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 = STATIC_LOCKDEP_MAP_INIT("cpu_hotplug.dep_map", &cpu_hotplug.dep_map),
 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  * hotplug_pcp  - per cpu hotplug descriptor
 244  * @unplug:     set when pin_current_cpu() needs to sync tasks
 245  * @sync_tsk:   the task that waits for tasks to finish pinned sections
 246  * @refcount:   counter of tasks in pinned sections
 247  * @grab_lock:  set when the tasks entering pinned sections should wait
 248  * @synced:     notifier for @sync_tsk to tell cpu_down it's finished
 249  * @mutex:      the mutex to make tasks wait (used when @grab_lock is true)
 250  * @mutex_init: zero if the mutex hasn't been initialized yet.
 251  *
 252  * Although @unplug and @sync_tsk may point to the same task, the @unplug
 253  * is used as a flag and still exists after @sync_tsk has exited and
 254  * @sync_tsk set to NULL.
 255  */
 256 struct hotplug_pcp {
 257         struct task_struct *unplug;
 258         struct task_struct *sync_tsk;
 259         int refcount;
 260         int grab_lock;
 261         struct completion synced;
 262         struct completion unplug_wait;
 263 #ifdef CONFIG_PREEMPT_RT_FULL
 264         /*
 265          * Note, on PREEMPT_RT, the hotplug lock must save the state of
 266          * the task, otherwise the mutex will cause the task to fail
 267          * to sleep when required. (Because it's called from migrate_disable())
 268          *
 269          * The spinlock_t on PREEMPT_RT is a mutex that saves the task's
 270          * state.
 271          */
 272         spinlock_t lock;
 273 #else
 274         struct mutex mutex;
 275 #endif
 276         int mutex_init;
 277 };
 278
 279 #ifdef CONFIG_PREEMPT_RT_FULL
 280 # define hotplug_lock(hp) rt_spin_lock__no_mg(&(hp)->lock)
 281 # define hotplug_unlock(hp) rt_spin_unlock__no_mg(&(hp)->lock)
 282 #else
 283 # define hotplug_lock(hp) mutex_lock(&(hp)->mutex)
 284 # define hotplug_unlock(hp) mutex_unlock(&(hp)->mutex)
 285 #endif
 286
 287 static DEFINE_PER_CPU(struct hotplug_pcp, hotplug_pcp);
 288
 289 /**
 290  * pin_current_cpu - Prevent the current cpu from being unplugged
 291  *
 292  * Lightweight version of get_online_cpus() to prevent cpu from being
 293  * unplugged when code runs in a migration disabled region.
 294  *
 295  * Must be called with preemption disabled (preempt_count = 1)!
 296  */
 297 void pin_current_cpu(void)
 298 {
 299         struct hotplug_pcp *hp;
 300         int force = 0;
 301
 302 retry:
 303         hp = this_cpu_ptr(&hotplug_pcp);
 304
 305         if (!hp->unplug || hp->refcount || force || preempt_count() > 1 ||
 306             hp->unplug == current) {
 307                 hp->refcount++;
 308                 return;
 309         }
 310         if (hp->grab_lock) {
 311                 preempt_enable();
 312                 hotplug_lock(hp);
 313                 hotplug_unlock(hp);
 314         } else {
 315                 preempt_enable();
 316                 /*
 317                  * Try to push this task off of this CPU.
 318                  */
 319                 if (!migrate_me()) {
 320                         preempt_disable();
 321                         hp = this_cpu_ptr(&hotplug_pcp);
 322                         if (!hp->grab_lock) {
 323                                 /*
 324                                  * Just let it continue it's already pinned
 325                                  * or about to sleep.
 326                                  */
 327                                 force = 1;
 328                                 goto retry;
 329                         }
 330                         preempt_enable();
 331                 }
 332         }
 333         preempt_disable();
 334         goto retry;
 335 }
 336
 337 /**
 338  * unpin_current_cpu - Allow unplug of current cpu
 339  *
 340  * Must be called with preemption or interrupts disabled!
 341  */
 342 void unpin_current_cpu(void)
 343 {
 344         struct hotplug_pcp *hp = this_cpu_ptr(&hotplug_pcp);
 345
 346         WARN_ON(hp->refcount <= 0);
 347
 348         /* This is safe. sync_unplug_thread is pinned to this cpu */
 349         if (!--hp->refcount && hp->unplug && hp->unplug != current)
 350                 wake_up_process(hp->unplug);
 351 }
 352
 353 static void wait_for_pinned_cpus(struct hotplug_pcp *hp)
 354 {
 355         set_current_state(TASK_UNINTERRUPTIBLE);
 356         while (hp->refcount) {
 357                 schedule_preempt_disabled();
 358                 set_current_state(TASK_UNINTERRUPTIBLE);
 359         }
 360 }
 361
 362 static int sync_unplug_thread(void *data)
 363 {
 364         struct hotplug_pcp *hp = data;
 365
 366         wait_for_completion(&hp->unplug_wait);
 367         preempt_disable();
 368         hp->unplug = current;
 369         wait_for_pinned_cpus(hp);
 370
 371         /*
 372          * This thread will synchronize the cpu_down() with threads
 373          * that have pinned the CPU. When the pinned CPU count reaches
 374          * zero, we inform the cpu_down code to continue to the next step.
 375          */
 376         set_current_state(TASK_UNINTERRUPTIBLE);
 377         preempt_enable();
 378         complete(&hp->synced);
 379
 380         /*
 381          * If all succeeds, the next step will need tasks to wait till
 382          * the CPU is offline before continuing. To do this, the grab_lock
 383          * is set and tasks going into pin_current_cpu() will block on the
 384          * mutex. But we still need to wait for those that are already in
 385          * pinned CPU sections. If the cpu_down() failed, the kthread_should_stop()
 386          * will kick this thread out.
