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

From: Peter Zijlstra <[email-masked]>
Date: Fri, 16 Apr 2010 12:38:43 +0200

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.