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 <linux/smpboot.h>
  26
  27 #include <trace/events/power.h>
  28 #define CREATE_TRACE_POINTS
  29 #include <trace/events/cpuhp.h>
  30
  31 #include "smpboot.h"
  32
  33 /**
  34  * cpuhp_cpu_state - Per cpu hotplug state storage
  35  * @state:      The current cpu state
  36  * @target:     The target state
  37  * @thread:     Pointer to the hotplug thread
  38  * @should_run: Thread should execute
  39  * @cb_stat:    The state for a single callback (install/uninstall)
  40  * @cb:         Single callback function (install/uninstall)
  41  * @result:     Result of the operation
  42  * @done:       Signal completion to the issuer of the task
  43  */
  44 struct cpuhp_cpu_state {
  45         enum cpuhp_state        state;
  46         enum cpuhp_state        target;
  47 #ifdef CONFIG_SMP
  48         struct task_struct      *thread;
  49         bool                    should_run;
  50         enum cpuhp_state        cb_state;
  51         int                     (*cb)(unsigned int cpu);
  52         int                     result;
  53         struct completion       done;
  54 #endif
  55 };
  56
  57 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
  58
  59 /**
  60  * cpuhp_step - Hotplug state machine step
  61  * @name:       Name of the step
  62  * @startup:    Startup function of the step
  63  * @teardown:   Teardown function of the step
  64  * @skip_onerr: Do not invoke the functions on error rollback
  65  *              Will go away once the notifiers are gone
  66  * @cant_stop:  Bringup/teardown can't be stopped at this step
  67  */
  68 struct cpuhp_step {
  69         const char      *name;
  70         int             (*startup)(unsigned int cpu);
  71         int             (*teardown)(unsigned int cpu);
  72         bool            skip_onerr;
  73         bool            cant_stop;
  74 };
  75
  76 static DEFINE_MUTEX(cpuhp_state_mutex);
  77 static struct cpuhp_step cpuhp_bp_states[];
  78 static struct cpuhp_step cpuhp_ap_states[];
  79
  80 /**
  81  * cpuhp_invoke_callback _ Invoke the callbacks for a given state
  82  * @cpu:        The cpu for which the callback should be invoked
  83  * @step:       The step in the state machine
  84  * @cb:         The callback function to invoke
  85  *
  86  * Called from cpu hotplug and from the state register machinery
  87  */
  88 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
  89                                  int (*cb)(unsigned int))
  90 {
  91         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
  92         int ret = 0;
  93
  94         if (cb) {
  95                 trace_cpuhp_enter(cpu, st->target, step, cb);
  96                 ret = cb(cpu);
  97                 trace_cpuhp_exit(cpu, st->state, step, ret);
  98         }
  99         return ret;
 100 }
 101
 102 #ifdef CONFIG_SMP
 103 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
 104 static DEFINE_MUTEX(cpu_add_remove_lock);
 105 bool cpuhp_tasks_frozen;
 106 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 107
 108 /*
 109  * The following two APIs (cpu_maps_update_begin/done) must be used when
 110  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 111  * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
 112  * hotplug callback (un)registration performed using __register_cpu_notifier()
 113  * or __unregister_cpu_notifier().
 114  */
 115 void cpu_maps_update_begin(void)
 116 {
 117         mutex_lock(&cpu_add_remove_lock);
 118 }
 119 EXPORT_SYMBOL(cpu_notifier_register_begin);
 120
 121 void cpu_maps_update_done(void)
 122 {
 123         mutex_unlock(&cpu_add_remove_lock);
 124 }
 125 EXPORT_SYMBOL(cpu_notifier_register_done);
 126
 127 static RAW_NOTIFIER_HEAD(cpu_chain);
 128
 129 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 130  * Should always be manipulated under cpu_add_remove_lock
 131  */
 132 static int cpu_hotplug_disabled;
 133
 134 #ifdef CONFIG_HOTPLUG_CPU
 135
 136 static struct {
 137         struct task_struct *active_writer;
 138         /* wait queue to wake up the active_writer */
 139         wait_queue_head_t wq;
 140         /* verifies that no writer will get active while readers are active */
 141         struct mutex lock;
 142         /*
 143          * Also blocks the new readers during
 144          * an ongoing cpu hotplug operation.
 145          */
 146         atomic_t refcount;
 147
 148 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 149         struct lockdep_map dep_map;
 150 #endif
 151 } cpu_hotplug = {
 152         .active_writer = NULL,
 153         .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
 154         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
 155 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 156         .dep_map = {.name = "cpu_hotplug.lock" },
 157 #endif
 158 };
 159
 160 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
 161 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
 162 #define cpuhp_lock_acquire_tryread() \
 163                                   lock_map_acquire_tryread(&cpu_hotplug.dep_map)
 164 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 165 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 166
 167
 168 void get_online_cpus(void)
 169 {
 170         might_sleep();
 171         if (cpu_hotplug.active_writer == current)
 172                 return;
 173         cpuhp_lock_acquire_read();
 174         mutex_lock(&cpu_hotplug.lock);
 175         atomic_inc(&cpu_hotplug.refcount);
 176         mutex_unlock(&cpu_hotplug.lock);
 177 }
 178 EXPORT_SYMBOL_GPL(get_online_cpus);
 179
 180 void put_online_cpus(void)
 181 {
 182         int refcount;
 183
 184         if (cpu_hotplug.active_writer == current)
 185                 return;
 186
 187         refcount = atomic_dec_return(&cpu_hotplug.refcount);
 188         if (WARN_ON(refcount < 0)) /* try to fix things up */
 189                 atomic_inc(&cpu_hotplug.refcount);
 190
 191         if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 192                 wake_up(&cpu_hotplug.wq);
 193
 194         cpuhp_lock_release();
 195
 196 }
 197 EXPORT_SYMBOL_GPL(put_online_cpus);
 198
 199 /*
 200  * This ensures that the hotplug operation can begin only when the
 201  * refcount goes to zero.
 202  *
 203  * Note that during a cpu-hotplug operation, the new readers, if any,
 204  * will be blocked by the cpu_hotplug.lock
 205  *
 206  * Since cpu_hotplug_begin() is always called after invoking
 207  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 208  *
 209  * Note that theoretically, there is a possibility of a livelock:
 210  * - Refcount goes to zero, last reader wakes up the sleeping
 211  *   writer.
