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

Rafael J. Wysocki
2014-05-13T10:35:23Z

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().

> > 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.