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  *ifdef CONFIG_HAS_CPUMASK_OF_CPU
  66  * cpumask_of_cpu_ptr_declare(v)        Declares cpumask_t *v
  67  * cpumask_of_cpu_ptr_next(v, cpu)      Sets v = &cpumask_of_cpu_map[cpu]
  68  * cpumask_of_cpu_ptr(v, cpu)           Combines above two operations
  69  *else
  70  * cpumask_of_cpu_ptr_declare(v)        Declares cpumask_t _v and *v = &_v
  71  * cpumask_of_cpu_ptr_next(v, cpu)      Sets _v = cpumask_of_cpu(cpu)
  72  * cpumask_of_cpu_ptr(v, cpu)           Combines above two operations
  73  *endif
  74  * CPU_MASK_ALL                         Initializer - all bits set
  75  * CPU_MASK_NONE                        Initializer - no bits set
  76  * unsigned long *cpus_addr(mask)       Array of unsigned long's in mask
  77  *
  78  * CPUMASK_ALLOC kmalloc's a structure that is a composite of many cpumask_t
  79  * variables, and CPUMASK_PTR provides pointers to each field.
  80  *
  81  * The structure should be defined something like this:
  82  * struct my_cpumasks {
  83  *      cpumask_t mask1;
  84  *      cpumask_t mask2;
  85  * };
  86  *
  87  * Usage is then:
  88  *      CPUMASK_ALLOC(my_cpumasks);
  89  *      CPUMASK_PTR(mask1, my_cpumasks);
  90  *      CPUMASK_PTR(mask2, my_cpumasks);
  91  *
  92  *      --- DO NOT reference cpumask_t pointers until this check ---
  93  *      if (my_cpumasks == NULL)
  94  *              "kmalloc failed"...
  95  *
  96  * References are now pointers to the cpumask_t variables (*mask1, ...)
  97  *
  98  *if NR_CPUS > BITS_PER_LONG
  99  *   CPUMASK_ALLOC(m)                   Declares and allocates struct m *m =
 100  *                                              kmalloc(sizeof(*m), GFP_KERNEL)
 101  *   CPUMASK_FREE(m)                    Macro for kfree(m)
 102  *else
 103  *   CPUMASK_ALLOC(m)                   Declares struct m _m, *m = &_m
 104  *   CPUMASK_FREE(m)                    Nop
 105  *endif
 106  *   CPUMASK_PTR(v, m)                  Declares cpumask_t *v = &(m->v)
 107  * ------------------------------------------------------------------------
 108  *
 109  * int cpumask_scnprintf(buf, len, mask) Format cpumask for printing
 110  * int cpumask_parse_user(ubuf, ulen, mask)     Parse ascii string as cpumask
 111  * int cpulist_scnprintf(buf, len, mask) Format cpumask as list for printing
 112  * int cpulist_parse(buf, map)          Parse ascii string as cpulist
 113  * int cpu_remap(oldbit, old, new)      newbit = map(old, new)(oldbit)
 114  * void cpus_remap(dst, src, old, new)  *dst = map(old, new)(src)
 115  * void cpus_onto(dst, orig, relmap)    *dst = orig relative to relmap
 116  * void cpus_fold(dst, orig, sz)        dst bits = orig bits mod sz
 117  *
 118  * for_each_cpu_mask(cpu, mask)         for-loop cpu over mask using NR_CPUS
 119  * for_each_cpu_mask_nr(cpu, mask)      for-loop cpu over mask using nr_cpu_ids
 120  *
 121  * int num_online_cpus()                Number of online CPUs
 122  * int num_possible_cpus()              Number of all possible CPUs
 123  * int num_present_cpus()               Number of present CPUs
 124  *
 125  * int cpu_online(cpu)                  Is some cpu online?
 126  * int cpu_possible(cpu)                Is some cpu possible?
 127  * int cpu_present(cpu)                 Is some cpu present (can schedule)?
