Date: Fri, 12 Apr 2013 07:37:18 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Robin Holt <holt@sgi.com>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Paul Mackerras <paulus@samba.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Russ Anderson <rja@sgi.com>, Shawn Guo <shawn.guo@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Tejun Heo <tj@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Michel Lespinasse <walken@google.com>,
        "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: Bulk CPU Hotplug (Was Re: [PATCH] Do not force shutdown/reboot
 to boot cpu.)
Message-ID: <20130412053718.GC3887@gmail.com>
References: <20130403193743.GB29151@sgi.com>
 <20130408155701.GB19974@gmail.com>
 <5162EC1A.4050204@zytor.com>
 <20130408165916.GA3672@sgi.com>
 <20130410111620.GB29752@gmail.com>
 <CA+55aFw8bRwMRm8cWtTGRvd1AEP-LR7pYL-pEoBkHqJUuJrjSg@mail.gmail.com>
 <20130411053106.GA9042@drongo>
 <5166B05E.8010904@linux.vnet.ibm.com>
 <20130411134837.GE3672@sgi.com>
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* Robin Holt <holt@sgi.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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