system/freebsd-src
system/freebsd-src
1
0
Fork 0
mirror of https://github.com/freebsd/freebsd-src synced 2024-10-18 22:33:39 +00:00
Code Issues Packages Projects Releases Wiki Activity

Like on i386, bypass lock prefix for atomic ops on !SMP kernels.

Browse source
This commit is contained in:
Peter Wemm 2005-07-21 22:35:02 +00:00
parent 5bc15201f4
commit 9e76f9ad3f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=148267
1 changed files with 27 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
sys/amd64/include/atomic.h
View file

@ -152,6 +152,31 @@ atomic_cmpset_long(volatile u_long *dst, u_long exp, u_long src)
return (res);
}
#if defined(_KERNEL) && !defined(SMP)
/*
* We assume that a = b will do atomic loads and stores. However, on a
* PentiumPro or higher, reads may pass writes, so for that case we have
* to use a serializing instruction (i.e. with LOCK) to do the load in
* SMP kernels. For UP kernels, however, the cache of the single processor
* is always consistent, so we don't need any memory barriers.
*/
#define ATOMIC_STORE_LOAD(TYPE, LOP, SOP) \
static __inline u_##TYPE \
atomic_load_acq_##TYPE(volatile u_##TYPE *p) \
{ \
return (*p); \
} \
\
static __inline void \
atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
{ \
*p = v; \
} \
struct __hack
#else /* defined(SMP) */
#define ATOMIC_STORE_LOAD(TYPE, LOP, SOP) \
static __inline u_##TYPE \
atomic_load_acq_##TYPE(volatile u_##TYPE *p) \
@ -179,6 +204,8 @@ atomic_store_rel_##TYPE(volatile u_##TYPE *p, u_##TYPE v)\
} \
struct __hack
#endif /* SMP */
#endif /* KLD_MODULE || !(__GNUCLIKE_ASM && __CC_SUPPORTS___INLINE) */
ATOMIC_ASM(set, char, "orb %b1,%0", "iq", v);