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 #define __HAVE_ARCH_CMPXCHG 1
   8
   9 /*
  10  * Non-existant functions to indicate usage errors at link time
  11  * (or compile-time if the compiler implements __compiletime_error().
  12  */
  13 extern void __xchg_wrong_size(void)
  14         __compiletime_error("Bad argument size for xchg");
  15 extern void __cmpxchg_wrong_size(void)
  16         __compiletime_error("Bad argument size for cmpxchg");
  17 extern void __xadd_wrong_size(void)
  18         __compiletime_error("Bad argument size for xadd");
  19 extern void __add_wrong_size(void)
  20         __compiletime_error("Bad argument size for add");
  21
  22 /*
  23  * Constants for operation sizes. On 32-bit, the 64-bit size it set to
  24  * -1 because sizeof will never return -1, thereby making those switch
  25  * case statements guaranteeed dead code which the compiler will
  26  * eliminate, and allowing the "missing symbol in the default case" to
  27  * indicate a usage error.
  28  */
  29 #define __X86_CASE_B    1
  30 #define __X86_CASE_W    2
  31 #define __X86_CASE_L    4
  32 #ifdef CONFIG_64BIT
  33 #define __X86_CASE_Q    8
  34 #else
  35 #define __X86_CASE_Q    -1              /* sizeof will never return -1 */
  36 #endif
  37
  38 /*
  39  * An exchange-type operation, which takes a value and a pointer, and
  40  * returns the old value.
  41  */
  42 #define __xchg_op(ptr, arg, op, lock)                                   \
  43         ({                                                              \
  44                 __typeof__ (*(ptr)) __ret = (arg);                      \
  45                 switch (sizeof(*(ptr))) {                               \
  46                 case __X86_CASE_B:                                      \
  47                         asm volatile (lock #op "b %b0, %1\n"            \
  48                                       : "+q" (__ret), "+m" (*(ptr))     \
  49                                       : : "memory", "cc");              \
  50                         break;                                          \
  51                 case __X86_CASE_W:                                      \
  52                         asm volatile (lock #op "w %w0, %1\n"            \
  53                                       : "+r" (__ret), "+m" (*(ptr))     \
  54                                       : : "memory", "cc");              \
  55                         break;                                          \
  56                 case __X86_CASE_L:                                      \
  57                         asm volatile (lock #op "l %0, %1\n"             \
  58                                       : "+r" (__ret), "+m" (*(ptr))     \
  59                                       : : "memory", "cc");              \
  60                         break;                                          \
  61                 case __X86_CASE_Q:                                      \
  62                         asm volatile (lock #op "q %q0, %1\n"            \
  63                                       : "+r" (__ret), "+m" (*(ptr))     \
  64                                       : : "memory", "cc");              \
  65                         break;                                          \
  66                 default:                                                \
  67                         __ ## op ## _wrong_size();                      \
  68                 }                                                       \
  69                 __ret;                                                  \
  70         })
  71
  72 /*
  73  * Note: no "lock" prefix even on SMP: xchg always implies lock anyway.
  74  * Since this is generally used to protect other memory information, we
  75  * use "asm volatile" and "memory" clobbers to prevent gcc from moving
  76  * information around.
  77  */
  78 #define xchg(ptr, v)    __xchg_op((ptr), (v), xchg, "")
  79
  80 /*
  81  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
  82  * store NEW in MEM.  Return the initial value in MEM.  Success is
  83  * indicated by comparing RETURN with OLD.
  84  */
  85 #define __raw_cmpxchg(ptr, old, new, size, lock)                        \
  86 ({                                                                      \
  87         __typeof__(*(ptr)) __ret;                                       \
  88         __typeof__(*(ptr)) __old = (old);                               \
  89         __typeof__(*(ptr)) __new = (new);                               \
  90         switch (size) {                                                 \
  91         case __X86_CASE_B:                                              \
  92         {                                                               \
  93                 volatile u8 *__ptr = (volatile u8 *)(ptr);              \
  94                 asm volatile(lock "cmpxchgb %2,%1"                      \
  95                              : "=a" (__ret), "+m" (*__ptr)              \
  96                              : "q" (__new), "0" (__old)                 \
  97                              : "memory");                               \
  98                 break;                                                  \
  99         }                                                               \
 100         case __X86_CASE_W:                                              \
 101         {                                                               \
 102                 volatile u16 *__ptr = (volatile u16 *)(ptr);            \
 103                 asm volatile(lock "cmpxchgw %2,%1"                      \
 104                              : "=a" (__ret), "+m" (*__ptr)              \
 105                              : "r" (__new), "0" (__old)                 \
 106                              : "memory");                               \
 107                 break;                                                  \
 108         }                                                               \
 109         case __X86_CASE_L:                                              \
 110         {                                                               \
 111                 volatile u32 *__ptr = (volatile u32 *)(ptr);            \
 112                 asm volatile(lock "cmpxchgl %2,%1"                      \
 113                              : "=a" (__ret), "+m" (*__ptr)              \
 114                              : "r" (__new), "0" (__old)                 \
 115                              : "memory");                               \
 116                 break;                                                  \
