linux-kernel - Re: [RFC 0/4] Migrate timers away from cpuset on setting cpuset.quiesce

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Message-ID: <CAKohpokk4rGeP3QfVT5_HBO4pc=22yPBLV78D++y1Ab72y1OJQ@mail.gmail.com>
Date:	Thu, 24 Apr 2014 14:11:52 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
	Li Zefan <lizefan@...wei.com>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [RFC 0/4] Migrate timers away from cpuset on setting cpuset.quiesce

On 24 April 2014 14:01, Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp> wrote:
> In kernel/cpuset.c:quiesce_cpuset() you are using the function
> 'smp_call_function_any' which asks CPU cores in 'cpumask' to
> execute the functions 'hrtimer_quiesce_cpu' and 'timer_quiesce_cpu'.
>
> In the case above, 'cpumask' corresponds to core 0. Since I'm forcing
> the call to be executed from core 1 (by using taskset),
> an inter-processor interrupt is sent to core 0 for those functions
> to be executed.

Ahh, I understood that now :) .. So we are setting cpuset.quiesce from CPU1
which will do a IPI to get migrate_timers called on CPU0.. I was setting quiesce
from CPU0 only in my tests :)

But how does this work fine on x86 then? There we should have exactly same
problem, isn't it?

> Ok, thank you! I see that you have already fixed the problem. I tested
> your tree on ARM and now it seems to work correctly.

Yeah, I just pushed your changes as well at the time I wrote last mail :)
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