Subject: Re: [PATCH v2 1/4] Revert"x86/acpi: Set persistent cpuid <-> nodeid
 mapping when booting"
To: Thomas Gleixner <tglx@linutronix.de>
References: <1487580471-17665-1-git-send-email-douly.fnst@cn.fujitsu.com>
 <1487580471-17665-2-git-send-email-douly.fnst@cn.fujitsu.com>
 <alpine.DEB.2.20.1703011137560.4005@nanos>
CC: <mingo@kernel.org>, <peterz@infradead.org>, <rjw@rjwysocki.net>,
        <hpa@zytor.com>, <rafael@kernel.org>, <cl@linux.com>, <tj@kernel.org>,
        <akpm@linux-foundation.org>, <rafael.j.wysocki@intel.com>,
        <len.brown@intel.com>, <izumi.taku@jp.fujitsu.com>,
        <xiaolong.ye@intel.com>, <x86@kernel.org>,
        <linux-acpi@vger.kernel.org>, <linux-kernel@vger.kernel.org>
From: Dou Liyang <douly.fnst@cn.fujitsu.com>
Message-ID: <da62bc3d-c153-6c4f-93a6-d7b9037f4755@cn.fujitsu.com>
Date: Thu, 2 Mar 2017 15:58:27 +0800
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Hi tglx,

Thank you very much for your guidance! It makes me more profound
understanding of the changelog. And you also rewrote my changelog for
giving me an example.

I am so grateful that you can help me so carefully.
Once I heard the charm of the open source community, Now i can
really feel it. I love it so much.

I will try to improve myself and help others.  :)

Thanks,
	Liyang.

At 03/01/2017 06:51 PM, Thomas Gleixner wrote:
> On Mon, 20 Feb 2017, Dou Liyang wrote:
>
>> Currently, We make the mapping of "cpuid <-> nodeid" fixed at the booting time.
>> It keeps consistent with the WorkQueue and avoids some bugs which may be caused
>> by the dynamic assignment.
>>
>> But, The ACPI table is unreliable and it is very risky that we use the entity
>> which isn't related to a physical device at booting time.
>>
>> Now, we revert our patches. Do the last mapping of "cpuid <-> nodeid" at
>> hot-plug time, not at booting time where we did some useless work.
>> It also can make the mapping of "cpuid <-> nodeid" fixed and avoid excessive
>> use of the ACPI table.
>>
>> The patch revert the commit dc6db24d24:
>>   "x86/acpi: Set persistent cpuid <-> nodeid mapping when booting".
>
> That changelog needs some massaging. Something like this:
>
>   The mapping of "cpuid <-> nodeid" is established at boot time via ACPI
>   tables to keep associations of workqueues and other node related items
>   consistent across cpu hotplug.
>
>   But, ACPI tables are unreliable and failures with that boot time mapping
>   have been reported on machines where the ACPI table and the physical
>   information which is retrieved at actual hotplug is inconsistent.
>
>   Revert the mapping implementation so it can be replaced with a less error
>   prone approach.
>
> This clearly describes:
>
>   1) The context
>
>   2) The problem
>
>   3) The solution (revert)
>
> You don't have to explain what the new solution will be in the changelog of
> the revert. For the revert it's only relevant WHY we do the revert.
>
> Please avoid writing changelogs in 'we' form. Write it pure technical, like
> a manual.
>
> Also avoid phrases like: "The patch/This patch". We all know already that
> this is a patch, otherwise it wouldn't have been sent.
>
> Documentation/process/submitting-patches.rst says:
>
>   Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
>   instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
>   to do frotz", as if you are giving orders to the codebase to change
>   its behaviour.
>
> Thanks,
>
> 	tglx
>
>
>
>