Re: [PATCH 4/6] PM / sleep: Make it possible to quiesce timers during suspend-to-idle

Peter Zijlstra
2015-02-12T13:24:56Z

On Wed, Feb 11, 2015 at 05:03:44AM +0100, Rafael J. Wysocki wrote:
> Index: linux-pm/include/linux/cpuidle.h
> ===================================================================
> --- linux-pm.orig/include/linux/cpuidle.h
> +++ linux-pm/include/linux/cpuidle.h
> @@ -50,6 +50,10 @@ struct cpuidle_state {
> int index);
>
> int (*enter_dead) (struct cpuidle_device *dev, int index);

Do we want a comment here describing that enter_freeze() must not
re-enable interrupts _ever_?

To help people who want to enable this on their platform.

> +
> + void (*enter_freeze) (struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index);
> };

> +static void enter_freeze_proper(struct cpuidle_driver *drv,
> + struct cpuidle_device *dev, int index)
> +{
> + tick_freeze();
> + /*
> + * The state used here cannot be a "coupled" one, because the "coupled"
> + * cpuidle mechanism enables interrupts and doing that with timekeeping
> + * suspended is generally unsafe.
> + */
> + drv->states[index].enter_freeze(dev, drv, index);

WARN_ON(!irqs_disabled());

To go along with the comment and catch fail?

> + /*
> + * timekeeping_resume() that will be called by tick_unfreeze() for the
> + * last CPU executing it calls functions containing RCU read-side
> + * critical sections, so tell RCU about that.
> + */
> + RCU_NONIDLE(tick_unfreeze());
> +}