linux-kernel - Re: [PATCH] random: fix possible sleeping allocation from irq context

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Date:   Wed, 25 Apr 2018 09:46:42 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     "\"\\\"Theodore Ts\'o\\\"\"" <tytso@....edu>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] random: fix possible sleeping allocation from irq context

Theodore Ts\'o wrote:
> We can do a sleeping allocation from an irq context when CONFIG_NUMA
> is enabled.  Fix this by initializing the NUMA crng instances in a
> workqueue.

Offloading to workqueue context itself would be OK,
but this patch makes linux.git unbootable because

	if (crng == &primary_crng && crng_init < 2) {
		invalidate_batched_entropy();
		numa_crng_init(); // <= Deferred to workqueue context.
		crng_init = 2; // <= Not waiting for workqueue context, and oops before console becomes ready. ;-)
		process_random_ready_list();
		wake_up_interruptible(&crng_init_wait);
		pr_notice(\"random: crng init done\\n\");
	}

Please don\'t pretend rng_ready() before workqueue context is processed.