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 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 void cpu_hotplug_done(void)
 131 {
 132         cpu_hotplug.active_writer = NULL;
 133         mutex_unlock(&cpu_hotplug.lock);
 134 }
 135
 136 /*
 137  * Wait for currently running CPU hotplug operations to complete (if any) and
 138  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 139  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 140  * hotplug path before performing hotplug operations. So acquiring that lock
 141  * guarantees mutual exclusion from any currently running hotplug operations.
 142  */
 143 void cpu_hotplug_disable(void)
 144 {
 145         cpu_maps_update_begin();
 146         cpu_hotplug_disabled = 1;
 147         cpu_maps_update_done();
 148 }
 149
 150 void cpu_hotplug_enable(void)
 151 {
 152         cpu_maps_update_begin();
 153         cpu_hotplug_disabled = 0;
 154         cpu_maps_update_done();
 155 }
 156
 157 #endif  /* CONFIG_HOTPLUG_CPU */
 158
 159 /* Need to know about CPUs going up/down? */
 160 int __ref register_cpu_notifier(struct notifier_block *nb)
 161 {
 162         int ret;
 163         cpu_maps_update_begin();
 164         ret = raw_notifier_chain_register(&cpu_chain, nb);
 165         cpu_maps_update_done();
 166         return ret;
 167 }
 168
 169 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
 170                         int *nr_calls)
 171 {
 172         int ret;
 173
 174         ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
 175                                         nr_calls);
 176
 177         return notifier_to_errno(ret);
 178 }
 179
 180 static int cpu_notify(unsigned long val, void *v)
 181 {
 182         return __cpu_notify(val, v, -1, NULL);
 183 }
 184
 185 #ifdef CONFIG_HOTPLUG_CPU
 186
 187 static void cpu_notify_nofail(unsigned long val, void *v)
 188 {
 189         BUG_ON(cpu_notify(val, v));
 190 }
 191 EXPORT_SYMBOL(register_cpu_notifier);
 192
 193 void __ref unregister_cpu_notifier(struct notifier_block *nb)
 194 {
 195         cpu_maps_update_begin();
 196         raw_notifier_chain_unregister(&cpu_chain, nb);
 197         cpu_maps_update_done();
 198 }
 199 EXPORT_SYMBOL(unregister_cpu_notifier);
 200
 201 /**
 202  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 203  * @cpu: a CPU id
 204  *
 205  * This function walks all processes, finds a valid mm struct for each one and
 206  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 207  * trivial, there are various non-obvious corner cases, which this function
 208  * tries to solve in a safe manner.
 209  *
 210  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 211  * be called only for an already offlined CPU.
 212  */
 213 void clear_tasks_mm_cpumask(int cpu)
 214 {
 215         struct task_struct *p;
 216
 217         /*
 218          * This function is called after the cpu is taken down and marked
 219          * offline, so its not like new tasks will ever get this cpu set in
 220          * their mm mask. -- Peter Zijlstra
 221          * Thus, we may use rcu_read_lock() here, instead of grabbing
 222          * full-fledged tasklist_lock.
 223          */
 224         WARN_ON(cpu_online(cpu));
 225         rcu_read_lock();
 226         for_each_process(p) {
 227                 struct task_struct *t;
 228
 229                 /*
 230                  * Main thread might exit, but other threads may still have
 231                  * a valid mm. Find one.
 232                  */
 233                 t = find_lock_task_mm(p);
 234                 if (!t)
 235                         continue;
 236                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 237                 task_unlock(t);
 238         }
 239         rcu_read_unlock();
 240 }
 241
 242 static inline void check_for_tasks(int cpu)
 243 {
 244         struct task_struct *p;
 245         cputime_t utime, stime;
 246
 247         write_lock_irq(&tasklist_lock);
 248         for_each_process(p) {
 249                 task_cputime(p, &utime, &stime);
 250                 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
 251                     (utime || stime))
 252                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 253                                 "(state = %ld, flags = %x)\n",
 254                                 p->comm, task_pid_nr(p), cpu,
 255                                 p->state, p->flags);
 256         }
 257         write_unlock_irq(&tasklist_lock);
 258 }
 259
 260 struct take_cpu_down_param {
 261         unsigned long mod;
 262         void *hcpu;
 263 };
 264
 265 /* Take this CPU down. */
 266 static int __ref take_cpu_down(void *_param)
 267 {
 268         struct take_cpu_down_param *param = _param;
 269         int err;
 270
 271         /* Ensure this CPU doesn't handle any more interrupts. */
 272         err = __cpu_disable();
 273         if (err < 0)
 274                 return err;
 275
 276         cpu_notify(CPU_DYING | param->mod, param->hcpu);
 277         /* Park the stopper thread */
 278         kthread_park(current);
 279         return 0;
 280 }
 281
 282 /* Requires cpu_add_remove_lock to be held */
 283 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 284 {
 285         int err, nr_calls = 0;
 286         void *hcpu = (void *)(long)cpu;
 287         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 288         struct take_cpu_down_param tcd_param = {
 289                 .mod = mod,
 290                 .hcpu = hcpu,
 291         };
 292
 293         if (num_online_cpus() == 1)
 294                 return -EBUSY;
 295
 296         if (!cpu_online(cpu))
 297                 return -EINVAL;
 298
 299         cpu_hotplug_begin();
 300
 301         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
 302         if (err) {
 303                 nr_calls--;
 304                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
 305                 printk("%s: attempt to take down CPU %u failed\n",
 306                                 __func__, cpu);
 307                 goto out_release;
 308         }
 309         smpboot_park_threads(cpu);
 310
 311         /*
 312          * By now we've cleared cpu_active_mask, wait for all preempt-disabled
 313          * and RCU users of this state to go away such that all new such users
 314          * will observe it.
