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 12:35:23 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Ulf Hansson <ulf.hansson@...aro.org>
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 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().

> >         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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