include/linux/cpumask.h

   1 #ifndef __LINUX_CPUMASK_H
   2 #define __LINUX_CPUMASK_H
   3
   4 /*
   5  * Cpumasks provide a bitmap suitable for representing the
   6  * set of CPU's in a system, one bit position per CPU number.
   7  *
   8  * See detailed comments in the file linux/bitmap.h describing the
   9  * data type on which these cpumasks are based.
  10  *
  11  * For details of cpumask_scnprintf() and cpumask_parse_user(),
  12  * see bitmap_scnprintf() and bitmap_parse_user() in lib/bitmap.c.
  13  * For details of cpulist_scnprintf() and cpulist_parse(), see
  14  * bitmap_scnlistprintf() and bitmap_parselist(), also in bitmap.c.
  15  * For details of cpu_remap(), see bitmap_bitremap in lib/bitmap.c
  16  * For details of cpus_remap(), see bitmap_remap in lib/bitmap.c.
  17  * For details of cpus_onto(), see bitmap_onto in lib/bitmap.c.
  18  * For details of cpus_fold(), see bitmap_fold in lib/bitmap.c.
  19  *
  20  * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
  21  * Note: The alternate operations with the suffix "_nr" are used
  22  *       to limit the range of the loop to nr_cpu_ids instead of
  23  *       NR_CPUS when NR_CPUS > 64 for performance reasons.
  24  *       If NR_CPUS is <= 64 then most assembler bitmask
  25  *       operators execute faster with a constant range, so
  26  *       the operator will continue to use NR_CPUS.
  27  *
  28  *       Another consideration is that nr_cpu_ids is initialized
  29  *       to NR_CPUS and isn't lowered until the possible cpus are
  30  *       discovered (including any disabled cpus).  So early uses
  31  *       will span the entire range of NR_CPUS.
  32  * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
  33  *
  34  * The available cpumask operations are:
  35  *
  36  * void cpu_set(cpu, mask)              turn on bit 'cpu' in mask
  37  * void cpu_clear(cpu, mask)            turn off bit 'cpu' in mask
  38  * void cpus_setall(mask)               set all bits
  39  * void cpus_clear(mask)                clear all bits
  40  * int cpu_isset(cpu, mask)             true iff bit 'cpu' set in mask
  41  * int cpu_test_and_set(cpu, mask)      test and set bit 'cpu' in mask
  42  *
  43  * void cpus_and(dst, src1, src2)       dst = src1 & src2  [intersection]
  44  * void cpus_or(dst, src1, src2)        dst = src1 | src2  [union]
  45  * void cpus_xor(dst, src1, src2)       dst = src1 ^ src2
  46  * void cpus_andnot(dst, src1, src2)    dst = src1 & ~src2
  47  * void cpus_complement(dst, src)       dst = ~src
  48  *
  49  * int cpus_equal(mask1, mask2)         Does mask1 == mask2?
  50  * int cpus_intersects(mask1, mask2)    Do mask1 and mask2 intersect?
  51  * int cpus_subset(mask1, mask2)        Is mask1 a subset of mask2?
  52  * int cpus_empty(mask)                 Is mask empty (no bits sets)?
  53  * int cpus_full(mask)                  Is mask full (all bits sets)?
  54  * int cpus_weight(mask)                Hamming weigh - number of set bits
  55  * int cpus_weight_nr(mask)             Same using nr_cpu_ids instead of NR_CPUS
  56  *
  57  * void cpus_shift_right(dst, src, n)   Shift right
  58  * void cpus_shift_left(dst, src, n)    Shift left
  59  *
  60  * int first_cpu(mask)                  Number lowest set bit, or NR_CPUS
  61  * int next_cpu(cpu, mask)              Next cpu past 'cpu', or NR_CPUS
  62  * int next_cpu_nr(cpu, mask)           Next cpu past 'cpu', or nr_cpu_ids
  63  *
  64  * cpumask_t cpumask_of_cpu(cpu)        Return cpumask with bit 'cpu' set
  65  *                                      (can be used as an lvalue)
  66  * CPU_MASK_ALL                         Initializer - all bits set
  67  * CPU_MASK_NONE                        Initializer - no bits set
  68  * unsigned long *cpus_addr(mask)       Array of unsigned long's in mask
  69  *
  70  * CPUMASK_ALLOC kmalloc's a structure that is a composite of many cpumask_t
  71  * variables, and CPUMASK_PTR provides pointers to each field.