 212  * - Last reader unlocks the cpu_hotplug.lock.
 213  * - A new reader arrives at this moment, bumps up the refcount.
 214  * - The writer acquires the cpu_hotplug.lock finds the refcount
 215  *   non zero and goes to sleep again.
 216  *
 217  * However, this is very difficult to achieve in practice since
 218  * get_online_cpus() not an api which is called all that often.
 219  *
 220  */
 221 void cpu_hotplug_begin(void)
 222 {
 223         DEFINE_WAIT(wait);
 224
 225         cpu_hotplug.active_writer = current;
 226         cpuhp_lock_acquire();
 227
 228         for (;;) {
 229                 mutex_lock(&cpu_hotplug.lock);
 230                 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 231                 if (likely(!atomic_read(&cpu_hotplug.refcount)))
 232                                 break;
 233                 mutex_unlock(&cpu_hotplug.lock);
 234                 schedule();
 235         }
 236         finish_wait(&cpu_hotplug.wq, &wait);
 237 }
 238
 239 void cpu_hotplug_done(void)
 240 {
 241         cpu_hotplug.active_writer = NULL;
 242         mutex_unlock(&cpu_hotplug.lock);
 243         cpuhp_lock_release();
 244 }
 245
 246 /*
 247  * Wait for currently running CPU hotplug operations to complete (if any) and
 248  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 249  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 250  * hotplug path before performing hotplug operations. So acquiring that lock
 251  * guarantees mutual exclusion from any currently running hotplug operations.
 252  */
 253 void cpu_hotplug_disable(void)
 254 {
 255         cpu_maps_update_begin();
 256         cpu_hotplug_disabled++;
 257         cpu_maps_update_done();
 258 }
 259 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 260
 261 void cpu_hotplug_enable(void)
 262 {
 263         cpu_maps_update_begin();
 264         WARN_ON(--cpu_hotplug_disabled < 0);
 265         cpu_maps_update_done();
 266 }
 267 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 268 #endif  /* CONFIG_HOTPLUG_CPU */
 269
 270 /* Need to know about CPUs going up/down? */
 271 int register_cpu_notifier(struct notifier_block *nb)
 272 {
 273         int ret;
 274         cpu_maps_update_begin();
 275         ret = raw_notifier_chain_register(&cpu_chain, nb);
 276         cpu_maps_update_done();
 277         return ret;
 278 }
 279
 280 int __register_cpu_notifier(struct notifier_block *nb)
 281 {
 282         return raw_notifier_chain_register(&cpu_chain, nb);
 283 }
 284
 285 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 286                         int *nr_calls)
 287 {
 288         unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 289         void *hcpu = (void *)(long)cpu;
 290
 291         int ret;
 292
 293         ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 294                                         nr_calls);
 295
 296         return notifier_to_errno(ret);
 297 }
 298
 299 static int cpu_notify(unsigned long val, unsigned int cpu)
 300 {
 301         return __cpu_notify(val, cpu, -1, NULL);
 302 }
 303
 304 /* Notifier wrappers for transitioning to state machine */
 305 static int notify_prepare(unsigned int cpu)
 306 {
 307         int nr_calls = 0;
 308         int ret;
 309
 310         ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 311         if (ret) {
 312                 nr_calls--;
 313                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 314                                 __func__, cpu);
 315                 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 316         }
 317         return ret;
 318 }
 319
 320 static int notify_online(unsigned int cpu)
 321 {
 322         cpu_notify(CPU_ONLINE, cpu);
 323         return 0;
 324 }
 325
 326 static int notify_starting(unsigned int cpu)
 327 {
 328         cpu_notify(CPU_STARTING, cpu);
 329         return 0;
 330 }
 331
 332 static int bringup_wait_for_ap(unsigned int cpu)
 333 {
 334         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 335
 336         wait_for_completion(&st->done);
 337         return st->result;
 338 }
 339
 340 static int bringup_cpu(unsigned int cpu)
 341 {
 342         struct task_struct *idle = idle_thread_get(cpu);
 343         int ret;
 344
 345         /* Arch-specific enabling code. */
 346         ret = __cpu_up(cpu, idle);
 347         if (ret) {
 348                 cpu_notify(CPU_UP_CANCELED, cpu);
 349                 return ret;
 350         }
 351         ret = bringup_wait_for_ap(cpu);
 352         BUG_ON(!cpu_online(cpu));
 353         return ret;
 354 }
 355
 356 /*
 357  * Hotplug state machine related functions
 358  */
 359 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st,
 360                           struct cpuhp_step *steps)
 361 {
 362         for (st->state++; st->state < st->target; st->state++) {
 363                 struct cpuhp_step *step = steps + st->state;
 364
 365                 if (!step->skip_onerr)
 366                         cpuhp_invoke_callback(cpu, st->state, step->startup);
 367         }
 368 }
 369
 370 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 371                                 struct cpuhp_step *steps, enum cpuhp_state target)
 372 {
 373         enum cpuhp_state prev_state = st->state;
 374         int ret = 0;
 375
 376         for (; st->state > target; st->state--) {
 377                 struct cpuhp_step *step = steps + st->state;
 378
 379                 ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
 380                 if (ret) {
 381                         st->target = prev_state;
 382                         undo_cpu_down(cpu, st, steps);
 383                         break;
 384                 }
 385         }
 386         return ret;
 387 }
 388
 389 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st,
 390                         struct cpuhp_step *steps)
 391 {
 392         for (st->state--; st->state > st->target; st->state--) {
 393                 struct cpuhp_step *step = steps + st->state;
 394
 395                 if (!step->skip_onerr)
 396                         cpuhp_invoke_callback(cpu, st->state, step->teardown);
 397         }
 398 }
 399
 400 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 401                               struct cpuhp_step *steps, enum cpuhp_state target)
 402 {
 403         enum cpuhp_state prev_state = st->state;
 404         int ret = 0;
 405
 406         while (st->state < target) {
 407                 struct cpuhp_step *step;
 408
 409                 st->state++;
 410                 step = steps + st->state;
 411                 ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
 412                 if (ret) {
 413                         st->target = prev_state;
 414                         undo_cpu_up(cpu, st, steps);
 415                         break;
 416                 }
 417         }
 418         return ret;
 419 }
 420
 421 /*
 422  * The cpu hotplug threads manage the bringup and teardown of the cpus
 423  */
 424 static void cpuhp_create(unsigned int cpu)
 425 {
 426         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 427
 428         init_completion(&st->done);
 429 }
 430
 431 static int cpuhp_should_run(unsigned int cpu)
 432 {
 433         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 434
 435         return st->should_run;
 436 }
 437
 438 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
 439 static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
 440 {
 441         enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
 442
 443         return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
 444 }
 445
 446 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
 447 static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
 448 {
 449         return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
 450 }
 451
 452 /*
 453  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 454  * callbacks when a state gets [un]installed at runtime.
