include/asm-i386/cmpxchg.h

   1 #ifndef __ASM_CMPXCHG_H
   2 #define __ASM_CMPXCHG_H
   3
   4 #include <linux/bitops.h> /* for LOCK_PREFIX */
   5
   6 #define xchg(ptr,v) ((__typeof__(*(ptr)))__xchg((unsigned long)(v),(ptr),sizeof(*(ptr))))
   7
   8 struct __xchg_dummy { unsigned long a[100]; };
   9 #define __xg(x) ((struct __xchg_dummy *)(x))
  10
  11
  12 #ifdef CONFIG_X86_CMPXCHG64
  13
  14 /*
  15  * The semantics of XCHGCMP8B are a bit strange, this is why
  16  * there is a loop and the loading of %%eax and %%edx has to
  17  * be inside. This inlines well in most cases, the cached
  18  * cost is around ~38 cycles. (in the future we might want
  19  * to do an SIMD/3DNOW!/MMX/FPU 64-bit store here, but that
  20  * might have an implicit FPU-save as a cost, so it's not
  21  * clear which path to go.)
  22  *
  23  * cmpxchg8b must be used with the lock prefix here to allow
  24  * the instruction to be executed atomically, see page 3-102
  25  * of the instruction set reference 24319102.pdf. We need
  26  * the reader side to see the coherent 64bit value.
  27  */
  28 static inline void __set_64bit (unsigned long long * ptr,
  29                 unsigned int low, unsigned int high)
  30 {
  31         __asm__ __volatile__ (
  32                 "\n1:\t"
  33                 "movl (%0), %%eax\n\t"
  34                 "movl 4(%0), %%edx\n\t"
  35                 "lock cmpxchg8b (%0)\n\t"
  36                 "jnz 1b"
  37                 : /* no outputs */
  38                 :       "D"(ptr),
  39                         "b"(low),
  40                         "c"(high)
  41                 :       "ax","dx","memory");
  42 }
  43
  44 static inline void __set_64bit_constant (unsigned long long *ptr,
  45                                                  unsigned long long value)
  46 {
  47         __set_64bit(ptr,(unsigned int)(value), (unsigned int)((value)>>32ULL));
  48 }
  49 #define ll_low(x)       *(((unsigned int*)&(x))+0)
  50 #define ll_high(x)      *(((unsigned int*)&(x))+1)
  51
  52 static inline void __set_64bit_var (unsigned long long *ptr,
  53                          unsigned long long value)
  54 {
  55         __set_64bit(ptr,ll_low(value), ll_high(value));
  56 }
  57
  58 #define set_64bit(ptr,value) \
  59 (__builtin_constant_p(value) ? \
  60  __set_64bit_constant(ptr, value) : \
  61  __set_64bit_var(ptr, value) )
  62
  63 #define _set_64bit(ptr,value) \
  64 (__builtin_constant_p(value) ? \
  65  __set_64bit(ptr, (unsigned int)(value), (unsigned int)((value)>>32ULL) ) : \
  66  __set_64bit(ptr, ll_low(value), ll_high(value)) )
  67
  68 #endif
  69
  70 /*
  71  * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
  72  * Note 2: xchg has side effect, so that attribute volatile is necessary,
  73  *        but generally the primitive is invalid, *ptr is output argument. --ANK
  74  */
  75 static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
  76 {
  77         switch (size) {
  78                 case 1:
  79                         __asm__ __volatile__("xchgb %b0,%1"
  80                                 :"=q" (x)
  81                                 :"m" (*__xg(ptr)), "0" (x)
  82                                 :"memory");
  83                         break;
  84                 case 2:
  85                         __asm__ __volatile__("xchgw %w0,%1"
  86                                 :"=r" (x)
  87                                 :"m" (*__xg(ptr)), "0" (x)
  88                                 :"memory");
  89                         break;
  90                 case 4:
  91                         __asm__ __volatile__("xchgl %0,%1"
  92                                 :"=r" (x)
  93                                 :"m" (*__xg(ptr)), "0" (x)
  94                                 :"memory");
  95                         break;
  96         }
  97         return x;
  98 }
  99
 100 /*
 101  * Atomic compare and exchange.  Compare OLD with MEM, if identical,
 102  * store NEW in MEM.  Return the initial value in MEM.  Success is
 103  * indicated by comparing RETURN with OLD.
