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

From: Rafael J. Wysocki
Date: Sun Jul 27 2014 - 19:00:16 EST


On Friday, July 25, 2014 02:06:48 PM 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>
> ---
> Hi,
>
> This is my second shot at this. I followed John's suggestion to keep the
> timekeeping suspend where it is and just move the shutdown of the clockevent
> devices around.

John, what do you think?


> kernel/power/hibernate.c | 9 +++++++++
> kernel/power/suspend.c | 5 +++++
> kernel/time/timekeeping.c | 1 -
> 3 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index fcc2611d3f14..ab9f807e2ccb 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -285,6 +285,8 @@ static int create_image(int platform_mode)
> if (error || hibernation_test(TEST_CPUS))
> goto Enable_cpus;
>
> + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> +
> local_irq_disable();
>
> error = syscore_suspend();
> @@ -316,6 +318,7 @@ static int create_image(int platform_mode)
> syscore_resume();
>
> Enable_irqs:
> + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
> local_irq_enable();
>
> Enable_cpus:
> @@ -440,6 +443,8 @@ static int resume_target_kernel(bool platform_mode)
> if (error)
> goto Enable_cpus;
>
> + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> +
> local_irq_disable();
>
> error = syscore_suspend();
> @@ -474,6 +479,7 @@ static int resume_target_kernel(bool platform_mode)
> syscore_resume();
>
> Enable_irqs:
> + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
> local_irq_enable();
>
> Enable_cpus:
> @@ -555,6 +561,8 @@ int hibernation_platform_enter(void)
> if (error)
> goto Platform_finish;
>
> + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> +
> local_irq_disable();
> syscore_suspend();
> if (pm_wakeup_pending()) {
> @@ -568,6 +576,7 @@ int hibernation_platform_enter(void)
>
> Power_up:
> syscore_resume();
> + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
> local_irq_enable();
> enable_nonboot_cpus();
>
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index ed35a4790afe..ca6c56a87ea3 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -12,6 +12,7 @@
> #include <linux/delay.h>
> #include <linux/errno.h>
> #include <linux/init.h>
> +#include <linux/clockchips.h>
> #include <linux/console.h>
> #include <linux/cpu.h>
> #include <linux/cpuidle.h>
> @@ -253,6 +254,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
> if (error || suspend_test(TEST_CPUS))
> goto Enable_cpus;
>
> + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> +
> arch_suspend_disable_irqs();
> BUG_ON(!irqs_disabled());
>
> @@ -270,6 +273,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
> syscore_resume();
> }
>
> + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
> +
> arch_suspend_enable_irqs();
> BUG_ON(irqs_disabled());
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 32d8d6aaedb8..d2f21cbe2bfd 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1032,7 +1032,6 @@ static int timekeeping_suspend(void)
> write_seqcount_end(&timekeeper_seq);
> raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
>
> - clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> clocksource_suspend();
> clockevents_suspend();
>
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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