 387          */
 388         while (!hp->grab_lock && !kthread_should_stop()) {
 389                 schedule();
 390                 set_current_state(TASK_UNINTERRUPTIBLE);
 391         }
 392
 393         /* Make sure grab_lock is seen before we see a stale completion */
 394         smp_mb();
 395
 396         /*
 397          * Now just before cpu_down() enters stop machine, we need to make
 398          * sure all tasks that are in pinned CPU sections are out, and new
 399          * tasks will now grab the lock, keeping them from entering pinned
 400          * CPU sections.
 401          */
 402         if (!kthread_should_stop()) {
 403                 preempt_disable();
 404                 wait_for_pinned_cpus(hp);
 405                 preempt_enable();
 406                 complete(&hp->synced);
 407         }
 408
 409         set_current_state(TASK_UNINTERRUPTIBLE);
 410         while (!kthread_should_stop()) {
 411                 schedule();
 412                 set_current_state(TASK_UNINTERRUPTIBLE);
 413         }
 414         set_current_state(TASK_RUNNING);
 415
 416         /*
 417          * Force this thread off this CPU as it's going down and
 418          * we don't want any more work on this CPU.
 419          */
 420         current->flags &= ~PF_NO_SETAFFINITY;
 421         set_cpus_allowed_ptr(current, cpu_present_mask);
 422         migrate_me();
 423         return 0;
 424 }
 425
 426 static void __cpu_unplug_sync(struct hotplug_pcp *hp)
 427 {
 428         wake_up_process(hp->sync_tsk);
 429         wait_for_completion(&hp->synced);
 430 }
 431
 432 static void __cpu_unplug_wait(unsigned int cpu)
 433 {
 434         struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
 435
 436         complete(&hp->unplug_wait);
 437         wait_for_completion(&hp->synced);
 438 }
 439
 440 /*
 441  * Start the sync_unplug_thread on the target cpu and wait for it to
 442  * complete.
 443  */
 444 static int cpu_unplug_begin(unsigned int cpu)
 445 {
 446         struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
 447         int err;
 448
 449         /* Protected by cpu_hotplug.lock */
 450         if (!hp->mutex_init) {
 451 #ifdef CONFIG_PREEMPT_RT_FULL
 452                 spin_lock_init(&hp->lock);
 453 #else
 454                 mutex_init(&hp->mutex);
 455 #endif
 456                 hp->mutex_init = 1;
 457         }
 458
 459         /* Inform the scheduler to migrate tasks off this CPU */
 460         tell_sched_cpu_down_begin(cpu);
 461
 462         init_completion(&hp->synced);
 463         init_completion(&hp->unplug_wait);
 464
 465         hp->sync_tsk = kthread_create(sync_unplug_thread, hp, "sync_unplug/%d", cpu);
 466         if (IS_ERR(hp->sync_tsk)) {
 467                 err = PTR_ERR(hp->sync_tsk);
 468                 hp->sync_tsk = NULL;
 469                 return err;
 470         }
 471         kthread_bind(hp->sync_tsk, cpu);
 472
 473         /*
 474          * Wait for tasks to get out of the pinned sections,
 475          * it's still OK if new tasks enter. Some CPU notifiers will
 476          * wait for tasks that are going to enter these sections and
 477          * we must not have them block.
 478          */
 479         wake_up_process(hp->sync_tsk);
 480         return 0;
 481 }
 482
 483 static void cpu_unplug_sync(unsigned int cpu)
 484 {
 485         struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
 486
 487         init_completion(&hp->synced);
 488         /* The completion needs to be initialzied before setting grab_lock */
 489         smp_wmb();
 490
 491         /* Grab the mutex before setting grab_lock */
 492         hotplug_lock(hp);
 493         hp->grab_lock = 1;
 494
 495         /*
 496          * The CPU notifiers have been completed.
 497          * Wait for tasks to get out of pinned CPU sections and have new
 498          * tasks block until the CPU is completely down.
 499          */
 500         __cpu_unplug_sync(hp);
 501
 502         /* All done with the sync thread */
 503         kthread_stop(hp->sync_tsk);
 504         hp->sync_tsk = NULL;
 505 }
 506
 507 static void cpu_unplug_done(unsigned int cpu)
 508 {
 509         struct hotplug_pcp *hp = &per_cpu(hotplug_pcp, cpu);
 510
 511         hp->unplug = NULL;
 512         /* Let all tasks know cpu unplug is finished before cleaning up */
 513         smp_wmb();
 514
 515         if (hp->sync_tsk)
 516                 kthread_stop(hp->sync_tsk);
 517
 518         if (hp->grab_lock) {
 519                 hotplug_unlock(hp);
 520                 /* protected by cpu_hotplug.lock */
 521                 hp->grab_lock = 0;
 522         }
 523         tell_sched_cpu_down_done(cpu);
 524 }
 525
 526 void get_online_cpus(void)
 527 {
 528         might_sleep();
 529         if (cpu_hotplug.active_writer == current)
 530                 return;
 531         cpuhp_lock_acquire_read();
 532         mutex_lock(&cpu_hotplug.lock);
 533         atomic_inc(&cpu_hotplug.refcount);
 534         mutex_unlock(&cpu_hotplug.lock);
 535 }
 536 EXPORT_SYMBOL_GPL(get_online_cpus);
 537
 538 void put_online_cpus(void)
 539 {
 540         int refcount;
 541
 542         if (cpu_hotplug.active_writer == current)
 543                 return;
 544
 545         refcount = atomic_dec_return(&cpu_hotplug.refcount);
 546         if (WARN_ON(refcount < 0)) /* try to fix things up */
 547                 atomic_inc(&cpu_hotplug.refcount);
 548
 549         if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 550                 wake_up(&cpu_hotplug.wq);
 551
 552         cpuhp_lock_release();
 553
 554 }
 555 EXPORT_SYMBOL_GPL(put_online_cpus);
 556
 557 /*
 558  * This ensures that the hotplug operation can begin only when the
 559  * refcount goes to zero.
 560  *
 561  * Note that during a cpu-hotplug operation, the new readers, if any,
 562  * will be blocked by the cpu_hotplug.lock
 563  *
 564  * Since cpu_hotplug_begin() is always called after invoking
 565  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 566  *
 567  * Note that theoretically, there is a possibility of a livelock:
 568  * - Refcount goes to zero, last reader wakes up the sleeping
 569  *   writer.
