linux-kernel - Re: [REPORT] cfs-v4 vs sd-0.44

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Message-Id: <200704241038.32766.gene.heskett@gmail.com>
Date:	Tue, 24 Apr 2007 10:38:32 -0400
From:	Gene Heskett <gene.heskett@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	David Lang <david.lang@...italinsight.com>,
	Peter Williams <pwil3058@...pond.net.au>,
	Arjan van de Ven <arjan@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Juliusz Chroboczek <jch@....jussieu.fr>,
	Con Kolivas <kernel@...ivas.org>, ck list <ck@....kolivas.org>,
	Bill Davidsen <davidsen@....com>, Willy Tarreau <w@....eu>,
	William Lee Irwin III <wli@...omorphy.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr
Subject: Re: [REPORT] cfs-v4 vs sd-0.44

On Tuesday 24 April 2007, Ingo Molnar wrote:
>* David Lang <david.lang@...italinsight.com> wrote:
>> > (Btw., to protect against such mishaps in the future i have changed
>> > the SysRq-N [SysRq-Nice] implementation in my tree to not only
>> > change real-time tasks to SCHED_OTHER, but to also renice negative
>> > nice levels back to 0 - this will show up in -v6. That way you'd
>> > only have had to hit SysRq-N to get the system out of the wedge.)
>>
>> if you are trying to unwedge a system it may be a good idea to renice
>> all tasks to 0, it could be that a task at +19 is holding a lock that
>> something else is waiting for.
>
>Yeah, that's possible too, but +19 tasks are getting a small but
>guaranteed share of the CPU so eventually it ought to release it. It's
>still a possibility, but i think i'll wait for a specific incident to
>happen first, and then react to that incident :-)
>
>	Ingo

In the instance I created, even the SysRq+b was ignored, and ISTR thats 
supposed to initiate a reboot is it not?  So it was well and truly wedged.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
I use technology in order to hate it more properly.
		-- Nam June Paik
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