linux-kernel - Re: [RFD] resctrl: reassigning a running container's CTRL

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Message-ID: <CALPaoCikWKz8VLf5QdeYm5k58tePTpb3nTKMGJ+qeGmevjvMpg@mail.gmail.com>
Date:   Tue, 1 Nov 2022 16:53:12 +0100
From:   Peter Newman <peternewman@...gle.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     James Morse <james.morse@....com>, Tony Luck <tony.luck@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Eranian, Stephane" <eranian@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Babu Moger <Babu.Moger@....com>,
        Gaurang Upasani <gupasani@...gle.com>
Subject: Re: [RFD] resctrl: reassigning a running container's CTRL_MON group

On Tue, Nov 1, 2022 at 4:23 PM Peter Newman <peternewman@...gle.com> wrote:
> Yes it looks like the task's rq_lock would provide the necessary
> ordering. It's not feasible to ensure the IPI arrives before the target
> task migrates away, but the task would need to obtain the same lock in
> order to migrate off of its current CPU, so that alone would ensure the
> next migration would observe the updates.
>
> The difficulty is this lock is private to sched/, so I'd have to propose
> some API.

Actually it looks like I can just use task_call_func() to lock down the
task while we do our updates and decide if or where to send IPIs. That
seems easy enough.

-Peter