Re: [patch update] PM: Introduce core framework for run-time PM of I/O devices (rev. 6)

Rafael J. Wysocki
2009-06-26T22:32:31Z

On Friday 26 June 2009, Alan Stern wrote:
> On Fri, 26 Jun 2009, Rafael J. Wysocki wrote:
>
> > > It occurs to me that the problem would be solved if were a cancel_work
> > > routine. In the same vein, it ought to be possible for
> > > cancel_delayed_work to run in interrupt context. I'll see what can be
> > > done.
> >
> > Having looked at the workqueue code I'm not sure if there's a way to implement
> > that in a non-racy way. Which may be the reason why there are no such
> > functions already. :-)
>
> Well, I'll give it a try.
>
> Speaking of races, have you noticed that the way power.work_done gets
> used is racy?

Not really. :-)

> You can't wait for the completion before releasing the
> lock, but then anything could happen.
>
> A safer approach would be to use a wait_queue.

I'm not sure what you mean exactly. What's the race?

> > In the meantime I reworked the patch (below) to use more RPM_* flags and I
> > removed the runtime_break and runtime_notify bits from it. Also added some
> > comments to explain some non-obvious steps (hope that helps).
> >
> > I also added the pm_runtime_put_atomic() and pm_runtime_put() as per the
> > comment above.
> >
> > It seems to be a bit cleaner this way, but that's my personal view. :-)
>
> I'll look at it over the weekend. And I'll try to see if proper
> cancel_work and cancel_delayed_work functions can help clean it up.

Great, thanks!

Best,
Rafael