Re: [RFC][PATCH 1/3] PM / sleep: Move runtime PM barrier invocation to device_prepare()

Ulf Hansson
2014-05-13T10:59:43Z

On 13 May 2014 12:35, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Tuesday, May 13, 2014 11:16:34 AM Ulf Hansson wrote:
>> On 13 May 2014 03:03, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> >
>> > Move the invocation of the runtime PM barrier during system suspend
>> > (or hibernation) from __device_suspend() to device_prepare() to make
>> > all runtime PM transitions in progress complete before executing
>> > ->prepare() callbacks for devices.
>> >
>> > That will allow those callbacks to check if devices are runtime
>> > suspended in a non-racy way.
>> >
>> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> > ---
>> > drivers/base/power/main.c | 31 +++++++++++++------------------
>> > 1 file changed, 13 insertions(+), 18 deletions(-)
>> >
>> > Index: linux-pm/drivers/base/power/main.c
>> > ===================================================================
>> > --- linux-pm.orig/drivers/base/power/main.c
>> > +++ linux-pm/drivers/base/power/main.c
>> > @@ -1312,24 +1312,7 @@ static int __device_suspend(struct devic
>> >
>> > dpm_wait_for_children(dev, async);
>> >
>> > - if (async_error)
>> > - goto Complete;
>> > -
>> > - /*
>> > - * If a device configured to wake up the system from sleep states
>> > - * has been suspended at run time and there's a resume request pending
>> > - * for it, this is equivalent to the device signaling wakeup, so the
>> > - * system suspend operation should be aborted.
>> > - */
>> > - if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
>> > - pm_wakeup_event(dev, 0);
>> > -
>> > - if (pm_wakeup_pending()) {
>> > - async_error = -EBUSY;
>> > - goto Complete;
>> > - }
>>
>> I suppose you went a bit too far here!?
>>
>> We can still have wakeup pending at this point, and thus we should
>> bail out, right?
>
> That pm_wakeup_pending() is part of the barrier handling, so ->
>
>> > -
>> > - if (dev->power.syscore)
>> > + if (async_error || dev->power.syscore)
>> > goto Complete;
>> >
>> > dpm_watchdog_set(&wd, dev);
>> > @@ -1500,6 +1483,18 @@ static int device_prepare(struct device
>> > */
>> > pm_runtime_get_noresume(dev);
>> >
>> > + /*
>> > + * If a device configured to wake up the system from sleep states
>> > + * has been suspended at run time and there's a resume request pending
>> > + * for it, this is equivalent to the device signaling wakeup, so the
>> > + * system suspend operation should be aborted.
>> > + */
>> > + if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
>> > + pm_wakeup_event(dev, 0);
>> > +
>> > + if (pm_wakeup_pending())
>> > + return -EBUSY;
>> > +
>
> -> it is done here now.
>
> I don't see why it would be still necessary in __device_suspend().

Can't we have wakeup configured for !CONFIG_PM_RUNTIME case?
pm_runtime_barrier() won't handle those scenarios, right?

Similar check for pm_wakeup_pending() is done at
__device_suspend_noirq, __device_suspend_late - I assumed it was
because of the same reasons.

Kind regards
Ulf Hansson

>
>> > device_lock(dev);
>> >
>> > dev->power.wakeup_path = device_may_wakeup(dev);
>> >
>
> Thanks!
>
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.