 128  *
 129  * int any_online_cpu(mask)             First online cpu in mask
 130  *
 131  * for_each_possible_cpu(cpu)           for-loop cpu over cpu_possible_map
 132  * for_each_online_cpu(cpu)             for-loop cpu over cpu_online_map
 133  * for_each_present_cpu(cpu)            for-loop cpu over cpu_present_map
 134  *
 135  * Subtlety:
 136  * 1) The 'type-checked' form of cpu_isset() causes gcc (3.3.2, anyway)
 137  *    to generate slightly worse code.  Note for example the additional
 138  *    40 lines of assembly code compiling the "for each possible cpu"
 139  *    loops buried in the disk_stat_read() macros calls when compiling
 140  *    drivers/block/genhd.c (arch i386, CONFIG_SMP=y).  So use a simple
 141  *    one-line #define for cpu_isset(), instead of wrapping an inline
 142  *    inside a macro, the way we do the other calls.
 143  */
 144
 145 #include <linux/kernel.h>
 146 #include <linux/threads.h>
 147 #include <linux/bitmap.h>
 148
 149 typedef struct { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;
 150 extern cpumask_t _unused_cpumask_arg_;
 151
 152 #define cpu_set(cpu, dst) __cpu_set((cpu), &(dst))
 153 static inline void __cpu_set(int cpu, volatile cpumask_t *dstp)
 154 {
 155         set_bit(cpu, dstp->bits);
 156 }
 157
 158 #define cpu_clear(cpu, dst) __cpu_clear((cpu), &(dst))
 159 static inline void __cpu_clear(int cpu, volatile cpumask_t *dstp)
 160 {
 161         clear_bit(cpu, dstp->bits);
 162 }
 163
 164 #define cpus_setall(dst) __cpus_setall(&(dst), NR_CPUS)
 165 static inline void __cpus_setall(cpumask_t *dstp, int nbits)
 166 {
 167         bitmap_fill(dstp->bits, nbits);
 168 }
 169
 170 #define cpus_clear(dst) __cpus_clear(&(dst), NR_CPUS)
 171 static inline void __cpus_clear(cpumask_t *dstp, int nbits)
 172 {
 173         bitmap_zero(dstp->bits, nbits);
 174 }
 175
 176 /* No static inline type checking - see Subtlety (1) above. */
 177 #define cpu_isset(cpu, cpumask) test_bit((cpu), (cpumask).bits)
 178
 179 #define cpu_test_and_set(cpu, cpumask) __cpu_test_and_set((cpu), &(cpumask))
 180 static inline int __cpu_test_and_set(int cpu, cpumask_t *addr)
 181 {
 182         return test_and_set_bit(cpu, addr->bits);
 183 }
 184
 185 #define cpus_and(dst, src1, src2) __cpus_and(&(dst), &(src1), &(src2), NR_CPUS)
 186 static inline void __cpus_and(cpumask_t *dstp, const cpumask_t *src1p,
 187                                         const cpumask_t *src2p, int nbits)
 188 {
 189         bitmap_and(dstp->bits, src1p->bits, src2p->bits, nbits);
 190 }
 191
 192 #define cpus_or(dst, src1, src2) __cpus_or(&(dst), &(src1), &(src2), NR_CPUS)
 193 static inline void __cpus_or(cpumask_t *dstp, const cpumask_t *src1p,
 194                                         const cpumask_t *src2p, int nbits)
 195 {
 196         bitmap_or(dstp->bits, src1p->bits, src2p->bits, nbits);
 197 }
 198
 199 #define cpus_xor(dst, src1, src2) __cpus_xor(&(dst), &(src1), &(src2), NR_CPUS)
 200 static inline void __cpus_xor(cpumask_t *dstp, const cpumask_t *src1p,
 201                                         const cpumask_t *src2p, int nbits)
 202 {
 203         bitmap_xor(dstp->bits, src1p->bits, src2p->bits, nbits);
 204 }
 205
 206 #define cpus_andnot(dst, src1, src2) \
 207                                 __cpus_andnot(&(dst), &(src1), &(src2), NR_CPUS)
 208 static inline void __cpus_andnot(cpumask_t *dstp, const cpumask_t *src1p,
 209                                         const cpumask_t *src2p, int nbits)
 210 {
 211         bitmap_andnot(dstp->bits, src1p->bits, src2p->bits, nbits);
 212 }
 213
 214 #define cpus_complement(dst, src) __cpus_complement(&(dst), &(src), NR_CPUS)
 215 static inline void __cpus_complement(cpumask_t *dstp,
 216                                         const cpumask_t *srcp, int nbits)
 217 {
