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 #include <linux/relay.h>
  27 #include <linux/slab.h>
  28
  29 #include <trace/events/power.h>
  30 #define CREATE_TRACE_POINTS
  31 #include <trace/events/cpuhp.h>
  32
  33 #include "smpboot.h"
  34
  35 /**
  36  * cpuhp_cpu_state - Per cpu hotplug state storage
  37  * @state:      The current cpu state
  38  * @target:     The target state
  39  * @thread:     Pointer to the hotplug thread
  40  * @should_run: Thread should execute
  41  * @rollback:   Perform a rollback
  42  * @single:     Single callback invocation
  43  * @bringup:    Single callback bringup or teardown selector
  44  * @cb_state:   The state for a single callback (install/uninstall)
  45  * @result:     Result of the operation
  46  * @done:       Signal completion to the issuer of the task
  47  */
  48 struct cpuhp_cpu_state {
  49         enum cpuhp_state        state;
  50         enum cpuhp_state        target;
  51 #ifdef CONFIG_SMP
  52         struct task_struct      *thread;
  53         bool                    should_run;
  54         bool                    rollback;
  55         bool                    single;
  56         bool                    bringup;
  57         struct hlist_node       *node;
  58         enum cpuhp_state        cb_state;
  59         int                     result;
  60         struct completion       done;
  61 #endif
  62 };
  63
  64 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
  65
  66 /**
  67  * cpuhp_step - Hotplug state machine step
  68  * @name:       Name of the step
  69  * @startup:    Startup function of the step
  70  * @teardown:   Teardown function of the step
  71  * @skip_onerr: Do not invoke the functions on error rollback
  72  *              Will go away once the notifiers are gone
  73  * @cant_stop:  Bringup/teardown can't be stopped at this step
  74  */
  75 struct cpuhp_step {
  76         const char              *name;
  77         union {
  78                 int             (*single)(unsigned int cpu);
  79                 int             (*multi)(unsigned int cpu,
  80                                          struct hlist_node *node);
  81         } startup;
  82         union {
  83                 int             (*single)(unsigned int cpu);
  84                 int             (*multi)(unsigned int cpu,
  85                                          struct hlist_node *node);
  86         } teardown;
  87         struct hlist_head       list;
  88         bool                    skip_onerr;
  89         bool                    cant_stop;
  90         bool                    multi_instance;
  91 };
  92
  93 static DEFINE_MUTEX(cpuhp_state_mutex);
  94 static struct cpuhp_step cpuhp_bp_states[];
  95 static struct cpuhp_step cpuhp_ap_states[];
  96
  97 static bool cpuhp_is_ap_state(enum cpuhp_state state)
  98 {
  99         /*
 100          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
 101          * purposes as that state is handled explicitly in cpu_down.
 102          */
 103         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
 104 }
 105
 106 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
 107 {
 108         struct cpuhp_step *sp;
 109
 110         sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
 111         return sp + state;
 112 }
 113
 114 /**
 115  * cpuhp_invoke_callback _ Invoke the callbacks for a given state
 116  * @cpu:        The cpu for which the callback should be invoked
 117  * @step:       The step in the state machine
 118  * @bringup:    True if the bringup callback should be invoked
 119  *
 120  * Called from cpu hotplug and from the state register machinery.
 121  */
 122 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 123                                  bool bringup, struct hlist_node *node)
 124 {
 125         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 126         struct cpuhp_step *step = cpuhp_get_step(state);
 127         int (*cbm)(unsigned int cpu, struct hlist_node *node);
 128         int (*cb)(unsigned int cpu);
 129         int ret, cnt;
 130
 131         if (!step->multi_instance) {
 132                 cb = bringup ? step->startup.single : step->teardown.single;
 133                 if (!cb)
 134                         return 0;
 135                 trace_cpuhp_enter(cpu, st->target, state, cb);
 136                 ret = cb(cpu);
 137                 trace_cpuhp_exit(cpu, st->state, state, ret);
 138                 return ret;
 139         }
 140         cbm = bringup ? step->startup.multi : step->teardown.multi;
 141         if (!cbm)
 142                 return 0;
 143
 144         /* Single invocation for instance add/remove */
 145         if (node) {
 146                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 147                 ret = cbm(cpu, node);
 148                 trace_cpuhp_exit(cpu, st->state, state, ret);
 149                 return ret;
 150         }
 151
 152         /* State transition. Invoke on all instances */
 153         cnt = 0;
 154         hlist_for_each(node, &step->list) {
 155                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 156                 ret = cbm(cpu, node);
 157                 trace_cpuhp_exit(cpu, st->state, state, ret);
 158                 if (ret)
 159                         goto err;
 160                 cnt++;
 161         }
 162         return 0;
 163 err:
 164         /* Rollback the instances if one failed */
 165         cbm = !bringup ? step->startup.multi : step->teardown.multi;
 166         if (!cbm)
 167                 return ret;
 168
 169         hlist_for_each(node, &step->list) {
 170                 if (!cnt--)
 171                         break;
 172                 cbm(cpu, node);
 173         }
 174         return ret;
 175 }
 176
 177 #ifdef CONFIG_SMP
 178 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
 179 static DEFINE_MUTEX(cpu_add_remove_lock);
 180 bool cpuhp_tasks_frozen;
 181 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 182
 183 /*
 184  * The following two APIs (cpu_maps_update_begin/done) must be used when
 185  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 186  * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
 187  * hotplug callback (un)registration performed using __register_cpu_notifier()
 188  * or __unregister_cpu_notifier().
 189  */
 190 void cpu_maps_update_begin(void)
 191 {
 192         mutex_lock(&cpu_add_remove_lock);
 193 }
 194 EXPORT_SYMBOL(cpu_notifier_register_begin);
 195
 196 void cpu_maps_update_done(void)
 197 {
 198         mutex_unlock(&cpu_add_remove_lock);
 199 }
 200 EXPORT_SYMBOL(cpu_notifier_register_done);
 201
 202 static RAW_NOTIFIER_HEAD(cpu_chain);
 203
 204 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 205  * Should always be manipulated under cpu_add_remove_lock
 206  */
 207 static int cpu_hotplug_disabled;
 208
 209 #ifdef CONFIG_HOTPLUG_CPU
 210
 211 static struct {
 212         struct task_struct *active_writer;
 213         /* wait queue to wake up the active_writer */
 214         wait_queue_head_t wq;
 215         /* verifies that no writer will get active while readers are active */
 216         struct mutex lock;
 217         /*
 218          * Also blocks the new readers during
 219          * an ongoing cpu hotplug operation.
 220          */
 221         atomic_t refcount;
 222
 223 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 224         struct lockdep_map dep_map;
 225 #endif
 226 } cpu_hotplug = {
 227         .active_writer = NULL,
 228         .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
 229         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
 230 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 231         .dep_map = {.name = "cpu_hotplug.lock" },
 232 #endif
 233 };
 234
 235 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
 236 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
 237 #define cpuhp_lock_acquire_tryread() \
 238                                   lock_map_acquire_tryread(&cpu_hotplug.dep_map)
 239 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 240 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 241
 242
 243 void get_online_cpus(void)
 244 {
 245         might_sleep();
 246         if (cpu_hotplug.active_writer == current)
 247                 return;
 248         cpuhp_lock_acquire_read();
 249         mutex_lock(&cpu_hotplug.lock);
 250         atomic_inc(&cpu_hotplug.refcount);
 251         mutex_unlock(&cpu_hotplug.lock);
 252 }
 253 EXPORT_SYMBOL_GPL(get_online_cpus);
 254
 255 void put_online_cpus(void)
 256 {
 257         int refcount;
 258
 259         if (cpu_hotplug.active_writer == current)
 260                 return;
 261
 262         refcount = atomic_dec_return(&cpu_hotplug.refcount);
 263         if (WARN_ON(refcount < 0)) /* try to fix things up */
 264                 atomic_inc(&cpu_hotplug.refcount);
 265
 266         if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 267                 wake_up(&cpu_hotplug.wq);
 268
 269         cpuhp_lock_release();
 270
 271 }
 272 EXPORT_SYMBOL_GPL(put_online_cpus);
 273
 274 /*
 275  * This ensures that the hotplug operation can begin only when the
 276  * refcount goes to zero.
