arch/x86/include/asm/cmpxchg.h

   1 #ifndef ASM_X86_CMPXCHG_H
   2 #define ASM_X86_CMPXCHG_H
   3
   4 #include <linux/compiler.h>
   5 #include <asm/cpufeatures.h>
   6 #include <asm/alternative.h> /* Provides LOCK_PREFIX */
   7
   8 /*
   9  * Non-existant functions to indicate usage errors at link time
  10  * (or compile-time if the compiler implements __compiletime_error().
  11  */
  12 extern void __xchg_wrong_size(void)
  13         __compiletime_error("Bad argument size for xchg");
  14 extern void __cmpxchg_wrong_size(void)
  15         __compiletime_error("Bad argument size for cmpxchg");
  16 extern void __xadd_wrong_size(void)
  17         __compiletime_error("Bad argument size for xadd");
  18 extern void __add_wrong_size(void)
  19         __compiletime_error("Bad argument size for add");
  20
  21 /*
  22  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
  23  * -1 because sizeof will never return -1, thereby making those switch
  24  * case statements guaranteeed dead code which the compiler will
  25  * eliminate, and allowing the "missing symbol in the default case" to
  26  * indicate a usage error.
  27  */
  28 #define __X86_CASE_B    1
  29 #define __X86_CASE_W    2
  30 #define __X86_CASE_L    4
  31 #ifdef CONFIG_64BIT
  32 #define __X86_CASE_Q    8
  33 #else
  34 #define __X86_CASE_Q    -1              /* sizeof will never return -1 */
  35 #endif
  36
  37 /*
  38  * An exchange-type operation, which takes a value and a pointer, and
  39  * returns the old value.
  40  */
  41 #define __xchg_op(ptr, arg, op, lock)                                   \
  42         ({                                                              \
  43                 __typeof__ (*(ptr)) __ret = (arg);                      \
  44                 switch (sizeof(*(ptr))) {                               \
  45                 case __X86_CASE_B:                                      \
  46                         asm volatile (lock #op "b %b0, %1\n"            \
  47                                       : "+q" (__ret), "+m" (*(ptr))     \
  48                                       : : "memory", "cc");              \
  49                         break;                                          \
  50                 case __X86_CASE_W:                                      \
  51                         asm volatile (lock #op "w %w0, %1\n"            \
  52                                       : "+r" (__ret), "+m" (*(ptr))     \
  53                                       : : "memory", "cc");              \
  54                         break;                                          \
  55                 case __X86_CASE_L:                                      \
  56                         asm volatile (lock #op "l %0, %1\n"             \
  57                                       : "+r" (__ret), "+m" (*(ptr))     \
  58                                       : : "memory", "cc");              \
  59                         break;                                          \
  60                 case __X86_CASE_Q:                                      \
  61                         asm volatile (lock #op "q %q0, %1\n"            \
  62                                       : "+r" (__ret), "+m" (*(ptr))     \
  63                                       : : "memory", "cc");              \
  64                         break;                                          \
  65                 default:                                                \
  66                         __ ## op ## _wrong_size();                      \
  67                 }                                                       \
  68                 __ret;                                                  \
  69         })
  70
  71 /*
  72  * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
  73  * Since this is generally used to protect other memory information, we
  74  * use "asm volatile" and "memory" clobbers to prevent gcc from moving
  75  * information around.
  76  */
  77 #define xchg(ptr, v)    __xchg_op((ptr), (v), xchg, "")
  78
  79 /*
  80  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  81  * store NEW in MEM.  Return the initial value in MEM.  Success is
  82  * indicated by comparing RETURN with OLD.
