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

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Message-ID: <20091211041041.GJ30608@discord.disaster>
Date:	Fri, 11 Dec 2009 15:10:41 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Zhang Rui <rui.zhang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Lachlan McIlroy <lachlan@....com>
Subject: Re: spinlock in completion_done() (was: Re: Async resume patch
	(was: Re: [GIT PULL] PM updates for 2.6.33))

On Thu, Dec 10, 2009 at 08:59:47AM +0100, Ingo Molnar wrote:
> * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Wednesday 09 December 2009, Ingo Molnar wrote:
> > > * Rafael J. Wysocki <rjw@...k.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@...morbit.com
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