 455  */
 456 static void cpuhp_thread_fun(unsigned int cpu)
 457 {
 458         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 459         int ret = 0;
 460
 461         /*
 462          * Paired with the mb() in cpuhp_kick_ap_work and
 463          * cpuhp_invoke_ap_callback, so the work set is consistent visible.
 464          */
 465         smp_mb();
 466         if (!st->should_run)
 467                 return;
 468
 469         st->should_run = false;
 470
 471         /* Single callback invocation for [un]install ? */
 472         if (st->cb) {
 473                 if (st->cb_state < CPUHP_AP_ONLINE) {
 474                         local_irq_disable();
 475                         ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
 476                         local_irq_enable();
 477                 } else {
 478                         ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
 479                 }
 480         } else {
 481                 /* Cannot happen .... */
 482                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 483
 484                 /* Regular hotplug work */
 485                 if (st->state < st->target)
 486                         ret = cpuhp_ap_online(cpu, st);
 487                 else if (st->state > st->target)
 488                         ret = cpuhp_ap_offline(cpu, st);
 489         }
 490         st->result = ret;
 491         complete(&st->done);
 492 }
 493
 494 /* Invoke a single callback on a remote cpu */
 495 static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
 496                                     int (*cb)(unsigned int))
 497 {
 498         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 499
 500         if (!cpu_online(cpu))
 501                 return 0;
 502
 503         st->cb_state = state;
 504         st->cb = cb;
 505         /*
 506          * Make sure the above stores are visible before should_run becomes
 507          * true. Paired with the mb() above in cpuhp_thread_fun()
 508          */
 509         smp_mb();
 510         st->should_run = true;
 511         wake_up_process(st->thread);
 512         wait_for_completion(&st->done);
 513         return st->result;
 514 }
 515
 516 /* Regular hotplug invocation of the AP hotplug thread */
 517 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
 518 {
 519         st->result = 0;
 520         st->cb = NULL;
 521         /*
 522          * Make sure the above stores are visible before should_run becomes
 523          * true. Paired with the mb() above in cpuhp_thread_fun()
 524          */
 525         smp_mb();
 526         st->should_run = true;
 527         wake_up_process(st->thread);
 528 }
 529
 530 static int cpuhp_kick_ap_work(unsigned int cpu)
 531 {
 532         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 533         enum cpuhp_state state = st->state;
 534
 535         trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
 536         __cpuhp_kick_ap_work(st);
 537         wait_for_completion(&st->done);
 538         trace_cpuhp_exit(cpu, st->state, state, st->result);
 539         return st->result;
 540 }
 541
 542 static struct smp_hotplug_thread cpuhp_threads = {
 543         .store                  = &cpuhp_state.thread,
 544         .create                 = &cpuhp_create,
 545         .thread_should_run      = cpuhp_should_run,
 546         .thread_fn              = cpuhp_thread_fun,
 547         .thread_comm            = "cpuhp/%u",
 548         .selfparking            = true,
 549 };
 550
 551 void __init cpuhp_threads_init(void)
 552 {
 553         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 554         kthread_unpark(this_cpu_read(cpuhp_state.thread));
 555 }
 556
 557 #ifdef CONFIG_HOTPLUG_CPU
 558 EXPORT_SYMBOL(register_cpu_notifier);
 559 EXPORT_SYMBOL(__register_cpu_notifier);
 560 void unregister_cpu_notifier(struct notifier_block *nb)
 561 {
 562         cpu_maps_update_begin();
 563         raw_notifier_chain_unregister(&cpu_chain, nb);
 564         cpu_maps_update_done();
 565 }
 566 EXPORT_SYMBOL(unregister_cpu_notifier);
 567
 568 void __unregister_cpu_notifier(struct notifier_block *nb)
 569 {
 570         raw_notifier_chain_unregister(&cpu_chain, nb);
 571 }
 572 EXPORT_SYMBOL(__unregister_cpu_notifier);
 573
 574 /**
 575  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 576  * @cpu: a CPU id
 577  *
 578  * This function walks all processes, finds a valid mm struct for each one and
 579  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 580  * trivial, there are various non-obvious corner cases, which this function
 581  * tries to solve in a safe manner.
 582  *
 583  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 584  * be called only for an already offlined CPU.
 585  */
 586 void clear_tasks_mm_cpumask(int cpu)
 587 {
 588         struct task_struct *p;
 589
 590         /*
 591          * This function is called after the cpu is taken down and marked
 592          * offline, so its not like new tasks will ever get this cpu set in
 593          * their mm mask. -- Peter Zijlstra
 594          * Thus, we may use rcu_read_lock() here, instead of grabbing
 595          * full-fledged tasklist_lock.
 596          */
 597         WARN_ON(cpu_online(cpu));
 598         rcu_read_lock();
 599         for_each_process(p) {
 600                 struct task_struct *t;
 601
 602                 /*
 603                  * Main thread might exit, but other threads may still have
 604                  * a valid mm. Find one.
 605                  */
 606                 t = find_lock_task_mm(p);
 607                 if (!t)
 608                         continue;
 609                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 610                 task_unlock(t);
 611         }
 612         rcu_read_unlock();
 613 }
 614
 615 static inline void check_for_tasks(int dead_cpu)
 616 {
 617         struct task_struct *g, *p;
 618
 619         read_lock(&tasklist_lock);
 620         for_each_process_thread(g, p) {
 621                 if (!p->on_rq)
 622                         continue;
 623                 /*
 624                  * We do the check with unlocked task_rq(p)->lock.