  72  *
  73  * The structure should be defined something like this:
  74  * struct my_cpumasks {
  75  *      cpumask_t mask1;
  76  *      cpumask_t mask2;
  77  * };
  78  *
  79  * Usage is then:
  80  *      CPUMASK_ALLOC(my_cpumasks);
  81  *      CPUMASK_PTR(mask1, my_cpumasks);
  82  *      CPUMASK_PTR(mask2, my_cpumasks);
  83  *
  84  *      --- DO NOT reference cpumask_t pointers until this check ---
  85  *      if (my_cpumasks == NULL)
  86  *              "kmalloc failed"...
  87  *
  88  * References are now pointers to the cpumask_t variables (*mask1, ...)
  89  *
  90  *if NR_CPUS > BITS_PER_LONG
  91  *   CPUMASK_ALLOC(m)                   Declares and allocates struct m *m =
  92  *                                              kmalloc(sizeof(*m), GFP_KERNEL)
  93  *   CPUMASK_FREE(m)                    Macro for kfree(m)
  94  *else
  95  *   CPUMASK_ALLOC(m)                   Declares struct m _m, *m = &_m
  96  *   CPUMASK_FREE(m)                    Nop
  97  *endif
  98  *   CPUMASK_PTR(v, m)                  Declares cpumask_t *v = &(m->v)
  99  * ------------------------------------------------------------------------
 100  *
 101  * int cpumask_scnprintf(buf, len, mask) Format cpumask for printing
 102  * int cpumask_parse_user(ubuf, ulen, mask)     Parse ascii string as cpumask
 103  * int cpulist_scnprintf(buf, len, mask) Format cpumask as list for printing
 104  * int cpulist_parse(buf, map)          Parse ascii string as cpulist
 105  * int cpu_remap(oldbit, old, new)      newbit = map(old, new)(oldbit)
 106  * void cpus_remap(dst, src, old, new)  *dst = map(old, new)(src)
 107  * void cpus_onto(dst, orig, relmap)    *dst = orig relative to relmap
 108  * void cpus_fold(dst, orig, sz)        dst bits = orig bits mod sz
 109  *
 110  * for_each_cpu_mask(cpu, mask)         for-loop cpu over mask using NR_CPUS
 111  * for_each_cpu_mask_nr(cpu, mask)      for-loop cpu over mask using nr_cpu_ids
 112  *
 113  * int num_online_cpus()                Number of online CPUs
 114  * int num_possible_cpus()              Number of all possible CPUs
 115  * int num_present_cpus()               Number of present CPUs
 116  *
 117  * int cpu_online(cpu)                  Is some cpu online?
 118  * int cpu_possible(cpu)                Is some cpu possible?
 119  * int cpu_present(cpu)                 Is some cpu present (can schedule)?
 120  *
 121  * int any_online_cpu(mask)             First online cpu in mask
 122  *
 123  * for_each_possible_cpu(cpu)           for-loop cpu over cpu_possible_map
 124  * for_each_online_cpu(cpu)             for-loop cpu over cpu_online_map
 125  * for_each_present_cpu(cpu)            for-loop cpu over cpu_present_map
 126  *
 127  * Subtlety:
 128  * 1) The 'type-checked' form of cpu_isset() causes gcc (3.3.2, anyway)
 129  *    to generate slightly worse code.  Note for example the additional
 130  *    40 lines of assembly code compiling the "for each possible cpu"
 131  *    loops buried in the disk_stat_read() macros calls when compiling
 132  *    drivers/block/genhd.c (arch i386, CONFIG_SMP=y).  So use a simple
 133  *    one-line #define for cpu_isset(), instead of wrapping an inline
 134  *    inside a macro, the way we do the other calls.
