linux-kernel - Re: [PATCH] random: remove batched entropy locking

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Message-ID: <YfQPVp8TULSq3V+l@linutronix.de>
Date:   Fri, 28 Jan 2022 16:44:22 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Theodore Ts'o <tytso@....edu>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andy Lutomirski <luto@...nel.org>, stable@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] random: remove batched entropy locking

On 2022-01-28 16:33:44 [+0100], Jason A. Donenfeld wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> We don't need spinlocks to protect batched entropy -- all we need
> is a little bit of care. This should fix up the following splat that
> Jonathan received with a PROVE_LOCKING=y/PROVE_RAW_LOCK_NESTING=y
> kernel:

NO. Could we please look at my RANDOM patches first?
This affects PREEMPT_RT. There is no need to stuff this in and tag it
stable.

I can repost my rebased patched if there no objection.
This patch invokes extract_crng() with disabled interrupts so we didn't
gain anything IMHO.

Sebastian