 104  */
 105
 106 #ifdef CONFIG_X86_CMPXCHG
 107 #define __HAVE_ARCH_CMPXCHG 1
 108 #define cmpxchg(ptr,o,n)\
 109         ((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
 110                                         (unsigned long)(n),sizeof(*(ptr))))
 111 #define sync_cmpxchg(ptr,o,n)\
 112         ((__typeof__(*(ptr)))__sync_cmpxchg((ptr),(unsigned long)(o),\
 113                                         (unsigned long)(n),sizeof(*(ptr))))
 114 #define cmpxchg_local(ptr,o,n)\
 115         ((__typeof__(*(ptr)))__cmpxchg_local((ptr),(unsigned long)(o),\
 116                                         (unsigned long)(n),sizeof(*(ptr))))
 117 #endif
 118
 119 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 120                                       unsigned long new, int size)
 121 {
 122         unsigned long prev;
 123         switch (size) {
 124         case 1:
 125                 __asm__ __volatile__(LOCK_PREFIX "cmpxchgb %b1,%2"
 126                                      : "=a"(prev)
 127                                      : "q"(new), "m"(*__xg(ptr)), "0"(old)
 128                                      : "memory");
 129                 return prev;
 130         case 2:
 131                 __asm__ __volatile__(LOCK_PREFIX "cmpxchgw %w1,%2"
 132                                      : "=a"(prev)
 133                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 134                                      : "memory");
 135                 return prev;
 136         case 4:
 137                 __asm__ __volatile__(LOCK_PREFIX "cmpxchgl %1,%2"
 138                                      : "=a"(prev)
 139                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 140                                      : "memory");
 141                 return prev;
 142         }
 143         return old;
 144 }
 145
 146 /*
 147  * Always use locked operations when touching memory shared with a
 148  * hypervisor, since the system may be SMP even if the guest kernel
 149  * isn't.
 150  */
 151 static inline unsigned long __sync_cmpxchg(volatile void *ptr,
 152                                             unsigned long old,
 153                                             unsigned long new, int size)
 154 {
 155         unsigned long prev;
 156         switch (size) {
 157         case 1:
 158                 __asm__ __volatile__("lock; cmpxchgb %b1,%2"
 159                                      : "=a"(prev)
 160                                      : "q"(new), "m"(*__xg(ptr)), "0"(old)
 161                                      : "memory");
 162                 return prev;
 163         case 2:
 164                 __asm__ __volatile__("lock; cmpxchgw %w1,%2"
 165                                      : "=a"(prev)
 166                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 167                                      : "memory");
 168                 return prev;
 169         case 4:
 170                 __asm__ __volatile__("lock; cmpxchgl %1,%2"
 171                                      : "=a"(prev)
 172                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 173                                      : "memory");
 174                 return prev;
 175         }
 176         return old;
 177 }
 178
 179 static inline unsigned long __cmpxchg_local(volatile void *ptr,
 180                         unsigned long old, unsigned long new, int size)
 181 {
 182         unsigned long prev;
 183         switch (size) {
 184         case 1:
 185                 __asm__ __volatile__("cmpxchgb %b1,%2"
 186                                      : "=a"(prev)
 187                                      : "q"(new), "m"(*__xg(ptr)), "0"(old)
 188                                      : "memory");
 189                 return prev;
 190         case 2:
 191                 __asm__ __volatile__("cmpxchgw %w1,%2"
 192                                      : "=a"(prev)
 193                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 194                                      : "memory");
 195                 return prev;
 196         case 4:
 197                 __asm__ __volatile__("cmpxchgl %1,%2"
 198                                      : "=a"(prev)
 199                                      : "r"(new), "m"(*__xg(ptr)), "0"(old)
 200                                      : "memory");
 201                 return prev;
 202         }
 203         return old;
 204 }
 205
 206 #ifndef CONFIG_X86_CMPXCHG
 207 /*
 208  * Building a kernel capable running on 80386. It may be necessary to
 209  * simulate the cmpxchg on the 80386 CPU. For that purpose we define
 210  * a function for each of the sizes we support.