 135  */
 136
 137 #include <linux/kernel.h>
 138 #include <linux/threads.h>
 139 #include <linux/bitmap.h>
 140
 141 typedef struct { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;
 142 extern cpumask_t _unused_cpumask_arg_;
 143
 144 #define cpu_set(cpu, dst) __cpu_set((cpu), &(dst))
 145 static inline void __cpu_set(int cpu, volatile cpumask_t *dstp)
 146 {
 147         set_bit(cpu, dstp->bits);
 148 }
 149
 150 #define cpu_clear(cpu, dst) __cpu_clear((cpu), &(dst))
 151 static inline void __cpu_clear(int cpu, volatile cpumask_t *dstp)
 152 {
 153         clear_bit(cpu, dstp->bits);
 154 }
 155
 156 #define cpus_setall(dst) __cpus_setall(&(dst), NR_CPUS)
 157 static inline void __cpus_setall(cpumask_t *dstp, int nbits)
 158 {
 159         bitmap_fill(dstp->bits, nbits);
 160 }
 161
 162 #define cpus_clear(dst) __cpus_clear(&(dst), NR_CPUS)
 163 static inline void __cpus_clear(cpumask_t *dstp, int nbits)
 164 {
 165         bitmap_zero(dstp->bits, nbits);
 166 }
 167
 168 /* No static inline type checking - see Subtlety (1) above. */
 169 #define cpu_isset(cpu, cpumask) test_bit((cpu), (cpumask).bits)
 170
 171 #define cpu_test_and_set(cpu, cpumask) __cpu_test_and_set((cpu), &(cpumask))
 172 static inline int __cpu_test_and_set(int cpu, cpumask_t *addr)
 173 {
 174         return test_and_set_bit(cpu, addr->bits);
 175 }
 176
 177 #define cpus_and(dst, src1, src2) __cpus_and(&(dst), &(src1), &(src2), NR_CPUS)
 178 static inline void __cpus_and(cpumask_t *dstp, const cpumask_t *src1p,
 179                                         const cpumask_t *src2p, int nbits)
 180 {
 181         bitmap_and(dstp->bits, src1p->bits, src2p->bits, nbits);
 182 }
 183
 184 #define cpus_or(dst, src1, src2) __cpus_or(&(dst), &(src1), &(src2), NR_CPUS)
 185 static inline void __cpus_or(cpumask_t *dstp, const cpumask_t *src1p,
 186                                         const cpumask_t *src2p, int nbits)
 187 {
 188         bitmap_or(dstp->bits, src1p->bits, src2p->bits, nbits);
 189 }
 190
 191 #define cpus_xor(dst, src1, src2) __cpus_xor(&(dst), &(src1), &(src2), NR_CPUS)
 192 static inline void __cpus_xor(cpumask_t *dstp, const cpumask_t *src1p,
 193                                         const cpumask_t *src2p, int nbits)
 194 {
 195         bitmap_xor(dstp->bits, src1p->bits, src2p->bits, nbits);
 196 }
 197
 198 #define cpus_andnot(dst, src1, src2) \
 199                                 __cpus_andnot(&(dst), &(src1), &(src2), NR_CPUS)
 200 static inline void __cpus_andnot(cpumask_t *dstp, const cpumask_t *src1p,
 201                                         const cpumask_t *src2p, int nbits)
 202 {
 203         bitmap_andnot(dstp->bits, src1p->bits, src2p->bits, nbits);
 204 }
 205
 206 #define cpus_complement(dst, src) __cpus_complement(&(dst), &(src), NR_CPUS)
