linux-kernel - Re: [PATCH 0/1] x86/resctrl: fix task CLOSID update race

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Message-ID: <CALPaoCj2t8=BNG=nTs6bvZ9ed0qpFCyCertEOTyMQtzKkdjRCg@mail.gmail.com>
Date:   Thu, 10 Nov 2022 16:28:03 +0100
From:   Peter Newman <peternewman@...gle.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org, jannh@...gle.com, eranian@...gle.com,
        kpsingh@...gle.com, derkling@...gle.com, james.morse@....com
Subject: Re: [PATCH 0/1] x86/resctrl: fix task CLOSID update race

Hi Reinette,

On Tue, Nov 8, 2022 at 7:50 PM Reinette Chatre
<reinette.chatre@...el.com> wrote:
> I do not see it as an either/or though. I think that using task_call_func()
> to serialize with context switching is a good idea when moving a single
> task. Sending IPIs to all CPUs in this case seems overkill. On the other hand,
> when moving a group of tasks I think that notifying all CPUs would be
> simpler. The current code already ensures that it does not modify the
> PQR register unnecessarily. I would really like to learn more about this
> from the experts but at this point I am most comfortable with such a
> solution and look forward to to learning from the experts when it is
> presented to the x86 maintainers for inclusion.

Great, that should allow me to post my mon group rename patch
independent of this one. As it is written today, it depends on this
patch to reliably notify moved tasks' CPUs.

Thanks!
-Peter