Re: [PATCH] PM-runtime: fix deadlock when canceling hrtimer

2019-02-21 Thread Vincent Guittot 
On Thu, 21 Feb 2019 at 10:35, Rafael J. Wysocki  wrote:
>
> On Thu, Feb 21, 2019 at 8:59 AM Vincent Guittot
>  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) 
> > Signed-off-by: Vincent Guittot 
> > ---
> >  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(>power.suspend_timer);
> > +   hrtimer_try_to_cancel(>power.suspend_timer);
> > dev->power.timer_expires = 0;
> > }
> >  }
> > --
>
> Applied with some changelog modifications, thanks!

Thanks

Re: [PATCH] PM-runtime: fix deadlock when canceling hrtimer

2019-02-21 Thread Rafael J. Wysocki 
On Thu, Feb 21, 2019 at 8:59 AM Vincent Guittot
 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.

> 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) 
> Signed-off-by: Vincent Guittot 
> ---
>  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(>power.suspend_timer);
> +   hrtimer_try_to_cancel(>power.suspend_timer);
> dev->power.timer_expires = 0;
> }
>  }
> --

Applied with some changelog modifications, thanks!

[PATCH] PM-runtime: fix deadlock when canceling hrtimer

2019-02-20 Thread Vincent Guittot 
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) 
Signed-off-by: Vincent Guittot 
---
 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(>power.suspend_timer);
+   hrtimer_try_to_cancel(>power.suspend_timer);
dev->power.timer_expires = 0;
}
 }
-- 
2.7.4