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Subject: Re: linux-next: PowerPC WARN_ON_ONCE() after merge of the final
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From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
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Date: Fri, 16 Apr 2010 12:38:43 +0200
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Cc: Stephen Rothwell <sfr@canb.auug.org.au>, linux-kernel@vger.kernel.org,
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On Thu, 2010-04-15 at 19:15 +0200, Frederic Weisbecker wrote:
> > that looks rather ugly. Why not do a raw:
> >=20
> >       this_cpu_inc(lockdep_stats.redundant_hardirqs_on);
> >=20
> > which basically open-codes debug_atomic_inc(), but without the warning?
>=20
>=20
> 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.