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