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/alternative.h> /* Provides LOCK_PREFIX */
   6
   7 /*
   8  * Non-existant functions to indicate usage errors at link time
   9  * (or compile-time if the compiler implements __compiletime_error().
  10  */
  11 extern void __xchg_wrong_size(void)
  12         __compiletime_error("Bad argument size for xchg");
  13 extern void __cmpxchg_wrong_size(void)
  14         __compiletime_error("Bad argument size for cmpxchg");
  15 extern void __xadd_wrong_size(void)
  16         __compiletime_error("Bad argument size for xadd");
  17 extern void __add_wrong_size(void)
  18         __compiletime_error("Bad argument size for add");
  19
  20 /*
  21  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
  22  * -1 because sizeof will never return -1, thereby making those switch
  23  * case statements guaranteeed dead code which the compiler will
  24  * eliminate, and allowing the "missing symbol in the default case" to
  25  * indicate a usage error.
  26  */
  27 #define __X86_CASE_B    1
  28 #define __X86_CASE_W    2
  29 #define __X86_CASE_L    4
  30 #ifdef CONFIG_64BIT
  31 #define __X86_CASE_Q    8
  32 #else
  33 #define __X86_CASE_Q    -1              /* sizeof will never return -1 */
  34 #endif
  35
  36 /*
  37  * An exchange-type operation, which takes a value and a pointer, and
  38  * returns the old value.
  39  */
  40 #define __xchg_op(ptr, arg, op, lock)                                   \
  41         ({                                                              \
  42                 __typeof__ (*(ptr)) __ret = (arg);                      \
  43                 switch (sizeof(*(ptr))) {                               \
  44                 case __X86_CASE_B:                                      \
  45                         asm volatile (lock #op "b %b0, %1\n"            \
  46                                       : "+q" (__ret), "+m" (*(ptr))     \
  47                                       : : "memory", "cc");              \
  48                         break;                                          \
  49                 case __X86_CASE_W:                                      \
  50                         asm volatile (lock #op "w %w0, %1\n"            \
  51                                       : "+r" (__ret), "+m" (*(ptr))     \
  52                                       : : "memory", "cc");              \
  53                         break;                                          \
  54                 case __X86_CASE_L:                                      \
  55                         asm volatile (lock #op "l %0, %1\n"             \
  56                                       : "+r" (__ret), "+m" (*(ptr))     \
  57                                       : : "memory", "cc");              \
  58                         break;                                          \
  59                 case __X86_CASE_Q:                                      \
  60                         asm volatile (lock #op "q %q0, %1\n"            \
  61                                       : "+r" (__ret), "+m" (*(ptr))     \
  62                                       : : "memory", "cc");              \
  63                         break;                                          \
  64                 default:                                                \
  65                         __ ## op ## _wrong_size();                      \
  66                 }                                                       \
  67                 __ret;                                                  \
  68         })
  69
  70 /*
  71  * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
  72  * Since this is generally used to protect other memory information, we
  73  * use "asm volatile" and "memory" clobbers to prevent gcc from moving
  74  * information around.
  75  */
  76 #define xchg(ptr, v)    __xchg_op((ptr), (v), xchg, "")
  77
  78 /*
  79  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  80  * store NEW in MEM.  Return the initial value in MEM.  Success is
  81  * indicated by comparing RETURN with OLD.
  82  */
  83 #define __raw_cmpxchg(ptr, old, new, size, lock)                        \
  84 ({                                                                      \
  85         __typeof__(*(ptr)) __ret;                                       \
  86         __typeof__(*(ptr)) __old = (old);                               \
  87         __typeof__(*(ptr)) __new = (new);                               \
  88         switch (size) {                                                 \
  89         case __X86_CASE_B:                                              \
  90         {                                                               \
  91                 volatile u8 *__ptr = (volatile u8 *)(ptr);              \
  92                 asm volatile(lock "cmpxchgb %2,%1"                      \
  93                              : "=a" (__ret), "+m" (*__ptr)              \
  94                              : "q" (__new), "0" (__old)                 \
  95                              : "memory");                               \
  96                 break;                                                  \
  97         }                                                               \
  98         case __X86_CASE_W:                                              \
  99         {                                                               \
 100                 volatile u16 *__ptr = (volatile u16 *)(ptr);            \
 101                 asm volatile(lock "cmpxchgw %2,%1"                      \
 102                              : "=a" (__ret), "+m" (*__ptr)              \
 103                              : "r" (__new), "0" (__old)                 \
 104                              : "memory");                               \
 105                 break;                                                  \
 106         }                                                               \
 107         case __X86_CASE_L:                                              \
 108         {                                                               \
 109                 volatile u32 *__ptr = (volatile u32 *)(ptr);            \
 110                 asm volatile(lock "cmpxchgl %2,%1"                      \
 111                              : "=a" (__ret), "+m" (*__ptr)              \
 112                              : "r" (__new), "0" (__old)                 \
 113                              : "memory");                               \
 114                 break;                                                  \
 115         }                                                               \