 570  * - Last reader unlocks the cpu_hotplug.lock.
 571  * - A new reader arrives at this moment, bumps up the refcount.
 572  * - The writer acquires the cpu_hotplug.lock finds the refcount
 573  *   non zero and goes to sleep again.
 574  *
 575  * However, this is very difficult to achieve in practice since
 576  * get_online_cpus() not an api which is called all that often.
 577  *
 578  */
 579 void cpu_hotplug_begin(void)
 580 {
 581         DEFINE_WAIT(wait);
 582
 583         cpu_hotplug.active_writer = current;
 584         cpuhp_lock_acquire();
 585
 586         for (;;) {
 587                 mutex_lock(&cpu_hotplug.lock);
 588                 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 589                 if (likely(!atomic_read(&cpu_hotplug.refcount)))
 590                                 break;
 591                 mutex_unlock(&cpu_hotplug.lock);
 592                 schedule();
 593         }
 594         finish_wait(&cpu_hotplug.wq, &wait);
 595 }
 596
 597 void cpu_hotplug_done(void)
 598 {
 599         cpu_hotplug.active_writer = NULL;
 600         mutex_unlock(&cpu_hotplug.lock);
 601         cpuhp_lock_release();
 602 }
 603
 604 /*
 605  * Wait for currently running CPU hotplug operations to complete (if any) and
 606  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 607  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 608  * hotplug path before performing hotplug operations. So acquiring that lock
 609  * guarantees mutual exclusion from any currently running hotplug operations.
 610  */
 611 void cpu_hotplug_disable(void)
 612 {
 613         cpu_maps_update_begin();
 614         cpu_hotplug_disabled++;
 615         cpu_maps_update_done();
 616 }
 617 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 618
 619 static void __cpu_hotplug_enable(void)
 620 {
 621         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
 622                 return;
 623         cpu_hotplug_disabled--;
 624 }
 625
 626 void cpu_hotplug_enable(void)
 627 {
 628         cpu_maps_update_begin();
 629         __cpu_hotplug_enable();
 630         cpu_maps_update_done();
 631 }
 632 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 633 #endif  /* CONFIG_HOTPLUG_CPU */
 634
 635 /* Need to know about CPUs going up/down? */
 636 int register_cpu_notifier(struct notifier_block *nb)
 637 {
 638         int ret;
 639         cpu_maps_update_begin();
 640         ret = raw_notifier_chain_register(&cpu_chain, nb);
 641         cpu_maps_update_done();
 642         return ret;
 643 }
 644
 645 int __register_cpu_notifier(struct notifier_block *nb)
 646 {
 647         return raw_notifier_chain_register(&cpu_chain, nb);
 648 }
 649
 650 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 651                         int *nr_calls)
 652 {
 653         unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 654         void *hcpu = (void *)(long)cpu;
 655
 656         int ret;
 657
 658         ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 659                                         nr_calls);
 660
 661         return notifier_to_errno(ret);
 662 }
 663
 664 static int cpu_notify(unsigned long val, unsigned int cpu)
 665 {
 666         return __cpu_notify(val, cpu, -1, NULL);
 667 }
 668
 669 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 670 {
 671         BUG_ON(cpu_notify(val, cpu));
 672 }
 673
 674 /* Notifier wrappers for transitioning to state machine */
 675 static int notify_prepare(unsigned int cpu)
 676 {
 677         int nr_calls = 0;
 678         int ret;
 679
 680         ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 681         if (ret) {
 682                 nr_calls--;
 683                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 684                                 __func__, cpu);
 685                 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 686         }
 687         return ret;
 688 }
 689
 690 static int notify_online(unsigned int cpu)
 691 {
 692         cpu_notify(CPU_ONLINE, cpu);
 693         return 0;
 694 }
 695
 696 static int bringup_wait_for_ap(unsigned int cpu)
 697 {
 698         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 699
 700         wait_for_completion(&st->done);
 701         return st->result;
 702 }
 703
 704 static int bringup_cpu(unsigned int cpu)
 705 {
 706         struct task_struct *idle = idle_thread_get(cpu);
 707         int ret;
 708
 709         /*
 710          * Some architectures have to walk the irq descriptors to
 711          * setup the vector space for the cpu which comes online.
 712          * Prevent irq alloc/free across the bringup.
 713          */
 714         irq_lock_sparse();
 715
 716         /* Arch-specific enabling code. */
 717         ret = __cpu_up(cpu, idle);
 718         irq_unlock_sparse();
 719         if (ret) {
 720                 cpu_notify(CPU_UP_CANCELED, cpu);
 721                 return ret;
 722         }
 723         ret = bringup_wait_for_ap(cpu);
 724         BUG_ON(!cpu_online(cpu));
 725         return ret;
 726 }
 727
 728 /*
 729  * Hotplug state machine related functions
 730  */
 731 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
 732 {
 733         for (st->state++; st->state < st->target; st->state++) {
 734                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 735
 736                 if (!step->skip_onerr)
 737                         cpuhp_invoke_callback(cpu, st->state, true, NULL);
 738         }
 739 }
 740
 741 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 742                                 enum cpuhp_state target)
 743 {
 744         enum cpuhp_state prev_state = st->state;
 745         int ret = 0;
 746
 747         for (; st->state > target; st->state--) {
 748                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL);
 749                 if (ret) {
 750                         st->target = prev_state;
 751                         undo_cpu_down(cpu, st);
 752                         break;
 753                 }
 754         }
 755         return ret;
 756 }
 757
 758 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
 759 {
 760         for (st->state--; st->state > st->target; st->state--) {
 761                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 762
 763                 if (!step->skip_onerr)
 764                         cpuhp_invoke_callback(cpu, st->state, false, NULL);
 765         }
 766 }
 767
 768 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 769                               enum cpuhp_state target)
 770 {
 771         enum cpuhp_state prev_state = st->state;
 772         int ret = 0;
 773
 774         while (st->state < target) {
 775                 st->state++;
 776                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL);
 777                 if (ret) {
 778                         st->target = prev_state;
 779                         undo_cpu_up(cpu, st);
 780                         break;
 781                 }
 782         }
 783         return ret;
 784 }
 785
 786 /*
 787  * The cpu hotplug threads manage the bringup and teardown of the cpus
 788  */
 789 static void cpuhp_create(unsigned int cpu)
 790 {
 791         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 792
 793         init_completion(&st->done);
 794 }
 795
 796 static int cpuhp_should_run(unsigned int cpu)
 797 {
 798         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 799
 800         return st->should_run;
 801 }
 802
 803 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
 804 static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
 805 {
 806         enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
 807
 808         return cpuhp_down_callbacks(cpu, st, target);
 809 }
 810
 811 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
 812 static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
 813 {
 814         return cpuhp_up_callbacks(cpu, st, st->target);
 815 }
 816
 817 /*
 818  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 819  * callbacks when a state gets [un]installed at runtime.
