netdev - Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after

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Message-ID: <20090703152951.GA28837@gondor.apana.org.au>
Date:	Fri, 3 Jul 2009 23:29:51 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	mingo@...e.hu, jolsa@...hat.com, a.p.zijlstra@...llo.nl,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	fbl@...hat.com, nhorman@...hat.com, davem@...hat.com,
	htejun@...il.com, jarkao2@...il.com, oleg@...hat.com,
	davidel@...ilserver.org, eric.dumazet@...il.com,
	Paul.McKenney@...ibm.com
Subject: Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after_lock

Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:
> 
> Why don't we create a read_lock without acquire semantic instead (e.g.
> read_lock_nomb(), or something with a better name like __read_lock()) ?
> On architectures where memory barriers are needed to provide the acquire
> semantic, it would be faster to do :
> 
> __read_lock();
> smp_mb();
> 
> than :
> 
> read_lock(); <- e.g. lwsync + isync or something like that
> smp_mb(); <- full sync.

Hmm, why do we even care when read_lock should just die?

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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