src/util/u_atomic.h

   1 /**
   2  * Many similar implementations exist. See for example libwsbm
   3  * or the linux kernel include/atomic.h
   4  *
   5  * No copyright claimed on this file.
   6  *
   7  */
   8
   9 #ifndef U_ATOMIC_H
  10 #define U_ATOMIC_H
  11
  12 #include <stdbool.h>
  13
  14 /* Favor OS-provided implementations.
  15  *
  16  * Where no OS-provided implementation is available, fall back to
  17  * locally coded assembly, compiler intrinsic or ultimately a
  18  * mutex-based implementation.
  19  */
  20 #if defined(__sun)
  21 #define PIPE_ATOMIC_OS_SOLARIS
  22 #elif defined(_MSC_VER)
  23 #define PIPE_ATOMIC_MSVC_INTRINSIC
  24 #elif defined(__GNUC__)
  25 #define PIPE_ATOMIC_GCC_INTRINSIC
  26 #else
  27 #error "Unsupported platform"
  28 #endif
  29
  30
  31 /* Implementation using GCC-provided synchronization intrinsics
  32  */
  33 #if defined(PIPE_ATOMIC_GCC_INTRINSIC)
  34
  35 #define PIPE_ATOMIC "GCC Sync Intrinsics"
  36
  37 #define p_atomic_set(_v, _i) (*(_v) = (_i))
  38 #define p_atomic_read(_v) (*(_v))
  39 #define p_atomic_dec_zero(v) (__sync_sub_and_fetch((v), 1) == 0)
  40 #define p_atomic_inc(v) (void) __sync_add_and_fetch((v), 1)
  41 #define p_atomic_dec(v) (void) __sync_sub_and_fetch((v), 1)
  42 #define p_atomic_inc_return(v) __sync_add_and_fetch((v), 1)
  43 #define p_atomic_dec_return(v) __sync_sub_and_fetch((v), 1)
  44 #define p_atomic_cmpxchg(v, old, _new) \
  45    __sync_val_compare_and_swap((v), (old), (_new))
  46
  47 #endif
  48
  49
  50
  51 /* Unlocked version for single threaded environments, such as some
  52  * windows kernel modules.
  53  */
  54 #if defined(PIPE_ATOMIC_OS_UNLOCKED)
  55
  56 #define PIPE_ATOMIC "Unlocked"
  57
  58 #define p_atomic_set(_v, _i) (*(_v) = (_i))
  59 #define p_atomic_read(_v) (*(_v))
  60 #define p_atomic_dec_zero(_v) (p_atomic_dec_return(_v) == 0)
  61 #define p_atomic_inc(_v) ((void) p_atomic_inc_return(_v))
  62 #define p_atomic_dec(_v) ((void) p_atomic_dec_return(_v))
  63 #define p_atomic_inc_return(_v) (++(*(_v)))
  64 #define p_atomic_dec_return(_v) (--(*(_v)))
  65 #define p_atomic_cmpxchg(_v, _old, _new) (*(_v) == (_old) ? (*(_v) = (_new), (_old)) : *(_v))
  66
  67 #endif
  68
  69
  70 #if defined(PIPE_ATOMIC_MSVC_INTRINSIC)
  71
  72 #define PIPE_ATOMIC "MSVC Intrinsics"
  73
  74 /* We use the Windows header's Interlocked*64 functions instead of the
  75  * _Interlocked*64 intrinsics wherever we can, as support for the latter varies
  76  * with target CPU, whereas Windows headers take care of all portability
  77  * issues: using intrinsics where available, falling back to library
  78  * implementations where not.
