linux-kernel - [Regression] 2.6.24-git9: RT sched mishandles artswrapper (bisected)

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Message-Id: <200802010237.59320.rjw@sisk.pl>
Date:	Fri, 1 Feb 2008 02:37:58 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [Regression] 2.6.24-git9: RT sched mishandles artswrapper (bisected)

Hi,

This is related to the problem I reported earlier this week:
http://lkml.org/lkml/2008/1/30/554

Apparently artswrapper, run by KDE in openSUSE 10.3 with a real time priority,
is mishandled by the scheduler.  The problem is that after the user logs out,
artswrapper stays in TASK_RUNNING forever and prevents other tasks from being
scheduled on the CPU occupied by it.  In this state it also breaks suspend and
hibernation (it cannot be frozen).

Since the problem is 100% reproducible on my test boxes, I carried out a
bisection which turned out the following commit:

commit 6f505b16425a51270058e4a93441fe64de3dd435
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Fri Jan 25 21:08:30 2008 +0100

    sched: rt group scheduling

I'm now checking if the problem disappears after reverting this patch (along a
couple of dependent ones).

Thanks,
Rafael
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