diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-i386/system.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h index 5d5588788fe5..fc8f116430bc 100644 --- a/include/asm-i386/system.h +++ b/include/asm-i386/system.h @@ -150,6 +150,11 @@ struct __xchg_dummy { unsigned long a[100]; }; * to do an SIMD/3DNOW!/MMX/FPU 64-bit store here, but that * might have an implicit FPU-save as a cost, so it's not * clear which path to go.) + * + * cmpxchg8b must be used with the lock prefix here to allow + * the instruction to be executed atomically, see page 3-102 + * of the instruction set reference 24319102.pdf. We need + * the reader side to see the coherent 64bit value. */ static inline void __set_64bit (unsigned long long * ptr, unsigned int low, unsigned int high) @@ -158,7 +163,7 @@ static inline void __set_64bit (unsigned long long * ptr, "\n1:\t" "movl (%0), %%eax\n\t" "movl 4(%0), %%edx\n\t" - "cmpxchg8b (%0)\n\t" + "lock cmpxchg8b (%0)\n\t" "jnz 1b" : /* no outputs */ : "D"(ptr), |