 277  *
 278  * Note that during a cpu-hotplug operation, the new readers, if any,
 279  * will be blocked by the cpu_hotplug.lock
 280  *
 281  * Since cpu_hotplug_begin() is always called after invoking
 282  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 283  *
 284  * Note that theoretically, there is a possibility of a livelock:
 285  * - Refcount goes to zero, last reader wakes up the sleeping
 286  *   writer.
 287  * - Last reader unlocks the cpu_hotplug.lock.
 288  * - A new reader arrives at this moment, bumps up the refcount.
 289  * - The writer acquires the cpu_hotplug.lock finds the refcount
 290  *   non zero and goes to sleep again.
 291  *
 292  * However, this is very difficult to achieve in practice since
 293  * get_online_cpus() not an api which is called all that often.
 294  *
 295  */
 296 void cpu_hotplug_begin(void)
 297 {
 298         DEFINE_WAIT(wait);
 299
 300         cpu_hotplug.active_writer = current;
 301         cpuhp_lock_acquire();
 302
 303         for (;;) {
 304                 mutex_lock(&cpu_hotplug.lock);
 305                 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 306                 if (likely(!atomic_read(&cpu_hotplug.refcount)))
 307                                 break;
 308                 mutex_unlock(&cpu_hotplug.lock);
 309                 schedule();
 310         }
 311         finish_wait(&cpu_hotplug.wq, &wait);
 312 }
 313
 314 void cpu_hotplug_done(void)
 315 {
 316         cpu_hotplug.active_writer = NULL;
 317         mutex_unlock(&cpu_hotplug.lock);
 318         cpuhp_lock_release();
 319 }
 320
 321 /*
 322  * Wait for currently running CPU hotplug operations to complete (if any) and
 323  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 324  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 325  * hotplug path before performing hotplug operations. So acquiring that lock
 326  * guarantees mutual exclusion from any currently running hotplug operations.
 327  */
 328 void cpu_hotplug_disable(void)
 329 {
 330         cpu_maps_update_begin();
 331         cpu_hotplug_disabled++;
 332         cpu_maps_update_done();
 333 }
 334 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 335
 336 static void __cpu_hotplug_enable(void)
 337 {
 338         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
 339                 return;
 340         cpu_hotplug_disabled--;
 341 }
 342
 343 void cpu_hotplug_enable(void)
 344 {
 345         cpu_maps_update_begin();
 346         __cpu_hotplug_enable();
 347         cpu_maps_update_done();
 348 }
 349 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 350 #endif  /* CONFIG_HOTPLUG_CPU */
 351
 352 /* Need to know about CPUs going up/down? */
 353 int register_cpu_notifier(struct notifier_block *nb)
 354 {
 355         int ret;
 356         cpu_maps_update_begin();
 357         ret = raw_notifier_chain_register(&cpu_chain, nb);
 358         cpu_maps_update_done();
 359         return ret;
 360 }
 361
 362 int __register_cpu_notifier(struct notifier_block *nb)
 363 {
 364         return raw_notifier_chain_register(&cpu_chain, nb);
 365 }
 366
 367 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 368                         int *nr_calls)
 369 {
 370         unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 371         void *hcpu = (void *)(long)cpu;
 372
 373         int ret;
 374
 375         ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 376                                         nr_calls);
 377
 378         return notifier_to_errno(ret);
 379 }
 380
 381 static int cpu_notify(unsigned long val, unsigned int cpu)
 382 {
 383         return __cpu_notify(val, cpu, -1, NULL);
 384 }
 385
 386 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 387 {
 388         BUG_ON(cpu_notify(val, cpu));
 389 }
 390
 391 /* Notifier wrappers for transitioning to state machine */
 392 static int notify_prepare(unsigned int cpu)
 393 {
 394         int nr_calls = 0;
 395         int ret;
 396
 397         ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 398         if (ret) {
 399                 nr_calls--;
 400                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 401                                 __func__, cpu);
 402                 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 403         }
 404         return ret;
 405 }
 406
 407 static int notify_online(unsigned int cpu)
 408 {
 409         cpu_notify(CPU_ONLINE, cpu);
 410         return 0;
 411 }
 412
 413 static int bringup_wait_for_ap(unsigned int cpu)
 414 {
 415         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 416
 417         wait_for_completion(&st->done);
 418         return st->result;
 419 }
 420
 421 static int bringup_cpu(unsigned int cpu)
 422 {
 423         struct task_struct *idle = idle_thread_get(cpu);
 424         int ret;
 425
 426         /*
 427          * Some architectures have to walk the irq descriptors to
 428          * setup the vector space for the cpu which comes online.
 429          * Prevent irq alloc/free across the bringup.
 430          */
 431         irq_lock_sparse();
 432
 433         /* Arch-specific enabling code. */
 434         ret = __cpu_up(cpu, idle);
 435         irq_unlock_sparse();
 436         if (ret) {
 437                 cpu_notify(CPU_UP_CANCELED, cpu);
 438                 return ret;
 439         }
 440         ret = bringup_wait_for_ap(cpu);
 441         BUG_ON(!cpu_online(cpu));
 442         return ret;
 443 }
 444
 445 /*
 446  * Hotplug state machine related functions
 447  */
 448 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
 449 {
 450         for (st->state++; st->state < st->target; st->state++) {
 451                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 452
 453                 if (!step->skip_onerr)
 454                         cpuhp_invoke_callback(cpu, st->state, true, NULL);
 455         }
 456 }
 457
 458 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 459                                 enum cpuhp_state target)
 460 {
 461         enum cpuhp_state prev_state = st->state;
 462         int ret = 0;
 463
 464         for (; st->state > target; st->state--) {
 465                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL);
 466                 if (ret) {
 467                         st->target = prev_state;
 468                         undo_cpu_down(cpu, st);
 469                         break;
 470                 }
 471         }
 472         return ret;
 473 }
 474
 475 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
 476 {
 477         for (st->state--; st->state > st->target; st->state--) {
 478                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 479
 480                 if (!step->skip_onerr)
 481                         cpuhp_invoke_callback(cpu, st->state, false, NULL);
 482         }
 483 }
 484
 485 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 486                               enum cpuhp_state target)
 487 {
 488         enum cpuhp_state prev_state = st->state;
 489         int ret = 0;
 490
 491         while (st->state < target) {
 492                 st->state++;
 493                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL);
 494                 if (ret) {
 495                         st->target = prev_state;
 496                         undo_cpu_up(cpu, st);
 497                         break;
 498                 }
 499         }
 500         return ret;
 501 }
 502
 503 /*
 504  * The cpu hotplug threads manage the bringup and teardown of the cpus
 505  */
 506 static void cpuhp_create(unsigned int cpu)
 507 {
 508         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 509
 510         init_completion(&st->done);
 511 }
 512
 513 static int cpuhp_should_run(unsigned int cpu)
 514 {
 515         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 516
 517         return st->should_run;
 518 }
 519
 520 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
 521 static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
 522 {
 523         enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
 524
 525         return cpuhp_down_callbacks(cpu, st, target);
 526 }
 527
 528 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
 529 static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
 530 {
 531         return cpuhp_up_callbacks(cpu, st, st->target);
 532 }
 533
 534 /*
 535  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 536  * callbacks when a state gets [un]installed at runtime.