 218         bitmap_complement(dstp->bits, srcp->bits, nbits);
 219 }
 220
 221 #define cpus_equal(src1, src2) __cpus_equal(&(src1), &(src2), NR_CPUS)
 222 static inline int __cpus_equal(const cpumask_t *src1p,
 223                                         const cpumask_t *src2p, int nbits)
 224 {
 225         return bitmap_equal(src1p->bits, src2p->bits, nbits);
 226 }
 227
 228 #define cpus_intersects(src1, src2) __cpus_intersects(&(src1), &(src2), NR_CPUS)
 229 static inline int __cpus_intersects(const cpumask_t *src1p,
 230                                         const cpumask_t *src2p, int nbits)
 231 {
 232         return bitmap_intersects(src1p->bits, src2p->bits, nbits);
 233 }
 234
 235 #define cpus_subset(src1, src2) __cpus_subset(&(src1), &(src2), NR_CPUS)
 236 static inline int __cpus_subset(const cpumask_t *src1p,
 237                                         const cpumask_t *src2p, int nbits)
 238 {
 239         return bitmap_subset(src1p->bits, src2p->bits, nbits);
 240 }
 241
 242 #define cpus_empty(src) __cpus_empty(&(src), NR_CPUS)
 243 static inline int __cpus_empty(const cpumask_t *srcp, int nbits)
 244 {
 245         return bitmap_empty(srcp->bits, nbits);
 246 }
 247
 248 #define cpus_full(cpumask) __cpus_full(&(cpumask), NR_CPUS)
 249 static inline int __cpus_full(const cpumask_t *srcp, int nbits)
 250 {
 251         return bitmap_full(srcp->bits, nbits);
 252 }
 253
 254 #define cpus_weight(cpumask) __cpus_weight(&(cpumask), NR_CPUS)
 255 static inline int __cpus_weight(const cpumask_t *srcp, int nbits)
 256 {
 257         return bitmap_weight(srcp->bits, nbits);
 258 }
 259
 260 #define cpus_shift_right(dst, src, n) \
 261                         __cpus_shift_right(&(dst), &(src), (n), NR_CPUS)
 262 static inline void __cpus_shift_right(cpumask_t *dstp,
 263                                         const cpumask_t *srcp, int n, int nbits)
 264 {
 265         bitmap_shift_right(dstp->bits, srcp->bits, n, nbits);
 266 }
 267
 268 #define cpus_shift_left(dst, src, n) \
 269                         __cpus_shift_left(&(dst), &(src), (n), NR_CPUS)
 270 static inline void __cpus_shift_left(cpumask_t *dstp,
 271                                         const cpumask_t *srcp, int n, int nbits)
 272 {
 273         bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
 274 }
 275
 276
 277 #ifdef CONFIG_HAVE_CPUMASK_OF_CPU_MAP
 278 extern cpumask_t *cpumask_of_cpu_map;
 279 #define cpumask_of_cpu(cpu)     (cpumask_of_cpu_map[cpu])
 280 #define cpumask_of_cpu_ptr(v, cpu)                                      \
 281                 const cpumask_t *v = &cpumask_of_cpu(cpu)
 282 #define cpumask_of_cpu_ptr_declare(v)                                   \
 283                 const cpumask_t *v
 284 #define cpumask_of_cpu_ptr_next(v, cpu)                                 \
 285                                         v = &cpumask_of_cpu(cpu)
 286 #else
 287 #define cpumask_of_cpu(cpu)                                             \
 288 ({                                                                      \
 289         typeof(_unused_cpumask_arg_) m;                                 \
 290         if (sizeof(m) == sizeof(unsigned long)) {                       \
 291                 m.bits[0] = 1UL<<(cpu);                                 \
 292         } else {                                                        \
 293                 cpus_clear(m);                                          \
 294                 cpu_set((cpu), m);                                      \
 295         }                                                               \
 296         m;                                                              \
 297 })
 298 #define cpumask_of_cpu_ptr(v, cpu)                                      \
 299                 cpumask_t _##v = cpumask_of_cpu(cpu);                   \
