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@@ -11,38 +11,42 @@
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extern void __xchg_wrong_size(void);
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/*
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- * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
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- * Note 2: xchg has side effect, so that attribute volatile is necessary,
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- * but generally the primitive is invalid, *ptr is output argument. --ANK
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+ * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
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+ * Since this is generally used to protect other memory information, we
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+ * use "asm volatile" and "memory" clobbers to prevent gcc from moving
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+ * information around.
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*/
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-
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-struct __xchg_dummy {
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- unsigned long a[100];
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-};
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-#define __xg(x) ((struct __xchg_dummy *)(x))
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-
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#define __xchg(x, ptr, size) \
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({ \
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__typeof(*(ptr)) __x = (x); \
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switch (size) { \
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case 1: \
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- asm volatile("xchgb %b0,%1" \
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- : "=q" (__x) \
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- : "m" (*__xg(ptr)), "0" (__x) \
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+ { \
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+ volatile u8 *__ptr = (volatile u8 *)(ptr); \
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+ asm volatile("xchgb %0,%1" \
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+ : "=q" (__x), "+m" (*__ptr) \
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+ : "0" (__x) \
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: "memory"); \
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break; \
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+ } \
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case 2: \
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- asm volatile("xchgw %w0,%1" \
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- : "=r" (__x) \
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- : "m" (*__xg(ptr)), "0" (__x) \
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+ { \
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+ volatile u16 *__ptr = (volatile u16 *)(ptr); \
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+ asm volatile("xchgw %0,%1" \
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+ : "=r" (__x), "+m" (*__ptr) \
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+ : "0" (__x) \
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: "memory"); \
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break; \
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+ } \
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case 4: \
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+ { \
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+ volatile u32 *__ptr = (volatile u32 *)(ptr); \
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asm volatile("xchgl %0,%1" \
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- : "=r" (__x) \
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- : "m" (*__xg(ptr)), "0" (__x) \
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+ : "=r" (__x), "+m" (*__ptr) \
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+ : "0" (__x) \
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: "memory"); \
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break; \
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+ } \
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default: \
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__xchg_wrong_size(); \
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} \
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@@ -53,60 +57,33 @@ struct __xchg_dummy {
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__xchg((v), (ptr), sizeof(*ptr))
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/*
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- * The semantics of XCHGCMP8B are a bit strange, this is why
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- * there is a loop and the loading of %%eax and %%edx has to
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- * be inside. This inlines well in most cases, the cached
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- * cost is around ~38 cycles. (in the future we might want
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- * to do an SIMD/3DNOW!/MMX/FPU 64-bit store here, but that
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- * might have an implicit FPU-save as a cost, so it's not
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- * clear which path to go.)
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+ * CMPXCHG8B only writes to the target if we had the previous
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+ * value in registers, otherwise it acts as a read and gives us the
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+ * "new previous" value. That is why there is a loop. Preloading
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+ * EDX:EAX is a performance optimization: in the common case it means
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+ * we need only one locked operation.
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*
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- * cmpxchg8b must be used with the lock prefix here to allow
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- * the instruction to be executed atomically, see page 3-102
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- * of the instruction set reference 24319102.pdf. We need
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- * the reader side to see the coherent 64bit value.
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+ * A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
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+ * least an FPU save and/or %cr0.ts manipulation.
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+ *
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+ * cmpxchg8b must be used with the lock prefix here to allow the
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+ * instruction to be executed atomically. We need to have the reader
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+ * side to see the coherent 64bit value.
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*/
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-static inline void __set_64bit(unsigned long long *ptr,
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- unsigned int low, unsigned int high)
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+static inline void set_64bit(volatile u64 *ptr, u64 value)
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{
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+ u32 low = value;
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+ u32 high = value >> 32;
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+ u64 prev = *ptr;
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+
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asm volatile("\n1:\t"
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- "movl (%0), %%eax\n\t"
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- "movl 4(%0), %%edx\n\t"
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- LOCK_PREFIX "cmpxchg8b (%0)\n\t"
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+ LOCK_PREFIX "cmpxchg8b %0\n\t"
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"jnz 1b"
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- : /* no outputs */
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- : "D"(ptr),
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- "b"(low),
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- "c"(high)
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- : "ax", "dx", "memory");
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-}
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-
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-static inline void __set_64bit_constant(unsigned long long *ptr,
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- unsigned long long value)
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-{
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- __set_64bit(ptr, (unsigned int)value, (unsigned int)(value >> 32));
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-}
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-
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-#define ll_low(x) *(((unsigned int *)&(x)) + 0)
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-#define ll_high(x) *(((unsigned int *)&(x)) + 1)
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-
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-static inline void __set_64bit_var(unsigned long long *ptr,
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- unsigned long long value)
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-{
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- __set_64bit(ptr, ll_low(value), ll_high(value));
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+ : "=m" (*ptr), "+A" (prev)
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+ : "b" (low), "c" (high)
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+ : "memory");
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}
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-#define set_64bit(ptr, value) \
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- (__builtin_constant_p((value)) \
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- ? __set_64bit_constant((ptr), (value)) \
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- : __set_64bit_var((ptr), (value)))
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-
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-#define _set_64bit(ptr, value) \