 537  */
 538 static void cpuhp_thread_fun(unsigned int cpu)
 539 {
 540         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 541         int ret = 0;
 542
 543         /*
 544          * Paired with the mb() in cpuhp_kick_ap_work and
 545          * cpuhp_invoke_ap_callback, so the work set is consistent visible.
 546          */
 547         smp_mb();
 548         if (!st->should_run)
 549                 return;
 550
 551         st->should_run = false;
 552
 553         /* Single callback invocation for [un]install ? */
 554         if (st->single) {
 555                 if (st->cb_state < CPUHP_AP_ONLINE) {
 556                         local_irq_disable();
 557                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 558                                                     st->bringup, st->node);
 559                         local_irq_enable();
 560                 } else {
 561                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 562                                                     st->bringup, st->node);
 563                 }
 564         } else if (st->rollback) {
 565                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 566
 567                 undo_cpu_down(cpu, st);
 568                 /*
 569                  * This is a momentary workaround to keep the notifier users
 570                  * happy. Will go away once we got rid of the notifiers.
 571                  */
 572                 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 573                 st->rollback = false;
 574         } else {
 575                 /* Cannot happen .... */
 576                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 577
 578                 /* Regular hotplug work */
 579                 if (st->state < st->target)
 580                         ret = cpuhp_ap_online(cpu, st);
 581                 else if (st->state > st->target)
 582                         ret = cpuhp_ap_offline(cpu, st);
 583         }
 584         st->result = ret;
 585         complete(&st->done);
 586 }
 587
 588 /* Invoke a single callback on a remote cpu */
 589 static int
 590 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
 591                          struct hlist_node *node)
 592 {
 593         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 594
 595         if (!cpu_online(cpu))
 596                 return 0;
 597
 598         /*
 599          * If we are up and running, use the hotplug thread. For early calls
 600          * we invoke the thread function directly.
 601          */
 602         if (!st->thread)
 603                 return cpuhp_invoke_callback(cpu, state, bringup, node);
 604
 605         st->cb_state = state;
 606         st->single = true;
 607         st->bringup = bringup;
 608         st->node = node;
 609
 610         /*
 611          * Make sure the above stores are visible before should_run becomes
 612          * true. Paired with the mb() above in cpuhp_thread_fun()
 613          */
 614         smp_mb();
 615         st->should_run = true;
 616         wake_up_process(st->thread);
 617         wait_for_completion(&st->done);
 618         return st->result;
 619 }
 620
 621 /* Regular hotplug invocation of the AP hotplug thread */
 622 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
 623 {
 624         st->result = 0;
 625         st->single = false;
 626         /*
 627          * Make sure the above stores are visible before should_run becomes
 628          * true. Paired with the mb() above in cpuhp_thread_fun()
 629          */
 630         smp_mb();
 631         st->should_run = true;
 632         wake_up_process(st->thread);
 633 }
 634
 635 static int cpuhp_kick_ap_work(unsigned int cpu)
 636 {
 637         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 638         enum cpuhp_state state = st->state;
 639
 640         trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
 641         __cpuhp_kick_ap_work(st);
 642         wait_for_completion(&st->done);
 643         trace_cpuhp_exit(cpu, st->state, state, st->result);
 644         return st->result;
 645 }
 646
 647 static struct smp_hotplug_thread cpuhp_threads = {
 648         .store                  = &cpuhp_state.thread,
 649         .create                 = &cpuhp_create,
 650         .thread_should_run      = cpuhp_should_run,
 651         .thread_fn              = cpuhp_thread_fun,
 652         .thread_comm            = "cpuhp/%u",
 653         .selfparking            = true,
 654 };
 655
 656 void __init cpuhp_threads_init(void)
 657 {
 658         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 659         kthread_unpark(this_cpu_read(cpuhp_state.thread));
 660 }
 661
 662 #ifdef CONFIG_HOTPLUG_CPU
 663 EXPORT_SYMBOL(register_cpu_notifier);
 664 EXPORT_SYMBOL(__register_cpu_notifier);
 665 void unregister_cpu_notifier(struct notifier_block *nb)
 666 {
 667         cpu_maps_update_begin();
 668         raw_notifier_chain_unregister(&cpu_chain, nb);
 669         cpu_maps_update_done();
 670 }
 671 EXPORT_SYMBOL(unregister_cpu_notifier);
 672
 673 void __unregister_cpu_notifier(struct notifier_block *nb)
 674 {
 675         raw_notifier_chain_unregister(&cpu_chain, nb);
 676 }
 677 EXPORT_SYMBOL(__unregister_cpu_notifier);
 678
 679 /**
 680  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 681  * @cpu: a CPU id
 682  *
 683  * This function walks all processes, finds a valid mm struct for each one and
 684  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 685  * trivial, there are various non-obvious corner cases, which this function
 686  * tries to solve in a safe manner.
 687  *
 688  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 689  * be called only for an already offlined CPU.
 690  */
 691 void clear_tasks_mm_cpumask(int cpu)
 692 {
 693         struct task_struct *p;
 694
 695         /*
 696          * This function is called after the cpu is taken down and marked
 697          * offline, so its not like new tasks will ever get this cpu set in
 698          * their mm mask. -- Peter Zijlstra
 699          * Thus, we may use rcu_read_lock() here, instead of grabbing
 700          * full-fledged tasklist_lock.
 701          */
 702         WARN_ON(cpu_online(cpu));
 703         rcu_read_lock();
 704         for_each_process(p) {
 705                 struct task_struct *t;
 706
 707                 /*
 708                  * Main thread might exit, but other threads may still have
 709                  * a valid mm. Find one.
 710                  */
 711                 t = find_lock_task_mm(p);
 712                 if (!t)
 713                         continue;
 714                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 715                 task_unlock(t);
 716         }
 717         rcu_read_unlock();
 718 }
 719
 720 static inline void check_for_tasks(int dead_cpu)
 721 {
 722         struct task_struct *g, *p;
 723
 724         read_lock(&tasklist_lock);
 725         for_each_process_thread(g, p) {
 726                 if (!p->on_rq)
 727                         continue;
 728                 /*
 729                  * We do the check with unlocked task_rq(p)->lock.
 730                  * Order the reading to do not warn about a task,
 731                  * which was running on this cpu in the past, and
 732                  * it's just been woken on another cpu.
