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 #include <linux/lockdep.h>
  23 #include <linux/tick.h>
  24 #include <linux/irq.h>
  25 #include <trace/events/power.h>
  26
  27 #include "smpboot.h"
  28
  29 #ifdef CONFIG_SMP
  30 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
  31 static DEFINE_MUTEX(cpu_add_remove_lock);
  32 bool cpuhp_tasks_frozen;
  33 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
  34
  35 /*
  36  * The following two APIs (cpu_maps_update_begin/done) must be used when
  37  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
  38  * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
  39  * hotplug callback (un)registration performed using __register_cpu_notifier()
  40  * or __unregister_cpu_notifier().
  41  */
  42 void cpu_maps_update_begin(void)
  43 {
  44         mutex_lock(&cpu_add_remove_lock);
  45 }
  46 EXPORT_SYMBOL(cpu_notifier_register_begin);
  47
  48 void cpu_maps_update_done(void)
  49 {
  50         mutex_unlock(&cpu_add_remove_lock);
  51 }
  52 EXPORT_SYMBOL(cpu_notifier_register_done);
  53
  54 static RAW_NOTIFIER_HEAD(cpu_chain);
  55
  56 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
  57  * Should always be manipulated under cpu_add_remove_lock
  58  */
  59 static int cpu_hotplug_disabled;
  60
  61 #ifdef CONFIG_HOTPLUG_CPU
  62
  63 static struct {
  64         struct task_struct *active_writer;
  65         /* wait queue to wake up the active_writer */
  66         wait_queue_head_t wq;
  67         /* verifies that no writer will get active while readers are active */
  68         struct mutex lock;
  69         /*
  70          * Also blocks the new readers during
  71          * an ongoing cpu hotplug operation.
  72          */
  73         atomic_t refcount;
  74
  75 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  76         struct lockdep_map dep_map;
  77 #endif
  78 } cpu_hotplug = {
  79         .active_writer = NULL,
  80         .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
  81         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
  82 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  83         .dep_map = {.name = "cpu_hotplug.lock" },
  84 #endif
  85 };
  86
  87 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
  88 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
  89 #define cpuhp_lock_acquire_tryread() \
  90                                   lock_map_acquire_tryread(&cpu_hotplug.dep_map)
  91 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
  92 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
  93
  94
  95 void get_online_cpus(void)
  96 {
  97         might_sleep();
  98         if (cpu_hotplug.active_writer == current)
  99                 return;
 100         cpuhp_lock_acquire_read();
 101         mutex_lock(&cpu_hotplug.lock);
 102         atomic_inc(&cpu_hotplug.refcount);
 103         mutex_unlock(&cpu_hotplug.lock);
 104 }
 105 EXPORT_SYMBOL_GPL(get_online_cpus);
 106
 107 void put_online_cpus(void)
 108 {
 109         int refcount;
 110
 111         if (cpu_hotplug.active_writer == current)
 112                 return;
 113
 114         refcount = atomic_dec_return(&cpu_hotplug.refcount);
 115         if (WARN_ON(refcount < 0)) /* try to fix things up */
 116                 atomic_inc(&cpu_hotplug.refcount);
 117
 118         if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 119                 wake_up(&cpu_hotplug.wq);
 120
 121         cpuhp_lock_release();
 122
 123 }
 124 EXPORT_SYMBOL_GPL(put_online_cpus);
 125
 126 /*
 127  * This ensures that the hotplug operation can begin only when the
 128  * refcount goes to zero.
 129  *
 130  * Note that during a cpu-hotplug operation, the new readers, if any,
 131  * will be blocked by the cpu_hotplug.lock
 132  *
 133  * Since cpu_hotplug_begin() is always called after invoking
 134  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 135  *
 136  * Note that theoretically, there is a possibility of a livelock:
 137  * - Refcount goes to zero, last reader wakes up the sleeping
 138  *   writer.
 139  * - Last reader unlocks the cpu_hotplug.lock.
 140  * - A new reader arrives at this moment, bumps up the refcount.
 141  * - The writer acquires the cpu_hotplug.lock finds the refcount
 142  *   non zero and goes to sleep again.
