Subject: Re: [BUG] How to get real-time priority using idle priority
From: Mike Galbraith <efault@gmx.de>
To: Brian Rogers <brian@xyzw.org>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
In-Reply-To: <496BE8F6.1040308@xyzw.org>
References: <4969D0D7.2060401@xyzw.org>
	 <1231736941.6003.7.camel@marge.simson.net>
	 <1231765433.5789.35.camel@marge.simson.net> <20090112131406.GB670@elte.hu>
	 <496BE8F6.1040308@xyzw.org>
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Date: Tue, 13 Jan 2009 03:58:43 +0100
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On Mon, 2009-01-12 at 17:05 -0800, Brian Rogers wrote:
> Ingo Molnar wrote:
> > i've applied your fix to tip/sched/urgent and merged it into tip/master.
> > Brian, you might want to test tip/master, as per:
> >
> >  http://people.redhat.com/mingo/tip.git/README
> >
> > which now has this fix included. Can you make it break?
> >   
> Yeah, I was able to trigger the same freeze again once on my desktop, 
> but it appears to be harder to trigger now. I couldn't get my program to 
> freeze the system, but one of the times I suspended then resumed BOINC, 
> it happened.

Drat.

> While experimenting on my laptop, things got into a funny state where 
> konsole froze, then gnome-terminal froze, so I just started launching 
> xterms. pgrep and pidof would freeze and never terminate. ps axl froze 
> after listing process 23681, which was a BOINC process. The next 
> process, 23682, was another BOINC process. Going into /proc/23682 and 
> running ls -l as root froze the shell. I figured out that ls -l exe was 
> enough to freeze it. I couldn't shut down BOINC because process 23682 
> wouldn't close, and kill -9 did nothing to it. top, which actually did 
> work, showed that process just continuing to run with around 100% CPU 
> time. I had to power cycle the system.
> 
> I'll try Mike's "more complete" patch on top of 2.6.29-rc1 and see what 
> that does.

Don't bother.  I just tried a SCHED_IDLE make -j8 and had character
repeats while typing.  Must be another spot.

	-Mike

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