linux-kernel - Re: [RFC/PATCH] debug workqueue deadlocks with lockdep

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Date:	Wed, 04 Jul 2007 15:59:54 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Oleg Nesterov <oleg@...sign.ru>, Ingo Molnar <mingo@...hat.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Sattler <tsattler@....de>
Subject: Re: [RFC/PATCH] debug workqueue deadlocks with lockdep

On Wed, 2007-07-04 at 14:21 +0200, Ingo Molnar wrote:

> well, in this case the lock/unlock should nest perfectly (i.e. it should 
> always be balanced perfectly), so indeed calling with nested==1 leads to 
> stricter checking.
> 
> non-nested unlocks occur when people do stuff like:
> 
> 	spin_lock(&lock1);
> 	spin_lock(&lock2);
> 	spin_unlock(&lock1);
> 	spin_unlock(&lock2);
> 
> the first unlock is not 'nested perfectly'. Now for the workqueue 
> dep_map this shouldnt be a legal combination, right?

I don't think so, will change to use nested==1.

johannes

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