 300                 const cpumask_t *v = &_##v
 301 #define cpumask_of_cpu_ptr_declare(v)                                   \
 302                 cpumask_t _##v;                                         \
 303                 const cpumask_t *v = &_##v
 304 #define cpumask_of_cpu_ptr_next(v, cpu)                                 \
 305                                         _##v = cpumask_of_cpu(cpu)
 306 #endif
 307
 308 #define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)
 309
 310 #if NR_CPUS <= BITS_PER_LONG
 311
 312 #define CPU_MASK_ALL                                                    \
 313 (cpumask_t) { {                                                         \
 314         [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD                 \
 315 } }
 316
 317 #define CPU_MASK_ALL_PTR        (&CPU_MASK_ALL)
 318
 319 #else
 320
 321 #define CPU_MASK_ALL                                                    \
 322 (cpumask_t) { {                                                         \
 323         [0 ... BITS_TO_LONGS(NR_CPUS)-2] = ~0UL,                        \
 324         [BITS_TO_LONGS(NR_CPUS)-1] = CPU_MASK_LAST_WORD                 \
 325 } }
 326
 327 /* cpu_mask_all is in init/main.c */
 328 extern cpumask_t cpu_mask_all;
 329 #define CPU_MASK_ALL_PTR        (&cpu_mask_all)
 330
 331 #endif
 332
 333 #define CPU_MASK_NONE                                                   \
 334 (cpumask_t) { {                                                         \
 335         [0 ... BITS_TO_LONGS(NR_CPUS)-1] =  0UL                         \
 336 } }
 337
 338 #define CPU_MASK_CPU0                                                   \
 339 (cpumask_t) { {                                                         \
 340         [0] =  1UL                                                      \
 341 } }
 342
 343 #define cpus_addr(src) ((src).bits)
 344
 345 #if NR_CPUS > BITS_PER_LONG
 346 #define CPUMASK_ALLOC(m)        struct m *m = kmalloc(sizeof(*m), GFP_KERNEL)
 347 #define CPUMASK_FREE(m)         kfree(m)
 348 #else
 349 #define CPUMASK_ALLOC(m)        struct m _m, *m = &_m
 350 #define CPUMASK_FREE(m)
 351 #endif
 352 #define CPUMASK_PTR(v, m)       cpumask_t *v = &(m->v)
 353
 354 #define cpumask_scnprintf(buf, len, src) \
 355                         __cpumask_scnprintf((buf), (len), &(src), NR_CPUS)
 356 static inline int __cpumask_scnprintf(char *buf, int len,
 357                                         const cpumask_t *srcp, int nbits)
 358 {
 359         return bitmap_scnprintf(buf, len, srcp->bits, nbits);
 360 }
 361
 362 #define cpumask_parse_user(ubuf, ulen, dst) \
 363                         __cpumask_parse_user((ubuf), (ulen), &(dst), NR_CPUS)
 364 static inline int __cpumask_parse_user(const char __user *buf, int len,
 365                                         cpumask_t *dstp, int nbits)
 366 {
 367         return bitmap_parse_user(buf, len, dstp->bits, nbits);
 368 }
 369
 370 #define cpulist_scnprintf(buf, len, src) \
 371                         __cpulist_scnprintf((buf), (len), &(src), NR_CPUS)
 372 static inline int __cpulist_scnprintf(char *buf, int len,
 373                                         const cpumask_t *srcp, int nbits)
 374 {
 375         return bitmap_scnlistprintf(buf, len, srcp->bits, nbits);
 376 }
 377
 378 #define cpulist_parse(buf, dst) __cpulist_parse((buf), &(dst), NR_CPUS)
 379 static inline int __cpulist_parse(const char *buf, cpumask_t *dstp, int nbits)
 380 {
 381         return bitmap_parselist(buf, dstp->bits, nbits);
 382 }
 383
 384 #define cpu_remap(oldbit, old, new) \
 385                 __cpu_remap((oldbit), &(old), &(new), NR_CPUS)
 386 static inline int __cpu_remap(int oldbit,
 387                 const cpumask_t *oldp, const cpumask_t *newp, int nbits)
 388 {
