linux-kernel - Re: freeze vs freezer

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Message-ID: <20080623071601.GA1553@elf.ucw.cz>
Date:	Mon, 23 Jun 2008 09:16:01 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Kyle Moffett <mrmacman_g4@....com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	David Chinner <dgc@....com>,
	Jeremy Fitzhardinge <jeremy@...p.org>, xfs-masters@....sgi.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: freeze vs freezer

Hi!

(replying to *very* old mail).

>>>> We wait until they can continue.
>>>
>>> So if I have a process blocked on an unavilable NFS mount, I can't
>>> suspend?
>>
>> That's correct, you can't.
>>
>> [And I know what you're going to say. ;-)]
>
> Why exactly does suspend/hibernation depend on "TASK_INTERRUPTIBLE" instead 
> of a zero preempt_count()?  Really what we should do is just iterate over 
> all of the actual physical devices and tell each one "Block new IO requests 
> preemptably, finish pending DMA, put the hardware in low-power mode, and 
> prepare for suspend/hibernate".  As long as each driver knows how to do 
> those simple things we can have an entirely consistent kernel image for 
> both suspend and for hibernation.

Patch would be welcome, actually. It turns out blocking new
IO-requests is not completely trivial.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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