 207 static inline void __cpus_complement(cpumask_t *dstp,
 208                                         const cpumask_t *srcp, int nbits)
 209 {
 210         bitmap_complement(dstp->bits, srcp->bits, nbits);
 211 }
 212
 213 #define cpus_equal(src1, src2) __cpus_equal(&(src1), &(src2), NR_CPUS)
 214 static inline int __cpus_equal(const cpumask_t *src1p,
 215                                         const cpumask_t *src2p, int nbits)
 216 {
 217         return bitmap_equal(src1p->bits, src2p->bits, nbits);
 218 }
 219
 220 #define cpus_intersects(src1, src2) __cpus_intersects(&(src1), &(src2), NR_CPUS)
 221 static inline int __cpus_intersects(const cpumask_t *src1p,
 222                                         const cpumask_t *src2p, int nbits)
 223 {
 224         return bitmap_intersects(src1p->bits, src2p->bits, nbits);
 225 }
 226
 227 #define cpus_subset(src1, src2) __cpus_subset(&(src1), &(src2), NR_CPUS)
 228 static inline int __cpus_subset(const cpumask_t *src1p,
 229                                         const cpumask_t *src2p, int nbits)
 230 {
 231         return bitmap_subset(src1p->bits, src2p->bits, nbits);
 232 }
 233
 234 #define cpus_empty(src) __cpus_empty(&(src), NR_CPUS)
 235 static inline int __cpus_empty(const cpumask_t *srcp, int nbits)
 236 {
 237         return bitmap_empty(srcp->bits, nbits);
 238 }
 239
 240 #define cpus_full(cpumask) __cpus_full(&(cpumask), NR_CPUS)
 241 static inline int __cpus_full(const cpumask_t *srcp, int nbits)
 242 {
 243         return bitmap_full(srcp->bits, nbits);
 244 }
 245
 246 #define cpus_weight(cpumask) __cpus_weight(&(cpumask), NR_CPUS)
 247 static inline int __cpus_weight(const cpumask_t *srcp, int nbits)
 248 {
 249         return bitmap_weight(srcp->bits, nbits);
 250 }
 251
 252 #define cpus_shift_right(dst, src, n) \
 253                         __cpus_shift_right(&(dst), &(src), (n), NR_CPUS)
 254 static inline void __cpus_shift_right(cpumask_t *dstp,
 255                                         const cpumask_t *srcp, int n, int nbits)
 256 {
 257         bitmap_shift_right(dstp->bits, srcp->bits, n, nbits);
 258 }
 259
 260 #define cpus_shift_left(dst, src, n) \
 261                         __cpus_shift_left(&(dst), &(src), (n), NR_CPUS)
 262 static inline void __cpus_shift_left(cpumask_t *dstp,
 263                                         const cpumask_t *srcp, int n, int nbits)
 264 {
 265         bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
 266 }
 267
 268 /*
 269  * Special-case data structure for "single bit set only" constant CPU masks.
 270  *
 271  * We pre-generate all the 64 (or 32) possible bit positions, with enough
 272  * padding to the left and the right, and return the constant pointer
 273  * appropriately offset.