 116         case __X86_CASE_Q:                                              \
 117         {                                                               \
 118                 volatile u64 *__ptr = (volatile u64 *)(ptr);            \
 119                 asm volatile(lock "cmpxchgq %2,%1"                      \
 120                              : "=a" (__ret), "+m" (*__ptr)              \
 121                              : "r" (__new), "0" (__old)                 \
 122                              : "memory");                               \
 123                 break;                                                  \
 124         }                                                               \
 125         default:                                                        \
 126                 __cmpxchg_wrong_size();                                 \
 127         }                                                               \
 128         __ret;                                                          \
 129 })
 130
 131 #define __cmpxchg(ptr, old, new, size)                                  \
 132         __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
 133
 134 #define __sync_cmpxchg(ptr, old, new, size)                             \
 135         __raw_cmpxchg((ptr), (old), (new), (size), "lock; ")
 136
 137 #define __cmpxchg_local(ptr, old, new, size)                            \
 138         __raw_cmpxchg((ptr), (old), (new), (size), "")
 139
 140 #ifdef CONFIG_X86_32
 141 # include <asm/cmpxchg_32.h>
 142 #else
 143 # include <asm/cmpxchg_64.h>
 144 #endif
 145
 146 #define cmpxchg(ptr, old, new)                                          \
 147         __cmpxchg(ptr, old, new, sizeof(*(ptr)))
 148
 149 #define sync_cmpxchg(ptr, old, new)                                     \
 150         __sync_cmpxchg(ptr, old, new, sizeof(*(ptr)))
 151
 152 #define cmpxchg_local(ptr, old, new)                                    \
 153         __cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
 154
 155 /*
 156  * xadd() adds "inc" to "*ptr" and atomically returns the previous
 157  * value of "*ptr".
 158  *
 159  * xadd() is locked when multiple CPUs are online
 160  * xadd_sync() is always locked
 161  * xadd_local() is never locked
 162  */
 163 #define __xadd(ptr, inc, lock)  __xchg_op((ptr), (inc), xadd, lock)
 164 #define xadd(ptr, inc)          __xadd((ptr), (inc), LOCK_PREFIX)
 165 #define xadd_sync(ptr, inc)     __xadd((ptr), (inc), "lock; ")
 166 #define xadd_local(ptr, inc)    __xadd((ptr), (inc), "")
 167
 168 #define __add(ptr, inc, lock)                                           \
 169         ({                                                              \
 170                 __typeof__ (*(ptr)) __ret = (inc);                      \
 171                 switch (sizeof(*(ptr))) {                               \
 172                 case __X86_CASE_B:                                      \
 173                         asm volatile (lock "addb %b1, %0\n"             \
 174                                       : "+m" (*(ptr)) : "qi" (inc)      \
 175                                       : "memory", "cc");                \
 176                         break;                                          \
 177                 case __X86_CASE_W:                                      \
 178                         asm volatile (lock "addw %w1, %0\n"             \
 179                                       : "+m" (*(ptr)) : "ri" (inc)      \
 180                                       : "memory", "cc");                \
 181                         break;                                          \
 182                 case __X86_CASE_L:                                      \
 183                         asm volatile (lock "addl %1, %0\n"              \
 184                                       : "+m" (*(ptr)) : "ri" (inc)      \
 185                                       : "memory", "cc");                \
 186                         break;                                          \
 187                 case __X86_CASE_Q:                                      \
 188                         asm volatile (lock "addq %1, %0\n"              \
 189                                       : "+m" (*(ptr)) : "ri" (inc)      \
 190                                       : "memory", "cc");                \
 191                         break;                                          \
 192                 default:                                                \
 193                         __add_wrong_size();                             \
 194                 }                                                       \
 195                 __ret;                                                  \
 196         })
 197
 198 /*
 199  * add_*() adds "inc" to "*ptr"
 200  *
 201  * __add() takes a lock prefix
 202  * add_smp() is locked when multiple CPUs are online
 203  * add_sync() is always locked
 204  */
 205 #define add_smp(ptr, inc)       __add((ptr), (inc), LOCK_PREFIX)
 206 #define add_sync(ptr, inc)      __add((ptr), (inc), "lock; ")
 207
 208 #define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2)                   \
 209 ({                                                                      \
 210         bool __ret;                                                     \
 211         __typeof__(*(p1)) __old1 = (o1), __new1 = (n1);                 \
 212         __typeof__(*(p2)) __old2 = (o2), __new2 = (n2);                 \
 213         BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long));                    \
 214         BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long));                    \
 215         VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long)));            \
 216         VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2));    \
 217         asm volatile(pfx "cmpxchg%c4b %2; sete %0"                      \
 218                      : "=a" (__ret), "+d" (__old2),                     \
 219                        "+m" (*(p1)), "+m" (*(p2))                       \
 220                      : "i" (2 * sizeof(long)), "a" (__old1),            \
 221                        "b" (__new1), "c" (__new2));                     \
 222         __ret;                                                          \
 223 })
 224
 225 #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \
 226         __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2)
 227
 228 #define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \
 229         __cmpxchg_double(, p1, p2, o1, o2, n1, n2)
 230
 231 #endif  /* ASM_X86_CMPXCHG_H */