linux-kernel - Re: [PATCH v9 1/3] smpboot: allow excluding cpus from the smpboot threads

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Message-ID: <55425332.4050408@ezchip.com>
Date:	Thu, 30 Apr 2015 12:07:14 -0400
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	Don Zickus <dzickus@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Jones <drjones@...hat.com>,
	chai wen <chaiw.fnst@...fujitsu.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Fabian Frederick <fabf@...net.be>,
	Aaron Tomlin <atomlin@...hat.com>,
	Ben Zhang <benzh@...omium.org>,
	Christoph Lameter <cl@...ux.com>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	<linux-kernel@...r.kernel.org>, Jonathan Corbet <corbet@....net>,
	<linux-doc@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v9 1/3] smpboot: allow excluding cpus from the smpboot
 threads

On 04/29/2015 06:26 PM, Andrew Morton wrote:
> On Fri, 17 Apr 2015 14:37:16 -0400 Chris Metcalf <cmetcalf@...hip.com> wrote:
>
>> This change allows some cores to be excluded from running the
>> smp_hotplug_thread tasks.  The following commit to update
>> kernel/watchdog.c to use this functionality is the motivating
>> example, and more information on the motivation is provided there.
>>
>> A new smp_hotplug_thread field is introduced, "cpumask", which
>> is cpumask field managed by the smpboot subsystem that indicates whether
>> or not the given smp_hotplug_thread should run on that core; the
>> cpumask is checked when deciding whether to unpark the thread.
>>
>> To limit the cpumask to less than cpu_possible, you must call
>> smpboot_update_cpumask_percpu_thread() after registering.
> Has Thomas commented on any version of this?   t'would be nice.

He offered some specific feedback here:

   https://lkml.org/lkml/2015/4/8/684

that I reflected in the subsequent iteration of the patch series.

Thomas, any additional feedback would be appreciated.

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

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