Re: i915.ko WC writes are slow after ea8596bb2d8d379

[Ingo Molnar]

* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> On Wed, Nov 18, 2015 at 6:48 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> > Although
> >
> > diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
> > index d2abbdb..ff4f029 100644
> > --- a/include/linux/stop_machine.h
> > +++ b/include/linux/stop_machine.h
> > @@ -97,7 +97,7 @@ static inline int try_stop_cpus(const struct cpumask *cpumask,
> >   * grabbing every spinlock (and more).  So the "read" side to such a
> >   * lock is anything which disables preemption.
> >   */
> > -#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
> > +#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
> 
> [...]
> 
> This seems much better.  Having a set of stop_machine functions around
> that don't work depending on config seems dangerous.

Agreed.

Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>

Thanks,

	Ingo
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