 733                  */
 734                 rmb();
 735                 if (task_cpu(p) != dead_cpu)
 736                         continue;
 737
 738                 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
 739                         p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
 740         }
 741         read_unlock(&tasklist_lock);
 742 }
 743
 744 static int notify_down_prepare(unsigned int cpu)
 745 {
 746         int err, nr_calls = 0;
 747
 748         err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
 749         if (err) {
 750                 nr_calls--;
 751                 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
 752                 pr_warn("%s: attempt to take down CPU %u failed\n",
 753                                 __func__, cpu);
 754         }
 755         return err;
 756 }
 757
 758 /* Take this CPU down. */
 759 static int take_cpu_down(void *_param)
 760 {
 761         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 762         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 763         int err, cpu = smp_processor_id();
 764
 765         /* Ensure this CPU doesn't handle any more interrupts. */
 766         err = __cpu_disable();
 767         if (err < 0)
 768                 return err;
 769
 770         /*
 771          * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
 772          * do this step again.
 773          */
 774         WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
 775         st->state--;
 776         /* Invoke the former CPU_DYING callbacks */
 777         for (; st->state > target; st->state--)
 778                 cpuhp_invoke_callback(cpu, st->state, false, NULL);
 779
 780         /* Give up timekeeping duties */
 781         tick_handover_do_timer();
 782         /* Park the stopper thread */
 783         stop_machine_park(cpu);
 784         return 0;
 785 }
 786
 787 static int takedown_cpu(unsigned int cpu)
 788 {
 789         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 790         int err;
 791
 792         /* Park the smpboot threads */
 793         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 794         smpboot_park_threads(cpu);
 795
 796         /*
 797          * Prevent irq alloc/free while the dying cpu reorganizes the
 798          * interrupt affinities.
 799          */
 800         irq_lock_sparse();
 801
 802         /*
 803          * So now all preempt/rcu users must observe !cpu_active().
 804          */
 805         err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
 806         if (err) {
 807                 /* CPU refused to die */
 808                 irq_unlock_sparse();
 809                 /* Unpark the hotplug thread so we can rollback there */
 810                 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 811                 return err;
 812         }
 813         BUG_ON(cpu_online(cpu));
 814
 815         /*
 816          * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
 817          * runnable tasks from the cpu, there's only the idle task left now
 818          * that the migration thread is done doing the stop_machine thing.
 819          *
 820          * Wait for the stop thread to go away.
 821          */
 822         wait_for_completion(&st->done);
 823         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
 824
 825         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
 826         irq_unlock_sparse();
 827
 828         hotplug_cpu__broadcast_tick_pull(cpu);
 829         /* This actually kills the CPU. */
 830         __cpu_die(cpu);
 831
 832         tick_cleanup_dead_cpu(cpu);
 833         return 0;
 834 }
 835
 836 static int notify_dead(unsigned int cpu)
 837 {
 838         cpu_notify_nofail(CPU_DEAD, cpu);
 839         check_for_tasks(cpu);
 840         return 0;
 841 }
 842
 843 static void cpuhp_complete_idle_dead(void *arg)
 844 {
 845         struct cpuhp_cpu_state *st = arg;
 846
 847         complete(&st->done);
 848 }
 849
 850 void cpuhp_report_idle_dead(void)
 851 {
 852         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 853
 854         BUG_ON(st->state != CPUHP_AP_OFFLINE);
 855         rcu_report_dead(smp_processor_id());
 856         st->state = CPUHP_AP_IDLE_DEAD;
 857         /*
 858          * We cannot call complete after rcu_report_dead() so we delegate it
 859          * to an online cpu.
 860          */
 861         smp_call_function_single(cpumask_first(cpu_online_mask),
 862                                  cpuhp_complete_idle_dead, st, 0);
 863 }
 864
 865 #else
 866 #define notify_down_prepare     NULL
 867 #define takedown_cpu            NULL
 868 #define notify_dead             NULL
 869 #endif
 870
 871 #ifdef CONFIG_HOTPLUG_CPU
 872
 873 /* Requires cpu_add_remove_lock to be held */
 874 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 875                            enum cpuhp_state target)
 876 {
 877         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 878         int prev_state, ret = 0;
 879         bool hasdied = false;
 880
 881         if (num_online_cpus() == 1)
 882                 return -EBUSY;
 883
 884         if (!cpu_present(cpu))
 885                 return -EINVAL;
 886
 887         cpu_hotplug_begin();
 888
 889         cpuhp_tasks_frozen = tasks_frozen;
 890
 891         prev_state = st->state;
 892         st->target = target;
 893         /*
 894          * If the current CPU state is in the range of the AP hotplug thread,
 895          * then we need to kick the thread.
 896          */
 897         if (st->state > CPUHP_TEARDOWN_CPU) {
 898                 ret = cpuhp_kick_ap_work(cpu);
 899                 /*
 900                  * The AP side has done the error rollback already. Just
 901                  * return the error code..
 902                  */
 903                 if (ret)
 904                         goto out;
 905
 906                 /*
 907                  * We might have stopped still in the range of the AP hotplug
 908                  * thread. Nothing to do anymore.
 909                  */
 910                 if (st->state > CPUHP_TEARDOWN_CPU)
 911                         goto out;
 912         }
 913         /*
 914          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
 915          * to do the further cleanups.
 916          */
 917         ret = cpuhp_down_callbacks(cpu, st, target);
 918         if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
 919                 st->target = prev_state;
 920                 st->rollback = true;
 921                 cpuhp_kick_ap_work(cpu);
 922         }
 923
 924         hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
 925 out:
 926         cpu_hotplug_done();
 927         /* This post dead nonsense must die */
 928         if (!ret && hasdied)
 929                 cpu_notify_nofail(CPU_POST_DEAD, cpu);
 930         return ret;
 931 }
 932
 933 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
 934 {
 935         int err;
 936
 937         cpu_maps_update_begin();
 938
 939         if (cpu_hotplug_disabled) {
 940                 err = -EBUSY;
 941                 goto out;
 942         }
 943
 944         err = _cpu_down(cpu, 0, target);
 945
 946 out:
 947         cpu_maps_update_done();
 948         return err;
 949 }
 950 int cpu_down(unsigned int cpu)
 951 {
 952         return do_cpu_down(cpu, CPUHP_OFFLINE);
 953 }
 954 EXPORT_SYMBOL(cpu_down);
 955 #endif /*CONFIG_HOTPLUG_CPU*/
 956
 957 /**
 958  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
 959  * @cpu: cpu that just started
 960  *
 961  * It must be called by the arch code on the new cpu, before the new cpu
 962  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 963  */
 964 void notify_cpu_starting(unsigned int cpu)
 965 {
 966         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 967         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
 968
 969         while (st->state < target) {
 970                 st->state++;
 971                 cpuhp_invoke_callback(cpu, st->state, true, NULL);
 972         }
 973 }
 974
 975 /*
 976  * Called from the idle task. We need to set active here, so we can kick off
 977  * the stopper thread and unpark the smpboot threads. If the target state is
 978  * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
 979  * cpu further.
 980  */
 981 void cpuhp_online_idle(enum cpuhp_state state)
 982 {
 983         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 984         unsigned int cpu = smp_processor_id();
 985
 986         /* Happens for the boot cpu */
 987         if (state != CPUHP_AP_ONLINE_IDLE)
 988                 return;
 989
 990         st->state = CPUHP_AP_ONLINE_IDLE;
 991
 992         /* Unpark the stopper thread and the hotplug thread of this cpu */
 993         stop_machine_unpark(cpu);
 994         kthread_unpark(st->thread);
 995
 996         /* Should we go further up ? */
 997         if (st->target > CPUHP_AP_ONLINE_IDLE)
 998                 __cpuhp_kick_ap_work(st);
 999         else
1000                 complete(&st->done);
1001 }
1002
1003 /* Requires cpu_add_remove_lock to be held */
1004 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1005 {
1006         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1007         struct task_struct *idle;
1008         int ret = 0;
1009
1010         cpu_hotplug_begin();
1011
1012         if (!cpu_present(cpu)) {
1013                 ret = -EINVAL;
1014                 goto out;
1015         }
1016
1017         /*
1018          * The caller of do_cpu_up might have raced with another
1019          * caller. Ignore it for now.
