linux-kernel - Re: lockdep, false positive ?

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Message-ID: <20080409120803.ZZRA012@mailhub.coreip.homeip.net>
Date:	Wed, 9 Apr 2008 12:11:25 -0400
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	benh@...nel.crashing.org, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: lockdep, false positive ?

Hi Peter,

On Wed, Apr 09, 2008 at 11:44:41AM +0200, Peter Zijlstra wrote:
> 
> Yes, if both locks are of the same class it will report this. Lockdep
> does lock chain validation on classes, never on individual locks.
> 
> A class usually consists of all locks that share the lock init site; but
> there are ways to explicity set another class.
> 
> In case of these recursions we have helpers like spin_lock_nested(&lock,
> subclass) that allow you to annotate these. These sub-classes must then
> always be taken in the same order; subclass < 8.
> 
> In this case its probably easier to explicity set a class, as the
> nesting is not exposed to the input layer, so it doesn't know about it.
> 

Is there a way in lockdep to mark all instances of a given lock as distinct?
I'd rather do that in input core once and be done with it.

Also another question I've been meaning to ask - we have lockdep annotations
in serio code and they work fine first time around but if you reload
psmouse module lockdep will barf if you have SYnaptics touchpad with
pass-through port. What gives?

-- 
Dmitry
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