linux-kernel - Re: [PATCH v6] random: defer fast pool mixing to worker

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Message-ID: <YgaZuShru2HQiFXg@linutronix.de>
Date:   Fri, 11 Feb 2022 18:15:37 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Theodore Ts'o <tytso@....edu>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH v6] random: defer fast pool mixing to worker

On 2022-02-11 18:00:21 [+0100], Jason A. Donenfeld wrote:
> Hi Sebastian,
Hi Jason,

> On Fri, Feb 11, 2022 at 5:59 PM Sebastian Andrzej Siewior
> <bigeasy@...utronix.de> wrote:
> > > Okay, I'll do that then, and then in the process get rid of the
> > > cmpxchg loop since it's no longer required.
> >
> > So the only reason why we have that atomic_t is for rare case where run
> > on the remote CPU and need to remove the upper bit in the counter?
> 
> Yes. That's the only remaining reason. Annoying, but whatareyagonnado?

A CPU hotplug notifier which removes unconditionally that bit when the
CPU goes down or sets it to 0.
We can keep it as it. Just an idea for later maybe ;)

> Jason

Sebastian