Re: spinlock in completion_done() (was: Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33))

Dave Chinner
2009-12-11T04:10:41Z

On Thu, Dec 10, 2009 at 08:59:47AM +0100, Ingo Molnar wrote:
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Wednesday 09 December 2009, Ingo Molnar wrote:
> > > * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > > > On Tuesday 08 December 2009, Alan Stern wrote:
> > > > > On Tue, 8 Dec 2009, Rafael J. Wysocki wrote:
> > > > >
> > > > > > BTW, is there a good reason why completion_done() doesn't use spin_lock_irqsave
> > > > > > and spin_unlock_irqrestore? complete() and complete_all() use them, so why not
> > > > > > here?
> > > > >
> > > > > And likewise in try_wait_for_completion(). It looks like a bug. Maybe
> > > > > these routines were not intended to be called with interrupts disabled,
> > > > > but that requirement doesn't seem to be documented. And it isn't a
> > > > > natural requirement anyway.

When I implemented them they were not called from anywhere that
disabled interrupts. IIRC the main reason I used spin_lock_irq()
was because that is what wait_for_completion() used at the time....

> > > that's a bug that should be fixed - all the wakeup side (and atomic)
> > > variants of completetion API should be irq safe.

I see no problems with that ;)

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com