 820  */
 821 static void cpuhp_thread_fun(unsigned int cpu)
 822 {
 823         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 824         int ret = 0;
 825
 826         /*
 827          * Paired with the mb() in cpuhp_kick_ap_work and
 828          * cpuhp_invoke_ap_callback, so the work set is consistent visible.
 829          */
 830         smp_mb();
 831         if (!st->should_run)
 832                 return;
 833
 834         st->should_run = false;
 835
 836         /* Single callback invocation for [un]install ? */
 837         if (st->single) {
 838                 if (st->cb_state < CPUHP_AP_ONLINE) {
 839                         local_irq_disable();
 840                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 841                                                     st->bringup, st->node);
 842                         local_irq_enable();
 843                 } else {
 844                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 845                                                     st->bringup, st->node);
 846                 }
 847         } else if (st->rollback) {
 848                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 849
 850                 undo_cpu_down(cpu, st);
 851                 /*
 852                  * This is a momentary workaround to keep the notifier users
 853                  * happy. Will go away once we got rid of the notifiers.
 854                  */
 855                 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 856                 st->rollback = false;
 857         } else {
 858                 /* Cannot happen .... */
 859                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 860
 861                 /* Regular hotplug work */
 862                 if (st->state < st->target)
 863                         ret = cpuhp_ap_online(cpu, st);
 864                 else if (st->state > st->target)
 865                         ret = cpuhp_ap_offline(cpu, st);
 866         }
 867         st->result = ret;
 868         complete(&st->done);
 869 }
 870
 871 /* Invoke a single callback on a remote cpu */
 872 static int
 873 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
 874                          struct hlist_node *node)
 875 {
 876         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 877
 878         if (!cpu_online(cpu))
 879                 return 0;
 880
 881         /*
 882          * If we are up and running, use the hotplug thread. For early calls
 883          * we invoke the thread function directly.
 884          */
 885         if (!st->thread)
 886                 return cpuhp_invoke_callback(cpu, state, bringup, node);
 887
 888         st->cb_state = state;
 889         st->single = true;
 890         st->bringup = bringup;
 891         st->node = node;
 892
 893         /*
 894          * Make sure the above stores are visible before should_run becomes
 895          * true. Paired with the mb() above in cpuhp_thread_fun()
 896          */
 897         smp_mb();
 898         st->should_run = true;
 899         wake_up_process(st->thread);
 900         wait_for_completion(&st->done);
 901         return st->result;
 902 }
 903
 904 /* Regular hotplug invocation of the AP hotplug thread */
 905 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
 906 {
 907         st->result = 0;
 908         st->single = false;
 909         /*
 910          * Make sure the above stores are visible before should_run becomes
 911          * true. Paired with the mb() above in cpuhp_thread_fun()
 912          */
 913         smp_mb();
 914         st->should_run = true;
 915         wake_up_process(st->thread);
 916 }
 917
 918 static int cpuhp_kick_ap_work(unsigned int cpu)
 919 {
 920         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 921         enum cpuhp_state state = st->state;
 922
 923         trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
 924         __cpuhp_kick_ap_work(st);
 925         wait_for_completion(&st->done);
 926         trace_cpuhp_exit(cpu, st->state, state, st->result);
 927         return st->result;
 928 }
 929
 930 static struct smp_hotplug_thread cpuhp_threads = {
 931         .store                  = &cpuhp_state.thread,
 932         .create                 = &cpuhp_create,
 933         .thread_should_run      = cpuhp_should_run,
 934         .thread_fn              = cpuhp_thread_fun,
 935         .thread_comm            = "cpuhp/%u",
 936         .selfparking            = true,
 937 };
 938
 939 void __init cpuhp_threads_init(void)
 940 {
 941         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 942         kthread_unpark(this_cpu_read(cpuhp_state.thread));
 943 }
 944
 945 #ifdef CONFIG_HOTPLUG_CPU
 946 EXPORT_SYMBOL(register_cpu_notifier);
 947 EXPORT_SYMBOL(__register_cpu_notifier);
 948 void unregister_cpu_notifier(struct notifier_block *nb)
 949 {
 950         cpu_maps_update_begin();
 951         raw_notifier_chain_unregister(&cpu_chain, nb);
 952         cpu_maps_update_done();
 953 }
 954 EXPORT_SYMBOL(unregister_cpu_notifier);
 955
 956 void __unregister_cpu_notifier(struct notifier_block *nb)
 957 {
 958         raw_notifier_chain_unregister(&cpu_chain, nb);
 959 }
 960 EXPORT_SYMBOL(__unregister_cpu_notifier);
 961
 962 /**
 963  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 964  * @cpu: a CPU id
 965  *
 966  * This function walks all processes, finds a valid mm struct for each one and
 967  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 968  * trivial, there are various non-obvious corner cases, which this function
 969  * tries to solve in a safe manner.
 970  *
 971  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 972  * be called only for an already offlined CPU.
