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