kernel/cpu.c

   1 /* CPU control.
   2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
   3  *
   4  * This code is licenced under the GPL.
   5  */
   6 #include <linux/proc_fs.h>
   7 #include <linux/smp.h>
   8 #include <linux/init.h>
   9 #include <linux/notifier.h>
  10 #include <linux/sched.h>
  11 #include <linux/unistd.h>
  12 #include <linux/cpu.h>
  13 #include <linux/oom.h>
  14 #include <linux/rcupdate.h>
  15 #include <linux/export.h>
  16 #include <linux/bug.h>
  17 #include <linux/kthread.h>
  18 #include <linux/stop_machine.h>
  19 #include <linux/mutex.h>
  20 #include <linux/gfp.h>
  21 #include <linux/suspend.h>
  22
  23 #include "smpboot.h"
  24
  25 #ifdef CONFIG_SMP
  26 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
  27 static DEFINE_MUTEX(cpu_add_remove_lock);
  28
  29 /*
  30  * The following two API's must be used when attempting
  31  * to serialize the updates to cpu_online_mask, cpu_present_mask.
  32  */
  33 void cpu_maps_update_begin(void)
  34 {
  35         mutex_lock(&cpu_add_remove_lock);
  36 }
  37
  38 void cpu_maps_update_done(void)
  39 {
  40         mutex_unlock(&cpu_add_remove_lock);
  41 }
  42
  43 static RAW_NOTIFIER_HEAD(cpu_chain);
  44
  45 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
  46  * Should always be manipulated under cpu_add_remove_lock
  47  */
  48 static int cpu_hotplug_disabled;
  49
  50 #ifdef CONFIG_HOTPLUG_CPU
  51
  52 static struct {
  53         struct task_struct *active_writer;
  54         struct mutex lock; /* Synchronizes accesses to refcount, */
  55         /*
  56          * Also blocks the new readers during
  57          * an ongoing cpu hotplug operation.
  58          */
  59         int refcount;
  60 } cpu_hotplug = {
  61         .active_writer = NULL,
  62         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
  63         .refcount = 0,
  64 };
  65
  66 void get_online_cpus(void)
  67 {
  68         might_sleep();
  69         if (cpu_hotplug.active_writer == current)
  70                 return;
  71         mutex_lock(&cpu_hotplug.lock);
  72         cpu_hotplug.refcount++;
  73         mutex_unlock(&cpu_hotplug.lock);
  74
  75 }
  76 EXPORT_SYMBOL_GPL(get_online_cpus);
  77
  78 void put_online_cpus(void)
  79 {
  80         if (cpu_hotplug.active_writer == current)
  81                 return;
  82         mutex_lock(&cpu_hotplug.lock);
  83
  84         if (WARN_ON(!cpu_hotplug.refcount))
  85                 cpu_hotplug.refcount++; /* try to fix things up */
  86
  87         if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
  88                 wake_up_process(cpu_hotplug.active_writer);
  89         mutex_unlock(&cpu_hotplug.lock);
  90
  91 }
  92 EXPORT_SYMBOL_GPL(put_online_cpus);
  93
  94 /*
  95  * This ensures that the hotplug operation can begin only when the
  96  * refcount goes to zero.
  97  *
  98  * Note that during a cpu-hotplug operation, the new readers, if any,
  99  * will be blocked by the cpu_hotplug.lock
 100  *
 101  * Since cpu_hotplug_begin() is always called after invoking
 102  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 103  *
 104  * Note that theoretically, there is a possibility of a livelock:
 105  * - Refcount goes to zero, last reader wakes up the sleeping
 106  *   writer.
 107  * - Last reader unlocks the cpu_hotplug.lock.
 108  * - A new reader arrives at this moment, bumps up the refcount.
 109  * - The writer acquires the cpu_hotplug.lock finds the refcount
 110  *   non zero and goes to sleep again.
 111  *
 112  * However, this is very difficult to achieve in practice since
 113  * get_online_cpus() not an api which is called all that often.