 973  */
 974 void clear_tasks_mm_cpumask(int cpu)
 975 {
 976         struct task_struct *p;
 977
 978         /*
 979          * This function is called after the cpu is taken down and marked
 980          * offline, so its not like new tasks will ever get this cpu set in
 981          * their mm mask. -- Peter Zijlstra
 982          * Thus, we may use rcu_read_lock() here, instead of grabbing
 983          * full-fledged tasklist_lock.
 984          */
 985         WARN_ON(cpu_online(cpu));
 986         rcu_read_lock();
 987         for_each_process(p) {
 988                 struct task_struct *t;
 989
 990                 /*
 991                  * Main thread might exit, but other threads may still have
 992                  * a valid mm. Find one.
 993                  */
 994                 t = find_lock_task_mm(p);
 995                 if (!t)
 996                         continue;
 997                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 998                 task_unlock(t);
 999         }
1000         rcu_read_unlock();
1001 }
1002
1003 static inline void check_for_tasks(int dead_cpu)
1004 {
1005         struct task_struct *g, *p;
1006
1007         read_lock(&tasklist_lock);
1008         for_each_process_thread(g, p) {
1009                 if (!p->on_rq)
1010                         continue;
1011                 /*
1012                  * We do the check with unlocked task_rq(p)->lock.
1013                  * Order the reading to do not warn about a task,
1014                  * which was running on this cpu in the past, and
1015                  * it's just been woken on another cpu.
1016                  */
1017                 rmb();
1018                 if (task_cpu(p) != dead_cpu)
1019                         continue;
1020
1021                 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
1022                         p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
1023         }
1024         read_unlock(&tasklist_lock);
1025 }
1026
1027 static int notify_down_prepare(unsigned int cpu)
1028 {
1029         int err, nr_calls = 0;
1030
1031         err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
1032         if (err) {
1033                 nr_calls--;
1034                 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
1035                 pr_warn("%s: attempt to take down CPU %u failed\n",
1036                                 __func__, cpu);
1037         }
1038         return err;
1039 }
1040
1041 /* Take this CPU down. */
1042 static int take_cpu_down(void *_param)
1043 {
1044         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1045         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1046         int err, cpu = smp_processor_id();
1047
1048         /* Ensure this CPU doesn't handle any more interrupts. */
1049         err = __cpu_disable();
1050         if (err < 0)
1051                 return err;
1052
1053         /*
1054          * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
1055          * do this step again.
1056          */
1057         WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
1058         st->state--;
1059         /* Invoke the former CPU_DYING callbacks */
1060         for (; st->state > target; st->state--)
1061                 cpuhp_invoke_callback(cpu, st->state, false, NULL);
1062
1063         /* Give up timekeeping duties */
1064         tick_handover_do_timer();
1065         /* Park the stopper thread */
1066         stop_machine_park(cpu);
1067         return 0;
1068 }
1069
1070 static int takedown_cpu(unsigned int cpu)
1071 {
1072         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1073         int err;
1074
1075         __cpu_unplug_wait(cpu);
1076         /* Park the smpboot threads */
1077         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
1078         smpboot_park_threads(cpu);
1079
1080         /* Notifiers are done. Don't let any more tasks pin this CPU. */
1081         cpu_unplug_sync(cpu);
1082
1083         /*
1084          * Prevent irq alloc/free while the dying cpu reorganizes the
1085          * interrupt affinities.
1086          */
1087         irq_lock_sparse();
1088
1089         /*
1090          * So now all preempt/rcu users must observe !cpu_active().
1091          */
1092         err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
1093         if (err) {
1094                 /* CPU refused to die */
1095                 irq_unlock_sparse();
1096                 /* Unpark the hotplug thread so we can rollback there */
1097                 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
1098                 return err;
1099         }
1100         BUG_ON(cpu_online(cpu));
1101
1102         /*
1103          * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
1104          * runnable tasks from the cpu, there's only the idle task left now
1105          * that the migration thread is done doing the stop_machine thing.
1106          *
1107          * Wait for the stop thread to go away.
1108          */
1109         wait_for_completion(&st->done);
1110         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1111
1112         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1113         irq_unlock_sparse();
1114
1115         hotplug_cpu__broadcast_tick_pull(cpu);
1116         /* This actually kills the CPU. */
1117         __cpu_die(cpu);
1118
1119         tick_cleanup_dead_cpu(cpu);
1120         return 0;
1121 }
1122
1123 static int notify_dead(unsigned int cpu)
1124 {
1125         cpu_notify_nofail(CPU_DEAD, cpu);
1126         check_for_tasks(cpu);
1127         return 0;
1128 }
1129
1130 static void cpuhp_complete_idle_dead(void *arg)
1131 {
1132         struct cpuhp_cpu_state *st = arg;
1133
1134         complete(&st->done);
1135 }
1136
1137 void cpuhp_report_idle_dead(void)
1138 {
1139         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1140
1141         BUG_ON(st->state != CPUHP_AP_OFFLINE);
1142         rcu_report_dead(smp_processor_id());
1143         st->state = CPUHP_AP_IDLE_DEAD;
1144         /*
1145          * We cannot call complete after rcu_report_dead() so we delegate it
1146          * to an online cpu.
