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

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Thu, Apr 15, 2010 at 04:03:58PM +0200, Ingo Molnar wrote:
> > >
> > >
> > > diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> > > index 78325f8..65d4336 100644
> > > --- a/kernel/lockdep.c
> > > +++ b/kernel/lockdep.c
> > > @@ -2298,7 +2298,11 @@ void trace_hardirqs_on_caller(unsigned long ip)
> > > return;
> > >
> > > if (unlikely(curr->hardirqs_enabled)) {
> > > + unsigned long flags;
> > > +
> > > + raw_local_irq_save(flags);
> > > debug_atomic_inc(redundant_hardirqs_on);
> > > + raw_local_irq_restore(flags);
> > > return;
> > > }
> > > /* we'll do an OFF -> ON transition: */
> >
> > 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?
>
>
> There is also no guarantee we are in a non-preemptable section. We can then
> also race against another cpu.
>
> I'm not sure what to do.

it's a statistics counter so worst-case we lose a count. It's not a real issue
- but might be worth adding a comment.

Ingo


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