 143  *
 144  * However, this is very difficult to achieve in practice since
 145  * get_online_cpus() not an api which is called all that often.
 146  *
 147  */
 148 void cpu_hotplug_begin(void)
 149 {
 150         DEFINE_WAIT(wait);
 151
 152         cpu_hotplug.active_writer = current;
 153         cpuhp_lock_acquire();
 154
 155         for (;;) {
 156                 mutex_lock(&cpu_hotplug.lock);
 157                 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 158                 if (likely(!atomic_read(&cpu_hotplug.refcount)))
 159                                 break;
 160                 mutex_unlock(&cpu_hotplug.lock);
 161                 schedule();
 162         }
 163         finish_wait(&cpu_hotplug.wq, &wait);
 164 }
 165
 166 void cpu_hotplug_done(void)
 167 {
 168         cpu_hotplug.active_writer = NULL;
 169         mutex_unlock(&cpu_hotplug.lock);
 170         cpuhp_lock_release();
 171 }
 172
 173 /*
 174  * Wait for currently running CPU hotplug operations to complete (if any) and
 175  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 176  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 177  * hotplug path before performing hotplug operations. So acquiring that lock
 178  * guarantees mutual exclusion from any currently running hotplug operations.
 179  */
 180 void cpu_hotplug_disable(void)
 181 {
 182         cpu_maps_update_begin();
 183         cpu_hotplug_disabled++;
 184         cpu_maps_update_done();
 185 }
 186 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 187
 188 void cpu_hotplug_enable(void)
 189 {
 190         cpu_maps_update_begin();
 191         WARN_ON(--cpu_hotplug_disabled < 0);
 192         cpu_maps_update_done();
 193 }
 194 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 195 #endif  /* CONFIG_HOTPLUG_CPU */
 196
 197 /* Need to know about CPUs going up/down? */
 198 int register_cpu_notifier(struct notifier_block *nb)
 199 {
 200         int ret;
 201         cpu_maps_update_begin();
 202         ret = raw_notifier_chain_register(&cpu_chain, nb);
 203         cpu_maps_update_done();
 204         return ret;
 205 }
 206
 207 int __register_cpu_notifier(struct notifier_block *nb)
 208 {
 209         return raw_notifier_chain_register(&cpu_chain, nb);
 210 }
 211
 212 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 213                         int *nr_calls)
 214 {
 215         unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 216         void *hcpu = (void *)(long)cpu;
 217
 218         int ret;
 219
 220         ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 221                                         nr_calls);
 222
 223         return notifier_to_errno(ret);
 224 }
 225
 226 static int cpu_notify(unsigned long val, unsigned int cpu)
 227 {
 228         return __cpu_notify(val, cpu, -1, NULL);
 229 }
 230
 231 /* Notifier wrappers for transitioning to state machine */
 232 static int notify_prepare(unsigned int cpu)
 233 {
 234         int nr_calls = 0;
 235         int ret;
 236
 237         ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 238         if (ret) {
 239                 nr_calls--;
 240                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 241                                 __func__, cpu);
 242                 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 243         }
 244         return ret;
 245 }
 246
 247 static int notify_online(unsigned int cpu)
 248 {
 249         cpu_notify(CPU_ONLINE, cpu);
 250         return 0;
 251 }
 252
 253 static int bringup_cpu(unsigned int cpu)
 254 {
 255         struct task_struct *idle = idle_thread_get(cpu);
 256         int ret;
 257
 258         /* Arch-specific enabling code. */
 259         ret = __cpu_up(cpu, idle);
 260         if (ret) {
 261                 cpu_notify(CPU_UP_CANCELED, cpu);
 262                 return ret;
 263         }
 264         BUG_ON(!cpu_online(cpu));
 265         return 0;
 266 }
 267
 268 #ifdef CONFIG_HOTPLUG_CPU
 269
 270 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 271 {
 272         BUG_ON(cpu_notify(val, cpu));
 273 }
 274 EXPORT_SYMBOL(register_cpu_notifier);
 275 EXPORT_SYMBOL(__register_cpu_notifier);
 276
 277 void unregister_cpu_notifier(struct notifier_block *nb)
 278 {
 279         cpu_maps_update_begin();
 280         raw_notifier_chain_unregister(&cpu_chain, nb);
 281         cpu_maps_update_done();
 282 }
 283 EXPORT_SYMBOL(unregister_cpu_notifier);
 284
 285 void __unregister_cpu_notifier(struct notifier_block *nb)
 286 {
 287         raw_notifier_chain_unregister(&cpu_chain, nb);
 288 }
 289 EXPORT_SYMBOL(__unregister_cpu_notifier);
 290
 291 /**
 292  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 293  * @cpu: a CPU id
 294  *
 295  * This function walks all processes, finds a valid mm struct for each one and
 296  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 297  * trivial, there are various non-obvious corner cases, which this function
 298  * tries to solve in a safe manner.
