diff options
Diffstat (limited to 'include/atomic/x86-gcc.h')
| -rw-r--r-- | include/atomic/x86-gcc.h | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/include/atomic/x86-gcc.h b/include/atomic/x86-gcc.h index 90602ef900c..ea3202aa9c9 100644 --- a/include/atomic/x86-gcc.h +++ b/include/atomic/x86-gcc.h @@ -78,15 +78,15 @@ : "memory") /* - Actually 32-bit reads/writes are always atomic on x86 - But we add LOCK_prefix here anyway to force memory barriers + Actually 32/64-bit reads/writes are always atomic on x86_64, + nonetheless issue memory barriers as appropriate. */ #define make_atomic_load_body(S) \ - ret=0; \ - asm volatile (LOCK_prefix "; cmpxchg %2, %0" \ - : "=m" (*a), "=a" (ret) \ - : "r" (ret), "m" (*a) \ - : "memory") + /* Serialize prior load and store operations. */ \ + asm volatile ("mfence" ::: "memory"); \ + ret= *a; \ + /* Prevent compiler from reordering instructions. */ \ + asm volatile ("" ::: "memory") #define make_atomic_store_body(S) \ asm volatile ("; xchg %0, %1;" \ : "=m" (*a), "+r" (v) \ |