Date: Fri, 3 Jul 2009 11:56:59 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       netdev@vger.kernel.org, linux-kernel@vger.kernel.org, fbl@redhat.com,
       nhorman@redhat.com, davem@redhat.com, htejun@gmail.com,
       jarkao2@gmail.com, oleg@redhat.com, davidel@xmailserver.org
Subject: Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after_lock
Message-ID: <20090703095659.GA4518@jolsa.lab.eng.brq.redhat.com>
References: <20090703081219.GE2902@jolsa.lab.eng.brq.redhat.com> <20090703081445.GG2902@jolsa.lab.eng.brq.redhat.com> <20090703090606.GA3902@elte.hu> <4A4DCD54.1080908@gmail.com> <20090703092438.GE3902@elte.hu>
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On Fri, Jul 03, 2009 at 11:24:38AM +0200, Ingo Molnar wrote:
> 
> * Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> > Ingo Molnar a ?crit :
> > > * Jiri Olsa <jolsa@redhat.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
> > 
> > This was following existing implementations of various smp_mb__??? helpers :
> > 
> > # grep -4 smp_mb__before_clear_bit include/asm-generic/bitops.h
> > 
> > /*
> >  * clear_bit may not imply a memory barrier
> >  */
> > #ifndef smp_mb__before_clear_bit
> > #define smp_mb__before_clear_bit()      smp_mb()
> > #define smp_mb__after_clear_bit()       smp_mb()
> > #endif
> 
> Did i mention that those should be fixed too? :-)
> 
> 	Ingo

ok, could I include it in the 2/2 or you prefer separate patch?

jirka
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