libkern/gen/OSAtomicOperations.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22
  23 #include <libkern/OSAtomic.h>
  24
  25 enum {
  26         false   = 0,
  27         true    = 1
  28 };
  29 #define NULL 0L
  30
  31
  32 /*
  33  * atomic operations
  34  *      these are _the_ atomic operations, currently cast atop CompareAndSwap,
  35  *      which is implemented in assembler.  if we are worried about the cost of
  36  *      this layering (we shouldn't be), then all this stuff could be
  37  *      implemented in assembler, as it is in MacOS8/9
  38  *      (derived from SuperMario/NativeLibs/IO/DriverServices/Synchronization.s,
  39  *      which I wrote for NuKernel in a previous life with a different last name...)
  40  *
  41  * native Boolean       CompareAndSwap(UInt32 oldValue, UInt32 newValue, UInt32 * oldValuePtr);
  42  *
  43  * We've since implemented a few more of these -- OSAddAtomic, OSDequeueAtomic,
  44  * OSEnqueueAtomic etc -- in assembler, either for speed or correctness.  See also the
  45  * commpage atomic operations, and the platform specific versions.
  46  * Like standards, there are a lot of atomic ops to choose from!
  47  */
  48
  49 #ifndef __ppc__
  50
  51 SInt32  OSAddAtomic(SInt32 amount, SInt32 * value)
  52 {
  53         SInt32  oldValue;
  54         SInt32  newValue;
  55
  56         do {
  57                 oldValue = *value;
  58                 newValue = oldValue + amount;
  59         } while (! OSCompareAndSwap((UInt32) oldValue, (UInt32) newValue, (UInt32 *) value));
  60
  61         return oldValue;
  62 }
  63
  64 SInt32  OSIncrementAtomic(SInt32 * value)
  65 {
  66         return OSAddAtomic(1, value);
  67 }
  68
  69 SInt32  OSDecrementAtomic(SInt32 * value)
  70 {
  71         return OSAddAtomic(-1, value);
  72 }
  73
  74 void *  OSDequeueAtomic(void ** inList, SInt32 inOffset)
  75 {
  76         void *  oldListHead;
  77         void *  newListHead;
  78
  79         do {
  80                 oldListHead = *inList;
  81                 if (oldListHead == NULL) {
  82                         break;
  83                 }
  84
  85                 newListHead = *(void **) (((char *) oldListHead) + inOffset);
  86         } while (! OSCompareAndSwap((UInt32)oldListHead,
  87                                         (UInt32)newListHead, (UInt32 *)inList));
  88
  89         return oldListHead;
  90 }
  91
  92 void    OSEnqueueAtomic(void ** inList, void * inNewLink, SInt32 inOffset)
  93 {
  94         void *  oldListHead;
  95         void *  newListHead = inNewLink;
  96         void ** newLinkNextPtr = (void **) (((char *) inNewLink) + inOffset);
  97
  98         do {
  99                 oldListHead = *inList;
 100                 *newLinkNextPtr = oldListHead;
 101         } while (! OSCompareAndSwap((UInt32)oldListHead, (UInt32)newListHead,
 102                                         (UInt32 *)inList));
 103 }
 104
 105 #endif  /* !__ppc__ */
 106
 107 static UInt32   OSBitwiseAtomic(UInt32 and_mask, UInt32 or_mask, UInt32 xor_mask, UInt32 * value)
 108 {
 109         UInt32  oldValue;
 110         UInt32  newValue;
 111
 112         do {
 113                 oldValue = *value;
 114                 newValue = ((oldValue & and_mask) | or_mask) ^ xor_mask;
 115         } while (! OSCompareAndSwap(oldValue, newValue, value));
 116
 117         return oldValue;
 118 }
 119
 120 UInt32  OSBitAndAtomic(UInt32 mask, UInt32 * value)
 121 {
 122         return OSBitwiseAtomic(mask, 0, 0, value);
 123 }
 124
 125 UInt32  OSBitOrAtomic(UInt32 mask, UInt32 * value)
 126 {
 127         return OSBitwiseAtomic((UInt32) -1, mask, 0, value);
 128 }
 129
 130 UInt32  OSBitXorAtomic(UInt32 mask, UInt32 * value)
 131 {
 132         return OSBitwiseAtomic((UInt32) -1, 0, mask, value);
 133 }
 134
 135 static Boolean OSCompareAndSwap8(UInt8 oldValue8, UInt8 newValue8, UInt8 * value8)
 136 {
 137         UInt32          mask        = 0x000000ff;
 138         UInt32          alignment   = ((UInt32) value8) & (sizeof(UInt32) - 1);
 139     UInt32      shiftValues = (24 << 24) | (16 << 16) | (8 << 8);
 140     int                 shift       = (UInt32) *(((UInt8 *) &shiftValues) + alignment);
 141         UInt32 *        value32     = (UInt32 *) (value8 - alignment);
 142     UInt32      oldValue;
 143     UInt32      newValue;
 144
 145     mask <<= shift;
 146
 147     oldValue = *value32;
 148     oldValue = (oldValue & ~mask) | (oldValue8 << shift);
 149     newValue = (oldValue & ~mask) | (newValue8 << shift);
 150
 151         return OSCompareAndSwap(oldValue, newValue, value32);
 152 }
 153
 154 static Boolean  OSTestAndSetClear(UInt32 bit, Boolean wantSet, UInt8 * startAddress)