 274  */
 275 extern const unsigned long
 276         cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)];
 277
 278 static inline const cpumask_t *get_cpu_mask(unsigned int cpu)
 279 {
 280         const unsigned long *p = cpu_bit_bitmap[1 + cpu % BITS_PER_LONG];
 281         p -= cpu / BITS_PER_LONG;
 282         return (const cpumask_t *)p;
 283 }
 284
 285 /*
 286  * In cases where we take the address of the cpumask immediately,
 287  * gcc optimizes it out (it's a constant) and there's no huge stack
 288  * variable created:
 289  */
 290 #define cpumask_of_cpu(cpu) (*get_cpu_mask(cpu))
 291
 292
 293 #define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)
 294
 295 #if NR_CPUS <= BITS_PER_LONG
 296
 297 #define CPU_MASK_ALL                                                    \
 298 (cpumask_t) { {                                                         \
 299         [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD                 \
 300 } }
 301
 302 #define CPU_MASK_ALL_PTR        (&CPU_MASK_ALL)
 303
 304 #else
 305
 306 #define CPU_MASK_ALL                                                    \
 307 (cpumask_t) { {                                                         \
 308         [0 ... BITS_TO_LONGS(NR_CPUS)-2] = ~0UL,                        \
 309         [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD                 \
 310 } }
 311
 312 /* cpu_mask_all is in init/main.c */
 313 extern cpumask_t cpu_mask_all;
 314 #define CPU_MASK_ALL_PTR        (&cpu_mask_all)
 315
 316 #endif
 317
 318 #define CPU_MASK_NONE                                                   \
 319 (cpumask_t) { {                                                         \
 320         [0 ... BITS_TO_LONGS(NR_CPUS)-1] =  0UL                         \
 321 } }
 322
 323 #define CPU_MASK_CPU0                                                   \
 324 (cpumask_t) { {                                                         \
 325         [0] =  1UL                                                      \
 326 } }
 327
 328 #define cpus_addr(src) ((src).bits)
 329
 330 #if NR_CPUS > BITS_PER_LONG
 331 #define CPUMASK_ALLOC(m)        struct m *m = kmalloc(sizeof(*m), GFP_KERNEL)
 332 #define CPUMASK_FREE(m)         kfree(m)
 333 #else
 334 #define CPUMASK_ALLOC(m)        struct m _m, *m = &_m
 335 #define CPUMASK_FREE(m)
 336 #endif
 337 #define CPUMASK_PTR(v, m)       cpumask_t *v = &(m->v)
 338
 339 #define cpumask_scnprintf(buf, len, src) \
 340                         __cpumask_scnprintf((buf), (len), &(src), NR_CPUS)
 341 static inline int __cpumask_scnprintf(char *buf, int len,
 342                                         const cpumask_t *srcp, int nbits)
 343 {
 344         return bitmap_scnprintf(buf, len, srcp->bits, nbits);
 345 }
 346
 347 #define cpumask_parse_user(ubuf, ulen, dst) \
 348                         __cpumask_parse_user((ubuf), (ulen), &(dst), NR_CPUS)
 349 static inline int __cpumask_parse_user(const char __user *buf, int len,
 350                                         cpumask_t *dstp, int nbits)
 351 {
 352         return bitmap_parse_user(buf, len, dstp->bits, nbits);
 353 }
 354
 355 #define cpulist_scnprintf(buf, len, src) \
 356                         __cpulist_scnprintf((buf), (len), &(src), NR_CPUS)
 357 static inline int __cpulist_scnprintf(char *buf, int len,
 358                                         const cpumask_t *srcp, int nbits)
 359 {
 360         return bitmap_scnlistprintf(buf, len, srcp->bits, nbits);
 361 }
 362
 363 #define cpulist_parse(buf, dst) __cpulist_parse((buf), &(dst), NR_CPUS)
 364 static inline int __cpulist_parse(const char *buf, cpumask_t *dstp, int nbits)
 365 {
 366         return bitmap_parselist(buf, dstp->bits, nbits);
 367 }
 368
 369 #define cpu_remap(oldbit, old, new) \
 370                 __cpu_remap((oldbit), &(old), &(new), NR_CPUS)
 371 static inline int __cpu_remap(int oldbit,
