Re: [PATCH RFC v2] PM / sleep: Fix racing timers

From: Stephen Boyd
Date: Mon Jul 28 2014 - 15:19:31 EST

On 07/25/14 14:06, Soren Brinkmann wrote:
> On platforms that do not power off during suspend, successfully entering
> suspend races with timers.
> The race happening in a couple of location is:
> 1. disable IRQs (e.g. arch_suspend_disable_irqs())
> ...
> 2. syscore_suspend()
> -> timekeeping_suspend()
> -> clockevents_notify(SUSPEND)
> -> tick_suspend() (timers are turned off here)
> ...
> 3. wfi (wait for wake-IRQ here)
> Between steps 1 and 2 the timers can still generate interrupts that are
> not handled and stay pending until step 3. That pending IRQ causes an
> immediate - spurious - wake.
> The solution is to move the clockevents suspend/resume notification
> out of the syscore_suspend step and explictly call them at the appropriate
> time in the suspend/hibernation paths. I.e. timers are suspend _before_
> IRQs get disabled. And accordingly in the resume path.
> Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>

Do we know which timer_list or hrtimer wants to run while entering
suspend? I'd suspect the scheduler tick but perhaps we just forgot to
cancel some timer during suspend?

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