 315          *
 316          * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
 317          * not imply sync_sched(), so explicitly call both.
 318          */
 319 #ifdef CONFIG_PREEMPT
 320         synchronize_sched();
 321 #endif
 322         synchronize_rcu();
 323
 324         /*
 325          * So now all preempt/rcu users must observe !cpu_active().
 326          */
 327
 328         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 329         if (err) {
 330                 /* CPU didn't die: tell everyone.  Can't complain. */
 331                 smpboot_unpark_threads(cpu);
 332                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
 333                 goto out_release;
 334         }
 335         BUG_ON(cpu_online(cpu));
 336
 337         /*
 338          * The migration_call() CPU_DYING callback will have removed all
 339          * runnable tasks from the cpu, there's only the idle task left now
 340          * that the migration thread is done doing the stop_machine thing.
 341          *
 342          * Wait for the stop thread to go away.
 343          */
 344         while (!idle_cpu(cpu))
 345                 cpu_relax();
 346
 347         /* This actually kills the CPU. */
 348         __cpu_die(cpu);
 349
 350         /* CPU is completely dead: tell everyone.  Too late to complain. */
 351         cpu_notify_nofail(CPU_DEAD | mod, hcpu);
 352
 353         check_for_tasks(cpu);
 354
 355 out_release:
 356         cpu_hotplug_done();
 357         if (!err)
 358                 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
 359         return err;
 360 }
 361
 362 int __ref cpu_down(unsigned int cpu)
 363 {
 364         int err;
 365
 366         cpu_maps_update_begin();
 367
 368         if (cpu_hotplug_disabled) {
 369                 err = -EBUSY;
 370                 goto out;
 371         }
 372
 373         err = _cpu_down(cpu, 0);
 374
 375 out:
 376         cpu_maps_update_done();
 377         return err;
 378 }
 379 EXPORT_SYMBOL(cpu_down);
 380 #endif /*CONFIG_HOTPLUG_CPU*/
 381
 382 /* Requires cpu_add_remove_lock to be held */
 383 static int _cpu_up(unsigned int cpu, int tasks_frozen)
 384 {
 385         int ret, nr_calls = 0;
 386         void *hcpu = (void *)(long)cpu;
 387         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 388         struct task_struct *idle;
 389
 390         cpu_hotplug_begin();
 391
 392         if (cpu_online(cpu) || !cpu_present(cpu)) {
 393                 ret = -EINVAL;
 394                 goto out;
 395         }
 396
 397         idle = idle_thread_get(cpu);
 398         if (IS_ERR(idle)) {
 399                 ret = PTR_ERR(idle);
 400                 goto out;
 401         }
 402
 403         ret = smpboot_create_threads(cpu);
 404         if (ret)
 405                 goto out;
 406
 407         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
 408         if (ret) {
 409                 nr_calls--;
 410                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 411                                 __func__, cpu);
 412                 goto out_notify;
 413         }
 414
 415         /* Arch-specific enabling code. */
 416         ret = __cpu_up(cpu, idle);
 417         if (ret != 0)
 418                 goto out_notify;
 419         BUG_ON(!cpu_online(cpu));
 420
 421         /* Wake the per cpu threads */
 422         smpboot_unpark_threads(cpu);
 423
 424         /* Now call notifier in preparation. */
 425         cpu_notify(CPU_ONLINE | mod, hcpu);
 426
 427 out_notify:
 428         if (ret != 0)
 429                 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
 430 out:
 431         cpu_hotplug_done();
 432
 433         return ret;
 434 }
 435
 436 int cpu_up(unsigned int cpu)
 437 {
 438         int err = 0;
 439
 440 #ifdef  CONFIG_MEMORY_HOTPLUG
 441         int nid;
 442         pg_data_t       *pgdat;
 443 #endif
 444
 445         if (!cpu_possible(cpu)) {
 446                 printk(KERN_ERR "can't online cpu %d because it is not "
 447                         "configured as may-hotadd at boot time\n", cpu);
 448 #if defined(CONFIG_IA64)
 449                 printk(KERN_ERR "please check additional_cpus= boot "
