linux-kernel - Re: [PATCH HACK RFC] cpu: Prevent late-arriving interrupts from disrupting offline

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Message-ID: <6eb5d59f-37d0-0aab-1fc0-fcf48cc4164f@arm.com>
Date:   Tue, 4 Jun 2019 15:29:32 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     paulmck@...ux.ibm.com
Cc:     Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de,
        mingo@...nel.org, jpoimboe@...hat.com, mojha@...eaurora.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH HACK RFC] cpu: Prevent late-arriving interrupts from
 disrupting offline

On 6/4/19 9:45 AM, Paul E. McKenney wrote:
> On Mon, Jun 03, 2019 at 03:39:18PM +0200, Dietmar Eggemann wrote:
>> On 6/3/19 1:44 PM, Mark Rutland wrote:
>>> On Mon, Jun 03, 2019 at 10:38:48AM +0200, Peter Zijlstra wrote:
>>>> On Sat, Jun 01, 2019 at 06:12:53PM -0700, Paul E. McKenney wrote:
>>>>> Scheduling-clock interrupts can arrive late in the CPU-offline process,

[...]

>>>    05981277a4de1ad6 ("arm64: Use common outgoing-CPU-notification code")
>>>
>>> ... but it looks like Paul's patch to do so [1] fell through the cracks;
>>> I'm not aware of any reason that shouldn't have been taken.
>>> [1] https://lore.kernel.org/lkml/1431467407-1223-8-git-send-email-paulmck@linux.vnet.ibm.com/
>>>
>>> Paul, do you want to resend that?
>>
>> Please do. We're carrying this patch out-of-tree for while now in
>> our EAS integration to get cpu hotplug tests passing on TC2 (arm).
> 
> Huh.  It still applies.  But I have no means of testing it.

We can do the testing part on our TC2 platform, i.e. we're testing it 
with each of our EAS mainline integration right now.

https://developer.arm.com/tools-and-software/open-source-software/linux-kernel/energy-aware-scheduling/eas-mainline-development

http://linux-arm.org/git?p=linux-power.git;a=commit;h=8cd16f1dc2cd896a0b1e2010b4992b33fdc11fe0

> And it looks like the reason I dropped it was that I didn't get any
> response from the maintainer.  I sent a message to this effect to
> linux-arm-kernel@...ts.infradead.org and linux@....linux.org.uk on May
> 21, 2015.
> 
> So here it is again.  ;-)
> 
> I have queued this locally.  Left to myself, I add the two of you on its
> Cc: list and run it through my normal process.  But given the history,
> I would still want either an ack from the maintainer or, better, for
> the maintainer to take the patch.
> 
> Or is there a better way for us to proceed on this?

You could send this patch also to linux-arm-kernel@...ts.infradead.org 
and cc rmk to get his opinion on the patch.

[...]