Date: Wed, 2 Jan 2008 17:02:34 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Kyle Moffett <mrmacman_g4@mac.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Matthew Garrett <mjg59@srcf.ucam.org>,
       David Chinner <dgc@sgi.com>, Jeremy Fitzhardinge <jeremy@goop.org>,
       xfs-masters@oss.sgi.com,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: freeze vs freezer
Message-ID: <20080102160234.GA17070@ucw.cz>
References: <4744FD87.7010301@goop.org> <200711262253.35420.rjw@sisk.pl> <20071127053846.GA28884@srcf.ucam.org> <200711271840.24825.rjw@sisk.pl> <8B00F353-983F-40E7-931B-EA73CCD32F0A@mac.com>
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Hi!

> >>>>So how do you handle threads that are blocked on I/O or a lock  
> >>>>during the system freeze process, then?
> >>>
> >>>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.

"each driver" means this is a lot of work. But yes, that is probably
way to go, and patch would be welcome.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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