 299  *
 300  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 301  * be called only for an already offlined CPU.
 302  */
 303 void clear_tasks_mm_cpumask(int cpu)
 304 {
 305         struct task_struct *p;
 306
 307         /*
 308          * This function is called after the cpu is taken down and marked
 309          * offline, so its not like new tasks will ever get this cpu set in
 310          * their mm mask. -- Peter Zijlstra
 311          * Thus, we may use rcu_read_lock() here, instead of grabbing
 312          * full-fledged tasklist_lock.
 313          */
 314         WARN_ON(cpu_online(cpu));
 315         rcu_read_lock();
 316         for_each_process(p) {
 317                 struct task_struct *t;
 318
 319                 /*
 320                  * Main thread might exit, but other threads may still have
 321                  * a valid mm. Find one.
 322                  */
 323                 t = find_lock_task_mm(p);
 324                 if (!t)
 325                         continue;
 326                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 327                 task_unlock(t);
 328         }
 329         rcu_read_unlock();
 330 }
 331
 332 static inline void check_for_tasks(int dead_cpu)
 333 {
 334         struct task_struct *g, *p;
 335
 336         read_lock(&tasklist_lock);
 337         for_each_process_thread(g, p) {
 338                 if (!p->on_rq)
 339                         continue;
 340                 /*
 341                  * We do the check with unlocked task_rq(p)->lock.
 342                  * Order the reading to do not warn about a task,
 343                  * which was running on this cpu in the past, and
 344                  * it's just been woken on another cpu.
 345                  */
 346                 rmb();
 347                 if (task_cpu(p) != dead_cpu)
 348                         continue;
 349
 350                 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
 351                         p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
 352         }
 353         read_unlock(&tasklist_lock);
 354 }
 355
 356 /* Take this CPU down. */
 357 static int take_cpu_down(void *_param)
 358 {
 359         int err, cpu = smp_processor_id();
 360
 361         /* Ensure this CPU doesn't handle any more interrupts. */
 362         err = __cpu_disable();
 363         if (err < 0)
 364                 return err;
 365
 366         cpu_notify(CPU_DYING, cpu);
 367         /* Give up timekeeping duties */
 368         tick_handover_do_timer();
 369         /* Park the stopper thread */
 370         stop_machine_park(cpu);
 371         return 0;
 372 }
 373
 374 /* Requires cpu_add_remove_lock to be held */
 375 static int _cpu_down(unsigned int cpu, int tasks_frozen)
 376 {
 377         int err, nr_calls = 0;
 378
 379         if (num_online_cpus() == 1)
 380                 return -EBUSY;
 381
 382         if (!cpu_online(cpu))
 383                 return -EINVAL;
 384
 385         cpu_hotplug_begin();
 386
 387         cpuhp_tasks_frozen = tasks_frozen;
 388
 389         err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
 390         if (err) {
 391                 nr_calls--;
 392                 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
 393                 pr_warn("%s: attempt to take down CPU %u failed\n",
 394                         __func__, cpu);
 395                 goto out_release;
 396         }
 397
 398         /*
 399          * By now we've cleared cpu_active_mask, wait for all preempt-disabled
 400          * and RCU users of this state to go away such that all new such users
 401          * will observe it.
 402          *
 403          * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
 404          * not imply sync_sched(), so wait for both.
 405          *
 406          * Do sync before park smpboot threads to take care the rcu boost case.