 114  *
 115  */
 116 static void cpu_hotplug_begin(void)
 117 {
 118         cpu_hotplug.active_writer = current;
 119
 120         for (;;) {
 121                 mutex_lock(&cpu_hotplug.lock);
 122                 if (likely(!cpu_hotplug.refcount))
 123                         break;
 124                 __set_current_state(TASK_UNINTERRUPTIBLE);
 125                 mutex_unlock(&cpu_hotplug.lock);
 126                 schedule();
 127         }
 128 }
 129
 130 static void cpu_hotplug_done(void)
 131 {
 132         cpu_hotplug.active_writer = NULL;
 133         mutex_unlock(&cpu_hotplug.lock);
 134 }
 135
 136 #else /* #if CONFIG_HOTPLUG_CPU */
 137 static void cpu_hotplug_begin(void) {}
 138 static void cpu_hotplug_done(void) {}
 139 #endif  /* #else #if CONFIG_HOTPLUG_CPU */
 140
 141 /* Need to know about CPUs going up/down? */
 142 int __ref register_cpu_notifier(struct notifier_block *nb)
 143 {
 144         int ret;
 145         cpu_maps_update_begin();
 146         ret = raw_notifier_chain_register(&cpu_chain, nb);
 147         cpu_maps_update_done();
 148         return ret;
 149 }
 150
 151 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
 152                         int *nr_calls)
 153 {
 154         int ret;
 155
 156         ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
 157                                         nr_calls);
 158
 159         return notifier_to_errno(ret);
 160 }
 161
 162 static int cpu_notify(unsigned long val, void *v)
 163 {
 164         return __cpu_notify(val, v, -1, NULL);
 165 }
 166
 167 #ifdef CONFIG_HOTPLUG_CPU
 168
 169 static void cpu_notify_nofail(unsigned long val, void *v)
 170 {
 171         BUG_ON(cpu_notify(val, v));
 172 }
 173 EXPORT_SYMBOL(register_cpu_notifier);
 174
 175 void __ref unregister_cpu_notifier(struct notifier_block *nb)
 176 {
 177         cpu_maps_update_begin();
 178         raw_notifier_chain_unregister(&cpu_chain, nb);
 179         cpu_maps_update_done();
 180 }
 181 EXPORT_SYMBOL(unregister_cpu_notifier);
 182
 183 /**
 184  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 185  * @cpu: a CPU id
 186  *
 187  * This function walks all processes, finds a valid mm struct for each one and
 188  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 189  * trivial, there are various non-obvious corner cases, which this function
 190  * tries to solve in a safe manner.
 191  *
 192  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 193  * be called only for an already offlined CPU.
 194  */
 195 void clear_tasks_mm_cpumask(int cpu)
 196 {
 197         struct task_struct *p;
 198
 199         /*
 200          * This function is called after the cpu is taken down and marked
 201          * offline, so its not like new tasks will ever get this cpu set in
 202          * their mm mask. -- Peter Zijlstra
 203          * Thus, we may use rcu_read_lock() here, instead of grabbing
 204          * full-fledged tasklist_lock.
 205          */
 206         WARN_ON(cpu_online(cpu));
 207         rcu_read_lock();
 208         for_each_process(p) {
 209                 struct task_struct *t;
 210
 211                 /*
 212                  * Main thread might exit, but other threads may still have
 213                  * a valid mm. Find one.
 214                  */
 215                 t = find_lock_task_mm(p);
 216                 if (!t)
 217                         continue;
 218                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 219                 task_unlock(t);
 220         }
 221         rcu_read_unlock();
 222 }
 223
 224 static inline void check_for_tasks(int cpu)
 225 {
 226         struct task_struct *p;
 227
 228         write_lock_irq(&tasklist_lock);
 229         for_each_process(p) {
 230                 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
 231                     (p->utime || p->stime))
 232                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 233                                 "(state = %ld, flags = %x)\n",
 234                                 p->comm, task_pid_nr(p), cpu,
 235                                 p->state, p->flags);
 236         }
 237         write_unlock_irq(&tasklist_lock);
 238 }
 239
 240 struct take_cpu_down_param {
 241         unsigned long mod;
 242         void *hcpu;
 243 };
 244
 245 /* Take this CPU down. */
 246 static int __ref take_cpu_down(void *_param)
 247 {
 248         struct take_cpu_down_param *param = _param;
 249         int err;
 250
 251         /* Ensure this CPU doesn't handle any more interrupts. */
 252         err = __cpu_disable();
 253         if (err < 0)
 254                 return err;
 255
 256         cpu_notify(CPU_DYING | param->mod, param->hcpu);
 257         /* Park the stopper thread */
 258         kthread_park(current);
 259         return 0;
 260 }
 261
 262 /* Requires cpu_add_remove_lock to be held */
 263 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 264 {
 265         int err, nr_calls = 0;
 266         void *hcpu = (void *)(long)cpu;
 267         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 268         struct take_cpu_down_param tcd_param = {
 269                 .mod = mod,
 270                 .hcpu = hcpu,
 271         };
 272
 273         if (num_online_cpus() == 1)
 274                 return -EBUSY;
 275
 276         if (!cpu_online(cpu))
 277                 return -EINVAL;
 278
 279         cpu_hotplug_begin();
 280
 281         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
 282         if (err) {
 283                 nr_calls--;
 284                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
 285                 printk("%s: attempt to take down CPU %u failed\n",
 286                                 __func__, cpu);
 287                 goto out_release;
 288         }
 289         smpboot_park_threads(cpu);
 290
 291         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 292         if (err) {
 293                 /* CPU didn't die: tell everyone.  Can't complain. */
 294                 smpboot_unpark_threads(cpu);
 295                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
 296                 goto out_release;
 297         }
 298         BUG_ON(cpu_online(cpu));
 299
 300         /*
 301          * The migration_call() CPU_DYING callback will have removed all
 302          * runnable tasks from the cpu, there's only the idle task left now
 303          * that the migration thread is done doing the stop_machine thing.
