linux-kernel - Re: [RFC][PATCH 1/3] PM / sleep: Move runtime PM barrier invocation to device

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Date:	Tue, 13 May 2014 12:59:43 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Linux PM list <linux-pm@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>
Subject: Re: [RFC][PATCH 1/3] PM / sleep: Move runtime PM barrier invocation
 to device_prepare()

On 13 May 2014 12:35, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Tuesday, May 13, 2014 11:16:34 AM Ulf Hansson wrote:
>> On 13 May 2014 03:03, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.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@...el.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.
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