  83  */
  84 #define __raw_cmpxchg(ptr, old, new, size, lock)                        \
  85 ({                                                                      \
  86         __typeof__(*(ptr)) __ret;                                       \
  87         __typeof__(*(ptr)) __old = (old);                               \
  88         __typeof__(*(ptr)) __new = (new);                               \
  89         switch (size) {                                                 \
  90         case __X86_CASE_B:                                              \
  91         {                                                               \
  92                 volatile u8 *__ptr = (volatile u8 *)(ptr);              \
  93                 asm volatile(lock "cmpxchgb %2,%1"                      \
  94                              : "=a" (__ret), "+m" (*__ptr)              \
  95                              : "q" (__new), "0" (__old)                 \
  96                              : "memory");                               \
  97                 break;                                                  \
  98         }                                                               \
  99         case __X86_CASE_W:                                              \
 100         {                                                               \
 101                 volatile u16 *__ptr = (volatile u16 *)(ptr);            \
 102                 asm volatile(lock "cmpxchgw %2,%1"                      \
 103                              : "=a" (__ret), "+m" (*__ptr)              \
 104                              : "r" (__new), "0" (__old)                 \
 105                              : "memory");                               \
 106                 break;                                                  \
 107         }                                                               \
 108         case __X86_CASE_L:                                              \
 109         {                                                               \
 110                 volatile u32 *__ptr = (volatile u32 *)(ptr);            \
 111                 asm volatile(lock "cmpxchgl %2,%1"                      \
 112                              : "=a" (__ret), "+m" (*__ptr)              \
 113                              : "r" (__new), "0" (__old)                 \
 114                              : "memory");                               \
 115                 break;                                                  \
 116         }                                                               \
 117         case __X86_CASE_Q:                                              \
 118         {                                                               \
 119                 volatile u64 *__ptr = (volatile u64 *)(ptr);            \
 120                 asm volatile(lock "cmpxchgq %2,%1"                      \
 121                              : "=a" (__ret), "+m" (*__ptr)              \
 122                              : "r" (__new), "0" (__old)                 \
 123                              : "memory");                               \
 124                 break;                                                  \
 125         }                                                               \
 126         default:                                                        \
 127                 __cmpxchg_wrong_size();                                 \
 128         }                                                               \
 129         __ret;                                                          \
 130 })
 131
 132 #define __cmpxchg(ptr, old, new, size)                                  \
 133         __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
 134
 135 #define __sync_cmpxchg(ptr, old, new, size)                             \
 136         __raw_cmpxchg((ptr), (old), (new), (size), "lock; ")
 137
 138 #define __cmpxchg_local(ptr, old, new, size)                            \
 139         __raw_cmpxchg((ptr), (old), (new), (size), "")
 140
 141 #ifdef CONFIG_X86_32
 142 # include <asm/cmpxchg_32.h>
 143 #else
 144 # include <asm/cmpxchg_64.h>
 145 #endif
 146
 147 #define cmpxchg(ptr, old, new)                                          \
 148         __cmpxchg(ptr, old, new, sizeof(*(ptr)))
 149
 150 #define sync_cmpxchg(ptr, old, new)                                     \
 151         __sync_cmpxchg(ptr, old, new, sizeof(*(ptr)))
 152
 153 #define cmpxchg_local(ptr, old, new)                                    \
 154         __cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
 155
 156 /*
 157  * xadd() adds "inc" to "*ptr" and atomically returns the previous
 158  * value of "*ptr".
 159  *
 160  * xadd() is locked when multiple CPUs are online
 161  */
 162 #define __xadd(ptr, inc, lock)  __xchg_op((ptr), (inc), xadd, lock)
 163 #define xadd(ptr, inc)          __xadd((ptr), (inc), LOCK_PREFIX)
 164
 165 #define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2)                   \
 166 ({                                                                      \
 167         bool __ret;                                                     \
 168         __typeof__(*(p1)) __old1 = (o1), __new1 = (n1);                 \
 169         __typeof__(*(p2)) __old2 = (o2), __new2 = (n2);                 \
 170         BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long));                    \
 171         BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long));                    \
 172         VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long)));            \
 173         VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2));    \
 174         asm volatile(pfx "cmpxchg%c4b %2; sete %0"                      \
 175                      : "=a" (__ret), "+d" (__old2),                     \
 176                        "+m" (*(p1)), "+m" (*(p2))                       \
 177                      : "i" (2 * sizeof(long)), "a" (__old1),            \
 178                        "b" (__new1), "c" (__new2));                     \
 179         __ret;                                                          \
 180 })
 181
 182 #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \
 183         __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2)
 184
 185 #define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \
 186         __cmpxchg_double(, p1, p2, o1, o2, n1, n2)
 187
 188 #endif  /* ASM_X86_CMPXCHG_H */