 304          *
 305          * Wait for the stop thread to go away.
 306          */
 307         while (!idle_cpu(cpu))
 308                 cpu_relax();
 309
 310         /* This actually kills the CPU. */
 311         __cpu_die(cpu);
 312
 313         /* CPU is completely dead: tell everyone.  Too late to complain. */
 314         cpu_notify_nofail(CPU_DEAD | mod, hcpu);
 315
 316         check_for_tasks(cpu);
 317
 318 out_release:
 319         cpu_hotplug_done();
 320         if (!err)
 321                 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
 322         return err;
 323 }
 324
 325 int __ref cpu_down(unsigned int cpu)
 326 {
 327         int err;
 328
 329         cpu_maps_update_begin();
 330
 331         if (cpu_hotplug_disabled) {
 332                 err = -EBUSY;
 333                 goto out;
 334         }
 335
 336         err = _cpu_down(cpu, 0);
 337
 338 out:
 339         cpu_maps_update_done();
 340         return err;
 341 }
 342 EXPORT_SYMBOL(cpu_down);
 343 #endif /*CONFIG_HOTPLUG_CPU*/
 344
 345 /* Requires cpu_add_remove_lock to be held */
 346 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 347 {
 348         int ret, nr_calls = 0;
 349         void *hcpu = (void *)(long)cpu;
 350         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 351         struct task_struct *idle;
 352
 353         cpu_hotplug_begin();
 354
 355         if (cpu_online(cpu) || !cpu_present(cpu)) {
 356                 ret = -EINVAL;
 357                 goto out;
 358         }
 359
 360         idle = idle_thread_get(cpu);
 361         if (IS_ERR(idle)) {
 362                 ret = PTR_ERR(idle);
 363                 goto out;
 364         }
 365
 366         ret = smpboot_create_threads(cpu);
 367         if (ret)
 368                 goto out;
 369
 370         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
 371         if (ret) {
 372                 nr_calls--;
 373                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 374                                 __func__, cpu);
 375                 goto out_notify;
 376         }
 377
 378         /* Arch-specific enabling code. */
 379         ret = __cpu_up(cpu, idle);
 380         if (ret != 0)
 381                 goto out_notify;
 382         BUG_ON(!cpu_online(cpu));
 383
 384         /* Wake the per cpu threads */
 385         smpboot_unpark_threads(cpu);
 386
 387         /* Now call notifier in preparation. */
 388         cpu_notify(CPU_ONLINE | mod, hcpu);
 389
 390 out_notify:
 391         if (ret != 0)
 392                 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
 393 out:
 394         cpu_hotplug_done();
 395
 396         return ret;
 397 }
 398
 399 int __cpuinit cpu_up(unsigned int cpu)
 400 {
 401         int err = 0;
 402
 403 #ifdef  CONFIG_MEMORY_HOTPLUG
 404         int nid;
 405         pg_data_t       *pgdat;
 406 #endif
 407
 408         if (!cpu_possible(cpu)) {
 409                 printk(KERN_ERR "can't online cpu %d because it is not "
 410                         "configured as may-hotadd at boot time\n", cpu);
 411 #if defined(CONFIG_IA64)
 412                 printk(KERN_ERR "please check additional_cpus= boot "
 413                                 "parameter\n");
 414 #endif
 415                 return -EINVAL;
 416         }
 417
 418 #ifdef  CONFIG_MEMORY_HOTPLUG
 419         nid = cpu_to_node(cpu);
 420         if (!node_online(nid)) {
 421                 err = mem_online_node(nid);
 422                 if (err)
 423                         return err;
 424         }
 425
 426         pgdat = NODE_DATA(nid);
 427         if (!pgdat) {
 428                 printk(KERN_ERR
 429                         "Can't online cpu %d due to NULL pgdat\n", cpu);
 430                 return -ENOMEM;
 431         }
 432
 433         if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
 434                 mutex_lock(&zonelists_mutex);
 435                 build_all_zonelists(NULL, NULL);
 436                 mutex_unlock(&zonelists_mutex);
 437         }
 438 #endif
 439
 440         cpu_maps_update_begin();
 441
 442         if (cpu_hotplug_disabled) {
 443                 err = -EBUSY;
 444                 goto out;
 445         }
 446
 447         err = _cpu_up(cpu, 0);