 625                  * Order the reading to do not warn about a task,
 626                  * which was running on this cpu in the past, and
 627                  * it's just been woken on another cpu.
 628                  */
 629                 rmb();
 630                 if (task_cpu(p) != dead_cpu)
 631                         continue;
 632
 633                 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
 634                         p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
 635         }
 636         read_unlock(&tasklist_lock);
 637 }
 638
 639 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 640 {
 641         BUG_ON(cpu_notify(val, cpu));
 642 }
 643
 644 static int notify_down_prepare(unsigned int cpu)
 645 {
 646         int err, nr_calls = 0;
 647
 648         err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
 649         if (err) {
 650                 nr_calls--;
 651                 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
 652                 pr_warn("%s: attempt to take down CPU %u failed\n",
 653                                 __func__, cpu);
 654         }
 655         return err;
 656 }
 657
 658 static int notify_dying(unsigned int cpu)
 659 {
 660         cpu_notify(CPU_DYING, cpu);
 661         return 0;
 662 }
 663
 664 /* Take this CPU down. */
 665 static int take_cpu_down(void *_param)
 666 {
 667         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 668         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 669         int err, cpu = smp_processor_id();
 670
 671         /* Ensure this CPU doesn't handle any more interrupts. */
 672         err = __cpu_disable();
 673         if (err < 0)
 674                 return err;
 675
 676         /* Invoke the former CPU_DYING callbacks */
 677         for (; st->state > target; st->state--) {
 678                 struct cpuhp_step *step = cpuhp_ap_states + st->state;
 679
 680                 cpuhp_invoke_callback(cpu, st->state, step->teardown);
 681         }
 682         /* Give up timekeeping duties */
 683         tick_handover_do_timer();
 684         /* Park the stopper thread */
 685         stop_machine_park(cpu);
 686         return 0;
 687 }
 688
 689 static int takedown_cpu(unsigned int cpu)
 690 {
 691         int err;
 692
 693         /*
 694          * By now we've cleared cpu_active_mask, wait for all preempt-disabled
 695          * and RCU users of this state to go away such that all new such users
 696          * will observe it.
 697          *
 698          * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
 699          * not imply sync_sched(), so wait for both.
 700          *
 701          * Do sync before park smpboot threads to take care the rcu boost case.
 702          */
 703         if (IS_ENABLED(CONFIG_PREEMPT))
 704                 synchronize_rcu_mult(call_rcu, call_rcu_sched);
 705         else
 706                 synchronize_rcu();
 707
 708         /* Park the hotplug thread */
 709         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 710
 711         /*
 712          * Prevent irq alloc/free while the dying cpu reorganizes the
 713          * interrupt affinities.
 714          */
 715         irq_lock_sparse();
 716
 717         /*
 718          * So now all preempt/rcu users must observe !cpu_active().
 719          */
 720         err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
 721         if (err) {
 722                 /* CPU didn't die: tell everyone.  Can't complain. */
 723                 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 724                 irq_unlock_sparse();
 725                 return err;
 726         }
 727         BUG_ON(cpu_online(cpu));
 728
 729         /*
 730          * The migration_call() CPU_DYING callback will have removed all
 731          * runnable tasks from the cpu, there's only the idle task left now
 732          * that the migration thread is done doing the stop_machine thing.
 733          *
 734          * Wait for the stop thread to go away.
 735          */
 736         while (!per_cpu(cpu_dead_idle, cpu))
 737                 cpu_relax();
 738         smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
 739         per_cpu(cpu_dead_idle, cpu) = false;
 740
 741         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
 742         irq_unlock_sparse();
 743
 744         hotplug_cpu__broadcast_tick_pull(cpu);
 745         /* This actually kills the CPU. */
 746         __cpu_die(cpu);
 747
 748         tick_cleanup_dead_cpu(cpu);
 749         return 0;
 750 }
 751
 752 static int notify_dead(unsigned int cpu)
 753 {
 754         cpu_notify_nofail(CPU_DEAD, cpu);
 755         check_for_tasks(cpu);
 756         return 0;
 757 }
 758
 759 #else
 760 #define notify_down_prepare     NULL
 761 #define takedown_cpu            NULL
 762 #define notify_dead             NULL
 763 #define notify_dying            NULL
 764 #endif
 765
 766 #ifdef CONFIG_HOTPLUG_CPU
 767
 768 /* Requires cpu_add_remove_lock to be held */
 769 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 770                            enum cpuhp_state target)
 771 {
 772         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 773         int prev_state, ret = 0;
 774         bool hasdied = false;
 775
 776         if (num_online_cpus() == 1)
 777                 return -EBUSY;
 778
 779         if (!cpu_present(cpu))
 780                 return -EINVAL;
 781
 782         cpu_hotplug_begin();
 783
 784         cpuhp_tasks_frozen = tasks_frozen;
 785
 786         prev_state = st->state;
 787         st->target = target;
 788         /*
 789          * If the current CPU state is in the range of the AP hotplug thread,
 790          * then we need to kick the thread.
 791          */
 792         if (st->state > CPUHP_TEARDOWN_CPU) {
 793                 ret = cpuhp_kick_ap_work(cpu);
 794                 /*
 795                  * The AP side has done the error rollback already. Just
 796                  * return the error code..
 797                  */
 798                 if (ret)
 799                         goto out;
 800
 801                 /*
 802                  * We might have stopped still in the range of the AP hotplug
 803                  * thread. Nothing to do anymore.
 804                  */
 805                 if (st->state > CPUHP_TEARDOWN_CPU)
 806                         goto out;
 807         }
 808         /*
 809          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
 810          * to do the further cleanups.