 407          */
 408         if (IS_ENABLED(CONFIG_PREEMPT))
 409                 synchronize_rcu_mult(call_rcu, call_rcu_sched);
 410         else
 411                 synchronize_rcu();
 412
 413         smpboot_park_threads(cpu);
 414
 415         /*
 416          * Prevent irq alloc/free while the dying cpu reorganizes the
 417          * interrupt affinities.
 418          */
 419         irq_lock_sparse();
 420
 421         /*
 422          * So now all preempt/rcu users must observe !cpu_active().
 423          */
 424         err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
 425         if (err) {
 426                 /* CPU didn't die: tell everyone.  Can't complain. */
 427                 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 428                 irq_unlock_sparse();
 429                 goto out_release;
 430         }
 431         BUG_ON(cpu_online(cpu));
 432
 433         /*
 434          * The migration_call() CPU_DYING callback will have removed all
 435          * runnable tasks from the cpu, there's only the idle task left now
 436          * that the migration thread is done doing the stop_machine thing.
 437          *
 438          * Wait for the stop thread to go away.
 439          */
 440         while (!per_cpu(cpu_dead_idle, cpu))
 441                 cpu_relax();
 442         smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
 443         per_cpu(cpu_dead_idle, cpu) = false;
 444
 445         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
 446         irq_unlock_sparse();
 447
 448         hotplug_cpu__broadcast_tick_pull(cpu);
 449         /* This actually kills the CPU. */
 450         __cpu_die(cpu);
 451
 452         /* CPU is completely dead: tell everyone.  Too late to complain. */
 453         tick_cleanup_dead_cpu(cpu);
 454         cpu_notify_nofail(CPU_DEAD, cpu);
 455
 456         check_for_tasks(cpu);
 457
 458 out_release:
 459         cpu_hotplug_done();
 460         if (!err)
 461                 cpu_notify_nofail(CPU_POST_DEAD, cpu);
 462         return err;
 463 }
 464
 465 int cpu_down(unsigned int cpu)
 466 {
 467         int err;
 468
 469         cpu_maps_update_begin();
 470
 471         if (cpu_hotplug_disabled) {
 472                 err = -EBUSY;
 473                 goto out;
 474         }
 475
 476         err = _cpu_down(cpu, 0);
 477
 478 out:
 479         cpu_maps_update_done();
 480         return err;
 481 }
 482 EXPORT_SYMBOL(cpu_down);
 483 #endif /*CONFIG_HOTPLUG_CPU*/
 484
 485 /*
 486  * Unpark per-CPU smpboot kthreads at CPU-online time.
 487  */
 488 static int smpboot_thread_call(struct notifier_block *nfb,
 489                                unsigned long action, void *hcpu)
 490 {
 491         int cpu = (long)hcpu;
 492
 493         switch (action & ~CPU_TASKS_FROZEN) {
 494
 495         case CPU_DOWN_FAILED:
 496         case CPU_ONLINE:
 497                 smpboot_unpark_threads(cpu);
 498                 break;
 499
 500         default:
 501                 break;
 502         }
 503
 504         return NOTIFY_OK;
 505 }
 506
 507 static struct notifier_block smpboot_thread_notifier = {
 508         .notifier_call = smpboot_thread_call,
 509         .priority = CPU_PRI_SMPBOOT,
 510 };
 511
 512 void smpboot_thread_init(void)
 513 {
 514         register_cpu_notifier(&smpboot_thread_notifier);
 515 }
 516
 517 /* Requires cpu_add_remove_lock to be held */
 518 static int _cpu_up(unsigned int cpu, int tasks_frozen)
 519 {
 520         struct task_struct *idle;
 521         int ret;
 522
 523         cpu_hotplug_begin();
 524
 525         if (cpu_online(cpu) || !cpu_present(cpu)) {
 526                 ret = -EINVAL;
 527                 goto out;
 528         }
 529
 530         idle = idle_thread_get(cpu);
 531         if (IS_ERR(idle)) {
 532                 ret = PTR_ERR(idle);
 533                 goto out;
 534         }
 535
 536         cpuhp_tasks_frozen = tasks_frozen;
 537
 538         ret = smpboot_create_threads(cpu);
 539         if (ret)
 540                 goto out;
 541
 542         ret = notify_prepare(cpu);
 543         if (ret)
 544                 goto out;
 545
 546         ret = bringup_cpu(cpu);
 547         if (ret)
 548                 goto out;
 549
 550         notify_online(cpu);
 551 out:
 552         cpu_hotplug_done();
