linux-kernel - Re: current linux-2.6.git: cpusets completely broken

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Message-ID: <Pine.LNX.4.58.0807142320180.4530@gandalf.stny.rr.com>
Date:	Mon, 14 Jul 2008 23:23:09 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Paul Menage <menage@...gle.com>,
	Max Krasnyansky <maxk@...lcomm.com>, Paul Jackson <pj@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, miaox@...fujitsu.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: current linux-2.6.git: cpusets completely broken


On Mon, 14 Jul 2008, Linus Torvalds wrote:
> So by doing the test for cpu_active_map not at queuing time, but at the
> time when we actually try to do the migration, we can now also make that
> cpu_active_map be totally serialized.
>
> (Of course, anybody who clears the bit does need to take the runqueue lock
> of that CPU too, but cpu_down() will have to do that as it does the
> "migrate away live tasks" anyway, so that's not a problem)

Wouldn't simply doing a synchronize_sched() after clearing the bit also
make sure that no new task will be scheduled on that CPU?

-- Steve

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