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Date:   Wed, 20 Jul 2022 23:50:46 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     "Guozihua (Scott)" <guozihua@huawei.com>
Cc:     "Jason A. Donenfeld" <Jason@zx2c4.com>,
        linux-crypto@vger.kernel.org, luto@kernel.org, tytso@mit.edu
Subject: Re: Inquiry about the removal of flag O_NONBLOCK on /dev/random
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On Thu, Jul 21, 2022 at 02:44:54PM +0800, Guozihua (Scott) wrote:
> 
> Hi Eric
> 
> We have a userspace program that starts pretty early in the boot process and
> it tries to fetch random bits from /dev/random with O_NONBLOCK, if that
> returns -EAGAIN, it turns to /dev/urandom. Is this a correct handling of
> -EAGAIN? Or this is not one of the intended use case of O_NONBLOCK?

That doesn't make any sense; you should just use /dev/urandom unconditionally.

- Eric