arch/arm/include/asm/cmpxchg.h

   1 #ifndef __ASM_ARM_CMPXCHG_H
   2 #define __ASM_ARM_CMPXCHG_H
   3
   4 #include <linux/irqflags.h>
   5 #include <linux/prefetch.h>
   6 #include <asm/barrier.h>
   7
   8 #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
   9 /*
  10  * On the StrongARM, "swp" is terminally broken since it bypasses the
  11  * cache totally.  This means that the cache becomes inconsistent, and,
  12  * since we use normal loads/stores as well, this is really bad.
  13  * Typically, this causes oopsen in filp_close, but could have other,
  14  * more disastrous effects.  There are two work-arounds:
  15  *  1. Disable interrupts and emulate the atomic swap
  16  *  2. Clean the cache, perform atomic swap, flush the cache
  17  *
  18  * We choose (1) since its the "easiest" to achieve here and is not
  19  * dependent on the processor type.
  20  *
  21  * NOTE that this solution won't work on an SMP system, so explcitly
  22  * forbid it here.
  23  */
  24 #define swp_is_buggy
  25 #endif
  26
  27 static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
  28 {
  29         extern void __bad_xchg(volatile void *, int);
  30         unsigned long ret;
  31 #ifdef swp_is_buggy
  32         unsigned long flags;
  33 #endif
  34 #if __LINUX_ARM_ARCH__ >= 6
  35         unsigned int tmp;
  36 #endif
  37
  38         prefetchw((const void *)ptr);
  39
  40         switch (size) {
  41 #if __LINUX_ARM_ARCH__ >= 6
  42 #ifndef CONFIG_CPU_V6 /* MIN ARCH >= V6K */
  43         case 1:
  44                 asm volatile("@ __xchg1\n"
  45                 "1:     ldrexb  %0, [%3]\n"
  46                 "       strexb  %1, %2, [%3]\n"
  47                 "       teq     %1, #0\n"
  48                 "       bne     1b"
  49                         : "=&r" (ret), "=&r" (tmp)
  50                         : "r" (x), "r" (ptr)
  51                         : "memory", "cc");
  52                 break;
  53         case 2:
  54                 asm volatile("@ __xchg2\n"
  55                 "1:     ldrexh  %0, [%3]\n"
  56                 "       strexh  %1, %2, [%3]\n"
  57                 "       teq     %1, #0\n"
  58                 "       bne     1b"
  59                         : "=&r" (ret), "=&r" (tmp)
  60                         : "r" (x), "r" (ptr)
  61                         : "memory", "cc");
  62                 break;
  63 #endif
  64         case 4:
  65                 asm volatile("@ __xchg4\n"
  66                 "1:     ldrex   %0, [%3]\n"
  67                 "       strex   %1, %2, [%3]\n"
  68                 "       teq     %1, #0\n"
  69                 "       bne     1b"
  70                         : "=&r" (ret), "=&r" (tmp)
  71                         : "r" (x), "r" (ptr)
  72                         : "memory", "cc");
  73                 break;
  74 #elif defined(swp_is_buggy)
  75 #ifdef CONFIG_SMP
  76 #error SMP is not supported on this platform
  77 #endif
  78         case 1:
  79                 raw_local_irq_save(flags);
  80                 ret = *(volatile unsigned char *)ptr;
  81                 *(volatile unsigned char *)ptr = x;
  82                 raw_local_irq_restore(flags);
  83                 break;
  84
  85         case 4:
  86                 raw_local_irq_save(flags);
  87                 ret = *(volatile unsigned long *)ptr;
  88                 *(volatile unsigned long *)ptr = x;
  89                 raw_local_irq_restore(flags);
  90                 break;
  91 #else
  92         case 1:
  93                 asm volatile("@ __xchg1\n"
  94                 "       swpb    %0, %1, [%2]"
  95                         : "=&r" (ret)
  96                         : "r" (x), "r" (ptr)
  97                         : "memory", "cc");
  98                 break;
  99         case 4:
 100                 asm volatile("@ __xchg4\n"
 101                 "       swp     %0, %1, [%2]"
 102                         : "=&r" (ret)
 103                         : "r" (x), "r" (ptr)
 104                         : "memory", "cc");
 105                 break;
 106 #endif
 107         default:
 108                 /* Cause a link-time error, the xchg() size is not supported */
 109                 __bad_xchg(ptr, size), ret = 0;
 110                 break;
 111         }
 112
 113         return ret;
 114 }
 115
 116 #define xchg_relaxed(ptr, x) ({                                         \
 117         (__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr),           \
 118                                    sizeof(*(ptr)));                     \
 119 })
 120
 121 #include <asm-generic/cmpxchg-local.h>
 122
 123 #if __LINUX_ARM_ARCH__ < 6
 124 /* min ARCH < ARMv6 */
 125
 126 #ifdef CONFIG_SMP
 127 #error "SMP is not supported on this platform"
 128 #endif
 129
 130 #define xchg xchg_relaxed
 131
 132 /*
 133  * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
 134  * them available.
