linux-kernel - Re: Bulk CPU Hotplug (Was Re: [PATCH] Do not force shutdown/reboot to boot cpu.)

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Message-ID: <20130412053718.GC3887@gmail.com>
Date:	Fri, 12 Apr 2013 07:37:18 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Robin Holt <holt@....com>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Russ Anderson <rja@....com>, Shawn Guo <shawn.guo@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Michel Lespinasse <walken@...gle.com>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: Bulk CPU Hotplug (Was Re: [PATCH] Do not force shutdown/reboot
 to boot cpu.)


* Robin Holt <holt@....com> wrote:

> For the v3.9 release, can we consider my awful patch?

How about trying what I suggested, to make reboot affine to the boot CPU 
explicitly, not by shutting down all the other CPUs, but by set_cpus_allowed() or 
so?

That should solve the regression, without the ugly special-casing - while giving 
time to address the hot-unplug performance bottleneck.

Once that is done disable_nonboot_cpus() can be used again for reboot.

(But no strong feelings either way - both solutions are a workaround in a sense.)

Thanks,

	Ingo
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