linux-kernel - Re: [PATCH 1/2] lockdep: implement full check without irq checking

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Message-Id: <1225365316.7803.69.camel@twins>
Date:	Thu, 30 Oct 2008 12:15:16 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 1/2] lockdep: implement full check without irq checking

On Thu, 2008-10-30 at 11:36 +0100, Johannes Berg wrote:

> > del_timer_sync():
> > 
> >   local_irq_save(flags);
> >   lock_aquire(my fake timer lock);
> >   lock_release(...);
> >   local_irq_restore(flags);
> > 
> > and make that conditional CONFIG_PROVE_LOCKING and or wrap it up
> > somewhere..
> 
> Yeah, that is possible, but it seemed to me that would affect the
> performance of del_timer_sync() quite a bit. Not sure it matters. And on
> powerpc (which I care about) it won't actually affect performance much
> because we lazily disable IRQs, but still. The >= 2 change also seemed
> to generate smaller code?

Its debug code, and I the >= 2 change makes the code much less obvious.

So I prefer the slightly less performant but conceptually cleaner IRQ
disable variant.


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