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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Sultan Alsawaf <sultan@kerneltoast.com>,
        Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>,
        Dominik Brodowski <linux@dominikbrodowski.net>
Subject: Re: [PATCH v6] random: defer fast pool mixing to worker
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On 2022-02-13 18:37:33 [+0100], Jason A. Donenfeld wrote:
> I started looking at this and came up with this draft with questions:
> https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git/commit/?h=jd/no-irq-trylocks

to
| - Does anything anywhere call get_random_xx() before the worker has a
|   chance to run?

Once you queue a work item I don't think that the scheduler needs to put
it on the CPU right away. It may have already have other tasks waiting
including some with a RT priority.
Also, the lock is irqsave() so they can be users in an interrupt
handler. I remember the original reason why I made it irqsave is because
something did kmalloc() and SLUB somehow asked for random bits.

> Some research remains...
> 
> Jason

Sebastian