 372                 const cpumask_t *oldp, const cpumask_t *newp, int nbits)
 373 {
 374         return bitmap_bitremap(oldbit, oldp->bits, newp->bits, nbits);
 375 }
 376
 377 #define cpus_remap(dst, src, old, new) \
 378                 __cpus_remap(&(dst), &(src), &(old), &(new), NR_CPUS)
 379 static inline void __cpus_remap(cpumask_t *dstp, const cpumask_t *srcp,
 380                 const cpumask_t *oldp, const cpumask_t *newp, int nbits)
 381 {
 382         bitmap_remap(dstp->bits, srcp->bits, oldp->bits, newp->bits, nbits);
 383 }
 384
 385 #define cpus_onto(dst, orig, relmap) \
 386                 __cpus_onto(&(dst), &(orig), &(relmap), NR_CPUS)
 387 static inline void __cpus_onto(cpumask_t *dstp, const cpumask_t *origp,
 388                 const cpumask_t *relmapp, int nbits)
 389 {
 390         bitmap_onto(dstp->bits, origp->bits, relmapp->bits, nbits);
 391 }
 392
 393 #define cpus_fold(dst, orig, sz) \
 394                 __cpus_fold(&(dst), &(orig), sz, NR_CPUS)
 395 static inline void __cpus_fold(cpumask_t *dstp, const cpumask_t *origp,
 396                 int sz, int nbits)
 397 {
 398         bitmap_fold(dstp->bits, origp->bits, sz, nbits);
 399 }
 400
 401 #if NR_CPUS == 1
 402
 403 #define nr_cpu_ids              1
 404 #define first_cpu(src)          ({ (void)(src); 0; })
 405 #define next_cpu(n, src)        ({ (void)(src); 1; })
 406 #define any_online_cpu(mask)    0
 407 #define for_each_cpu_mask(cpu, mask)    \
 408         for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
 409
 410 #else /* NR_CPUS > 1 */
 411
 412 extern int nr_cpu_ids;
 413 int __first_cpu(const cpumask_t *srcp);
 414 int __next_cpu(int n, const cpumask_t *srcp);
 415 int __any_online_cpu(const cpumask_t *mask);
 416
 417 #define first_cpu(src)          __first_cpu(&(src))
 418 #define next_cpu(n, src)        __next_cpu((n), &(src))
 419 #define any_online_cpu(mask) __any_online_cpu(&(mask))
 420 #define for_each_cpu_mask(cpu, mask)                    \
 421         for ((cpu) = -1;                                \
 422                 (cpu) = next_cpu((cpu), (mask)),        \
 423                 (cpu) < NR_CPUS; )
 424 #endif
 425
 426 #if NR_CPUS <= 64
 427
 428 #define next_cpu_nr(n, src)             next_cpu(n, src)
 429 #define cpus_weight_nr(cpumask)         cpus_weight(cpumask)
 430 #define for_each_cpu_mask_nr(cpu, mask) for_each_cpu_mask(cpu, mask)
 431
 432 #else /* NR_CPUS > 64 */
 433
 434 int __next_cpu_nr(int n, const cpumask_t *srcp);
 435 #define next_cpu_nr(n, src)     __next_cpu_nr((n), &(src))
 436 #define cpus_weight_nr(cpumask) __cpus_weight(&(cpumask), nr_cpu_ids)
 437 #define for_each_cpu_mask_nr(cpu, mask)                 \
 438         for ((cpu) = -1;                                \
 439                 (cpu) = next_cpu_nr((cpu), (mask)),     \
 440                 (cpu) < nr_cpu_ids; )
 441
 442 #endif /* NR_CPUS > 64 */
 443
 444 /*
 445  * The following particular system cpumasks and operations manage
 446  * possible, present, active and online cpus.  Each of them is a fixed size
 447  * bitmap of size NR_CPUS.
 448  *
 449  *  #ifdef CONFIG_HOTPLUG_CPU
 450  *     cpu_possible_map - has bit 'cpu' set iff cpu is populatable
 451  *     cpu_present_map  - has bit 'cpu' set iff cpu is populated
 452  *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 453  *     cpu_active_map   - has bit 'cpu' set iff cpu available to migration
 454  *  #else
 455  *     cpu_possible_map - has bit 'cpu' set iff cpu is populated
 456  *     cpu_present_map  - copy of cpu_possible_map
 457  *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 458  *  #endif
 459  *
 460  *  In either case, NR_CPUS is fixed at compile time, as the static
 461  *  size of these bitmaps.  The cpu_possible_map is fixed at boot
 462  *  time, as the set of CPU id's that it is possible might ever
 463  *  be plugged in at anytime during the life of that system boot.
