Re: i915.ko WC writes are slow after ea8596bb2d8d379

[Andy Lutomirski]

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.

--Andy
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