On Mon, 14 Jan 2013, Rafael J. Wysocki wrote:
> On Tuesday, January 15, 2013 01:48:18 AM Chuansheng Liu wrote:
> >
> > In function rpm_suspend/resume(), when going into the for(;;),
> > the pre-condition judgement has been done, and the variable runtime_status
> > are always protected by &power.lock, so it is not necessary to judge
> > them again before unlock_irq &power.lock in for(;;).
> >
> > This patch clean them up.
>
> Well, I don't really think this fixes anything. Yes, we may save one check
> here and there, but the current code follows the wait_event() convention.
Indeed, this patch introduces a race. If runtime_status changes from
RPM_SUSPENDING and power.wait_queue is signalled in between the test at
the end of the loop and the prepare_to_wait() call, the loop will never
end.
Alan Stern
> Thanks,
> Rafael
>
>
> > Signed-off-by: liu chuansheng <chuansheng....@intel.com>
> > ---
> > drivers/base/power/runtime.c | 18 +++++++++---------
> > 1 files changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > index 3148b10..32d6497 100644
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -377,14 +377,14 @@ static int rpm_suspend(struct device *dev, int
> > rpmflags)
> > for (;;) {
> > prepare_to_wait(&dev->power.wait_queue, &wait,
> > TASK_UNINTERRUPTIBLE);
> > - if (dev->power.runtime_status != RPM_SUSPENDING)
> > - break;
> >
> > spin_unlock_irq(&dev->power.lock);
> >
> > schedule();
> >
> > spin_lock_irq(&dev->power.lock);
> > + if (dev->power.runtime_status != RPM_SUSPENDING)
> > + break;
> > }
--
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