1147          */
1148         smp_call_function_single(cpumask_first(cpu_online_mask),
1149                                  cpuhp_complete_idle_dead, st, 0);
1150 }
1151
1152 #else
1153 #define notify_down_prepare     NULL
1154 #define takedown_cpu            NULL
1155 #define notify_dead             NULL
1156 #endif
1157
1158 #ifdef CONFIG_HOTPLUG_CPU
1159
1160 /* Requires cpu_add_remove_lock to be held */
1161 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1162                            enum cpuhp_state target)
1163 {
1164         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1165         int prev_state, ret = 0;
1166         bool hasdied = false;
1167         int mycpu;
1168         cpumask_var_t cpumask;
1169         cpumask_var_t cpumask_org;
1170
1171         if (num_online_cpus() == 1)
1172                 return -EBUSY;
1173
1174         if (!cpu_present(cpu))
1175                 return -EINVAL;
1176
1177         /* Move the downtaker off the unplug cpu */
1178         if (!alloc_cpumask_var(&cpumask, GFP_KERNEL))
1179                 return -ENOMEM;
1180         if (!alloc_cpumask_var(&cpumask_org, GFP_KERNEL))  {
1181                 free_cpumask_var(cpumask);
1182                 return -ENOMEM;
1183         }
1184
1185         cpumask_copy(cpumask_org, tsk_cpus_allowed(current));
1186         cpumask_andnot(cpumask, cpu_online_mask, cpumask_of(cpu));
1187         set_cpus_allowed_ptr(current, cpumask);
1188         free_cpumask_var(cpumask);
1189         migrate_disable();
1190         mycpu = smp_processor_id();
1191         if (mycpu == cpu) {
1192                 printk(KERN_ERR "Yuck! Still on unplug CPU\n!");
1193                 migrate_enable();
1194                 ret = -EBUSY;
1195                 goto restore_cpus;
1196         }
1197
1198         migrate_enable();
1199         cpu_hotplug_begin();
1200         ret = cpu_unplug_begin(cpu);
1201         if (ret) {
1202                 printk("cpu_unplug_begin(%d) failed\n", cpu);
1203                 goto out_cancel;
1204         }
1205
1206         cpuhp_tasks_frozen = tasks_frozen;
1207
1208         prev_state = st->state;
1209         st->target = target;
1210         /*
1211          * If the current CPU state is in the range of the AP hotplug thread,
1212          * then we need to kick the thread.
1213          */
1214         if (st->state > CPUHP_TEARDOWN_CPU) {
1215                 ret = cpuhp_kick_ap_work(cpu);
1216                 /*
1217                  * The AP side has done the error rollback already. Just
1218                  * return the error code..
1219                  */
1220                 if (ret)
1221                         goto out;
1222
1223                 /*
1224                  * We might have stopped still in the range of the AP hotplug
1225                  * thread. Nothing to do anymore.
1226                  */
1227                 if (st->state > CPUHP_TEARDOWN_CPU)
1228                         goto out;
1229         }
1230         /*
1231          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1232          * to do the further cleanups.
1233          */
1234         ret = cpuhp_down_callbacks(cpu, st, target);
1235         if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1236                 st->target = prev_state;
1237                 st->rollback = true;
1238                 cpuhp_kick_ap_work(cpu);
1239         }
1240
1241         hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
1242 out:
1243         cpu_unplug_done(cpu);
1244 out_cancel:
1245         cpu_hotplug_done();
1246         /* This post dead nonsense must die */
1247         if (!ret && hasdied)
1248                 cpu_notify_nofail(CPU_POST_DEAD, cpu);
1249 restore_cpus:
1250         set_cpus_allowed_ptr(current, cpumask_org);
1251         free_cpumask_var(cpumask_org);
1252         return ret;
1253 }
1254
1255 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
1256 {
1257         int err;
1258
1259         cpu_maps_update_begin();
1260
1261         if (cpu_hotplug_disabled) {
1262                 err = -EBUSY;
1263                 goto out;
1264         }
1265
1266         err = _cpu_down(cpu, 0, target);
1267
1268 out:
1269         cpu_maps_update_done();
1270         return err;
1271 }
1272 int cpu_down(unsigned int cpu)
1273 {
1274         return do_cpu_down(cpu, CPUHP_OFFLINE);
1275 }
1276 EXPORT_SYMBOL(cpu_down);
1277 #endif /*CONFIG_HOTPLUG_CPU*/
1278
1279 /**
1280  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1281  * @cpu: cpu that just started
1282  *
1283  * It must be called by the arch code on the new cpu, before the new cpu
1284  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1285  */
1286 void notify_cpu_starting(unsigned int cpu)
1287 {
1288         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1289         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1290
1291         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1292         while (st->state < target) {
1293                 st->state++;
1294                 cpuhp_invoke_callback(cpu, st->state, true, NULL);
1295         }
1296 }
1297
1298 /*
1299  * Called from the idle task. We need to set active here, so we can kick off
1300  * the stopper thread and unpark the smpboot threads. If the target state is
1301  * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
1302  * cpu further.
1303  */
1304 void cpuhp_online_idle(enum cpuhp_state state)
1305 {
1306         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1307         unsigned int cpu = smp_processor_id();
1308
1309         /* Happens for the boot cpu */
1310         if (state != CPUHP_AP_ONLINE_IDLE)
1311                 return;
1312
1313         st->state = CPUHP_AP_ONLINE_IDLE;
1314
1315         /* Unpark the stopper thread and the hotplug thread of this cpu */
1316         stop_machine_unpark(cpu);
1317         kthread_unpark(st->thread);
1318
1319         /* Should we go further up ? */
1320         if (st->target > CPUHP_AP_ONLINE_IDLE)
1321                 __cpuhp_kick_ap_work(st);
1322         else
1323                 complete(&st->done);
1324 }
1325
1326 /* Requires cpu_add_remove_lock to be held */
1327 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1328 {
1329         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1330         struct task_struct *idle;
1331         int ret = 0;
1332
1333         cpu_hotplug_begin();
1334
1335         if (!cpu_present(cpu)) {
1336                 ret = -EINVAL;
1337                 goto out;
1338         }
1339
1340         /*
1341          * The caller of do_cpu_up might have raced with another
1342          * caller. Ignore it for now.
1343          */
1344         if (st->state >= target)
1345                 goto out;
1346
1347         if (st->state == CPUHP_OFFLINE) {
1348                 /* Let it fail before we try to bring the cpu up */
1349                 idle = idle_thread_get(cpu);
1350                 if (IS_ERR(idle)) {
1351                         ret = PTR_ERR(idle);
1352                         goto out;
1353                 }
1354         }
1355
1356         cpuhp_tasks_frozen = tasks_frozen;
1357
1358         st->target = target;
1359         /*
1360          * If the current CPU state is in the range of the AP hotplug thread,
1361          * then we need to kick the thread once more.
