[PATCH 2/2] memory barrier: adding smp_mb__after_lock
From: Jiri Olsa <hidden>
Date: 2009-06-29 14:16:32
Also in:
lkml
Subsystem:
locking primitives, networking [general], networking [sockets], the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Peter Zijlstra, Ingo Molnar, Will Deacon, Boqun Feng, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds, Thomas Gleixner, Borislav Petkov, Dave Hansen
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 <redacted>
---
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 e9137ed..05fbf8b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h@@ -1277,7 +1277,7 @@ static inline void sock_poll_wait(struct file *filp, struct sock *sk, * * This memory barrier is paired in the sk_has_sleeper. */ - smp_mb(); + smp_mb__after_lock(); } }