linux-kernel - Re: [PATCH v2] random: do crng pre-init loading in worker rather than irq

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Message-ID: <CAHmME9r7bRh+CeBh98UMVCFgmeMWHQ=r3b-8odgV0tR45hOTbw@mail.gmail.com>
Date:   Mon, 28 Feb 2022 15:17:19 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Biggers <ebiggers@...nel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH v2] random: do crng pre-init loading in worker rather than irq

Hey Sebastian,

On 2/28/22, Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:
> On 2022-02-24 16:29:37 [+0100], Jason A. Donenfeld wrote:
>> Taking spinlocks from IRQ context is problematic for PREEMPT_RT. That
>> is, in part, why we take trylocks instead. But apparently this still
>> trips up various lock dependency analyzers. That seems like a bug in the
>> analyzers that should be fixed, rather than having to change things
>> here.
>
> Could you please post a lockdep report so I can take a look?

I thought the problem with lockdep was stated by you somewhere in this thread?
https://lore.kernel.org/lkml/YfOqsOiNfURyvFRX@linutronix.de/
"But even then we need to find a way to move the crng init part
(crng_fast_load()) out of the hard-IRQ."
And Jonathan posted two related (?) splats he ran into.

I may have gotten that all wrong, in which case, I'll just excise that
part from the commit message. I'm pretty sure you want this patch
either way, right?

Jason