linux-kernel - Re: [RFC][PATCH][EXPERIMENTAL] Make kernel threads nonfreezable by default

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Message-ID: <20070528103302.GD18807@elf.ucw.cz>
Date:	Mon, 28 May 2007 12:33:02 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Gautham R Shenoy <ego@...ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Oleg Nesterov <oleg@...sign.ru>
Subject: Re: [RFC][PATCH][EXPERIMENTAL] Make kernel threads nonfreezable by default

Hi!

> Index: linux-2.6.22-rc3/Documentation/power/kernel_threads.txt
> ===================================================================
> --- linux-2.6.22-rc3.orig/Documentation/power/kernel_threads.txt
> +++ linux-2.6.22-rc3/Documentation/power/kernel_threads.txt
> @@ -1,13 +1,22 @@
> -KERNEL THREADS
> +The Freezer and Kernel Threads
>  
> -
> -Freezer
> -
> -Upon entering a suspended state the system will freeze all
> -tasks. This is done by delivering pseudosignals. This affects
> -kernel threads, too. To successfully freeze a kernel thread
> -the thread has to check for the pseudosignal and enter the
> -refrigerator. Code to do this looks like this:
> +Before entering a system-wide suspend state as well as before creating a
> +hibernation snapshot image the system will freeze all tasks, which is done
> +by delivering fake signals.  This affects kernel threads too, but they won't be
> +frozen unless they declare that they want to.  For this purpose

Well... and unless thread that does disk writes or DMA _wants_ to, you
have nice disk corruption... It should be pointed out that it is not
voluntary for those types of threads.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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