 389         return bitmap_bitremap(oldbit, oldp->bits, newp->bits, nbits);
 390 }
 391
 392 #define cpus_remap(dst, src, old, new) \
 393                 __cpus_remap(&(dst), &(src), &(old), &(new), NR_CPUS)
 394 static inline void __cpus_remap(cpumask_t *dstp, const cpumask_t *srcp,
 395                 const cpumask_t *oldp, const cpumask_t *newp, int nbits)
 396 {
 397         bitmap_remap(dstp->bits, srcp->bits, oldp->bits, newp->bits, nbits);
 398 }
 399
 400 #define cpus_onto(dst, orig, relmap) \
 401                 __cpus_onto(&(dst), &(orig), &(relmap), NR_CPUS)
 402 static inline void __cpus_onto(cpumask_t *dstp, const cpumask_t *origp,
 403                 const cpumask_t *relmapp, int nbits)
 404 {
 405         bitmap_onto(dstp->bits, origp->bits, relmapp->bits, nbits);
 406 }
 407
 408 #define cpus_fold(dst, orig, sz) \
 409                 __cpus_fold(&(dst), &(orig), sz, NR_CPUS)
 410 static inline void __cpus_fold(cpumask_t *dstp, const cpumask_t *origp,
 411                 int sz, int nbits)
 412 {
 413         bitmap_fold(dstp->bits, origp->bits, sz, nbits);
 414 }
 415
 416 #if NR_CPUS == 1
 417
 418 #define nr_cpu_ids              1
 419 #define first_cpu(src)          ({ (void)(src); 0; })
 420 #define next_cpu(n, src)        ({ (void)(src); 1; })
 421 #define any_online_cpu(mask)    0
 422 #define for_each_cpu_mask(cpu, mask)    \
 423         for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
 424
 425 #else /* NR_CPUS > 1 */
 426
 427 extern int nr_cpu_ids;
 428 int __first_cpu(const cpumask_t *srcp);
 429 int __next_cpu(int n, const cpumask_t *srcp);
 430 int __any_online_cpu(const cpumask_t *mask);
 431
 432 #define first_cpu(src)          __first_cpu(&(src))
 433 #define next_cpu(n, src)        __next_cpu((n), &(src))
 434 #define any_online_cpu(mask) __any_online_cpu(&(mask))
 435 #define for_each_cpu_mask(cpu, mask)                    \
 436         for ((cpu) = -1;                                \
 437                 (cpu) = next_cpu((cpu), (mask)),        \
 438                 (cpu) < NR_CPUS; )
 439 #endif
 440
 441 #if NR_CPUS <= 64
 442
 443 #define next_cpu_nr(n, src)             next_cpu(n, src)
 444 #define cpus_weight_nr(cpumask)         cpus_weight(cpumask)
 445 #define for_each_cpu_mask_nr(cpu, mask) for_each_cpu_mask(cpu, mask)
 446
 447 #else /* NR_CPUS > 64 */
 448
 449 int __next_cpu_nr(int n, const cpumask_t *srcp);
 450 #define next_cpu_nr(n, src)     __next_cpu_nr((n), &(src))
 451 #define cpus_weight_nr(cpumask) __cpus_weight(&(cpumask), nr_cpu_ids)
 452 #define for_each_cpu_mask_nr(cpu, mask)                 \
 453         for ((cpu) = -1;                                \
 454                 (cpu) = next_cpu_nr((cpu), (mask)),     \
 455                 (cpu) < nr_cpu_ids; )
 456
 457 #endif /* NR_CPUS > 64 */
 458
 459 /*
 460  * The following particular system cpumasks and operations manage
 461  * possible, present, active and online cpus.  Each of them is a fixed size
 462  * bitmap of size NR_CPUS.
 463  *
 464  *  #ifdef CONFIG_HOTPLUG_CPU
 465  *     cpu_possible_map - has bit 'cpu' set iff cpu is populatable
 466  *     cpu_present_map  - has bit 'cpu' set iff cpu is populated
 467  *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 468  *     cpu_active_map   - has bit 'cpu' set iff cpu available to migration
 469  *  #else
 470  *     cpu_possible_map - has bit 'cpu' set iff cpu is populated
 471  *     cpu_present_map  - copy of cpu_possible_map
 472  *     cpu_online_map   - has bit 'cpu' set iff cpu available to scheduler
 473  *  #endif
 474  *
 475  *  In either case, NR_CPUS is fixed at compile time, as the static
 476  *  size of these bitmaps.  The cpu_possible_map is fixed at boot
 477  *  time, as the set of CPU id's that it is possible might ever
 478  *  be plugged in at anytime during the life of that system boot.
