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

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Date:	Tue, 15 Jul 2008 00:16:07 -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:
> >
> > Oh, I'm not arguing. My mind is going off to an even bigger picture, where
> > something in the future would need to stop migration to a particular CPU,
> > and that it could simply clear the bit and call synchronize_sched. The run
> > queue lock is only visible to the scheduler.  Sorry, I may have been day
> > dreaming out loud ;-)
>
> Well, you'd be stuck right now anyway.
>
> At least in my trivial patch, the cpu_active_map locking is protected by
> 'cpu_add_remove_lock' which is static to cpu.c. The only thing that
> modifies it (apart from the initial setup before SMP has been brought up)
> is the hotplug code.

Yeah, I see that now. I was thinking back to a time I was doing some crazy
kernel hacking and would have liked this feature (stop new tasks from
migrating to a CPU). cpusets today are probably a better answer, and what
I was thinking with using the cpu_active_map is more of a hack.

Sorry for the noise, I'll go back to updating ftrace.txt

-- Steve

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