 450                                 "parameter\n");
 451 #endif
 452                 return -EINVAL;
 453         }
 454
 455 #ifdef  CONFIG_MEMORY_HOTPLUG
 456         nid = cpu_to_node(cpu);
 457         if (!node_online(nid)) {
 458                 err = mem_online_node(nid);
 459                 if (err)
 460                         return err;
 461         }
 462
 463         pgdat = NODE_DATA(nid);
 464         if (!pgdat) {
 465                 printk(KERN_ERR
 466                         "Can't online cpu %d due to NULL pgdat\n", cpu);
 467                 return -ENOMEM;
 468         }
 469
 470         if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
 471                 mutex_lock(&zonelists_mutex);
 472                 build_all_zonelists(NULL, NULL);
 473                 mutex_unlock(&zonelists_mutex);
 474         }
 475 #endif
 476
 477         cpu_maps_update_begin();
 478
 479         if (cpu_hotplug_disabled) {
 480                 err = -EBUSY;
 481                 goto out;
 482         }
 483
 484         err = _cpu_up(cpu, 0);
 485
 486 out:
 487         cpu_maps_update_done();
 488         return err;
 489 }
 490 EXPORT_SYMBOL_GPL(cpu_up);
 491
 492 #ifdef CONFIG_PM_SLEEP_SMP
 493 static cpumask_var_t frozen_cpus;
 494
 495 int disable_nonboot_cpus(void)
 496 {
 497         int cpu, first_cpu, error = 0;
 498
 499         cpu_maps_update_begin();
 500         first_cpu = cpumask_first(cpu_online_mask);
 501         /*
 502          * We take down all of the non-boot CPUs in one shot to avoid races
 503          * with the userspace trying to use the CPU hotplug at the same time
 504          */
 505         cpumask_clear(frozen_cpus);
 506
 507         printk("Disabling non-boot CPUs ...\n");
 508         for_each_online_cpu(cpu) {
 509                 if (cpu == first_cpu)
 510                         continue;
 511                 error = _cpu_down(cpu, 1);
 512                 if (!error)
 513                         cpumask_set_cpu(cpu, frozen_cpus);
 514                 else {
 515                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 516                                 cpu, error);
 517                         break;
 518                 }
 519         }
 520
 521         if (!error) {
 522                 BUG_ON(num_online_cpus() > 1);
 523                 /* Make sure the CPUs won't be enabled by someone else */
 524                 cpu_hotplug_disabled = 1;
 525         } else {
 526                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 527         }
 528         cpu_maps_update_done();
 529         return error;
 530 }
 531
 532 void __weak arch_enable_nonboot_cpus_begin(void)
 533 {
 534 }
 535
 536 void __weak arch_enable_nonboot_cpus_end(void)
 537 {
 538 }
 539
 540 void __ref enable_nonboot_cpus(void)
 541 {
 542         int cpu, error;
 543
 544         /* Allow everyone to use the CPU hotplug again */
 545         cpu_maps_update_begin();
 546         cpu_hotplug_disabled = 0;
 547         if (cpumask_empty(frozen_cpus))
 548                 goto out;
 549
 550         printk(KERN_INFO "Enabling non-boot CPUs ...\n");
 551
 552         arch_enable_nonboot_cpus_begin();
 553
 554         for_each_cpu(cpu, frozen_cpus) {
 555                 error = _cpu_up(cpu, 1);
 556                 if (!error) {
 557                         printk(KERN_INFO "CPU%d is up\n", cpu);
 558                         continue;
 559                 }
 560                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 561         }
 562
 563         arch_enable_nonboot_cpus_end();
 564
 565         cpumask_clear(frozen_cpus);
 566 out:
 567         cpu_maps_update_done();
 568 }
 569
 570 static int __init alloc_frozen_cpus(void)
 571 {
 572         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
 573                 return -ENOMEM;
 574         return 0;
 575 }
 576 core_initcall(alloc_frozen_cpus);
 577
 578 /*
 579  * When callbacks for CPU hotplug notifications are being executed, we must
 580  * ensure that the state of the system with respect to the tasks being frozen
 581  * or not, as reported by the notification, remains unchanged *throughout the
 582  * duration* of the execution of the callbacks.
