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From: Herbert Xu <herbert@gondor.apana.org.au>
To: Eric Biggers <ebiggers@kernel.org>
Cc: tytso@mit.edu, linux-kernel@vger.kernel.org,
	linux-crypto@vger.kernel.org, stable@vger.kernel.org,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] random: use correct memory barriers for crng_node_pool
Date: Mon, 21 Sep 2020 18:19:39 +1000	[thread overview]
Message-ID: <20200921081939.GA4193@gondor.apana.org.au> (raw)
In-Reply-To: <20200917165802.GC855@sol.localdomain>

On Thu, Sep 17, 2020 at 09:58:02AM -0700, Eric Biggers wrote:
>
> smp_load_acquire() is obviously correct, whereas READ_ONCE() is an optimization
> that is difficult to tell whether it's correct or not.  For trivial data
> structures it's "easy" to tell.  But whenever there is a->b where b is an
> internal implementation detail of another kernel subsystem, the use of which
> could involve accesses to global or static data (for example, spin_lock()
> accessing lockdep stuff), a control dependency can slip in.

If we're going to follow this line of reasoning, surely you should
be converting the RCU derference first and foremost, no?

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

  reply	other threads:[~2020-09-21  8:19 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16 23:30 [PATCH] random: use correct memory barriers for crng_node_pool Eric Biggers
2020-09-17  7:26 ` Herbert Xu
2020-09-17 16:58   ` Eric Biggers
2020-09-21  8:19     ` Herbert Xu [this message]
2020-09-21 15:27       ` Paul E. McKenney
2020-09-21 22:11         ` Herbert Xu
2020-09-21 23:26           ` Paul E. McKenney
2020-09-21 23:51             ` Herbert Xu
2020-09-22 18:42               ` Paul E. McKenney
2020-09-22 18:59                 ` Eric Biggers
2020-09-22 20:31                   ` Paul E. McKenney
2020-09-21 23:52             ` Eric Biggers
2020-09-22 18:31               ` Paul E. McKenney
2020-09-22 19:09                 ` Eric Biggers
2020-09-22 20:56                   ` Paul E. McKenney
2020-09-22 21:55                     ` Eric Biggers
2020-09-25  0:59                       ` Paul E. McKenney
2020-09-25  2:09                         ` Eric Biggers
2020-09-25  3:31                           ` Paul E. McKenney
2020-10-02  3:07                             ` Eric Biggers
2020-10-08 18:31                               ` Paul E. McKenney

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