diff options
| author | Jiri Olsa | 2009-07-08 12:10:31 +0000 |
|---|---|---|
| committer | David S. Miller | 2009-07-09 17:06:58 -0700 |
| commit | ad46276952f1af34cd91d46d49ba13d347d56367 (patch) | |
| tree | 55cf35156794ab34d8a607c25fd044c37231f9e4 | |
| parent | a57de0b4336e48db2811a2030bb68dba8dd09d88 (diff) | |
memory barrier: adding smp_mb__after_lock
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.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | arch/x86/include/asm/spinlock.h | 4 | ||||
| -rw-r--r-- | include/linux/spinlock.h | 5 | ||||
| -rw-r--r-- | include/net/sock.h | 5 |
3 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index b7e5db876399..4e77853321db 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -302,4 +302,8 @@ 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. */ +static inline void smp_mb__after_lock(void) { } +#define ARCH_HAS_SMP_MB_AFTER_LOCK + #endif /* _ASM_X86_SPINLOCK_H */ diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 252b245cfcf4..4be57ab03478 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 ARCH_HAS_SMP_MB_AFTER_LOCK +static inline void smp_mb__after_lock(void) { 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 4eb8409249f6..2c0da9239b95 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1271,6 +1271,9 @@ static inline int sk_has_allocations(const struct sock *sk) * in its cache, and so does the tp->rcv_nxt update on CPU2 side. The CPU1 * could then endup calling schedule and sleep forever if there are no more * data on the socket. + * + * The sk_has_sleeper is always called right after a call to read_lock, so we + * can use smp_mb__after_lock barrier. */ static inline int sk_has_sleeper(struct sock *sk) { @@ -1280,7 +1283,7 @@ static inline int sk_has_sleeper(struct sock *sk) * * This memory barrier is paired in the sock_poll_wait. */ - smp_mb(); + smp_mb__after_lock(); return sk->sk_sleep && waitqueue_active(sk->sk_sleep); } |