linux-kernel - Re: [PATCH v2] random: set fast pool count to zero in cpuhp teardown

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Message-ID: <CAHmME9qrhpRCox2mR2UEStWxev2Zu14htBkpv3mdFEkVqacvVQ@mail.gmail.com>
Date:   Mon, 14 Feb 2022 16:10:36 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH v2] random: set fast pool count to zero in cpuhp teardown

Hi Sebastian,

On Mon, Feb 14, 2022 at 4:06 PM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> But you acked my question regarding boot-up? So the teardown callback
> won't happen during boot-up.

I'd like to do only one method here, so we can set those fields in
startup, provided it happens early enough.
> > So I think it seems better to keep it before CPUHP_TIMERS_PREPARE, but
> > do it on startup rather than teardown. Seem reasonable? Would that
> > mean we zero out before IRQs are enabled?
> I would only zero it if the upper-most bit is there.

I still don't quite understand: why can't we just unconditionally
zero, always, before CPUHP_TIMERS_PREPARE?

> And then have another one after

Two of them seems a little bit out of hand in complexity here... Let's
just find one phase where we can simply set variables without too much
fiddly logic. I'll send a v+1 of what I have in mind for the startup
path.

Jason