netdev - Re: [PATCH 08/18] rhashtable: clean up dereference of ->future

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Message-ID: <20180601165428.gtefyay2dlus754p@gondor.apana.org.au>
Date:   Sat, 2 Jun 2018 00:54:28 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     NeilBrown <neilb@...e.com>
Cc:     Thomas Graf <tgraf@...g.ch>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/18] rhashtable: clean up dereference of ->future_tbl.

On Fri, Jun 01, 2018 at 02:44:09PM +1000, NeilBrown wrote:
> Using rht_dereference_bucket() to dereference
> ->future_tbl looks like a type error, and could be confusing.
> Using rht_dereference_rcu() to test a pointer for NULL
> adds an unnecessary barrier - rcu_access_pointer() is preferred
> for NULL tests when no lock is held.
> 
> This uses 3 different ways to access ->future_tbl.
> - if we know the mutex is held, use rht_dereference()
> - if we don't hold the mutex, and are only testing for NULL,
>   use rcu_access_pointer()
> - otherwise (using RCU protection for true dereference),
>   use rht_dereference_rcu().
> 
> Note that this includes a simplification of the call to
> rhashtable_last_table() - we don't do an extra dereference
> before the call any more.
> 
> Signed-off-by: NeilBrown <neilb@...e.com>

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