 117         }                                                               \
 118         case __X86_CASE_Q:                                              \
 119         {                                                               \
 120                 volatile u64 *__ptr = (volatile u64 *)(ptr);            \
 121                 asm volatile(lock "cmpxchgq %2,%1"                      \
 122                              : "=a" (__ret), "+m" (*__ptr)              \
 123                              : "r" (__new), "0" (__old)                 \
 124                              : "memory");                               \
 125                 break;                                                  \
 126         }                                                               \
 127         default:                                                        \
 128                 __cmpxchg_wrong_size();                                 \
 129         }                                                               \
 130         __ret;                                                          \
 131 })
 132
 133 #define __cmpxchg(ptr, old, new, size)                                  \
 134         __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX)
 135
 136 #define __sync_cmpxchg(ptr, old, new, size)                             \
 137         __raw_cmpxchg((ptr), (old), (new), (size), "lock; ")
 138
 139 #define __cmpxchg_local(ptr, old, new, size)                            \
 140         __raw_cmpxchg((ptr), (old), (new), (size), "")
 141
 142 #ifdef CONFIG_X86_32
 143 # include <asm/cmpxchg_32.h>
 144 #else
 145 # include <asm/cmpxchg_64.h>
 146 #endif
 147
 148 #define cmpxchg(ptr, old, new)                                          \
 149         __cmpxchg(ptr, old, new, sizeof(*(ptr)))
 150
 151 #define sync_cmpxchg(ptr, old, new)                                     \
 152         __sync_cmpxchg(ptr, old, new, sizeof(*(ptr)))
 153
 154 #define cmpxchg_local(ptr, old, new)                                    \
 155         __cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
 156
 157 /*
 158  * xadd() adds "inc" to "*ptr" and atomically returns the previous
 159  * value of "*ptr".
 160  *
 161  * xadd() is locked when multiple CPUs are online
 162  * xadd_sync() is always locked
 163  * xadd_local() is never locked
 164  */
 165 #define __xadd(ptr, inc, lock)  __xchg_op((ptr), (inc), xadd, lock)
 166 #define xadd(ptr, inc)          __xadd((ptr), (inc), LOCK_PREFIX)
 167 #define xadd_sync(ptr, inc)     __xadd((ptr), (inc), "lock; ")
 168 #define xadd_local(ptr, inc)    __xadd((ptr), (inc), "")
 169
 170 #define __add(ptr, inc, lock)                                           \
 171         ({                                                              \
 172                 __typeof__ (*(ptr)) __ret = (inc);                      \
 173                 switch (sizeof(*(ptr))) {                               \
 174                 case __X86_CASE_B:                                      \
 175                         asm volatile (lock "addb %b1, %0\n"             \
 176                                       : "+m" (*(ptr)) : "qi" (inc)      \
 177                                       : "memory", "cc");                \
 178                         break;                                          \
 179                 case __X86_CASE_W:                                      \
 180                         asm volatile (lock "addw %w1, %0\n"             \
 181                                       : "+m" (*(ptr)) : "ri" (inc)      \
 182                                       : "memory", "cc");                \
 183                         break;                                          \
 184                 case __X86_CASE_L:                                      \
 185                         asm volatile (lock "addl %1, %0\n"              \
 186                                       : "+m" (*(ptr)) : "ri" (inc)      \
 187                                       : "memory", "cc");                \
 188                         break;                                          \
 189                 case __X86_CASE_Q:                                      \
 190                         asm volatile (lock "addq %1, %0\n"              \
 191                                       : "+m" (*(ptr)) : "ri" (inc)      \
 192                                       : "memory", "cc");                \
 193                         break;                                          \
 194                 default:                                                \
 195                         __add_wrong_size();                             \
 196                 }                                                       \
 197                 __ret;                                                  \
 198         })
 199
 200 /*
 201  * add_*() adds "inc" to "*ptr"
 202  *
 203  * __add() takes a lock prefix
 204  * add_smp() is locked when multiple CPUs are online
 205  * add_sync() is always locked
 206  */
 207 #define add_smp(ptr, inc)       __add((ptr), (inc), LOCK_PREFIX)
 208 #define add_sync(ptr, inc)      __add((ptr), (inc), "lock; ")
 209
 210 #define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2)                   \
 211 ({                                                                      \
 212         bool __ret;                                                     \
 213         __typeof__(*(p1)) __old1 = (o1), __new1 = (n1);                 \
 214         __typeof__(*(p2)) __old2 = (o2), __new2 = (n2);                 \
 215         BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long));                    \
 216         BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long));                    \
 217         VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long)));            \
 218         VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2));    \
 219         asm volatile(pfx "cmpxchg%c4b %2; sete %0"                      \
 220                      : "=a" (__ret), "+d" (__old2),                     \
 221                        "+m" (*(p1)), "+m" (*(p2))                       \
 222                      : "i" (2 * sizeof(long)), "a" (__old1),            \
 223                        "b" (__new1), "c" (__new2));                     \
 224         __ret;                                                          \
 225 })
 226
 227 #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \
 228         __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2)
 229
 230 #define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \
 231         __cmpxchg_double(, p1, p2, o1, o2, n1, n2)
 232
 233 #endif  /* ASM_X86_CMPXCHG_H */