linux-kernel - Re: linux-next: PowerPC WARN_ON_ONCE() after merge of the final tree (tip related)

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Date:	Fri, 16 Apr 2010 12:38:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-next@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	ppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: linux-next: PowerPC WARN_ON_ONCE() after merge of the final
 tree (tip related)

On Thu, 2010-04-15 at 19:15 +0200, Frederic Weisbecker wrote:
> > that looks rather ugly. Why not do a raw:
> > 
> >       this_cpu_inc(lockdep_stats.redundant_hardirqs_on);
> > 
> > which basically open-codes debug_atomic_inc(), but without the warning?
> 
> 
> Because that would open a race against interrupts that might
> touch lockdep_stats.redundant_hardirqs_on too.


How so, its a pure per-cpu variable right? so either the increment
happens before the interrupts hits, or after, in either case there
should not be a race with interrupts.
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