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    SubjectRe: linux-next: PowerPC WARN_ON_ONCE() after merge of the final tree (tip related)
    On Thu, Apr 15, 2010 at 04:03:58PM +0200, Ingo Molnar wrote:
    > > In this case, I guess the following fix should be sufficient?
    > > I'm going to test it and provide a sane changelog.
    > >
    > >
    > > 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?


    Because that would open a race against interrupts that might
    touch lockdep_stats.redundant_hardirqs_on too.

    If you think it's not very important (this race must be pretty rare I guess),
    I can use your solution.



    >
    > Btw., using the this_cpu() methods might result in faster code for all the
    > debug_atomic_inc() macros as well?


    Indeed, will change that too.

    Thanks.



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