linux-kernel - Re: [PATCH RESEND] random: use correct memory barriers for crng_node

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Message-ID: <YcDM2cpwiGCb56Gp@quark>
Date:   Mon, 20 Dec 2021 12:35:05 -0600
From:   Eric Biggers <ebiggers@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH RESEND] random: use correct memory barriers for
 crng_node_pool

On Mon, Dec 20, 2021 at 10:31:40AM -0800, Paul E. McKenney wrote:
> On Mon, Dec 20, 2021 at 07:16:48PM +0100, Jason A. Donenfeld wrote:
> > On Mon, Dec 20, 2021 at 7:11 PM Paul E. McKenney <paulmck@...nel.org> wrote:
> > > First I would want
> > 
> > It looks like you've answered my question with four other questions,
> > which seem certainly technically warranted, but also indicates we're
> > probably not going to get to the nice easy resting place of, "it is
> > safe; go for it" that I was hoping for. In light of that, it seems
> > like merging Eric's patch is reasonable.
> 
> My hope would be that the questions can be quickly answered by the
> developers and maintainers.  But yes, hope springs eternal.
> 
> 							Thanx, Paul

I wouldn't expect READ_ONCE() to provide a noticable performance improvement
here, as it would be lost in the noise of the other work done, especially
chacha20_block().

The data structures in question are never freed, so your other questions are
irrelevant, if I understand correctly.

- Eric