From: Herbert Xu <herbert@gondor.apana.org.au>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>,
tytso@mit.edu, linux-kernel@vger.kernel.org,
linux-crypto@vger.kernel.org, stable@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] random: use correct memory barriers for crng_node_pool
Date: Tue, 22 Sep 2020 09:51:36 +1000 [thread overview]
Message-ID: <20200921235136.GA6796@gondor.apana.org.au> (raw)
In-Reply-To: <20200921232639.GK29330@paulmck-ThinkPad-P72>
On Mon, Sep 21, 2020 at 04:26:39PM -0700, Paul E. McKenney wrote:
>
> > But this reasoning could apply to any data structure that contains
> > a spin lock, in particular ones that are dereferenced through RCU.
>
> I lost you on this one. What is special about a spin lock?
I don't know, that was Eric's concern. He is inferring that
spin locks through lockdep debugging may trigger dependencies
that require smp_load_acquire.
Anyway, my point is if it applies to crng_node_pool then it
would equally apply to RCU in general.
> > So my question if this reasoning is valid, then why aren't we first
> > converting rcu_dereference to use smp_load_acquire?
>
> For LTO in ARM, rumor has it that Will is doing so. Which was what
> motivated the BoF on this topic at Linux Plumbers Conference.
Sure, if RCU switches over to smp_load_acquire then I would have
no problems with everybody else following in its footsteps.
Here is the original patch in question:
https://lore.kernel.org/lkml/20200916233042.51634-1-ebiggers@kernel.org/
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
next prev parent reply other threads:[~2020-09-21 23:51 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
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 [this message]
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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