linux-kernel - Re: [BUGFIX] PM: Fix active child counting when disabled and forbidden

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Date:	Fri, 16 Nov 2012 09:27:05 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [BUGFIX] PM: Fix active child counting when disabled and
 forbidden

On Fri, 2012-11-16 at 02:29 +0100, Rafael J. Wysocki wrote:
> On Friday, November 16, 2012 08:54:56 AM Huang Ying wrote:
> > On Fri, 2012-11-16 at 01:55 +0100, Rafael J. Wysocki wrote:
> > > On Friday, November 16, 2012 01:44:00 AM Rafael J. Wysocki wrote:
> > > > On Friday, November 16, 2012 08:36:14 AM Huang Ying wrote:
> > > > > On Thu, 2012-11-15 at 10:51 +0100, Rafael J. Wysocki wrote:
> > > 
> > > [...]
> > > 
> > > > > 
> > > > > For this situation, if user "echo auto > .../power/control" for the
> > > > > device, the runtime PM callbacks of device will be called.  I think that
> > > > > is not intended.  So I think it is better to use some kind of flag or
> > > > > state for that.
> > > > 
> > > > I'm not sure what situation exactly you have in mind.  Care to give an
> > > > exact scenario?
> > > 
> > > Ah, I see.  When we've just called drv->remove(), there is a window in
> > > which user space may cause the driver's runtime PM callbacks to be
> > > executed by changing its attribute to "auto".
> > > 
> > > So perhaps we should check pci_dev->driver rather than pci_dev->dev.driver
> > > in the runtime PM callbacks?  With a few more changes that should allow us
> > > to close that race.
> > 
> > Yes.  And I think, with pci_dev->driver (after some changes suggested by
> > Alan), we need not to use pm_runtime_get/put_skip_callbacks().
> 
> Good.  Can you please prepare a patch, then? :-)

Sure.

Best Regards,
Huang Ying



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