 135  */
 136 #define cmpxchg_local(ptr, o, n) ({                                     \
 137         (__typeof(*ptr))__cmpxchg_local_generic((ptr),                  \
 138                                                 (unsigned long)(o),     \
 139                                                 (unsigned long)(n),     \
 140                                                 sizeof(*(ptr)));        \
 141 })
 142
 143 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 144
 145 #include <asm-generic/cmpxchg.h>
 146
 147 #else   /* min ARCH >= ARMv6 */
 148
 149 extern void __bad_cmpxchg(volatile void *ptr, int size);
 150
 151 /*
 152  * cmpxchg only support 32-bits operands on ARMv6.
 153  */
 154
 155 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 156                                       unsigned long new, int size)
 157 {
 158         unsigned long oldval, res;
 159
 160         prefetchw((const void *)ptr);
 161
 162         switch (size) {
 163 #ifndef CONFIG_CPU_V6   /* min ARCH >= ARMv6K */
 164         case 1:
 165                 do {
 166                         asm volatile("@ __cmpxchg1\n"
 167                         "       ldrexb  %1, [%2]\n"
 168                         "       mov     %0, #0\n"
 169                         "       teq     %1, %3\n"
 170                         "       strexbeq %0, %4, [%2]\n"
 171                                 : "=&r" (res), "=&r" (oldval)
 172                                 : "r" (ptr), "Ir" (old), "r" (new)
 173                                 : "memory", "cc");
 174                 } while (res);
 175                 break;
 176         case 2:
 177                 do {
 178                         asm volatile("@ __cmpxchg1\n"
 179                         "       ldrexh  %1, [%2]\n"
 180                         "       mov     %0, #0\n"
 181                         "       teq     %1, %3\n"
 182                         "       strexheq %0, %4, [%2]\n"
 183                                 : "=&r" (res), "=&r" (oldval)
 184                                 : "r" (ptr), "Ir" (old), "r" (new)
 185                                 : "memory", "cc");
 186                 } while (res);
 187                 break;
 188 #endif
 189         case 4:
 190                 do {
 191                         asm volatile("@ __cmpxchg4\n"
 192                         "       ldrex   %1, [%2]\n"
 193                         "       mov     %0, #0\n"
 194                         "       teq     %1, %3\n"
 195                         "       strexeq %0, %4, [%2]\n"
 196                                 : "=&r" (res), "=&r" (oldval)
 197                                 : "r" (ptr), "Ir" (old), "r" (new)
 198                                 : "memory", "cc");
 199                 } while (res);
 200                 break;
 201         default:
 202                 __bad_cmpxchg(ptr, size);
 203                 oldval = 0;
 204         }
 205
 206         return oldval;
 207 }
 208
 209 #define cmpxchg_relaxed(ptr,o,n) ({                                     \
 210         (__typeof__(*(ptr)))__cmpxchg((ptr),                            \
 211                                       (unsigned long)(o),               \
 212                                       (unsigned long)(n),               \
 213                                       sizeof(*(ptr)));                  \
 214 })
 215
 216 static inline unsigned long __cmpxchg_local(volatile void *ptr,
 217                                             unsigned long old,
 218                                             unsigned long new, int size)
 219 {
 220         unsigned long ret;
 221
 222         switch (size) {
 223 #ifdef CONFIG_CPU_V6    /* min ARCH == ARMv6 */
 224         case 1:
 225         case 2:
 226                 ret = __cmpxchg_local_generic(ptr, old, new, size);
 227                 break;
 228 #endif
 229         default:
 230                 ret = __cmpxchg(ptr, old, new, size);
 231         }
 232
 233         return ret;
 234 }
 235
 236 #define cmpxchg_local(ptr, o, n) ({                                     \
 237         (__typeof(*ptr))__cmpxchg_local((ptr),                          \
 238                                         (unsigned long)(o),             \
 239                                         (unsigned long)(n),             \
 240                                         sizeof(*(ptr)));                \
 241 })
 242
 243 static inline unsigned long long __cmpxchg64(unsigned long long *ptr,
 244                                              unsigned long long old,
 245                                              unsigned long long new)
 246 {
 247         unsigned long long oldval;
 248         unsigned long res;
 249
 250         prefetchw(ptr);
 251
 252         __asm__ __volatile__(
 253 "1:     ldrexd          %1, %H1, [%3]\n"
 254 "       teq             %1, %4\n"
 255 "       teqeq           %H1, %H4\n"
 256 "       bne             2f\n"
 257 "       strexd          %0, %5, %H5, [%3]\n"
 258 "       teq             %0, #0\n"
 259 "       bne             1b\n"
 260 "2:"
 261         : "=&r" (res), "=&r" (oldval), "+Qo" (*ptr)
 262         : "r" (ptr), "r" (old), "r" (new)
 263         : "cc");
 264
 265         return oldval;
 266 }
 267
 268 #define cmpxchg64_relaxed(ptr, o, n) ({                                 \
 269         (__typeof__(*(ptr)))__cmpxchg64((ptr),                          \
 270                                         (unsigned long long)(o),        \
 271                                         (unsigned long long)(n));       \
 272 })
 273
 274 #define cmpxchg64_local(ptr, o, n) cmpxchg64_relaxed((ptr), (o), (n))
 275
 276 #endif  /* __LINUX_ARM_ARCH__ >= 6 */
 277
 278 #endif /* __ASM_ARM_CMPXCHG_H */