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

[Ingo Molnar <mingo@elte.hu>]

* 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.
> > > 
> > > OK, let's ask Ingo about that.
> > > 
> > > Ingo, is there any particular reason why completion_done() and
> > > try_wait_for_completion() don't use spin_lock_irqsave() and
> > > spin_unlock_irqrestore()?
> > 
> > that's a bug that should be fixed - all the wakeup side (and atomic) 
> > variants of completetion API should be irq safe.
> > 
> > It appears that these new completion APIs were added via the XFS tree 
> > about a year ago:
> > 
> >   39d2f1a: [XFS] extend completions to provide XFS object flush requirements
> > 
> > Please Cc: scheduler folks to all scheduler patches.
> 
> If you haven't fixed it locally yet, would you mind me posting a fix?

I wouldnt mind it at all.

Thanks,

	Ingo