Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after_lock

Ingo Molnar
2009-07-03T09:25:09Z

* Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Ingo Molnar a écrit :
> > * 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