 811          */
 812         ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
 813
 814         hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
 815 out:
 816         cpu_hotplug_done();
 817         /* This post dead nonsense must die */
 818         if (!ret && hasdied)
 819                 cpu_notify_nofail(CPU_POST_DEAD, cpu);
 820         return ret;
 821 }
 822
 823 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
 824 {
 825         int err;
 826
 827         cpu_maps_update_begin();
 828
 829         if (cpu_hotplug_disabled) {
 830                 err = -EBUSY;
 831                 goto out;
 832         }
 833
 834         err = _cpu_down(cpu, 0, target);
 835
 836 out:
 837         cpu_maps_update_done();
 838         return err;
 839 }
 840 int cpu_down(unsigned int cpu)
 841 {
 842         return do_cpu_down(cpu, CPUHP_OFFLINE);
 843 }
 844 EXPORT_SYMBOL(cpu_down);
 845 #endif /*CONFIG_HOTPLUG_CPU*/
 846
 847 /**
 848  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 849  * @cpu: cpu that just started
 850  *
 851  * This function calls the cpu_chain notifiers with CPU_STARTING.
 852  * It must be called by the arch code on the new cpu, before the new cpu
 853  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 854  */
 855 void notify_cpu_starting(unsigned int cpu)
 856 {
 857         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 858         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
 859
 860         while (st->state < target) {
 861                 struct cpuhp_step *step;
 862
 863                 st->state++;
 864                 step = cpuhp_ap_states + st->state;
 865                 cpuhp_invoke_callback(cpu, st->state, step->startup);
 866         }
 867 }
 868
 869 /*
 870  * Called from the idle task. We need to set active here, so we can kick off
 871  * the stopper thread and unpark the smpboot threads. If the target state is
 872  * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
 873  * cpu further.
 874  */
 875 void cpuhp_online_idle(enum cpuhp_state state)
 876 {
 877         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 878         unsigned int cpu = smp_processor_id();
 879
 880         /* Happens for the boot cpu */
 881         if (state != CPUHP_AP_ONLINE_IDLE)
 882                 return;
 883
 884         st->state = CPUHP_AP_ONLINE_IDLE;
 885
 886         /* The cpu is marked online, set it active now */
 887         set_cpu_active(cpu, true);
 888         /* Unpark the stopper thread and the hotplug thread of this cpu */
 889         stop_machine_unpark(cpu);
 890         kthread_unpark(st->thread);
 891
 892         /* Should we go further up ? */
 893         if (st->target > CPUHP_AP_ONLINE_IDLE)
 894                 __cpuhp_kick_ap_work(st);
 895         else
 896                 complete(&st->done);
 897 }
 898
 899 /* Requires cpu_add_remove_lock to be held */
 900 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
 901 {
 902         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 903         struct task_struct *idle;
 904         int ret = 0;
 905
 906         cpu_hotplug_begin();
 907
 908         if (!cpu_present(cpu)) {
 909                 ret = -EINVAL;
 910                 goto out;
 911         }
 912
 913         /*
 914          * The caller of do_cpu_up might have raced with another
 915          * caller. Ignore it for now.
 916          */
 917         if (st->state >= target)
 918                 goto out;
 919
 920         if (st->state == CPUHP_OFFLINE) {
 921                 /* Let it fail before we try to bring the cpu up */
 922                 idle = idle_thread_get(cpu);
 923                 if (IS_ERR(idle)) {
 924                         ret = PTR_ERR(idle);
 925                         goto out;
 926                 }
 927         }
 928
 929         cpuhp_tasks_frozen = tasks_frozen;
 930
 931         st->target = target;
 932         /*
 933          * If the current CPU state is in the range of the AP hotplug thread,
 934          * then we need to kick the thread once more.
 935          */
 936         if (st->state > CPUHP_BRINGUP_CPU) {
 937                 ret = cpuhp_kick_ap_work(cpu);
 938                 /*
 939                  * The AP side has done the error rollback already. Just
 940                  * return the error code..
 941                  */
 942                 if (ret)
 943                         goto out;
 944         }
 945
 946         /*
 947          * Try to reach the target state. We max out on the BP at
 948          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
 949          * responsible for bringing it up to the target state.
 950          */
 951         target = min((int)target, CPUHP_BRINGUP_CPU);
 952         ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
 953 out:
 954         cpu_hotplug_done();
 955         return ret;
 956 }
 957
 958 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
 959 {
 960         int err = 0;
 961
 962         if (!cpu_possible(cpu)) {
 963                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
 964                        cpu);
 965 #if defined(CONFIG_IA64)
 966                 pr_err("please check additional_cpus= boot parameter\n");
 967 #endif
 968                 return -EINVAL;
 969         }
 970
 971         err = try_online_node(cpu_to_node(cpu));
 972         if (err)
 973                 return err;
 974
 975         cpu_maps_update_begin();
 976
 977         if (cpu_hotplug_disabled) {
 978                 err = -EBUSY;
 979                 goto out;
 980         }
 981
 982         err = _cpu_up(cpu, 0, target);
 983 out:
 984         cpu_maps_update_done();
 985         return err;
 986 }
 987
 988 int cpu_up(unsigned int cpu)
 989 {
 990         return do_cpu_up(cpu, CPUHP_ONLINE);
 991 }
 992 EXPORT_SYMBOL_GPL(cpu_up);
 993
 994 #ifdef CONFIG_PM_SLEEP_SMP
 995 static cpumask_var_t frozen_cpus;
 996
 997 int disable_nonboot_cpus(void)
 998 {
 999         int cpu, first_cpu, error = 0;
1000
1001         cpu_maps_update_begin();
1002         first_cpu = cpumask_first(cpu_online_mask);
1003         /*
1004          * We take down all of the non-boot CPUs in one shot to avoid races
1005          * with the userspace trying to use the CPU hotplug at the same time
1006          */
1007         cpumask_clear(frozen_cpus);
1008
1009         pr_info("Disabling non-boot CPUs ...\n");
1010         for_each_online_cpu(cpu) {
1011                 if (cpu == first_cpu)
1012                         continue;
1013                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1014                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1015                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1016                 if (!error)
1017                         cpumask_set_cpu(cpu, frozen_cpus);
1018                 else {
1019                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1020                         break;
1021                 }
1022         }
1023
1024         if (!error)
1025                 BUG_ON(num_online_cpus() > 1);
1026         else
1027                 pr_err("Non-boot CPUs are not disabled\n");
1028
1029         /*
1030          * Make sure the CPUs won't be enabled by someone else. We need to do
1031          * this even in case of failure as all disable_nonboot_cpus() users are
1032          * supposed to do enable_nonboot_cpus() on the failure path.
