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

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Date:	Sat, 12 Jul 2008 13:05:49 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	miaox@...fujitsu.com
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"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>, rostedt@...dmis.org,
	"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

2008/7/12 Miao Xie <miaox@...fujitsu.com>:
> [ ... ]
>
> My explanation:
>        http://lkml.org/lkml/2008/7/7/75
> this bug occurred on the kernel compiled with CONFIG_CPUSETS=y.
>
> As Dmitry said in the following mail, modifying try_to_wake_up() to fix this bug
> is not perfect. Maybe we need update the sched domain before migrating tasks.
>        http://lkml.org/lkml/2008/7/7/94
>
> So I remake a patch to fix this bug by updating the sched domain when a cpu is in
> CPU_DOWN_PREPARE state.
>
> I think Vegard Nossum's patch is not so good because it is not necessary to detach
> all the sched domains when making a cpu offline.

(that was my "not so good" patch :-)

Yes, maybe. OTOH, your patch does it in a more drastic way which
should be analyzed more carefully.
Perhaps, for .27 but that's just my 2 cents.

Plus, rebuild_sched_domains() has to be called only for cpu-hotplug events.

(I guess it just shows once more that common_cpu_mem_hotplug_unplug()
should be re-designed a bit)


-- 
Best regards,
Dmitry Adamushko
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