1020          */
1021         if (st->state >= target)
1022                 goto out;
1023
1024         if (st->state == CPUHP_OFFLINE) {
1025                 /* Let it fail before we try to bring the cpu up */
1026                 idle = idle_thread_get(cpu);
1027                 if (IS_ERR(idle)) {
1028                         ret = PTR_ERR(idle);
1029                         goto out;
1030                 }
1031         }
1032
1033         cpuhp_tasks_frozen = tasks_frozen;
1034
1035         st->target = target;
1036         /*
1037          * If the current CPU state is in the range of the AP hotplug thread,
1038          * then we need to kick the thread once more.
1039          */
1040         if (st->state > CPUHP_BRINGUP_CPU) {
1041                 ret = cpuhp_kick_ap_work(cpu);
1042                 /*
1043                  * The AP side has done the error rollback already. Just
1044                  * return the error code..
1045                  */
1046                 if (ret)
1047                         goto out;
1048         }
1049
1050         /*
1051          * Try to reach the target state. We max out on the BP at
1052          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1053          * responsible for bringing it up to the target state.
1054          */
1055         target = min((int)target, CPUHP_BRINGUP_CPU);
1056         ret = cpuhp_up_callbacks(cpu, st, target);
1057 out:
1058         cpu_hotplug_done();
1059         return ret;
1060 }
1061
1062 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1063 {
1064         int err = 0;
1065
1066         if (!cpu_possible(cpu)) {
1067                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1068                        cpu);
1069 #if defined(CONFIG_IA64)
1070                 pr_err("please check additional_cpus= boot parameter\n");
1071 #endif
1072                 return -EINVAL;
1073         }
1074
1075         err = try_online_node(cpu_to_node(cpu));
1076         if (err)
1077                 return err;
1078
1079         cpu_maps_update_begin();
1080
1081         if (cpu_hotplug_disabled) {
1082                 err = -EBUSY;
1083                 goto out;
1084         }
1085
1086         err = _cpu_up(cpu, 0, target);
1087 out:
1088         cpu_maps_update_done();
1089         return err;
1090 }
1091
1092 int cpu_up(unsigned int cpu)
1093 {
1094         return do_cpu_up(cpu, CPUHP_ONLINE);
1095 }
1096 EXPORT_SYMBOL_GPL(cpu_up);
1097
1098 #ifdef CONFIG_PM_SLEEP_SMP
1099 static cpumask_var_t frozen_cpus;
1100
1101 int disable_nonboot_cpus(void)
1102 {
1103         int cpu, first_cpu, error = 0;
1104
1105         cpu_maps_update_begin();
1106         first_cpu = cpumask_first(cpu_online_mask);
1107         /*
1108          * We take down all of the non-boot CPUs in one shot to avoid races
1109          * with the userspace trying to use the CPU hotplug at the same time
1110          */
1111         cpumask_clear(frozen_cpus);
1112
1113         pr_info("Disabling non-boot CPUs ...\n");
1114         for_each_online_cpu(cpu) {
1115                 if (cpu == first_cpu)
1116                         continue;
1117                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1118                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1119                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1120                 if (!error)
1121                         cpumask_set_cpu(cpu, frozen_cpus);
1122                 else {
1123                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1124                         break;
1125                 }
1126         }
1127
1128         if (!error)
1129                 BUG_ON(num_online_cpus() > 1);
1130         else
1131                 pr_err("Non-boot CPUs are not disabled\n");
1132
1133         /*
1134          * Make sure the CPUs won't be enabled by someone else. We need to do
1135          * this even in case of failure as all disable_nonboot_cpus() users are
1136          * supposed to do enable_nonboot_cpus() on the failure path.
1137          */
1138         cpu_hotplug_disabled++;
1139
1140         cpu_maps_update_done();
1141         return error;
1142 }
1143
1144 void __weak arch_enable_nonboot_cpus_begin(void)
1145 {
1146 }
1147
1148 void __weak arch_enable_nonboot_cpus_end(void)
1149 {
1150 }
1151
1152 void enable_nonboot_cpus(void)
1153 {
1154         int cpu, error;
1155
1156         /* Allow everyone to use the CPU hotplug again */
1157         cpu_maps_update_begin();
1158         __cpu_hotplug_enable();
1159         if (cpumask_empty(frozen_cpus))
1160                 goto out;
1161
1162         pr_info("Enabling non-boot CPUs ...\n");
1163
1164         arch_enable_nonboot_cpus_begin();
1165
1166         for_each_cpu(cpu, frozen_cpus) {
1167                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1168                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1169                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1170                 if (!error) {
1171                         pr_info("CPU%d is up\n", cpu);
1172                         continue;
1173                 }
1174                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1175         }
1176
1177         arch_enable_nonboot_cpus_end();
1178
1179         cpumask_clear(frozen_cpus);
1180 out:
1181         cpu_maps_update_done();
1182 }
1183
1184 static int __init alloc_frozen_cpus(void)
1185 {
1186         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1187                 return -ENOMEM;
1188         return 0;
1189 }
1190 core_initcall(alloc_frozen_cpus);
1191
1192 /*
1193  * When callbacks for CPU hotplug notifications are being executed, we must
1194  * ensure that the state of the system with respect to the tasks being frozen
1195  * or not, as reported by the notification, remains unchanged *throughout the
1196  * duration* of the execution of the callbacks.
1197  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1198  *
1199  * This synchronization is implemented by mutually excluding regular CPU
1200  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1201  * Hibernate notifications.
1202  */
1203 static int
1204 cpu_hotplug_pm_callback(struct notifier_block *nb,
1205                         unsigned long action, void *ptr)
1206 {
1207         switch (action) {
1208
1209         case PM_SUSPEND_PREPARE:
1210         case PM_HIBERNATION_PREPARE:
1211                 cpu_hotplug_disable();
1212                 break;
1213
1214         case PM_POST_SUSPEND:
1215         case PM_POST_HIBERNATION:
1216                 cpu_hotplug_enable();
1217                 break;
1218
1219         default:
1220                 return NOTIFY_DONE;
1221         }
1222
1223         return NOTIFY_OK;
1224 }
1225
1226
1227 static int __init cpu_hotplug_pm_sync_init(void)
1228 {
1229         /*
1230          * cpu_hotplug_pm_callback has higher priority than x86
1231          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1232          * to disable cpu hotplug to avoid cpu hotplug race.
