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

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Message-ID: <16a424d1-0ab7-7e81-5c4f-93da23519b1d@arm.com>
Date:   Tue, 11 Jun 2019 15:14:54 +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 6/8/19 6:41 PM, Paul E. McKenney wrote:
> On Tue, Jun 04, 2019 at 03:29:32PM +0200, Dietmar Eggemann wrote:
>> 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,

[...]

>>> 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.
> 
> OK, please let me know how the testing goes.  My thought is to send the
> patch as you suggest with your Tested-by.

Tested your patch on top of v5.2-rc4* on Arm TC2 (32bit) and CPU hotplug 
stress test. W/o your patch, the test fails within seconds since CPUs 
are not coming up again. W/ your patch, the test runs for hours just fine.

You can add my:

Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>

* just for the record: one additional unrelated patch (to disable the 
NOR flash) is necessary on Arm TC2: 
https://patchwork.kernel.org/patch/10968391 .