 583  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
 584  *
 585  * This synchronization is implemented by mutually excluding regular CPU
 586  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
 587  * Hibernate notifications.
 588  */
 589 static int
 590 cpu_hotplug_pm_callback(struct notifier_block *nb,
 591                         unsigned long action, void *ptr)
 592 {
 593         switch (action) {
 594
 595         case PM_SUSPEND_PREPARE:
 596         case PM_HIBERNATION_PREPARE:
 597                 cpu_hotplug_disable();
 598                 break;
 599
 600         case PM_POST_SUSPEND:
 601         case PM_POST_HIBERNATION:
 602                 cpu_hotplug_enable();
 603                 break;
 604
 605         default:
 606                 return NOTIFY_DONE;
 607         }
 608
 609         return NOTIFY_OK;
 610 }
 611
 612
 613 static int __init cpu_hotplug_pm_sync_init(void)
 614 {
 615         /*
 616          * cpu_hotplug_pm_callback has higher priority than x86
 617          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
 618          * to disable cpu hotplug to avoid cpu hotplug race.
 619          */
 620         pm_notifier(cpu_hotplug_pm_callback, 0);
 621         return 0;
 622 }
 623 core_initcall(cpu_hotplug_pm_sync_init);
 624
 625 #endif /* CONFIG_PM_SLEEP_SMP */
 626
 627 /**
 628  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 629  * @cpu: cpu that just started
 630  *
 631  * This function calls the cpu_chain notifiers with CPU_STARTING.
 632  * It must be called by the arch code on the new cpu, before the new cpu
 633  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 634  */
 635 void notify_cpu_starting(unsigned int cpu)
 636 {
 637         unsigned long val = CPU_STARTING;
 638
 639 #ifdef CONFIG_PM_SLEEP_SMP
 640         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
 641                 val = CPU_STARTING_FROZEN;
 642 #endif /* CONFIG_PM_SLEEP_SMP */
 643         cpu_notify(val, (void *)(long)cpu);
 644 }
 645
 646 #endif /* CONFIG_SMP */
 647
 648 /*
 649  * cpu_bit_bitmap[] is a special, "compressed" data structure that
 650  * represents all NR_CPUS bits binary values of 1<<nr.
 651  *
 652  * It is used by cpumask_of() to get a constant address to a CPU
 653  * mask value that has a single bit set only.
 654  */
 655
 656 /* cpu_bit_bitmap[0] is empty - so we can back into it */
 657 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
 658 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
 659 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
 660 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
 661
 662 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
 663
 664         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
 665         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
 666 #if BITS_PER_LONG > 32
 667         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
 668         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
 669 #endif
 670 };
 671 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
 672
 673 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
 674 EXPORT_SYMBOL(cpu_all_bits);
 675
 676 #ifdef CONFIG_INIT_ALL_POSSIBLE
 677 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
 678         = CPU_BITS_ALL;
 679 #else
 680 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
 681 #endif
 682 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
 683 EXPORT_SYMBOL(cpu_possible_mask);
 684
 685 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
 686 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
 687 EXPORT_SYMBOL(cpu_online_mask);
 688
 689 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
 690 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
 691 EXPORT_SYMBOL(cpu_present_mask);
 692
 693 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
 694 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
 695 EXPORT_SYMBOL(cpu_active_mask);
 696
 697 void set_cpu_possible(unsigned int cpu, bool possible)
 698 {
 699         if (possible)
 700                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
 701         else
 702                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
 703 }
 704
 705 void set_cpu_present(unsigned int cpu, bool present)
 706 {
 707         if (present)
 708                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
 709         else
 710                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
 711 }
 712
 713 void set_cpu_online(unsigned int cpu, bool online)
 714 {
 715         if (online)
 716                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
 717         else
 718                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
 719 }
 720
 721 void set_cpu_active(unsigned int cpu, bool active)
 722 {
 723         if (active)
 724                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
 725         else
 726                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
 727 }
 728
 729 void init_cpu_present(const struct cpumask *src)
 730 {
 731         cpumask_copy(to_cpumask(cpu_present_bits), src);
 732 }
 733
 734 void init_cpu_possible(const struct cpumask *src)
 735 {
 736         cpumask_copy(to_cpumask(cpu_possible_bits), src);
 737 }
 738
 739 void init_cpu_online(const struct cpumask *src)
 740 {
 741         cpumask_copy(to_cpumask(cpu_online_bits), src);
 742 }