1233          */
1234         pm_notifier(cpu_hotplug_pm_callback, 0);
1235         return 0;
1236 }
1237 core_initcall(cpu_hotplug_pm_sync_init);
1238
1239 #endif /* CONFIG_PM_SLEEP_SMP */
1240
1241 #endif /* CONFIG_SMP */
1242
1243 /* Boot processor state steps */
1244 static struct cpuhp_step cpuhp_bp_states[] = {
1245         [CPUHP_OFFLINE] = {
1246                 .name                   = "offline",
1247                 .startup.single         = NULL,
1248                 .teardown.single        = NULL,
1249         },
1250 #ifdef CONFIG_SMP
1251         [CPUHP_CREATE_THREADS]= {
1252                 .name                   = "threads:prepare",
1253                 .startup.single         = smpboot_create_threads,
1254                 .teardown.single        = NULL,
1255                 .cant_stop              = true,
1256         },
1257         [CPUHP_PERF_PREPARE] = {
1258                 .name                   = "perf:prepare",
1259                 .startup.single         = perf_event_init_cpu,
1260                 .teardown.single        = perf_event_exit_cpu,
1261         },
1262         [CPUHP_WORKQUEUE_PREP] = {
1263                 .name                   = "workqueue:prepare",
1264                 .startup.single         = workqueue_prepare_cpu,
1265                 .teardown.single        = NULL,
1266         },
1267         [CPUHP_HRTIMERS_PREPARE] = {
1268                 .name                   = "hrtimers:prepare",
1269                 .startup.single         = hrtimers_prepare_cpu,
1270                 .teardown.single        = hrtimers_dead_cpu,
1271         },
1272         [CPUHP_SMPCFD_PREPARE] = {
1273                 .name                   = "smpcfd:prepare",
1274                 .startup.single         = smpcfd_prepare_cpu,
1275                 .teardown.single        = smpcfd_dead_cpu,
1276         },
1277         [CPUHP_RELAY_PREPARE] = {
1278                 .name                   = "relay:prepare",
1279                 .startup.single         = relay_prepare_cpu,
1280                 .teardown.single        = NULL,
1281         },
1282         [CPUHP_SLAB_PREPARE] = {
1283                 .name                   = "slab:prepare",
1284                 .startup.single         = slab_prepare_cpu,
1285                 .teardown.single        = slab_dead_cpu,
1286         },
1287         [CPUHP_RCUTREE_PREP] = {
1288                 .name                   = "RCU/tree:prepare",
1289                 .startup.single         = rcutree_prepare_cpu,
1290                 .teardown.single        = rcutree_dead_cpu,
1291         },
1292         /*
1293          * Preparatory and dead notifiers. Will be replaced once the notifiers
1294          * are converted to states.
1295          */
1296         [CPUHP_NOTIFY_PREPARE] = {
1297                 .name                   = "notify:prepare",
1298                 .startup.single         = notify_prepare,
1299                 .teardown.single        = notify_dead,
1300                 .skip_onerr             = true,
1301                 .cant_stop              = true,
1302         },
1303         /*
1304          * On the tear-down path, timers_dead_cpu() must be invoked
1305          * before blk_mq_queue_reinit_notify() from notify_dead(),
1306          * otherwise a RCU stall occurs.
1307          */
1308         [CPUHP_TIMERS_DEAD] = {
1309                 .name                   = "timers:dead",
1310                 .startup.single         = NULL,
1311                 .teardown.single        = timers_dead_cpu,
1312         },
1313         /* Kicks the plugged cpu into life */
1314         [CPUHP_BRINGUP_CPU] = {
1315                 .name                   = "cpu:bringup",
1316                 .startup.single         = bringup_cpu,
1317                 .teardown.single        = NULL,
1318                 .cant_stop              = true,
1319         },
1320         [CPUHP_AP_SMPCFD_DYING] = {
1321                 .name                   = "smpcfd:dying",
1322                 .startup.single         = NULL,
1323                 .teardown.single        = smpcfd_dying_cpu,
1324         },
1325         /*
1326          * Handled on controll processor until the plugged processor manages
1327          * this itself.
1328          */
1329         [CPUHP_TEARDOWN_CPU] = {
1330                 .name                   = "cpu:teardown",
1331                 .startup.single         = NULL,
1332                 .teardown.single        = takedown_cpu,
1333                 .cant_stop              = true,
1334         },
1335 #else
1336         [CPUHP_BRINGUP_CPU] = { },
1337 #endif
1338 };
1339
1340 /* Application processor state steps */
1341 static struct cpuhp_step cpuhp_ap_states[] = {
1342 #ifdef CONFIG_SMP
1343         /* Final state before CPU kills itself */
1344         [CPUHP_AP_IDLE_DEAD] = {
1345                 .name                   = "idle:dead",
1346         },
1347         /*
1348          * Last state before CPU enters the idle loop to die. Transient state
1349          * for synchronization.
1350          */
1351         [CPUHP_AP_OFFLINE] = {
1352                 .name                   = "ap:offline",
1353                 .cant_stop              = true,
1354         },
1355         /* First state is scheduler control. Interrupts are disabled */
1356         [CPUHP_AP_SCHED_STARTING] = {
1357                 .name                   = "sched:starting",
1358                 .startup.single         = sched_cpu_starting,
1359                 .teardown.single        = sched_cpu_dying,
1360         },
1361         [CPUHP_AP_RCUTREE_DYING] = {
1362                 .name                   = "RCU/tree:dying",
1363                 .startup.single         = NULL,
1364                 .teardown.single        = rcutree_dying_cpu,
1365         },
1366         /* Entry state on starting. Interrupts enabled from here on. Transient
1367          * state for synchronsization */
1368         [CPUHP_AP_ONLINE] = {
1369                 .name                   = "ap:online",
1370         },
1371         /* Handle smpboot threads park/unpark */
1372         [CPUHP_AP_SMPBOOT_THREADS] = {
1373                 .name                   = "smpboot/threads:online",
1374                 .startup.single         = smpboot_unpark_threads,
1375                 .teardown.single        = NULL,
1376         },
1377         [CPUHP_AP_PERF_ONLINE] = {
1378                 .name                   = "perf:online",
1379                 .startup.single         = perf_event_init_cpu,
1380                 .teardown.single        = perf_event_exit_cpu,
1381         },
1382         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1383                 .name                   = "workqueue:online",
1384                 .startup.single         = workqueue_online_cpu,
1385                 .teardown.single        = workqueue_offline_cpu,
1386         },
1387         [CPUHP_AP_RCUTREE_ONLINE] = {
1388                 .name                   = "RCU/tree:online",
1389                 .startup.single         = rcutree_online_cpu,
1390                 .teardown.single        = rcutree_offline_cpu,
1391         },
1392
1393         /*
1394          * Online/down_prepare notifiers. Will be removed once the notifiers
1395          * are converted to states.
1396          */
1397         [CPUHP_AP_NOTIFY_ONLINE] = {
1398                 .name                   = "notify:online",
1399                 .startup.single         = notify_online,
1400                 .teardown.single        = notify_down_prepare,
1401                 .skip_onerr             = true,
1402         },
1403 #endif
1404         /*
1405          * The dynamically registered state space is here
1406          */
1407
1408 #ifdef CONFIG_SMP
1409         /* Last state is scheduler control setting the cpu active */
1410         [CPUHP_AP_ACTIVE] = {
1411                 .name                   = "sched:active",
1412                 .startup.single         = sched_cpu_activate,
1413                 .teardown.single        = sched_cpu_deactivate,
1414         },
1415 #endif
1416
1417         /* CPU is fully up and running. */
1418         [CPUHP_ONLINE] = {
1419                 .name                   = "online",
1420                 .startup.single         = NULL,
1421                 .teardown.single        = NULL,
1422         },
1423 };
1424
1425 /* Sanity check for callbacks */
1426 static int cpuhp_cb_check(enum cpuhp_state state)
1427 {
1428         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1429                 return -EINVAL;
1430         return 0;
1431 }
1432
1433 static void cpuhp_store_callbacks(enum cpuhp_state state,
1434                                   const char *name,
1435                                   int (*startup)(unsigned int cpu),
1436                                   int (*teardown)(unsigned int cpu),
1437                                   bool multi_instance)
1438 {
1439         /* (Un)Install the callbacks for further cpu hotplug operations */
1440         struct cpuhp_step *sp;
1441
1442         mutex_lock(&cpuhp_state_mutex);
1443         sp = cpuhp_get_step(state);
1444         sp->startup.single = startup;
1445         sp->teardown.single = teardown;
1446         sp->name = name;
1447         sp->multi_instance = multi_instance;
1448         INIT_HLIST_HEAD(&sp->list);
1449         mutex_unlock(&cpuhp_state_mutex);
1450 }
1451
1452 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1453 {
1454         return cpuhp_get_step(state)->teardown.single;
1455 }
1456
1457 /*
1458  * Call the startup/teardown function for a step either on the AP or
1459  * on the current CPU.