 211  */
 212
 213 extern unsigned long cmpxchg_386_u8(volatile void *, u8, u8);
 214 extern unsigned long cmpxchg_386_u16(volatile void *, u16, u16);
 215 extern unsigned long cmpxchg_386_u32(volatile void *, u32, u32);
 216
 217 static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old,
 218                                       unsigned long new, int size)
 219 {
 220         switch (size) {
 221         case 1:
 222                 return cmpxchg_386_u8(ptr, old, new);
 223         case 2:
 224                 return cmpxchg_386_u16(ptr, old, new);
 225         case 4:
 226                 return cmpxchg_386_u32(ptr, old, new);
 227         }
 228         return old;
 229 }
 230
 231 #define cmpxchg(ptr,o,n)                                                \
 232 ({                                                                      \
 233         __typeof__(*(ptr)) __ret;                                       \
 234         if (likely(boot_cpu_data.x86 > 3))                              \
 235                 __ret = __cmpxchg((ptr), (unsigned long)(o),            \
 236                                         (unsigned long)(n), sizeof(*(ptr))); \
 237         else                                                            \
 238                 __ret = cmpxchg_386((ptr), (unsigned long)(o),          \
 239                                         (unsigned long)(n), sizeof(*(ptr))); \
 240         __ret;                                                          \
 241 })
 242 #define cmpxchg_local(ptr,o,n)                                          \
 243 ({                                                                      \
 244         __typeof__(*(ptr)) __ret;                                       \
 245         if (likely(boot_cpu_data.x86 > 3))                              \
 246                 __ret = __cmpxchg_local((ptr), (unsigned long)(o),      \
 247                                         (unsigned long)(n), sizeof(*(ptr))); \
 248         else                                                            \
 249                 __ret = cmpxchg_386((ptr), (unsigned long)(o),          \
 250                                         (unsigned long)(n), sizeof(*(ptr))); \
 251         __ret;                                                          \
 252 })
 253 #endif
 254
 255 #ifdef CONFIG_X86_CMPXCHG64
 256
 257 static inline unsigned long long __cmpxchg64(volatile void *ptr, unsigned long long old,
 258                                       unsigned long long new)
 259 {
 260         unsigned long long prev;
 261         __asm__ __volatile__(LOCK_PREFIX "cmpxchg8b %3"
 262                              : "=A"(prev)
 263                              : "b"((unsigned long)new),
 264                                "c"((unsigned long)(new >> 32)),
 265                                "m"(*__xg(ptr)),
 266                                "0"(old)
 267                              : "memory");
 268         return prev;
 269 }
 270
 271 static inline unsigned long long __cmpxchg64_local(volatile void *ptr,
 272                         unsigned long long old, unsigned long long new)
 273 {
 274         unsigned long long prev;
 275         __asm__ __volatile__("cmpxchg8b %3"
 276                              : "=A"(prev)
 277                              : "b"((unsigned long)new),
 278                                "c"((unsigned long)(new >> 32)),
 279                                "m"(*__xg(ptr)),
 280                                "0"(old)
 281                              : "memory");
 282         return prev;
 283 }
 284
 285 #define cmpxchg64(ptr,o,n)\
 286         ((__typeof__(*(ptr)))__cmpxchg64((ptr),(unsigned long long)(o),\
 287                                         (unsigned long long)(n)))
 288 #define cmpxchg64_local(ptr,o,n)\
 289         ((__typeof__(*(ptr)))__cmpxchg64_local((ptr),(unsigned long long)(o),\
 290                                         (unsigned long long)(n)))
 291 #endif
 292
 293 #endif