 464  *  The cpu_present_map is dynamic(*), representing which CPUs
 465  *  are currently plugged in.  And cpu_online_map is the dynamic
 466  *  subset of cpu_present_map, indicating those CPUs available
 467  *  for scheduling.
 468  *
 469  *  If HOTPLUG is enabled, then cpu_possible_map is forced to have
 470  *  all NR_CPUS bits set, otherwise it is just the set of CPUs that
 471  *  ACPI reports present at boot.
 472  *
 473  *  If HOTPLUG is enabled, then cpu_present_map varies dynamically,
 474  *  depending on what ACPI reports as currently plugged in, otherwise
 475  *  cpu_present_map is just a copy of cpu_possible_map.
 476  *
 477  *  (*) Well, cpu_present_map is dynamic in the hotplug case.  If not
 478  *      hotplug, it's a copy of cpu_possible_map, hence fixed at boot.
 479  *
 480  * Subtleties:
 481  * 1) UP arch's (NR_CPUS == 1, CONFIG_SMP not defined) hardcode
 482  *    assumption that their single CPU is online.  The UP
 483  *    cpu_{online,possible,present}_maps are placebos.  Changing them
 484  *    will have no useful affect on the following num_*_cpus()
 485  *    and cpu_*() macros in the UP case.  This ugliness is a UP
 486  *    optimization - don't waste any instructions or memory references
 487  *    asking if you're online or how many CPUs there are if there is
 488  *    only one CPU.
 489  * 2) Most SMP arch's #define some of these maps to be some
 490  *    other map specific to that arch.  Therefore, the following
 491  *    must be #define macros, not inlines.  To see why, examine
 492  *    the assembly code produced by the following.  Note that
 493  *    set1() writes phys_x_map, but set2() writes x_map:
 494  *        int x_map, phys_x_map;
 495  *        #define set1(a) x_map = a
 496  *        inline void set2(int a) { x_map = a; }
 497  *        #define x_map phys_x_map
 498  *        main(){ set1(3); set2(5); }
 499  */
 500
 501 extern cpumask_t cpu_possible_map;
 502 extern cpumask_t cpu_online_map;
 503 extern cpumask_t cpu_present_map;
 504 extern cpumask_t cpu_active_map;
 505
 506 #if NR_CPUS > 1
 507 #define num_online_cpus()       cpus_weight_nr(cpu_online_map)
 508 #define num_possible_cpus()     cpus_weight_nr(cpu_possible_map)
 509 #define num_present_cpus()      cpus_weight_nr(cpu_present_map)
 510 #define cpu_online(cpu)         cpu_isset((cpu), cpu_online_map)
 511 #define cpu_possible(cpu)       cpu_isset((cpu), cpu_possible_map)
 512 #define cpu_present(cpu)        cpu_isset((cpu), cpu_present_map)
 513 #define cpu_active(cpu)         cpu_isset((cpu), cpu_active_map)
 514 #else
 515 #define num_online_cpus()       1
 516 #define num_possible_cpus()     1
 517 #define num_present_cpus()      1
 518 #define cpu_online(cpu)         ((cpu) == 0)
 519 #define cpu_possible(cpu)       ((cpu) == 0)
 520 #define cpu_present(cpu)        ((cpu) == 0)
 521 #define cpu_active(cpu)         ((cpu) == 0)
 522 #endif
 523
 524 #define cpu_is_offline(cpu)     unlikely(!cpu_online(cpu))
 525
 526 #define for_each_possible_cpu(cpu) for_each_cpu_mask_nr((cpu), cpu_possible_map)
 527 #define for_each_online_cpu(cpu)   for_each_cpu_mask_nr((cpu), cpu_online_map)
 528 #define for_each_present_cpu(cpu)  for_each_cpu_mask_nr((cpu), cpu_present_map)
 529
 530 #endif /* __LINUX_CPUMASK_H */