1033          */
1034         cpu_hotplug_disabled++;
1035
1036         cpu_maps_update_done();
1037         return error;
1038 }
1039
1040 void __weak arch_enable_nonboot_cpus_begin(void)
1041 {
1042 }
1043
1044 void __weak arch_enable_nonboot_cpus_end(void)
1045 {
1046 }
1047
1048 void enable_nonboot_cpus(void)
1049 {
1050         int cpu, error;
1051
1052         /* Allow everyone to use the CPU hotplug again */
1053         cpu_maps_update_begin();
1054         WARN_ON(--cpu_hotplug_disabled < 0);
1055         if (cpumask_empty(frozen_cpus))
1056                 goto out;
1057
1058         pr_info("Enabling non-boot CPUs ...\n");
1059
1060         arch_enable_nonboot_cpus_begin();
1061
1062         for_each_cpu(cpu, frozen_cpus) {
1063                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1064                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1065                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1066                 if (!error) {
1067                         pr_info("CPU%d is up\n", cpu);
1068                         continue;
1069                 }
1070                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1071         }
1072
1073         arch_enable_nonboot_cpus_end();
1074
1075         cpumask_clear(frozen_cpus);
1076 out:
1077         cpu_maps_update_done();
1078 }
1079
1080 static int __init alloc_frozen_cpus(void)
1081 {
1082         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1083                 return -ENOMEM;
1084         return 0;
1085 }
1086 core_initcall(alloc_frozen_cpus);
1087
1088 /*
1089  * When callbacks for CPU hotplug notifications are being executed, we must
1090  * ensure that the state of the system with respect to the tasks being frozen
1091  * or not, as reported by the notification, remains unchanged *throughout the
1092  * duration* of the execution of the callbacks.
1093  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1094  *
1095  * This synchronization is implemented by mutually excluding regular CPU
1096  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1097  * Hibernate notifications.
1098  */
1099 static int
1100 cpu_hotplug_pm_callback(struct notifier_block *nb,
1101                         unsigned long action, void *ptr)
1102 {
1103         switch (action) {
1104
1105         case PM_SUSPEND_PREPARE:
1106         case PM_HIBERNATION_PREPARE:
1107                 cpu_hotplug_disable();
1108                 break;
1109
1110         case PM_POST_SUSPEND:
1111         case PM_POST_HIBERNATION:
1112                 cpu_hotplug_enable();
1113                 break;
1114
1115         default:
1116                 return NOTIFY_DONE;
1117         }
1118
1119         return NOTIFY_OK;
1120 }
1121
1122
1123 static int __init cpu_hotplug_pm_sync_init(void)
1124 {
1125         /*
1126          * cpu_hotplug_pm_callback has higher priority than x86
1127          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1128          * to disable cpu hotplug to avoid cpu hotplug race.
1129          */
1130         pm_notifier(cpu_hotplug_pm_callback, 0);
1131         return 0;
1132 }
1133 core_initcall(cpu_hotplug_pm_sync_init);
1134
1135 #endif /* CONFIG_PM_SLEEP_SMP */
1136
1137 #endif /* CONFIG_SMP */
1138
1139 /* Boot processor state steps */
1140 static struct cpuhp_step cpuhp_bp_states[] = {
1141         [CPUHP_OFFLINE] = {
1142                 .name                   = "offline",
1143                 .startup                = NULL,
1144                 .teardown               = NULL,
1145         },
1146 #ifdef CONFIG_SMP
1147         [CPUHP_CREATE_THREADS]= {
1148                 .name                   = "threads:create",
1149                 .startup                = smpboot_create_threads,
1150                 .teardown               = NULL,
1151                 .cant_stop              = true,
1152         },
1153         [CPUHP_NOTIFY_PREPARE] = {
1154                 .name                   = "notify:prepare",
1155                 .startup                = notify_prepare,
1156                 .teardown               = notify_dead,
1157                 .skip_onerr             = true,
1158                 .cant_stop              = true,
1159         },
1160         [CPUHP_BRINGUP_CPU] = {
1161                 .name                   = "cpu:bringup",
1162                 .startup                = bringup_cpu,
1163                 .teardown               = NULL,
1164                 .cant_stop              = true,
1165         },
1166         [CPUHP_TEARDOWN_CPU] = {
1167                 .name                   = "cpu:teardown",
1168                 .startup                = NULL,
1169                 .teardown               = takedown_cpu,
1170                 .cant_stop              = true,
1171         },
1172 #endif
1173 };
1174
1175 /* Application processor state steps */
1176 static struct cpuhp_step cpuhp_ap_states[] = {
1177 #ifdef CONFIG_SMP
1178         [CPUHP_AP_NOTIFY_STARTING] = {
1179                 .name                   = "notify:starting",
1180                 .startup                = notify_starting,
1181                 .teardown               = notify_dying,
1182                 .skip_onerr             = true,
1183                 .cant_stop              = true,
1184         },
1185         [CPUHP_AP_SMPBOOT_THREADS] = {
1186                 .name                   = "smpboot:threads",
1187                 .startup                = smpboot_unpark_threads,
1188                 .teardown               = smpboot_park_threads,
1189         },
1190         [CPUHP_AP_NOTIFY_ONLINE] = {
1191                 .name                   = "notify:online",
1192                 .startup                = notify_online,
1193                 .teardown               = notify_down_prepare,
1194         },
1195 #endif
1196         [CPUHP_ONLINE] = {
1197                 .name                   = "online",
1198                 .startup                = NULL,
1199                 .teardown               = NULL,
1200         },
1201 };
1202
1203 /* Sanity check for callbacks */
1204 static int cpuhp_cb_check(enum cpuhp_state state)
1205 {
1206         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1207                 return -EINVAL;
1208         return 0;
1209 }
1210
1211 static bool cpuhp_is_ap_state(enum cpuhp_state state)
1212 {
1213         if (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE)
1214                 return true;
1215         return state > CPUHP_BRINGUP_CPU;
1216 }
1217
1218 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
1219 {
1220         struct cpuhp_step *sp;
1221
1222         sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
1223         return sp + state;
1224 }
1225
1226 static void cpuhp_store_callbacks(enum cpuhp_state state,
1227                                   const char *name,
1228                                   int (*startup)(unsigned int cpu),
1229                                   int (*teardown)(unsigned int cpu))
1230 {
1231         /* (Un)Install the callbacks for further cpu hotplug operations */
1232         struct cpuhp_step *sp;
1233
1234         mutex_lock(&cpuhp_state_mutex);
1235         sp = cpuhp_get_step(state);
1236         sp->startup = startup;
1237         sp->teardown = teardown;
1238         sp->name = name;
1239         mutex_unlock(&cpuhp_state_mutex);
1240 }
1241
1242 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1243 {
1244         return cpuhp_get_step(state)->teardown;
1245 }
1246
1247 /*
1248  * Call the startup/teardown function for a step either on the AP or
1249  * on the current CPU.
