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SubjectRe: [PATCH] PM: Prevent waiting forever on asynchronous resume after abort
Date
On Thursday, September 02, 2010, Alan Stern wrote:
> On Wed, 1 Sep 2010, Colin Cross wrote:
>
> > Only wait on a parent device during resume if the parent device is
> > suspended.
> >
> > Consider three drivers, A, B, and C. The parent of A is C, and C
> > has async_suspend set. On boot, C->power.completion is initialized
> > to 0.
> >
> > During the first suspend:
> > suspend_devices_and_enter(...)
> > dpm_resume(...)
> > device_suspend(A)
> > device_suspend(B) returns error, aborts suspend
> > dpm_resume_end(...)
> > dpm_resume(...)
> > device_resume(A)
> > dpm_wait(A->parent == C)
> > wait_for_completion(C->power.completion)
> >
> > The wait_for_completion will never complete, because
> > complete_all(C->power.completion) will only be called from
> > device_suspend(C) or device_resume(C), neither of which is called
> > if suspend is aborted before C.
>
> This would work okay if C->power.completion had been initialized to the
> completed state during boot, right?
>
> > After a successful suspend->resume cycle, where B doesn't abort
> > suspend, C->power.completion is left in the completed state by the
> > call to device_resume(C), and the same call path will work if B
> > aborts suspend.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> > drivers/base/power/main.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index cb784a0..e159910 100644
> > --- a/drivers/base/power/main.c
> > +++ b/drivers/base/power/main.c
> > @@ -526,7 +526,8 @@ static int device_resume(struct device *dev, pm_message_t state, bool async)
> > TRACE_DEVICE(dev);
> > TRACE_RESUME(0);
> >
> > - dpm_wait(dev->parent, async);
> > + if (dev->parent && dev->parent->power.status >= DPM_OFF)
> > + dpm_wait(dev->parent, async);
> > device_lock(dev);
> >
> > dev->power.status = DPM_RESUMING;
>
> I think it would be better to change device_pm_init() and add a
> complete_all().

I agree.

Who's writing the patch?

Rafael


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