1460  */
1461 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1462                             struct hlist_node *node)
1463 {
1464         struct cpuhp_step *sp = cpuhp_get_step(state);
1465         int ret;
1466
1467         if ((bringup && !sp->startup.single) ||
1468             (!bringup && !sp->teardown.single))
1469                 return 0;
1470         /*
1471          * The non AP bound callbacks can fail on bringup. On teardown
1472          * e.g. module removal we crash for now.
1473          */
1474 #ifdef CONFIG_SMP
1475         if (cpuhp_is_ap_state(state))
1476                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1477         else
1478                 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1479 #else
1480         ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1481 #endif
1482         BUG_ON(ret && !bringup);
1483         return ret;
1484 }
1485
1486 /*
1487  * Called from __cpuhp_setup_state on a recoverable failure.
1488  *
1489  * Note: The teardown callbacks for rollback are not allowed to fail!
1490  */
1491 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1492                                    struct hlist_node *node)
1493 {
1494         int cpu;
1495
1496         /* Roll back the already executed steps on the other cpus */
1497         for_each_present_cpu(cpu) {
1498                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1499                 int cpustate = st->state;
1500
1501                 if (cpu >= failedcpu)
1502                         break;
1503
1504                 /* Did we invoke the startup call on that cpu ? */
1505                 if (cpustate >= state)
1506                         cpuhp_issue_call(cpu, state, false, node);
1507         }
1508 }
1509
1510 /*
1511  * Returns a free for dynamic slot assignment of the Online state. The states
1512  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1513  * by having no name assigned.
1514  */
1515 static int cpuhp_reserve_state(enum cpuhp_state state)
1516 {
1517         enum cpuhp_state i;
1518
1519         mutex_lock(&cpuhp_state_mutex);
1520         for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1521                 if (cpuhp_ap_states[i].name)
1522                         continue;
1523
1524                 cpuhp_ap_states[i].name = "Reserved";
1525                 mutex_unlock(&cpuhp_state_mutex);
1526                 return i;
1527         }
1528         mutex_unlock(&cpuhp_state_mutex);
1529         WARN(1, "No more dynamic states available for CPU hotplug\n");
1530         return -ENOSPC;
1531 }
1532
1533 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1534                                bool invoke)
1535 {
1536         struct cpuhp_step *sp;
1537         int cpu;
1538         int ret;
1539
1540         sp = cpuhp_get_step(state);
1541         if (sp->multi_instance == false)
1542                 return -EINVAL;
1543
1544         get_online_cpus();
1545
1546         if (!invoke || !sp->startup.multi)
1547                 goto add_node;
1548
1549         /*
1550          * Try to call the startup callback for each present cpu
1551          * depending on the hotplug state of the cpu.
1552          */
1553         for_each_present_cpu(cpu) {
1554                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1555                 int cpustate = st->state;
1556
1557                 if (cpustate < state)
1558                         continue;
1559
1560                 ret = cpuhp_issue_call(cpu, state, true, node);
1561                 if (ret) {
1562                         if (sp->teardown.multi)
1563                                 cpuhp_rollback_install(cpu, state, node);
1564                         goto err;
1565                 }
1566         }
1567 add_node:
1568         ret = 0;
1569         mutex_lock(&cpuhp_state_mutex);
1570         hlist_add_head(node, &sp->list);
1571         mutex_unlock(&cpuhp_state_mutex);
1572
1573 err:
1574         put_online_cpus();
1575         return ret;
1576 }
1577 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1578
1579 /**
1580  * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1581  * @state:      The state to setup
1582  * @invoke:     If true, the startup function is invoked for cpus where
1583  *              cpu state >= @state
1584  * @startup:    startup callback function
1585  * @teardown:   teardown callback function
1586  *
1587  * Returns 0 if successful, otherwise a proper error code
1588  */
1589 int __cpuhp_setup_state(enum cpuhp_state state,
1590                         const char *name, bool invoke,
1591                         int (*startup)(unsigned int cpu),
1592                         int (*teardown)(unsigned int cpu),
1593                         bool multi_instance)
1594 {
1595         int cpu, ret = 0;
1596         int dyn_state = 0;
1597
1598         if (cpuhp_cb_check(state) || !name)
1599                 return -EINVAL;
1600
1601         get_online_cpus();
1602
1603         /* currently assignments for the ONLINE state are possible */
1604         if (state == CPUHP_AP_ONLINE_DYN) {
1605                 dyn_state = 1;
1606                 ret = cpuhp_reserve_state(state);
1607                 if (ret < 0)
1608                         goto out;
1609                 state = ret;
1610         }
1611
1612         cpuhp_store_callbacks(state, name, startup, teardown, multi_instance);
1613
1614         if (!invoke || !startup)
1615                 goto out;
1616
1617         /*
1618          * Try to call the startup callback for each present cpu
1619          * depending on the hotplug state of the cpu.
1620          */
1621         for_each_present_cpu(cpu) {
1622                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1623                 int cpustate = st->state;
1624
1625                 if (cpustate < state)
1626                         continue;
1627
1628                 ret = cpuhp_issue_call(cpu, state, true, NULL);
1629                 if (ret) {
1630                         if (teardown)
1631                                 cpuhp_rollback_install(cpu, state, NULL);
1632                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1633                         goto out;
1634                 }
1635         }
1636 out:
1637         put_online_cpus();
1638         if (!ret && dyn_state)
1639                 return state;
1640         return ret;
1641 }
1642 EXPORT_SYMBOL(__cpuhp_setup_state);
1643
1644 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1645                                   struct hlist_node *node, bool invoke)
1646 {
1647         struct cpuhp_step *sp = cpuhp_get_step(state);
1648         int cpu;
1649
1650         BUG_ON(cpuhp_cb_check(state));
1651
1652         if (!sp->multi_instance)
1653                 return -EINVAL;
1654
1655         get_online_cpus();
1656         if (!invoke || !cpuhp_get_teardown_cb(state))
1657                 goto remove;
1658         /*
1659          * Call the teardown callback for each present cpu depending
1660          * on the hotplug state of the cpu. This function is not
1661          * allowed to fail currently!
1662          */
1663         for_each_present_cpu(cpu) {
1664                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1665                 int cpustate = st->state;
1666
1667                 if (cpustate >= state)
1668                         cpuhp_issue_call(cpu, state, false, node);
1669         }
1670
1671 remove:
1672         mutex_lock(&cpuhp_state_mutex);
1673         hlist_del(node);
1674         mutex_unlock(&cpuhp_state_mutex);
1675         put_online_cpus();
1676
1677         return 0;
1678 }
1679 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1680 /**
1681  * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1682  * @state:      The state to remove
1683  * @invoke:     If true, the teardown function is invoked for cpus where
1684  *              cpu state >= @state
1685  *
1686  * The teardown callback is currently not allowed to fail. Think
1687  * about module removal!