 553
 554         return ret;
 555 }
 556
 557 int cpu_up(unsigned int cpu)
 558 {
 559         int err = 0;
 560
 561         if (!cpu_possible(cpu)) {
 562                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
 563                        cpu);
 564 #if defined(CONFIG_IA64)
 565                 pr_err("please check additional_cpus= boot parameter\n");
 566 #endif
 567                 return -EINVAL;
 568         }
 569
 570         err = try_online_node(cpu_to_node(cpu));
 571         if (err)
 572                 return err;
 573
 574         cpu_maps_update_begin();
 575
 576         if (cpu_hotplug_disabled) {
 577                 err = -EBUSY;
 578                 goto out;
 579         }
 580
 581         err = _cpu_up(cpu, 0);
 582
 583 out:
 584         cpu_maps_update_done();
 585         return err;
 586 }
 587 EXPORT_SYMBOL_GPL(cpu_up);
 588
 589 #ifdef CONFIG_PM_SLEEP_SMP
 590 static cpumask_var_t frozen_cpus;
 591
 592 int disable_nonboot_cpus(void)
 593 {
 594         int cpu, first_cpu, error = 0;
 595
 596         cpu_maps_update_begin();
 597         first_cpu = cpumask_first(cpu_online_mask);
 598         /*
 599          * We take down all of the non-boot CPUs in one shot to avoid races
 600          * with the userspace trying to use the CPU hotplug at the same time
 601          */
 602         cpumask_clear(frozen_cpus);
 603
 604         pr_info("Disabling non-boot CPUs ...\n");
 605         for_each_online_cpu(cpu) {
 606                 if (cpu == first_cpu)
 607                         continue;
 608                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
 609                 error = _cpu_down(cpu, 1);
 610                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
 611                 if (!error)
 612                         cpumask_set_cpu(cpu, frozen_cpus);
 613                 else {
 614                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
 615                         break;
 616                 }
 617         }
 618
 619         if (!error)
 620                 BUG_ON(num_online_cpus() > 1);
 621         else
 622                 pr_err("Non-boot CPUs are not disabled\n");
 623
 624         /*
 625          * Make sure the CPUs won't be enabled by someone else. We need to do
 626          * this even in case of failure as all disable_nonboot_cpus() users are
 627          * supposed to do enable_nonboot_cpus() on the failure path.
 628          */
 629         cpu_hotplug_disabled++;
 630
 631         cpu_maps_update_done();
 632         return error;
 633 }
 634
 635 void __weak arch_enable_nonboot_cpus_begin(void)
 636 {
 637 }
 638
 639 void __weak arch_enable_nonboot_cpus_end(void)
 640 {
 641 }
 642
 643 void enable_nonboot_cpus(void)
 644 {
 645         int cpu, error;
 646
 647         /* Allow everyone to use the CPU hotplug again */
 648         cpu_maps_update_begin();
 649         WARN_ON(--cpu_hotplug_disabled < 0);
 650         if (cpumask_empty(frozen_cpus))
 651                 goto out;
 652
 653         pr_info("Enabling non-boot CPUs ...\n");
 654
 655         arch_enable_nonboot_cpus_begin();
 656
 657         for_each_cpu(cpu, frozen_cpus) {
 658                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
 659                 error = _cpu_up(cpu, 1);
 660                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
 661                 if (!error) {
 662                         pr_info("CPU%d is up\n", cpu);
 663                         continue;
 664                 }
 665                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
 666         }
 667
 668         arch_enable_nonboot_cpus_end();
 669
 670         cpumask_clear(frozen_cpus);
 671 out:
 672         cpu_maps_update_done();
 673 }
 674
 675 static int __init alloc_frozen_cpus(void)
 676 {
 677         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
 678                 return -ENOMEM;
 679         return 0;
 680 }
 681 core_initcall(alloc_frozen_cpus);
 682
 683 /*
 684  * When callbacks for CPU hotplug notifications are being executed, we must
 685  * ensure that the state of the system with respect to the tasks being frozen
 686  * or not, as reported by the notification, remains unchanged *throughout the
 687  * duration* of the execution of the callbacks.
