linux-kernel - Re: [PATCH] random: always use batched entropy for get_random

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Message-ID: <CAHmME9pJPhqX8kDCTiRQdqGMLctEZTWTaG0vTDPL0v5A9-rX2A@mail.gmail.com>
Date:   Sat, 22 Feb 2020 10:59:57 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Tony Luck <tony.luck@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] random: always use batched entropy for get_random_u{32,64}

Hi Ted,

On 2/22/20, Theodore Y. Ts'o <tytso@....edu> wrote:

> No, we can't; take a look at invalidate_batched_entropy(), where we
> need invalidate all of per-cpu batched entropy from a single CPU after
> we have initialized the the CRNG.
>
> Since most of the time after CRNG initialization, the spinlock for
> each CPU will be on that CPU's cacheline, the time to take and release
> the spinlock is not going to be material.

Ah, you're right. I hadn't looked in detail before, hence mentioning
"probably" and deferring to a new patch. Thanks for looking into it.

Regarding this patch here, can you apply the v2 that I posted to your
random.git tree?

Thanks,
Jason