  79  */
  80 #ifndef WIN32_LEAN_AND_MEAN
  81 #define WIN32_LEAN_AND_MEAN 1
  82 #endif
  83 #include <windows.h>
  84 #include <intrin.h>
  85 #include <assert.h>
  86
  87 #if _MSC_VER < 1600
  88
  89 /* Implement _InterlockedCompareExchange8 in terms of InterlockedCompareExchange16 */
  90 static __inline
  91 char _InterlockedCompareExchange8(char volatile *Destination8, char Exchange8, char Comparand8)
  92 {
  93    INT_PTR DestinationAddr = (INT_PTR)Destination8;
  94    short volatile *Destination16 = (short volatile *)(DestinationAddr & ~1);
  95    const short Shift8 = (DestinationAddr & 1) * 8;
  96    const short Mask8 = 0xff << Shift8;
  97    short Initial16 = *Destination16;
  98    char Initial8 = Initial16 >> Shift8;
  99    while (Initial8 == Comparand8) {
 100       /* initial *Destination8 matches, so try exchange it while keeping the
 101        * neighboring byte untouched */
 102       short Exchange16 = (Initial16 & ~Mask8) | ((short)Exchange8 << Shift8);
 103       short Comparand16 = Initial16;
 104       short Initial16 = InterlockedCompareExchange16(Destination16, Exchange16, Comparand16);
 105       if (Initial16 == Comparand16) {
 106          /* succeeded */
 107          return Comparand8;
 108       }
 109       /* something changed, retry with the new initial value */
 110       Initial8 = Initial16 >> Shift8;
 111    }
 112    return Initial8;
 113 }
 114
 115 #endif /* _MSC_VER < 1600 */
 116
 117 /* MSVC supports decltype keyword, but it's only supported on C++ and doesn't
 118  * quite work here; and if a C++-only solution is worthwhile, then it would be
 119  * better to use templates / function overloading, instead of decltype magic.
 120  * Therefore, we rely on implicit casting to LONGLONG for the functions that return
 121  */
 122
 123 #define p_atomic_set(_v, _i) (*(_v) = (_i))
 124 #define p_atomic_read(_v) (*(_v))
 125
 126 #define p_atomic_dec_zero(_v) \
 127    (p_atomic_dec_return(_v) == 0)
 128
 129 #define p_atomic_inc(_v) \
 130    ((void) p_atomic_inc_return(_v))
 131
 132 #define p_atomic_inc_return(_v) (\
 133    sizeof *(_v) == sizeof(short)   ? _InterlockedIncrement16((short *)  (_v)) : \
 134    sizeof *(_v) == sizeof(long)    ? _InterlockedIncrement  ((long *)   (_v)) : \
 135    sizeof *(_v) == sizeof(__int64) ? InterlockedIncrement64 ((__int64 *)(_v)) : \
 136                                      (assert(!"should not get here"), 0))
 137
 138 #define p_atomic_dec(_v) \
 139    ((void) p_atomic_dec_return(_v))
 140
 141 #define p_atomic_dec_return(_v) (\
 142    sizeof *(_v) == sizeof(short)   ? _InterlockedDecrement16((short *)  (_v)) : \
 143    sizeof *(_v) == sizeof(long)    ? _InterlockedDecrement  ((long *)   (_v)) : \
 144    sizeof *(_v) == sizeof(__int64) ? InterlockedDecrement64 ((__int64 *)(_v)) : \
 145                                      (assert(!"should not get here"), 0))
 146
 147 #define p_atomic_cmpxchg(_v, _old, _new) (\
 148    sizeof *(_v) == sizeof(char)    ? _InterlockedCompareExchange8 ((char *)   (_v), (char)   (_new), (char)   (_old)) : \
 149    sizeof *(_v) == sizeof(short)   ? _InterlockedCompareExchange16((short *)  (_v), (short)  (_new), (short)  (_old)) : \
 150    sizeof *(_v) == sizeof(long)    ? _InterlockedCompareExchange  ((long *)   (_v), (long)   (_new), (long)   (_old)) : \
