PM-runtime: fix deadlock when canceling hrtimer

Message ID 1550735942-3569-1-git-send-email-vincent.guittot@linaro.org
State New
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Series
  • PM-runtime: fix deadlock when canceling hrtimer
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Commit Message

Vincent Guittot Feb. 21, 2019, 7:59 a.m.
When rpm_resume() desactivates the autosuspend timer, it should only try
to cancel hrtimer but not wait for the handler to finish because both
rpm_resume() and pm_suspend_timer_fn() are taking the power.lock.
We can have the deadlock sequence:
CPU0                              CPU1
rpm_resume()
  spin_lock_irqsave
                                  pm_suspend_timer_fn()
                                    spin_lock_irqsave
  pm_runtime_deactivate_timer()
    hrtimer_cancel()

hrtimer_try_to_cancel() is enough because dev->power.timer_expires is also
set to 0.

Fixes: 8234f6734c5d ("PM-runtime: Switch autosuspend over to using hrtimers")
Reported-by: Sunzhaosheng Sun(Zhaosheng) <sunzhaosheng@hisilicon.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

---
 drivers/base/power/runtime.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.7.4

Comments

Vincent Guittot Feb. 21, 2019, 10:02 a.m. | #1
On Thu, 21 Feb 2019 at 10:35, Rafael J. Wysocki <rafael@kernel.org> wrote:
>

> On Thu, Feb 21, 2019 at 8:59 AM Vincent Guittot

> <vincent.guittot@linaro.org> wrote:

> >

> > When rpm_resume() desactivates the autosuspend timer, it should only try

> > to cancel hrtimer but not wait for the handler to finish because both

> > rpm_resume() and pm_suspend_timer_fn() are taking the power.lock.

> > We can have the deadlock sequence:

> > CPU0                              CPU1

> > rpm_resume()

> >   spin_lock_irqsave

> >                                   pm_suspend_timer_fn()

> >                                     spin_lock_irqsave

> >   pm_runtime_deactivate_timer()

> >     hrtimer_cancel()

>

> Everybody has missed this, not good.


yes. default behavior if different between timer and hrtimer
del_timer() is equivalent to hrtimer_try_to_cancel()
and hrtimer_cancel() to del_timer_sync()

>

> > hrtimer_try_to_cancel() is enough because dev->power.timer_expires is also

> > set to 0.

> >

> > Fixes: 8234f6734c5d ("PM-runtime: Switch autosuspend over to using hrtimers")

> > Reported-by: Sunzhaosheng Sun(Zhaosheng) <sunzhaosheng@hisilicon.com>

> > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

> > ---

> >  drivers/base/power/runtime.c | 2 +-

> >  1 file changed, 1 insertion(+), 1 deletion(-)

> >

> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c

> > index 04407d9..78937c4 100644

> > --- a/drivers/base/power/runtime.c

> > +++ b/drivers/base/power/runtime.c

> > @@ -121,7 +121,7 @@ EXPORT_SYMBOL_GPL(pm_runtime_suspended_time);

> >  static void pm_runtime_deactivate_timer(struct device *dev)

> >  {

> >         if (dev->power.timer_expires > 0) {

> > -               hrtimer_cancel(&dev->power.suspend_timer);

> > +               hrtimer_try_to_cancel(&dev->power.suspend_timer);

> >                 dev->power.timer_expires = 0;

> >         }

> >  }

> > --

>

> Applied with some changelog modifications, thanks!


Thanks

Patch

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 04407d9..78937c4 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -121,7 +121,7 @@  EXPORT_SYMBOL_GPL(pm_runtime_suspended_time);
 static void pm_runtime_deactivate_timer(struct device *dev)
 {
 	if (dev->power.timer_expires > 0) {
-		hrtimer_cancel(&dev->power.suspend_timer);
+		hrtimer_try_to_cancel(&dev->power.suspend_timer);
 		dev->power.timer_expires = 0;
 	}
 }