 479  *  The cpu_present_map is dynamic(*), representing which CPUs
 480  *  are currently plugged in.  And cpu_online_map is the dynamic
 481  *  subset of cpu_present_map, indicating those CPUs available
 482  *  for scheduling.
 483  *
 484  *  If HOTPLUG is enabled, then cpu_possible_map is forced to have
 485  *  all NR_CPUS bits set, otherwise it is just the set of CPUs that
 486  *  ACPI reports present at boot.
 487  *
 488  *  If HOTPLUG is enabled, then cpu_present_map varies dynamically,
 489  *  depending on what ACPI reports as currently plugged in, otherwise
 490  *  cpu_present_map is just a copy of cpu_possible_map.
 491  *
 492  *  (*) Well, cpu_present_map is dynamic in the hotplug case.  If not
 493  *      hotplug, it's a copy of cpu_possible_map, hence fixed at boot.
 494  *
 495  * Subtleties:
 496  * 1) UP arch's (NR_CPUS == 1, CONFIG_SMP not defined) hardcode
 497  *    assumption that their single CPU is online.  The UP
 498  *    cpu_{online,possible,present}_maps are placebos.  Changing them
 499  *    will have no useful affect on the following num_*_cpus()
 500  *    and cpu_*() macros in the UP case.  This ugliness is a UP
 501  *    optimization - don't waste any instructions or memory references
 502  *    asking if you're online or how many CPUs there are if there is
 503  *    only one CPU.
 504  * 2) Most SMP arch's #define some of these maps to be some
 505  *    other map specific to that arch.  Therefore, the following
 506  *    must be #define macros, not inlines.  To see why, examine
 507  *    the assembly code produced by the following.  Note that
 508  *    set1() writes phys_x_map, but set2() writes x_map:
 509  *        int x_map, phys_x_map;
 510  *        #define set1(a) x_map = a
 511  *        inline void set2(int a) { x_map = a; }
 512  *        #define x_map phys_x_map
 513  *        main(){ set1(3); set2(5); }
 514  */
 515
 516 extern cpumask_t cpu_possible_map;
 517 extern cpumask_t cpu_online_map;
 518 extern cpumask_t cpu_present_map;
 519 extern cpumask_t cpu_active_map;
 520
 521 #if NR_CPUS > 1
 522 #define num_online_cpus()       cpus_weight_nr(cpu_online_map)
 523 #define num_possible_cpus()     cpus_weight_nr(cpu_possible_map)
 524 #define num_present_cpus()      cpus_weight_nr(cpu_present_map)
 525 #define cpu_online(cpu)         cpu_isset((cpu), cpu_online_map)
 526 #define cpu_possible(cpu)       cpu_isset((cpu), cpu_possible_map)
 527 #define cpu_present(cpu)        cpu_isset((cpu), cpu_present_map)
 528 #define cpu_active(cpu)         cpu_isset((cpu), cpu_active_map)
 529 #else
 530 #define num_online_cpus()       1
 531 #define num_possible_cpus()     1
 532 #define num_present_cpus()      1
 533 #define cpu_online(cpu)         ((cpu) == 0)
 534 #define cpu_possible(cpu)       ((cpu) == 0)
 535 #define cpu_present(cpu)        ((cpu) == 0)
 536 #define cpu_active(cpu)         ((cpu) == 0)
 537 #endif
 538
 539 #define cpu_is_offline(cpu)     unlikely(!cpu_online(cpu))
 540
 541 #define for_each_possible_cpu(cpu) for_each_cpu_mask_nr((cpu), cpu_possible_map)
 542 #define for_each_online_cpu(cpu)   for_each_cpu_mask_nr((cpu), cpu_online_map)
 543 #define for_each_present_cpu(cpu)  for_each_cpu_mask_nr((cpu), cpu_present_map)
 544
 545 #endif /* __LINUX_CPUMASK_H */