Re: [PATCH 2/4] nmi_backtrace: generate one-line reports for idle cpus

From	Chris Metcalf <cmetcalf@mellanox.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/4] nmi_backtrace: generate one-line reports for idle cpus
Date	2016-03-07 18:10 +0100
Message-ID	<ra6Po-5Ig-3@gated-at.bofh.it> (permalink)
References	<r7GPo-1RU-7@gated-at.bofh.it> <r7Ttg-1QY-27@gated-at.bofh.it> <r7Ttg-1QY-25@gated-at.bofh.it> <r7V21-2XK-9@gated-at.bofh.it> <r9YIa-oh-21@gated-at.bofh.it>
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On 03/07/2016 03:26 AM, Daniel Thompson wrote:
>> Chris Metcalf wrote:
>> +static DEFINE_PER_CPU(bool, cpu_idling);
>> +
>> +/* Was the cpu was in the low-level idle code when interrupted? */
>> +bool in_cpu_idle(void)
>> +{
>> +    return this_cpu_read(cpu_idling);
>
> I think we continue to need the code to identify a core that is 
> running an interrupt handler. Interrupts are not masked at the point 
> we set cpu_idling to false meaning we can easily be preempted before 
> we clear the flag.

Yes, good catch.  However, mooted by PeterZ wanting to keep any extra 
state-switching code out of the idle path.  See my reply to him for more 
on that.

-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com

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Re: [PATCH 2/4] nmi_backtrace: generate one-line reports for idle  cpus Daniel Thompson <daniel.thompson@linaro.org> - 2016-03-07 09:30 +0100
  Re: [PATCH 2/4] nmi_backtrace: generate one-line reports for idle  cpus Chris Metcalf <cmetcalf@mellanox.com> - 2016-03-07 18:10 +0100

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