 448
 449 out:
 450         cpu_maps_update_done();
 451         return err;
 452 }
 453 EXPORT_SYMBOL_GPL(cpu_up);
 454
 455 #ifdef CONFIG_PM_SLEEP_SMP
 456 static cpumask_var_t frozen_cpus;
 457
 458 int disable_nonboot_cpus(void)
 459 {
 460         int cpu, first_cpu, error = 0;
 461
 462         cpu_maps_update_begin();
 463         first_cpu = cpumask_first(cpu_online_mask);
 464         /*
 465          * We take down all of the non-boot CPUs in one shot to avoid races
 466          * with the userspace trying to use the CPU hotplug at the same time
 467          */
 468         cpumask_clear(frozen_cpus);
 469
 470         printk("Disabling non-boot CPUs ...\n");
 471         for_each_online_cpu(cpu) {
 472                 if (cpu == first_cpu)
 473                         continue;
 474                 error = _cpu_down(cpu, 1);
 475                 if (!error)
 476                         cpumask_set_cpu(cpu, frozen_cpus);
 477                 else {
 478                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 479                                 cpu, error);
 480                         break;
 481                 }
 482         }
 483
 484         if (!error) {
 485                 BUG_ON(num_online_cpus() > 1);
 486                 /* Make sure the CPUs won't be enabled by someone else */
 487                 cpu_hotplug_disabled = 1;
 488         } else {
 489                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 490         }
 491         cpu_maps_update_done();
 492         return error;
 493 }
 494
 495 void __weak arch_enable_nonboot_cpus_begin(void)
 496 {
 497 }
 498
 499 void __weak arch_enable_nonboot_cpus_end(void)
 500 {
 501 }
 502
 503 void __ref enable_nonboot_cpus(void)
 504 {
 505         int cpu, error;
 506
 507         /* Allow everyone to use the CPU hotplug again */
 508         cpu_maps_update_begin();
 509         cpu_hotplug_disabled = 0;
 510         if (cpumask_empty(frozen_cpus))
 511                 goto out;
 512
 513         printk(KERN_INFO "Enabling non-boot CPUs ...\n");
 514
 515         arch_enable_nonboot_cpus_begin();
 516
 517         for_each_cpu(cpu, frozen_cpus) {
 518                 error = _cpu_up(cpu, 1);
 519                 if (!error) {
 520                         printk(KERN_INFO "CPU%d is up\n", cpu);
 521                         continue;
 522                 }
 523                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 524         }
 525
 526         arch_enable_nonboot_cpus_end();
 527
 528         cpumask_clear(frozen_cpus);
 529 out:
 530         cpu_maps_update_done();
 531 }
 532
 533 static int __init alloc_frozen_cpus(void)
 534 {
 535         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
 536                 return -ENOMEM;
 537         return 0;
 538 }
 539 core_initcall(alloc_frozen_cpus);
 540
 541 /*
 542  * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
 543  * hotplug when tasks are about to be frozen. Also, don't allow the freezer
 544  * to continue until any currently running CPU hotplug operation gets
 545  * completed.
 546  * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
 547  * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
 548  * CPU hotplug path and released only after it is complete. Thus, we
 549  * (and hence the freezer) will block here until any currently running CPU
 550  * hotplug operation gets completed.
 551  */
 552 void cpu_hotplug_disable_before_freeze(void)
 553 {
 554         cpu_maps_update_begin();
 555         cpu_hotplug_disabled = 1;
 556         cpu_maps_update_done();
 557 }
 558
 559
 560 /*
 561  * When tasks have been thawed, re-enable regular CPU hotplug (which had been
 562  * disabled while beginning to freeze tasks).
 563  */
 564 void cpu_hotplug_enable_after_thaw(void)
 565 {
 566         cpu_maps_update_begin();
 567         cpu_hotplug_disabled = 0;
 568         cpu_maps_update_done();
 569 }
 570
 571 /*
 572  * When callbacks for CPU hotplug notifications are being executed, we must
 573  * ensure that the state of the system with respect to the tasks being frozen
 574  * or not, as reported by the notification, remains unchanged *throughout the
 575  * duration* of the execution of the callbacks.
