linux-kernel - Re: [PATCH RFC v1] random: use static branch for crng

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Message-ID: <Ynug580srdedsiY9@zx2c4.com>
Date:   Wed, 11 May 2022 13:41:27 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Cc:     Theodore Ts'o <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH RFC v1] random: use static branch for crng_ready()

On Tue, May 03, 2022 at 03:40:52PM +0200, Jason A. Donenfeld wrote:
> +static bool crng_ready_slowpath(void)
> +{
> +	if (crng_init <= 1)
> +		return false;
> +	if (in_atomic() || irqs_disabled() || cmpxchg(&crng_init, 2, 3) != 2)
> +		return true;

Nobody chimed in here, but for posterity I thought I should point out
that this approach actually won't work, since in_atomic() doesn't work
with CONFIG_PREEMPT_COUNT=n kernels.

So back to the drawing board in trying to figure out the best way to do
this...
 
Jason