@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Folkert van Heusden <folkert@...heusden.com>,
	linux-kernel@...r.kernel.org,
	"J\. Bruce Fields" <bfields@...ldses.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] lockdep: lockdep_depth vs. debug_locks Re: [2.6.20]
 BUG: workqueue leaked lock

On Thu, 22 Mar 2007 07:11:19 +0100 Jarek Poplawski <jarkao2@...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@...heusden.com>
> Inspired-by: Oleg Nesterov <oleg@...sign.ru>
> Signed-off-by: Jarek Poplawski <jarkao2@...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?
-
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