1250  */
1251 static int cpuhp_issue_call(int cpu, enum cpuhp_state state,
1252                             int (*cb)(unsigned int), bool bringup)
1253 {
1254         int ret;
1255
1256         if (!cb)
1257                 return 0;
1258         /*
1259          * The non AP bound callbacks can fail on bringup. On teardown
1260          * e.g. module removal we crash for now.
1261          */
1262 #ifdef CONFIG_SMP
1263         if (cpuhp_is_ap_state(state))
1264                 ret = cpuhp_invoke_ap_callback(cpu, state, cb);
1265         else
1266                 ret = cpuhp_invoke_callback(cpu, state, cb);
1267 #else
1268         ret = cpuhp_invoke_callback(cpu, state, cb);
1269 #endif
1270         BUG_ON(ret && !bringup);
1271         return ret;
1272 }
1273
1274 /*
1275  * Called from __cpuhp_setup_state on a recoverable failure.
1276  *
1277  * Note: The teardown callbacks for rollback are not allowed to fail!
1278  */
1279 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1280                                    int (*teardown)(unsigned int cpu))
1281 {
1282         int cpu;
1283
1284         if (!teardown)
1285                 return;
1286
1287         /* Roll back the already executed steps on the other cpus */
1288         for_each_present_cpu(cpu) {
1289                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1290                 int cpustate = st->state;
1291
1292                 if (cpu >= failedcpu)
1293                         break;
1294
1295                 /* Did we invoke the startup call on that cpu ? */
1296                 if (cpustate >= state)
1297                         cpuhp_issue_call(cpu, state, teardown, false);
1298         }
1299 }
1300
1301 /*
1302  * Returns a free for dynamic slot assignment of the Online state. The states
1303  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1304  * by having no name assigned.
1305  */
1306 static int cpuhp_reserve_state(enum cpuhp_state state)
1307 {
1308         enum cpuhp_state i;
1309
1310         mutex_lock(&cpuhp_state_mutex);
1311         for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1312                 if (cpuhp_ap_states[i].name)
1313                         continue;
1314
1315                 cpuhp_ap_states[i].name = "Reserved";
1316                 mutex_unlock(&cpuhp_state_mutex);
1317                 return i;
1318         }
1319         mutex_unlock(&cpuhp_state_mutex);
1320         WARN(1, "No more dynamic states available for CPU hotplug\n");
1321         return -ENOSPC;
1322 }
1323
1324 /**
1325  * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1326  * @state:      The state to setup
1327  * @invoke:     If true, the startup function is invoked for cpus where
1328  *              cpu state >= @state
1329  * @startup:    startup callback function
1330  * @teardown:   teardown callback function
1331  *
1332  * Returns 0 if successful, otherwise a proper error code
1333  */
1334 int __cpuhp_setup_state(enum cpuhp_state state,
1335                         const char *name, bool invoke,
1336                         int (*startup)(unsigned int cpu),
1337                         int (*teardown)(unsigned int cpu))
1338 {
1339         int cpu, ret = 0;
1340         int dyn_state = 0;
1341
1342         if (cpuhp_cb_check(state) || !name)
1343                 return -EINVAL;
1344
1345         get_online_cpus();
1346
1347         /* currently assignments for the ONLINE state are possible */
1348         if (state == CPUHP_AP_ONLINE_DYN) {
1349                 dyn_state = 1;
1350                 ret = cpuhp_reserve_state(state);
1351                 if (ret < 0)
1352                         goto out;
1353                 state = ret;
1354         }
1355
1356         cpuhp_store_callbacks(state, name, startup, teardown);
1357
1358         if (!invoke || !startup)
1359                 goto out;
1360
1361         /*
1362          * Try to call the startup callback for each present cpu
1363          * depending on the hotplug state of the cpu.
1364          */
1365         for_each_present_cpu(cpu) {
1366                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1367                 int cpustate = st->state;
1368
1369                 if (cpustate < state)
1370                         continue;
1371
1372                 ret = cpuhp_issue_call(cpu, state, startup, true);
1373                 if (ret) {
1374                         cpuhp_rollback_install(cpu, state, teardown);
1375                         cpuhp_store_callbacks(state, NULL, NULL, NULL);
1376                         goto out;
1377                 }
1378         }
1379 out:
1380         put_online_cpus();
1381         if (!ret && dyn_state)
1382                 return state;
1383         return ret;
1384 }
1385 EXPORT_SYMBOL(__cpuhp_setup_state);
1386
1387 /**
1388  * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1389  * @state:      The state to remove
1390  * @invoke:     If true, the teardown function is invoked for cpus where
1391  *              cpu state >= @state
1392  *
1393  * The teardown callback is currently not allowed to fail. Think
1394  * about module removal!
1395  */
1396 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1397 {
1398         int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state);
1399         int cpu;
1400
1401         BUG_ON(cpuhp_cb_check(state));
1402
1403         get_online_cpus();
1404
1405         if (!invoke || !teardown)
1406                 goto remove;
1407
1408         /*
1409          * Call the teardown callback for each present cpu depending
1410          * on the hotplug state of the cpu. This function is not
1411          * allowed to fail currently!
