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

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Message-Id: <1225365905.3690.30.camel@johannes.berg>
Date:	Thu, 30 Oct 2008 12:25:05 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Peter Zijlstra <peterz@...radead.org>
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 12:15 +0100, Peter Zijlstra wrote:
> 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.

Alright. Thomas, shout if you want this code at all, then I'll clean it
up and resend, I don't particularly care, just did it to see if it was
possible.

johannes

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