 155 {
 156         UInt8           mask = 1;
 157         UInt8           oldValue;
 158         UInt8           wantValue;
 159
 160         startAddress += (bit / 8);
 161         mask <<= (7 - (bit % 8));
 162         wantValue = wantSet ? mask : 0;
 163
 164         do {
 165                 oldValue = *startAddress;
 166                 if ((oldValue & mask) == wantValue) {
 167                         break;
 168                 }
 169         } while (! OSCompareAndSwap8(oldValue, (oldValue & ~mask) | wantValue, startAddress));
 170
 171         return (oldValue & mask) == wantValue;
 172 }
 173
 174 Boolean OSTestAndSet(UInt32 bit, UInt8 * startAddress)
 175 {
 176         return OSTestAndSetClear(bit, true, startAddress);
 177 }
 178
 179 Boolean OSTestAndClear(UInt32 bit, UInt8 * startAddress)
 180 {
 181         return OSTestAndSetClear(bit, false, startAddress);
 182 }
 183
 184 /*
 185  * silly unaligned versions
 186  */
 187
 188 SInt8   OSIncrementAtomic8(SInt8 * value)
 189 {
 190         return OSAddAtomic8(1, value);
 191 }
 192
 193 SInt8   OSDecrementAtomic8(SInt8 * value)
 194 {
 195         return OSAddAtomic8(-1, value);
 196 }
 197
 198 SInt8   OSAddAtomic8(SInt32 amount, SInt8 * value)
 199 {
 200         SInt8   oldValue;
 201         SInt8   newValue;
 202
 203         do {
 204                 oldValue = *value;
 205                 newValue = oldValue + amount;
 206         } while (! OSCompareAndSwap8((UInt8) oldValue, (UInt8) newValue, (UInt8 *) value));
 207
 208         return oldValue;
 209 }
 210
 211 static UInt8    OSBitwiseAtomic8(UInt32 and_mask, UInt32 or_mask, UInt32 xor_mask, UInt8 * value)
 212 {
 213         UInt8   oldValue;
 214         UInt8   newValue;
 215
 216         do {
 217                 oldValue = *value;
 218                 newValue = ((oldValue & and_mask) | or_mask) ^ xor_mask;
 219         } while (! OSCompareAndSwap8(oldValue, newValue, value));
 220
 221         return oldValue;
 222 }
 223
 224 UInt8   OSBitAndAtomic8(UInt32 mask, UInt8 * value)
 225 {
 226         return OSBitwiseAtomic8(mask, 0, 0, value);
 227 }
 228
 229 UInt8   OSBitOrAtomic8(UInt32 mask, UInt8 * value)
 230 {
 231         return OSBitwiseAtomic8((UInt32) -1, mask, 0, value);
 232 }
 233
 234 UInt8   OSBitXorAtomic8(UInt32 mask, UInt8 * value)
 235 {
 236         return OSBitwiseAtomic8((UInt32) -1, 0, mask, value);
 237 }
 238
 239 static Boolean OSCompareAndSwap16(UInt16 oldValue16, UInt16 newValue16, UInt16 * value16)
 240 {
 241         UInt32          mask        = 0x0000ffff;
 242         UInt32          alignment   = ((UInt32) value16) & (sizeof(UInt32) - 1);
 243     UInt32      shiftValues = (16 << 24) | (16 << 16);
 244     UInt32              shift       = (UInt32) *(((UInt8 *) &shiftValues) + alignment);
 245         UInt32 *        value32     = (UInt32 *) (((UInt32) value16) - alignment);
 246     UInt32      oldValue;
 247     UInt32      newValue;
 248
 249     mask <<= shift;
 250
 251     oldValue = *value32;
 252     oldValue = (oldValue & ~mask) | (oldValue16 << shift);
 253     newValue = (oldValue & ~mask) | (newValue16 << shift);
 254
 255         return OSCompareAndSwap(oldValue, newValue, value32);
 256 }
 257
 258 SInt16  OSIncrementAtomic16(SInt16 * value)
 259 {
 260         return OSAddAtomic16(1, value);
 261 }
 262
 263 SInt16  OSDecrementAtomic16(SInt16 * value)
 264 {
 265         return OSAddAtomic16(-1, value);
 266 }
 267
 268 SInt16  OSAddAtomic16(SInt32 amount, SInt16 * value)
 269 {
 270         SInt16  oldValue;
 271         SInt16  newValue;
 272
 273         do {
 274                 oldValue = *value;
 275                 newValue = oldValue + amount;
 276         } while (! OSCompareAndSwap16((UInt16) oldValue, (UInt16) newValue, (UInt16 *) value));
 277
 278         return oldValue;
 279 }
 280
 281 static UInt16   OSBitwiseAtomic16(UInt32 and_mask, UInt32 or_mask, UInt32 xor_mask, UInt16 * value)
 282 {
 283         UInt16  oldValue;
 284         UInt16  newValue;
 285
 286         do {
 287                 oldValue = *value;
 288                 newValue = ((oldValue & and_mask) | or_mask) ^ xor_mask;
 289         } while (! OSCompareAndSwap16(oldValue, newValue, value));
 290
 291         return oldValue;
 292 }
 293
 294 UInt16  OSBitAndAtomic16(UInt32 mask, UInt16 * value)
 295 {
 296         return OSBitwiseAtomic16(mask, 0, 0, value);
 297 }
 298
 299 UInt16  OSBitOrAtomic16(UInt32 mask, UInt16 * value)
 300 {
 301         return OSBitwiseAtomic16((UInt32) -1, mask, 0, value);
 302 }
 303
 304 UInt16  OSBitXorAtomic16(UInt32 mask, UInt16 * value)
 305 {
 306         return OSBitwiseAtomic16((UInt32) -1, 0, mask, value);
 307 }
 308