1412          */
1413         for_each_present_cpu(cpu) {
1414                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1415                 int cpustate = st->state;
1416
1417                 if (cpustate >= state)
1418                         cpuhp_issue_call(cpu, state, teardown, false);
1419         }
1420 remove:
1421         cpuhp_store_callbacks(state, NULL, NULL, NULL);
1422         put_online_cpus();
1423 }
1424 EXPORT_SYMBOL(__cpuhp_remove_state);
1425
1426 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1427 static ssize_t show_cpuhp_state(struct device *dev,
1428                                 struct device_attribute *attr, char *buf)
1429 {
1430         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1431
1432         return sprintf(buf, "%d\n", st->state);
1433 }
1434 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1435
1436 static ssize_t write_cpuhp_target(struct device *dev,
1437                                   struct device_attribute *attr,
1438                                   const char *buf, size_t count)
1439 {
1440         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1441         struct cpuhp_step *sp;
1442         int target, ret;
1443
1444         ret = kstrtoint(buf, 10, &target);
1445         if (ret)
1446                 return ret;
1447
1448 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1449         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1450                 return -EINVAL;
1451 #else
1452         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1453                 return -EINVAL;
1454 #endif
1455
1456         ret = lock_device_hotplug_sysfs();
1457         if (ret)
1458                 return ret;
1459
1460         mutex_lock(&cpuhp_state_mutex);
1461         sp = cpuhp_get_step(target);
1462         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1463         mutex_unlock(&cpuhp_state_mutex);
1464         if (ret)
1465                 return ret;
1466
1467         if (st->state < target)
1468                 ret = do_cpu_up(dev->id, target);
1469         else
1470                 ret = do_cpu_down(dev->id, target);
1471
1472         unlock_device_hotplug();
1473         return ret ? ret : count;
1474 }
1475
1476 static ssize_t show_cpuhp_target(struct device *dev,
1477                                  struct device_attribute *attr, char *buf)
1478 {
1479         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1480
1481         return sprintf(buf, "%d\n", st->target);
1482 }
1483 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1484
1485 static struct attribute *cpuhp_cpu_attrs[] = {
1486         &dev_attr_state.attr,
1487         &dev_attr_target.attr,
1488         NULL
1489 };
1490
1491 static struct attribute_group cpuhp_cpu_attr_group = {
1492         .attrs = cpuhp_cpu_attrs,
1493         .name = "hotplug",
1494         NULL
1495 };
1496
1497 static ssize_t show_cpuhp_states(struct device *dev,
1498                                  struct device_attribute *attr, char *buf)
1499 {
1500         ssize_t cur, res = 0;
1501         int i;
1502
1503         mutex_lock(&cpuhp_state_mutex);
1504         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1505                 struct cpuhp_step *sp = cpuhp_get_step(i);
1506
1507                 if (sp->name) {
1508                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1509                         buf += cur;
1510                         res += cur;
1511                 }
1512         }
1513         mutex_unlock(&cpuhp_state_mutex);
1514         return res;
1515 }
1516 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1517
1518 static struct attribute *cpuhp_cpu_root_attrs[] = {
1519         &dev_attr_states.attr,
1520         NULL
1521 };
1522
1523 static struct attribute_group cpuhp_cpu_root_attr_group = {
1524         .attrs = cpuhp_cpu_root_attrs,
1525         .name = "hotplug",
1526         NULL
1527 };
1528
1529 static int __init cpuhp_sysfs_init(void)
1530 {
1531         int cpu, ret;
1532
1533         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1534                                  &cpuhp_cpu_root_attr_group);
1535         if (ret)
1536                 return ret;
1537
1538         for_each_possible_cpu(cpu) {
1539                 struct device *dev = get_cpu_device(cpu);
1540
1541                 if (!dev)
1542                         continue;
1543                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1544                 if (ret)
1545                         return ret;
1546         }
1547         return 0;
1548 }
1549 device_initcall(cpuhp_sysfs_init);
1550 #endif
1551
1552 /*
1553  * cpu_bit_bitmap[] is a special, "compressed" data structure that
1554  * represents all NR_CPUS bits binary values of 1<<nr.
1555  *
1556  * It is used by cpumask_of() to get a constant address to a CPU
1557  * mask value that has a single bit set only.
1558  */
1559
1560 /* cpu_bit_bitmap[0] is empty - so we can back into it */
1561 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
1562 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1563 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1564 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1565
1566 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1567
1568         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
1569         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
1570 #if BITS_PER_LONG > 32
1571         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
1572         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
1573 #endif
1574 };
1575 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1576
1577 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1578 EXPORT_SYMBOL(cpu_all_bits);
1579
1580 #ifdef CONFIG_INIT_ALL_POSSIBLE
1581 struct cpumask __cpu_possible_mask __read_mostly
1582         = {CPU_BITS_ALL};
1583 #else
1584 struct cpumask __cpu_possible_mask __read_mostly;
1585 #endif
1586 EXPORT_SYMBOL(__cpu_possible_mask);
1587
1588 struct cpumask __cpu_online_mask __read_mostly;
1589 EXPORT_SYMBOL(__cpu_online_mask);
1590
1591 struct cpumask __cpu_present_mask __read_mostly;
1592 EXPORT_SYMBOL(__cpu_present_mask);
1593
1594 struct cpumask __cpu_active_mask __read_mostly;
1595 EXPORT_SYMBOL(__cpu_active_mask);
1596
1597 void init_cpu_present(const struct cpumask *src)
1598 {
1599         cpumask_copy(&__cpu_present_mask, src);
1600 }
1601
1602 void init_cpu_possible(const struct cpumask *src)
1603 {
1604         cpumask_copy(&__cpu_possible_mask, src);
1605 }
1606
1607 void init_cpu_online(const struct cpumask *src)
1608 {
1609         cpumask_copy(&__cpu_online_mask, src);
1610 }
1611
1612 /*
1613  * Activate the first processor.
1614  */
1615 void __init boot_cpu_init(void)
1616 {
1617         int cpu = smp_processor_id();
1618
1619         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1620         set_cpu_online(cpu, true);
1621         set_cpu_active(cpu, true);
1622         set_cpu_present(cpu, true);
1623         set_cpu_possible(cpu, true);
1624 }
1625
1626 /*
1627  * Must be called _AFTER_ setting up the per_cpu areas
1628  */
1629 void __init boot_cpu_state_init(void)
1630 {
1631         per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1632 }