1362          */
1363         if (st->state > CPUHP_BRINGUP_CPU) {
1364                 ret = cpuhp_kick_ap_work(cpu);
1365                 /*
1366                  * The AP side has done the error rollback already. Just
1367                  * return the error code..
1368                  */
1369                 if (ret)
1370                         goto out;
1371         }
1372
1373         /*
1374          * Try to reach the target state. We max out on the BP at
1375          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1376          * responsible for bringing it up to the target state.
1377          */
1378         target = min((int)target, CPUHP_BRINGUP_CPU);
1379         ret = cpuhp_up_callbacks(cpu, st, target);
1380 out:
1381         cpu_hotplug_done();
1382         return ret;
1383 }
1384
1385 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1386 {
1387         int err = 0;
1388
1389         if (!cpu_possible(cpu)) {
1390                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1391                        cpu);
1392 #if defined(CONFIG_IA64)
1393                 pr_err("please check additional_cpus= boot parameter\n");
1394 #endif
1395                 return -EINVAL;
1396         }
1397
1398         err = try_online_node(cpu_to_node(cpu));
1399         if (err)
1400                 return err;
1401
1402         cpu_maps_update_begin();
1403
1404         if (cpu_hotplug_disabled) {
1405                 err = -EBUSY;
1406                 goto out;
1407         }
1408
1409         err = _cpu_up(cpu, 0, target);
1410 out:
1411         cpu_maps_update_done();
1412         return err;
1413 }
1414
1415 int cpu_up(unsigned int cpu)
1416 {
1417         return do_cpu_up(cpu, CPUHP_ONLINE);
1418 }
1419 EXPORT_SYMBOL_GPL(cpu_up);
1420
1421 #ifdef CONFIG_PM_SLEEP_SMP
1422 static cpumask_var_t frozen_cpus;
1423
1424 int freeze_secondary_cpus(int primary)
1425 {
1426         int cpu, error = 0;
1427
1428         cpu_maps_update_begin();
1429         if (!cpu_online(primary))
1430                 primary = cpumask_first(cpu_online_mask);
1431         /*
1432          * We take down all of the non-boot CPUs in one shot to avoid races
1433          * with the userspace trying to use the CPU hotplug at the same time
1434          */
1435         cpumask_clear(frozen_cpus);
1436
1437         pr_info("Disabling non-boot CPUs ...\n");
1438         for_each_online_cpu(cpu) {
1439                 if (cpu == primary)
1440                         continue;
1441                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1442                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1443                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1444                 if (!error)
1445                         cpumask_set_cpu(cpu, frozen_cpus);
1446                 else {
1447                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1448                         break;
1449                 }
1450         }
1451
1452         if (!error)
1453                 BUG_ON(num_online_cpus() > 1);
1454         else
1455                 pr_err("Non-boot CPUs are not disabled\n");
1456
1457         /*
1458          * Make sure the CPUs won't be enabled by someone else. We need to do
1459          * this even in case of failure as all disable_nonboot_cpus() users are
1460          * supposed to do enable_nonboot_cpus() on the failure path.
1461          */
1462         cpu_hotplug_disabled++;
1463
1464         cpu_maps_update_done();
1465         return error;
1466 }
1467
1468 void __weak arch_enable_nonboot_cpus_begin(void)
1469 {
1470 }
1471
1472 void __weak arch_enable_nonboot_cpus_end(void)
1473 {
1474 }
1475
1476 void enable_nonboot_cpus(void)
1477 {
1478         int cpu, error;
1479
1480         /* Allow everyone to use the CPU hotplug again */
1481         cpu_maps_update_begin();
1482         __cpu_hotplug_enable();
1483         if (cpumask_empty(frozen_cpus))
1484                 goto out;
1485
1486         pr_info("Enabling non-boot CPUs ...\n");
1487
1488         arch_enable_nonboot_cpus_begin();
1489
1490         for_each_cpu(cpu, frozen_cpus) {
1491                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1492                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1493                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1494                 if (!error) {
1495                         pr_info("CPU%d is up\n", cpu);
1496                         continue;
1497                 }
1498                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1499         }
1500
1501         arch_enable_nonboot_cpus_end();
1502
1503         cpumask_clear(frozen_cpus);
1504 out:
1505         cpu_maps_update_done();
1506 }
1507
1508 static int __init alloc_frozen_cpus(void)
1509 {
1510         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1511                 return -ENOMEM;
1512         return 0;
1513 }
1514 core_initcall(alloc_frozen_cpus);
1515
1516 /*
1517  * When callbacks for CPU hotplug notifications are being executed, we must
1518  * ensure that the state of the system with respect to the tasks being frozen
1519  * or not, as reported by the notification, remains unchanged *throughout the
1520  * duration* of the execution of the callbacks.
1521  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1522  *
1523  * This synchronization is implemented by mutually excluding regular CPU
1524  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1525  * Hibernate notifications.
1526  */
1527 static int
1528 cpu_hotplug_pm_callback(struct notifier_block *nb,
1529                         unsigned long action, void *ptr)
1530 {
1531         switch (action) {
1532
1533         case PM_SUSPEND_PREPARE:
1534         case PM_HIBERNATION_PREPARE:
1535                 cpu_hotplug_disable();
1536                 break;
1537
1538         case PM_POST_SUSPEND:
1539         case PM_POST_HIBERNATION:
1540                 cpu_hotplug_enable();
1541                 break;
1542
1543         default:
1544                 return NOTIFY_DONE;
1545         }
1546
1547         return NOTIFY_OK;
1548 }
1549
1550
1551 static int __init cpu_hotplug_pm_sync_init(void)
1552 {
1553         /*
1554          * cpu_hotplug_pm_callback has higher priority than x86
1555          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1556          * to disable cpu hotplug to avoid cpu hotplug race.