1688  */
1689 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1690 {
1691         struct cpuhp_step *sp = cpuhp_get_step(state);
1692         int cpu;
1693
1694         BUG_ON(cpuhp_cb_check(state));
1695
1696         get_online_cpus();
1697
1698         if (sp->multi_instance) {
1699                 WARN(!hlist_empty(&sp->list),
1700                      "Error: Removing state %d which has instances left.\n",
1701                      state);
1702                 goto remove;
1703         }
1704
1705         if (!invoke || !cpuhp_get_teardown_cb(state))
1706                 goto remove;
1707
1708         /*
1709          * Call the teardown callback for each present cpu depending
1710          * on the hotplug state of the cpu. This function is not
1711          * allowed to fail currently!
1712          */
1713         for_each_present_cpu(cpu) {
1714                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1715                 int cpustate = st->state;
1716
1717                 if (cpustate >= state)
1718                         cpuhp_issue_call(cpu, state, false, NULL);
1719         }
1720 remove:
1721         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1722         put_online_cpus();
1723 }
1724 EXPORT_SYMBOL(__cpuhp_remove_state);
1725
1726 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1727 static ssize_t show_cpuhp_state(struct device *dev,
1728                                 struct device_attribute *attr, char *buf)
1729 {
1730         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1731
1732         return sprintf(buf, "%d\n", st->state);
1733 }
1734 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1735
1736 static ssize_t write_cpuhp_target(struct device *dev,
1737                                   struct device_attribute *attr,
1738                                   const char *buf, size_t count)
1739 {
1740         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1741         struct cpuhp_step *sp;
1742         int target, ret;
1743
1744         ret = kstrtoint(buf, 10, &target);
1745         if (ret)
1746                 return ret;
1747
1748 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1749         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1750                 return -EINVAL;
1751 #else
1752         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1753                 return -EINVAL;
1754 #endif
1755
1756         ret = lock_device_hotplug_sysfs();
1757         if (ret)
1758                 return ret;
1759
1760         mutex_lock(&cpuhp_state_mutex);
1761         sp = cpuhp_get_step(target);
1762         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1763         mutex_unlock(&cpuhp_state_mutex);
1764         if (ret)
1765                 return ret;
1766
1767         if (st->state < target)
1768                 ret = do_cpu_up(dev->id, target);
1769         else
1770                 ret = do_cpu_down(dev->id, target);
1771
1772         unlock_device_hotplug();
1773         return ret ? ret : count;
1774 }
1775
1776 static ssize_t show_cpuhp_target(struct device *dev,
1777                                  struct device_attribute *attr, char *buf)
1778 {
1779         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1780
1781         return sprintf(buf, "%d\n", st->target);
1782 }
1783 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1784
1785 static struct attribute *cpuhp_cpu_attrs[] = {
1786         &dev_attr_state.attr,
1787         &dev_attr_target.attr,
1788         NULL
1789 };
1790
1791 static struct attribute_group cpuhp_cpu_attr_group = {
1792         .attrs = cpuhp_cpu_attrs,
1793         .name = "hotplug",
1794         NULL
1795 };
1796
1797 static ssize_t show_cpuhp_states(struct device *dev,
1798                                  struct device_attribute *attr, char *buf)
1799 {
1800         ssize_t cur, res = 0;
1801         int i;
1802
1803         mutex_lock(&cpuhp_state_mutex);
1804         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1805                 struct cpuhp_step *sp = cpuhp_get_step(i);
1806
1807                 if (sp->name) {
1808                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1809                         buf += cur;
1810                         res += cur;
1811                 }
1812         }
1813         mutex_unlock(&cpuhp_state_mutex);
1814         return res;
1815 }
1816 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1817
1818 static struct attribute *cpuhp_cpu_root_attrs[] = {
1819         &dev_attr_states.attr,
1820         NULL
1821 };
1822
1823 static struct attribute_group cpuhp_cpu_root_attr_group = {
1824         .attrs = cpuhp_cpu_root_attrs,
1825         .name = "hotplug",
1826         NULL
1827 };
1828
1829 static int __init cpuhp_sysfs_init(void)
1830 {
1831         int cpu, ret;
1832
1833         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1834                                  &cpuhp_cpu_root_attr_group);
1835         if (ret)
1836                 return ret;
1837
1838         for_each_possible_cpu(cpu) {
1839                 struct device *dev = get_cpu_device(cpu);
1840
1841                 if (!dev)
1842                         continue;
1843                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1844                 if (ret)
1845                         return ret;
1846         }
1847         return 0;
1848 }
1849 device_initcall(cpuhp_sysfs_init);
1850 #endif
1851
1852 /*
1853  * cpu_bit_bitmap[] is a special, "compressed" data structure that
1854  * represents all NR_CPUS bits binary values of 1<<nr.
1855  *
1856  * It is used by cpumask_of() to get a constant address to a CPU
1857  * mask value that has a single bit set only.
1858  */
1859
1860 /* cpu_bit_bitmap[0] is empty - so we can back into it */
1861 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
1862 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1863 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1864 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1865
1866 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1867
1868         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
1869         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
1870 #if BITS_PER_LONG > 32
1871         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
1872         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
1873 #endif
1874 };
1875 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1876
1877 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1878 EXPORT_SYMBOL(cpu_all_bits);
1879
1880 #ifdef CONFIG_INIT_ALL_POSSIBLE
1881 struct cpumask __cpu_possible_mask __read_mostly
1882         = {CPU_BITS_ALL};
1883 #else
1884 struct cpumask __cpu_possible_mask __read_mostly;
1885 #endif
1886 EXPORT_SYMBOL(__cpu_possible_mask);
1887
1888 struct cpumask __cpu_online_mask __read_mostly;
1889 EXPORT_SYMBOL(__cpu_online_mask);
1890
1891 struct cpumask __cpu_present_mask __read_mostly;
1892 EXPORT_SYMBOL(__cpu_present_mask);
1893
1894 struct cpumask __cpu_active_mask __read_mostly;
1895 EXPORT_SYMBOL(__cpu_active_mask);
1896
1897 void init_cpu_present(const struct cpumask *src)
1898 {
1899         cpumask_copy(&__cpu_present_mask, src);
1900 }
1901
1902 void init_cpu_possible(const struct cpumask *src)
1903 {
1904         cpumask_copy(&__cpu_possible_mask, src);
1905 }
1906
1907 void init_cpu_online(const struct cpumask *src)
1908 {
1909         cpumask_copy(&__cpu_online_mask, src);
1910 }
1911
1912 /*
1913  * Activate the first processor.
1914  */
1915 void __init boot_cpu_init(void)
1916 {
1917         int cpu = smp_processor_id();
1918
1919         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1920         set_cpu_online(cpu, true);
1921         set_cpu_active(cpu, true);
1922         set_cpu_present(cpu, true);
1923         set_cpu_possible(cpu, true);
1924 }
1925
1926 /*
1927  * Must be called _AFTER_ setting up the per_cpu areas
1928  */
1929 void __init boot_cpu_state_init(void)
1930 {
1931         per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1932 }