linux-kernel - Re: [RFC][PATCH -mm 3/3] PM: Disable _request

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Date:	Mon, 28 May 2007 13:22:51 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	nigel@...el.suspend2.net
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oliver@...kum.org>
Subject: Re: [RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend

On Monday, 28 May 2007 10:30, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-05-27 at 23:45 +0200, Rafael J. Wysocki wrote:
> > On Sunday, 27 May 2007 22:49, Matthew Garrett wrote:
> > > On Sun, May 27, 2007 at 10:31:53PM +0200, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > > 
> > > > Use a hibernation and suspend notifier to disable the firmware requesting
> > > > mechanism before a hibernation/suspend and enable it after the operation.
> > > 
> > > This avoids the problem of .resume methods calling userspace while 
> > > userspace is frozen and a resulting hang, but does it actually result in 
> > > the drivers beginning to work again?
> > 
> > Well, this was acutally invented before you've decided to remove the freezing
> > of tasks from the suspend code path (which I think is a mistake, but that's
> > only my personal opinion, so it doesn't matter very much ;-)) and I regard it
> > as a workaround.
> 
> Suspend-to-ram code paths shouldn't assume userspace is unfrozen anyway.
> Doesn't [u]swsusp have a code path like Suspend2 where we can suspend to
> ram after writing the hibernation image? In that case, it will still be
> possible that we seek to enter and leave S3 with processes frozen.

That's correct.

> Apologies if anyone has already mentioned this - I'm just starting to
> play catchup.

No one has and that's a valid point, I think. :-)

Greetings,
Rafael
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