 576  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
 577  *
 578  * This synchronization is implemented by mutually excluding regular CPU
 579  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
 580  * Hibernate notifications.
 581  */
 582 static int
 583 cpu_hotplug_pm_callback(struct notifier_block *nb,
 584                         unsigned long action, void *ptr)
 585 {
 586         switch (action) {
 587
 588         case PM_SUSPEND_PREPARE:
 589         case PM_HIBERNATION_PREPARE:
 590                 cpu_hotplug_disable_before_freeze();
 591                 break;
 592
 593         case PM_POST_SUSPEND:
 594         case PM_POST_HIBERNATION:
 595                 cpu_hotplug_enable_after_thaw();
 596                 break;
 597
 598         default:
 599                 return NOTIFY_DONE;
 600         }
 601
 602         return NOTIFY_OK;
 603 }
 604
 605
 606 static int __init cpu_hotplug_pm_sync_init(void)
 607 {
 608         /*
 609          * cpu_hotplug_pm_callback has higher priority than x86
 610          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
 611          * to disable cpu hotplug to avoid cpu hotplug race.
 612          */
 613         pm_notifier(cpu_hotplug_pm_callback, 0);
 614         return 0;
 615 }
 616 core_initcall(cpu_hotplug_pm_sync_init);
 617
 618 #endif /* CONFIG_PM_SLEEP_SMP */
 619
 620 /**
 621  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 622  * @cpu: cpu that just started
 623  *
 624  * This function calls the cpu_chain notifiers with CPU_STARTING.
 625  * It must be called by the arch code on the new cpu, before the new cpu
 626  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 627  */
 628 void __cpuinit notify_cpu_starting(unsigned int cpu)
 629 {
 630         unsigned long val = CPU_STARTING;
 631
 632 #ifdef CONFIG_PM_SLEEP_SMP
 633         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
 634                 val = CPU_STARTING_FROZEN;
 635 #endif /* CONFIG_PM_SLEEP_SMP */
 636         cpu_notify(val, (void *)(long)cpu);
 637 }
 638
 639 #endif /* CONFIG_SMP */
 640
 641 /*
 642  * cpu_bit_bitmap[] is a special, "compressed" data structure that
 643  * represents all NR_CPUS bits binary values of 1<<nr.
 644  *
 645  * It is used by cpumask_of() to get a constant address to a CPU
 646  * mask value that has a single bit set only.
 647  */
 648
 649 /* cpu_bit_bitmap[0] is empty - so we can back into it */
 650 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
 651 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
 652 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
 653 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
 654
 655 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
 656
 657         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
 658         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
 659 #if BITS_PER_LONG > 32
 660         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
 661         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
 662 #endif
 663 };
 664 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
 665
 666 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
 667 EXPORT_SYMBOL(cpu_all_bits);
 668
 669 #ifdef CONFIG_INIT_ALL_POSSIBLE
 670 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
 671         = CPU_BITS_ALL;
 672 #else
 673 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
 674 #endif
 675 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
 676 EXPORT_SYMBOL(cpu_possible_mask);
 677
 678 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
 679 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
 680 EXPORT_SYMBOL(cpu_online_mask);
 681
 682 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
 683 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
 684 EXPORT_SYMBOL(cpu_present_mask);
 685
 686 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
 687 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
 688 EXPORT_SYMBOL(cpu_active_mask);
 689
 690 void set_cpu_possible(unsigned int cpu, bool possible)
 691 {
 692         if (possible)
 693                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
 694         else
 695                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
 696 }
 697
 698 void set_cpu_present(unsigned int cpu, bool present)
 699 {
 700         if (present)
 701                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
 702         else
 703                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
 704 }
 705
 706 void set_cpu_online(unsigned int cpu, bool online)
 707 {
 708         if (online)
 709                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
 710         else
 711                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
 712 }
 713
 714 void set_cpu_active(unsigned int cpu, bool active)
 715 {
 716         if (active)
 717                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
 718         else
 719                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
 720 }
 721
 722 void init_cpu_present(const struct cpumask *src)
 723 {
 724         cpumask_copy(to_cpumask(cpu_present_bits), src);
 725 }
 726
 727 void init_cpu_possible(const struct cpumask *src)
 728 {
 729         cpumask_copy(to_cpumask(cpu_possible_bits), src);
 730 }
 731
 732 void init_cpu_online(const struct cpumask *src)
 733 {
 734         cpumask_copy(to_cpumask(cpu_online_bits), src);
 735 }