1 #ifndef _ASM_X86_CMPXCHG_32_H
2 #define _ASM_X86_CMPXCHG_32_H
5 * Note: if you use set64_bit(), __cmpxchg64(), or their variants, you
6 * you need to test for the feature in boot_cpu_data.
10 * CMPXCHG8B only writes to the target if we had the previous
11 * value in registers, otherwise it acts as a read and gives us the
12 * "new previous" value. That is why there is a loop. Preloading
13 * EDX:EAX is a performance optimization: in the common case it means
14 * we need only one locked operation.
16 * A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
17 * least an FPU save and/or %cr0.ts manipulation.
19 * cmpxchg8b must be used with the lock prefix here to allow the
20 * instruction to be executed atomically. We need to have the reader
21 * side to see the coherent 64bit value.
23 static inline void set_64bit(volatile u64
*ptr
, u64 value
)
26 u32 high
= value
>> 32;
30 LOCK_PREFIX
"cmpxchg8b %0\n\t"
32 : "=m" (*ptr
), "+A" (prev
)
33 : "b" (low
), "c" (high
)
37 #ifdef CONFIG_X86_CMPXCHG64
38 #define cmpxchg64(ptr, o, n) \
39 ((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
40 (unsigned long long)(n)))
41 #define cmpxchg64_local(ptr, o, n) \
42 ((__typeof__(*(ptr)))__cmpxchg64_local((ptr), (unsigned long long)(o), \
43 (unsigned long long)(n)))
46 static inline u64
__cmpxchg64(volatile u64
*ptr
, u64 old
, u64
new)
49 asm volatile(LOCK_PREFIX
"cmpxchg8b %1"
53 "c" ((u32
)(new >> 32)),
59 static inline u64
__cmpxchg64_local(volatile u64
*ptr
, u64 old
, u64
new)
62 asm volatile("cmpxchg8b %1"
66 "c" ((u32
)(new >> 32)),
72 #ifndef CONFIG_X86_CMPXCHG64
74 * Building a kernel capable running on 80386 and 80486. It may be necessary
75 * to simulate the cmpxchg8b on the 80386 and 80486 CPU.
78 #define cmpxchg64(ptr, o, n) \
80 __typeof__(*(ptr)) __ret; \
81 __typeof__(*(ptr)) __old = (o); \
82 __typeof__(*(ptr)) __new = (n); \
83 alternative_io(LOCK_PREFIX_HERE \
84 "call cmpxchg8b_emu", \
85 "lock; cmpxchg8b (%%esi)" , \
88 "S" ((ptr)), "0" (__old), \
89 "b" ((unsigned int)__new), \
90 "c" ((unsigned int)(__new>>32)) \
95 #define cmpxchg64_local(ptr, o, n) \
97 __typeof__(*(ptr)) __ret; \
98 __typeof__(*(ptr)) __old = (o); \
99 __typeof__(*(ptr)) __new = (n); \
100 alternative_io("call cmpxchg8b_emu", \
101 "cmpxchg8b (%%esi)" , \
104 "S" ((ptr)), "0" (__old), \
105 "b" ((unsigned int)__new), \
106 "c" ((unsigned int)(__new>>32)) \
112 #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
114 #endif /* _ASM_X86_CMPXCHG_32_H */
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