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

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Date:	Fri, 3 Jul 2009 11:06:06 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	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
Subject: Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after_lock


* Jiri Olsa <jolsa@...hat.com> wrote:

> +++ b/arch/x86/include/asm/spinlock.h
> @@ -302,4 +302,7 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw)
>  #define _raw_read_relax(lock)	cpu_relax()
>  #define _raw_write_relax(lock)	cpu_relax()
>  
> +/* The {read|write|spin}_lock() on x86 are full memory barriers. */
> +#define smp_mb__after_lock() do { } while (0)

Two small stylistic comments, please make this an inline function:

static inline void smp_mb__after_lock(void) { }
#define smp_mb__after_lock

(untested)

> +/* The lock does not imply full memory barrier. */
> +#ifndef smp_mb__after_lock
> +#define smp_mb__after_lock() smp_mb()
> +#endif

ditto.

	Ingo
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