 151    sizeof *(_v) == sizeof(__int64) ? InterlockedCompareExchange64 ((__int64 *)(_v), (__int64)(_new), (__int64)(_old)) : \
 152                                      (assert(!"should not get here"), 0))
 153
 154 #endif
 155
 156 #if defined(PIPE_ATOMIC_OS_SOLARIS)
 157
 158 #define PIPE_ATOMIC "Solaris OS atomic functions"
 159
 160 #include <atomic.h>
 161 #include <assert.h>
 162
 163 #define p_atomic_set(_v, _i) (*(_v) = (_i))
 164 #define p_atomic_read(_v) (*(_v))
 165
 166 #define p_atomic_dec_zero(v) (\
 167    sizeof(*v) == sizeof(uint8_t)  ? atomic_dec_8_nv ((uint8_t  *)(v)) == 0 : \
 168    sizeof(*v) == sizeof(uint16_t) ? atomic_dec_16_nv((uint16_t *)(v)) == 0 : \
 169    sizeof(*v) == sizeof(uint32_t) ? atomic_dec_32_nv((uint32_t *)(v)) == 0 : \
 170    sizeof(*v) == sizeof(uint64_t) ? atomic_dec_64_nv((uint64_t *)(v)) == 0 : \
 171                                     (assert(!"should not get here"), 0))
 172
 173 #define p_atomic_inc(v) (void) (\
 174    sizeof(*v) == sizeof(uint8_t)  ? atomic_inc_8 ((uint8_t  *)(v)) : \
 175    sizeof(*v) == sizeof(uint16_t) ? atomic_inc_16((uint16_t *)(v)) : \
 176    sizeof(*v) == sizeof(uint32_t) ? atomic_inc_32((uint32_t *)(v)) : \
 177    sizeof(*v) == sizeof(uint64_t) ? atomic_inc_64((uint64_t *)(v)) : \
 178                                     (assert(!"should not get here"), 0))
 179
 180 #define p_atomic_inc_return(v) ((typeof(*v)) \
 181    sizeof(*v) == sizeof(uint8_t)  ? atomic_inc_8_nv ((uint8_t  *)(v)) : \
 182    sizeof(*v) == sizeof(uint16_t) ? atomic_inc_16_nv((uint16_t *)(v)) : \
 183    sizeof(*v) == sizeof(uint32_t) ? atomic_inc_32_nv((uint32_t *)(v)) : \
 184    sizeof(*v) == sizeof(uint64_t) ? atomic_inc_64_nv((uint64_t *)(v)) : \
 185                                     (assert(!"should not get here"), 0))
 186
 187 #define p_atomic_dec(v) ((void) \
 188    sizeof(*v) == sizeof(uint8_t)  ? atomic_dec_8 ((uint8_t  *)(v)) : \
 189    sizeof(*v) == sizeof(uint16_t) ? atomic_dec_16((uint16_t *)(v)) : \
 190    sizeof(*v) == sizeof(uint32_t) ? atomic_dec_32((uint32_t *)(v)) : \
 191    sizeof(*v) == sizeof(uint64_t) ? atomic_dec_64((uint64_t *)(v)) : \
 192                                     (assert(!"should not get here"), 0))
 193
 194 #define p_atomic_dec_return(v) ((typeof(*v)) \
 195    sizeof(*v) == sizeof(uint8_t)  ? atomic_dec_8_nv ((uint8_t  *)(v)) : \
 196    sizeof(*v) == sizeof(uint16_t) ? atomic_dec_16_nv((uint16_t *)(v)) : \
 197    sizeof(*v) == sizeof(uint32_t) ? atomic_dec_32_nv((uint32_t *)(v)) : \
 198    sizeof(*v) == sizeof(uint64_t) ? atomic_dec_64_nv((uint64_t *)(v)) : \
 199                                     (assert(!"should not get here"), 0))
 200
 201 #define p_atomic_cmpxchg(v, old, _new) ((typeof(*v)) \
 202    sizeof(*v) == sizeof(uint8_t)  ? atomic_cas_8 ((uint8_t  *)(v), (uint8_t )(old), (uint8_t )(_new)) : \
 203    sizeof(*v) == sizeof(uint16_t) ? atomic_cas_16((uint16_t *)(v), (uint16_t)(old), (uint16_t)(_new)) : \
 204    sizeof(*v) == sizeof(uint32_t) ? atomic_cas_32((uint32_t *)(v), (uint32_t)(old), (uint32_t)(_new)) : \
 205    sizeof(*v) == sizeof(uint64_t) ? atomic_cas_64((uint64_t *)(v), (uint64_t)(old), (uint64_t)(_new)) : \
 206                                     (assert(!"should not get here"), 0))
 207
 208 #endif
 209
 210 #ifndef PIPE_ATOMIC
 211 #error "No pipe_atomic implementation selected"
 212 #endif
 213
 214
 215
 216 #endif /* U_ATOMIC_H */