Messages in this thread | | | Date | Tue, 30 Jun 2009 14:13:18 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCHv2 2/2] memory barrier: adding smp_mb__after_lock |
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On Tue, Jun 30, 2009 at 01:14:20PM +0200, Eric Dumazet wrote: > Jiri Olsa a écrit : > > Adding smp_mb__after_lock define to be used as a smp_mb call after > > a lock. > > > > Making it nop for x86, since {read|write|spin}_lock() on x86 are > > full memory barriers. > > > > wbr, > > jirka > > > > > > Signed-off-by: Jiri Olsa <jolsa@redhat.com> > > > > --- > > arch/x86/include/asm/spinlock.h | 3 +++ > > include/linux/spinlock.h | 5 +++++ > > include/net/sock.h | 2 +- > > 3 files changed, 9 insertions(+), 1 deletions(-) > > > > diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h > > index b7e5db8..39ecc5f 100644 > > --- a/arch/x86/include/asm/spinlock.h > > +++ 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) > > + > > #endif /* _ASM_X86_SPINLOCK_H */ > > diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h > > index 252b245..ae053bd 100644 > > --- a/include/linux/spinlock.h > > +++ b/include/linux/spinlock.h > > @@ -132,6 +132,11 @@ do { \ > > #endif /*__raw_spin_is_contended*/ > > #endif > > > > +/* The lock does not imply full memory barrier. */ > > +#ifndef smp_mb__after_lock > > +#define smp_mb__after_lock() smp_mb() > > +#endif > > + > > /** > > * spin_unlock_wait - wait until the spinlock gets unlocked > > * @lock: the spinlock in question. > > diff --git a/include/net/sock.h b/include/net/sock.h > > index a12df10..0d57e83 100644 > > --- a/include/net/sock.h > > +++ b/include/net/sock.h > > @@ -1277,7 +1277,7 @@ static inline void sock_poll_wait(struct file *filp, > > * > > * This memory barrier is paired in the sk_has_sleeper. > > */ > > - smp_mb(); > > + smp_mb__after_lock(); > > } > > } > > I believe you took wrong point to use this new thing :) > > It was meant to be used in sk_has_sleeper() only (as sk_has_sleeper() > follows a read_lock()) >
shoot, you're right.. I'll resend 2/2, thanks
jirka
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