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__cpu_simple_unlock: avoid instruction re-ordering by the compiler.

This commit is contained in:
pk 2003-11-09 21:04:44 +00:00
parent c55851c88b
commit 72c519a615
1 changed files with 10 additions and 2 deletions
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12
sys/arch/sparc/include/lock.h
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@ -1,4 +1,4 @@
/* $NetBSD: lock.h,v 1.11 2003/09/26 22:46:01 nathanw Exp $ */ /* $NetBSD: lock.h,v 1.12 2003/11/09 21:04:44 pk Exp $ */
/*- /*-
* Copyright (c) 1998, 1999 The NetBSD Foundation, Inc. * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc.
@ -69,6 +69,10 @@ static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *))
static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *)) static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *))
__attribute__((__unused__)); __attribute__((__unused__));
#if __SIMPLELOCK_UNLOCKED != 0
#error __SIMPLELOCK_UNLOCKED must be 0 for this implementation
#endif
static __inline void static __inline void
__cpu_simple_lock_init(__cpu_simple_lock_t *alp) __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
{ {
@ -104,7 +108,11 @@ static __inline void
__cpu_simple_unlock(__cpu_simple_lock_t *alp) __cpu_simple_unlock(__cpu_simple_lock_t *alp)
{ {
*alp = __SIMPLELOCK_UNLOCKED; /*
* Do `*alp = __SIMPLELOCK_UNLOCKED;' with a compiler barrier
* to prevent instruction re-ordering around the lock release.
*/
__asm __volatile("st %%g0,[%0]" : : "r" (alp) : "memory");
} }
#endif /* _MACHINE_LOCK_H */ #endif /* _MACHINE_LOCK_H */