linux-ext4 - Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and introduce getrandom2()

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Message-ID: <20190920131609.GC16111@mit.edu>
Date:   Fri, 20 Sep 2019 09:16:09 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     "Alexander E. Patrakov" <patrakov@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        lkml <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
        linux-man@...r.kernel.org
Subject: Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and
 introduce getrandom2()

On Fri, Sep 20, 2019 at 03:23:58AM +0500, Alexander E. Patrakov wrote:
> OTOH, I thought that at least part of the real entropy, if it exists, comes
> from the interference of the CPU's memory accesses with the refresh cycles
> that are clocked from an independent oscillator.

That's not a valid assumption; on *many* systems, there is only a
single master oscillator.  It saves on power, parts cost, reduces the
amount of RF interference, etc.

						- Ted