 688  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
 689  *
 690  * This synchronization is implemented by mutually excluding regular CPU
 691  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
 692  * Hibernate notifications.
 693  */
 694 static int
 695 cpu_hotplug_pm_callback(struct notifier_block *nb,
 696                         unsigned long action, void *ptr)
 697 {
 698         switch (action) {
 699
 700         case PM_SUSPEND_PREPARE:
 701         case PM_HIBERNATION_PREPARE:
 702                 cpu_hotplug_disable();
 703                 break;
 704
 705         case PM_POST_SUSPEND:
 706         case PM_POST_HIBERNATION:
 707                 cpu_hotplug_enable();
 708                 break;
 709
 710         default:
 711                 return NOTIFY_DONE;
 712         }
 713
 714         return NOTIFY_OK;
 715 }
 716
 717
 718 static int __init cpu_hotplug_pm_sync_init(void)
 719 {
 720         /*
 721          * cpu_hotplug_pm_callback has higher priority than x86
 722          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
 723          * to disable cpu hotplug to avoid cpu hotplug race.
 724          */
 725         pm_notifier(cpu_hotplug_pm_callback, 0);
 726         return 0;
 727 }
 728 core_initcall(cpu_hotplug_pm_sync_init);
 729
 730 #endif /* CONFIG_PM_SLEEP_SMP */
 731
 732 /**
 733  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 734  * @cpu: cpu that just started
 735  *
 736  * This function calls the cpu_chain notifiers with CPU_STARTING.
 737  * It must be called by the arch code on the new cpu, before the new cpu
 738  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 739  */
 740 void notify_cpu_starting(unsigned int cpu)
 741 {
 742         cpu_notify(CPU_STARTING, cpu);
 743 }
 744
 745 #endif /* CONFIG_SMP */
 746
 747 /*
 748  * cpu_bit_bitmap[] is a special, "compressed" data structure that
 749  * represents all NR_CPUS bits binary values of 1<<nr.
 750  *
 751  * It is used by cpumask_of() to get a constant address to a CPU
 752  * mask value that has a single bit set only.
 753  */
 754
 755 /* cpu_bit_bitmap[0] is empty - so we can back into it */
 756 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
 757 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
 758 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
 759 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
 760
 761 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
 762
 763         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
 764         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
 765 #if BITS_PER_LONG > 32
 766         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
 767         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
 768 #endif
 769 };
 770 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
 771
 772 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
 773 EXPORT_SYMBOL(cpu_all_bits);
 774
 775 #ifdef CONFIG_INIT_ALL_POSSIBLE
 776 struct cpumask __cpu_possible_mask __read_mostly
 777         = {CPU_BITS_ALL};
 778 #else
 779 struct cpumask __cpu_possible_mask __read_mostly;
 780 #endif
 781 EXPORT_SYMBOL(__cpu_possible_mask);
 782
 783 struct cpumask __cpu_online_mask __read_mostly;
 784 EXPORT_SYMBOL(__cpu_online_mask);
 785
 786 struct cpumask __cpu_present_mask __read_mostly;
 787 EXPORT_SYMBOL(__cpu_present_mask);
 788
 789 struct cpumask __cpu_active_mask __read_mostly;
 790 EXPORT_SYMBOL(__cpu_active_mask);
 791
 792 void init_cpu_present(const struct cpumask *src)
 793 {
 794         cpumask_copy(&__cpu_present_mask, src);
 795 }
 796
 797 void init_cpu_possible(const struct cpumask *src)
 798 {
 799         cpumask_copy(&__cpu_possible_mask, src);
 800 }
 801
 802 void init_cpu_online(const struct cpumask *src)
 803 {
 804         cpumask_copy(&__cpu_online_mask, src);
 805 }