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

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Date:	Fri, 16 Nov 2012 01:55:13 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Huang Ying <ying.huang@...el.com>
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 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.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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