Messages in this thread | | | Subject | Re: [PATCH 2/2] mm: page allocator: Do not drain per-cpu lists via IPI from page allocator context | From | Peter Zijlstra <> | Date | Thu, 12 Jan 2012 16:08:04 +0100 |
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On Thu, 2012-01-12 at 16:51 +0200, Gilad Ben-Yossef wrote: > What I can't figure out is why we don't need get/put_online_cpus() > pair around each and every call > to on_each_cpu everywhere? and if we do, perhaps making it a part of > on_each_cpu is the way to go? > > Something like: > > diff --git a/kernel/smp.c b/kernel/smp.c > index f66a1b2..cfa3882 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -691,11 +691,15 @@ void on_each_cpu(void (*func) (void *info), void > *info, int wait) > { > unsigned long flags; > > + BUG_ON(in_atomic()); > + > + get_online_cpus(); > preempt_disable();
Your preempt_disable() here serializes against hotplug..
> smp_call_function(func, info, wait); > local_irq_save(flags); > func(info); > local_irq_restore(flags); > preempt_enable(); > + put_online_cpus(); > } > EXPORT_SYMBOL(on_each_cpu);
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