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- (__builtin_constant_p(value) \
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- ? __set_64bit(ptr, (unsigned int)(value), \
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- (unsigned int)((value) >> 32)) \
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- : __set_64bit(ptr, ll_low((value)), ll_high((value))))
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-
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extern void __cmpxchg_wrong_size(void);
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/*
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@@ -121,23 +98,32 @@ extern void __cmpxchg_wrong_size(void);
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__typeof__(*(ptr)) __new = (new); \
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switch (size) { \
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case 1: \
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- asm volatile(lock "cmpxchgb %b1,%2" \
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- : "=a"(__ret) \
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- : "q"(__new), "m"(*__xg(ptr)), "0"(__old) \
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+ { \
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+ volatile u8 *__ptr = (volatile u8 *)(ptr); \
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+ asm volatile(lock "cmpxchgb %2,%1" \
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+ : "=a" (__ret), "+m" (*__ptr) \
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+ : "q" (__new), "0" (__old) \
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: "memory"); \
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break; \
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+ } \
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case 2: \
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- asm volatile(lock "cmpxchgw %w1,%2" \
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- : "=a"(__ret) \
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- : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \
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+ { \
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+ volatile u16 *__ptr = (volatile u16 *)(ptr); \
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+ asm volatile(lock "cmpxchgw %2,%1" \
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+ : "=a" (__ret), "+m" (*__ptr) \
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+ : "r" (__new), "0" (__old) \
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: "memory"); \
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break; \
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+ } \
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case 4: \
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- asm volatile(lock "cmpxchgl %1,%2" \
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- : "=a"(__ret) \
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- : "r"(__new), "m"(*__xg(ptr)), "0"(__old) \
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+ { \
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+ volatile u32 *__ptr = (volatile u32 *)(ptr); \
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+ asm volatile(lock "cmpxchgl %2,%1" \
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+ : "=a" (__ret), "+m" (*__ptr) \
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+ : "r" (__new), "0" (__old) \
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: "memory"); \
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break; \
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+ } \
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default: \
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__cmpxchg_wrong_size(); \
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} \
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@@ -175,32 +161,28 @@ extern void __cmpxchg_wrong_size(void);
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(unsigned long long)(n)))
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#endif
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-static inline unsigned long long __cmpxchg64(volatile void *ptr,
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- unsigned long long old,
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- unsigned long long new)
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+static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
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{
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- unsigned long long prev;
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- asm volatile(LOCK_PREFIX "cmpxchg8b %3"
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- : "=A"(prev)
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- : "b"((unsigned long)new),
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- "c"((unsigned long)(new >> 32)),
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- "m"(*__xg(ptr)),
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- "0"(old)
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+ u64 prev;
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+ asm volatile(LOCK_PREFIX "cmpxchg8b %1"
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+ : "=A" (prev),
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+ "+m" (*ptr)
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+ : "b" ((u32)new),
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+ "c" ((u32)(new >> 32)),
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+ "0" (old)
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: "memory");
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return prev;
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}
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-static inline unsigned long long __cmpxchg64_local(volatile void *ptr,
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- unsigned long long old,
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- unsigned long long new)
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+static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)
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{
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- unsigned long long prev;
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- asm volatile("cmpxchg8b %3"
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- : "=A"(prev)
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- : "b"((unsigned long)new),
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- "c"((unsigned long)(new >> 32)),
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- "m"(*__xg(ptr)),
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- "0"(old)
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+ u64 prev;
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+ asm volatile("cmpxchg8b %1"
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+ : "=A" (prev),
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+ "+m" (*ptr)
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+ : "b" ((u32)new),
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+ "c" ((u32)(new >> 32)),
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+ "0" (old)
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: "memory");
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return prev;
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}
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@@ -264,8 +246,6 @@ static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old,
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* to simulate the cmpxchg8b on the 80386 and 80486 CPU.
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*/
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-extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);
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-
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#define cmpxchg64(ptr, o, n) \
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({ \
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__typeof__(*(ptr)) __ret; \
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@@ -283,20 +263,20 @@ extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);
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__ret; })
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-
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-#define cmpxchg64_local(ptr, o, n) \
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-({ \
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- __typeof__(*(ptr)) __ret; \
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- if (likely(boot_cpu_data.x86 > 4)) \
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- __ret = (__typeof__(*(ptr)))__cmpxchg64_local((ptr), \
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- (unsigned long long)(o), \
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- (unsigned long long)(n)); \
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- else \
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- __ret = (__typeof__(*(ptr)))cmpxchg_486_u64((ptr), \
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- (unsigned long long)(o), \
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- (unsigned long long)(n)); \
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- __ret; \
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-})
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+#define cmpxchg64_local(ptr, o, n) \
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+({ \
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+ __typeof__(*(ptr)) __ret; \
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+ __typeof__(*(ptr)) __old = (o); \
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+ __typeof__(*(ptr)) __new = (n); \
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+ alternative_io("call cmpxchg8b_emu", \
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+ "cmpxchg8b (%%esi)" , \
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+ X86_FEATURE_CX8, \
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+ "=A" (__ret), \
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+ "S" ((ptr)), "0" (__old), \
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+ "b" ((unsigned int)__new), \
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+ "c" ((unsigned int)(__new>>32)) \
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+ : "memory"); \
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+ __ret; })
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#endif
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