1557          */
1558         pm_notifier(cpu_hotplug_pm_callback, 0);
1559         return 0;
1560 }
1561 core_initcall(cpu_hotplug_pm_sync_init);
1562
1563 #endif /* CONFIG_PM_SLEEP_SMP */
1564
1565 #endif /* CONFIG_SMP */
1566
1567 /* Boot processor state steps */
1568 static struct cpuhp_step cpuhp_bp_states[] = {
1569         [CPUHP_OFFLINE] = {
1570                 .name                   = "offline",
1571                 .startup.single         = NULL,
1572                 .teardown.single        = NULL,
1573         },
1574 #ifdef CONFIG_SMP
1575         [CPUHP_CREATE_THREADS]= {
1576                 .name                   = "threads:prepare",
1577                 .startup.single         = smpboot_create_threads,
1578                 .teardown.single        = NULL,
1579                 .cant_stop              = true,
1580         },
1581         [CPUHP_PERF_PREPARE] = {
1582                 .name                   = "perf:prepare",
1583                 .startup.single         = perf_event_init_cpu,
1584                 .teardown.single        = perf_event_exit_cpu,
1585         },
1586         [CPUHP_WORKQUEUE_PREP] = {
1587                 .name                   = "workqueue:prepare",
1588                 .startup.single         = workqueue_prepare_cpu,
1589                 .teardown.single        = NULL,
1590         },
1591         [CPUHP_HRTIMERS_PREPARE] = {
1592                 .name                   = "hrtimers:prepare",
1593                 .startup.single         = hrtimers_prepare_cpu,
1594                 .teardown.single        = hrtimers_dead_cpu,
1595         },
1596         [CPUHP_SMPCFD_PREPARE] = {
1597                 .name                   = "smpcfd:prepare",
1598                 .startup.single         = smpcfd_prepare_cpu,
1599                 .teardown.single        = smpcfd_dead_cpu,
1600         },
1601         [CPUHP_RELAY_PREPARE] = {
1602                 .name                   = "relay:prepare",
1603                 .startup.single         = relay_prepare_cpu,
1604                 .teardown.single        = NULL,
1605         },
1606         [CPUHP_SLAB_PREPARE] = {
1607                 .name                   = "slab:prepare",
1608                 .startup.single         = slab_prepare_cpu,
1609                 .teardown.single        = slab_dead_cpu,
1610         },
1611         [CPUHP_RCUTREE_PREP] = {
1612                 .name                   = "RCU/tree:prepare",
1613                 .startup.single         = rcutree_prepare_cpu,
1614                 .teardown.single        = rcutree_dead_cpu,
1615         },
1616         /*
1617          * Preparatory and dead notifiers. Will be replaced once the notifiers
1618          * are converted to states.
1619          */
1620         [CPUHP_NOTIFY_PREPARE] = {
1621                 .name                   = "notify:prepare",
1622                 .startup.single         = notify_prepare,
1623                 .teardown.single        = notify_dead,
1624                 .skip_onerr             = true,
1625                 .cant_stop              = true,
1626         },
1627         /*
1628          * On the tear-down path, timers_dead_cpu() must be invoked
1629          * before blk_mq_queue_reinit_notify() from notify_dead(),
1630          * otherwise a RCU stall occurs.
1631          */
1632         [CPUHP_TIMERS_DEAD] = {
1633                 .name                   = "timers:dead",
1634                 .startup.single         = NULL,
1635                 .teardown.single        = timers_dead_cpu,
1636         },
1637         /* Kicks the plugged cpu into life */
1638         [CPUHP_BRINGUP_CPU] = {
1639                 .name                   = "cpu:bringup",
1640                 .startup.single         = bringup_cpu,
1641                 .teardown.single        = NULL,
1642                 .cant_stop              = true,
1643         },
1644         [CPUHP_AP_SMPCFD_DYING] = {
1645                 .name                   = "smpcfd:dying",
1646                 .startup.single         = NULL,
1647                 .teardown.single        = smpcfd_dying_cpu,
1648         },
1649         /*
1650          * Handled on controll processor until the plugged processor manages
1651          * this itself.
1652          */
1653         [CPUHP_TEARDOWN_CPU] = {
1654                 .name                   = "cpu:teardown",
1655                 .startup.single         = NULL,
1656                 .teardown.single        = takedown_cpu,
1657                 .cant_stop              = true,
1658         },
1659 #else
1660         [CPUHP_BRINGUP_CPU] = { },
1661 #endif
1662 };
1663
1664 /* Application processor state steps */
1665 static struct cpuhp_step cpuhp_ap_states[] = {
1666 #ifdef CONFIG_SMP
1667         /* Final state before CPU kills itself */
1668         [CPUHP_AP_IDLE_DEAD] = {
1669                 .name                   = "idle:dead",
1670         },
1671         /*
1672          * Last state before CPU enters the idle loop to die. Transient state
1673          * for synchronization.
1674          */
1675         [CPUHP_AP_OFFLINE] = {
1676                 .name                   = "ap:offline",
1677                 .cant_stop              = true,
1678         },
1679         /* First state is scheduler control. Interrupts are disabled */
1680         [CPUHP_AP_SCHED_STARTING] = {
1681                 .name                   = "sched:starting",
1682                 .startup.single         = sched_cpu_starting,
1683                 .teardown.single        = sched_cpu_dying,
1684         },
1685         [CPUHP_AP_RCUTREE_DYING] = {
1686                 .name                   = "RCU/tree:dying",
1687                 .startup.single         = NULL,
1688                 .teardown.single        = rcutree_dying_cpu,
1689         },
1690         /* Entry state on starting. Interrupts enabled from here on. Transient
1691          * state for synchronsization */
1692         [CPUHP_AP_ONLINE] = {
1693                 .name                   = "ap:online",
1694         },
1695         /* Handle smpboot threads park/unpark */
1696         [CPUHP_AP_SMPBOOT_THREADS] = {
1697                 .name                   = "smpboot/threads:online",
1698                 .startup.single         = smpboot_unpark_threads,
1699                 .teardown.single        = NULL,
1700         },
1701         [CPUHP_AP_PERF_ONLINE] = {
1702                 .name                   = "perf:online",
1703                 .startup.single         = perf_event_init_cpu,
1704                 .teardown.single        = perf_event_exit_cpu,
1705         },
1706         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1707                 .name                   = "workqueue:online",
1708                 .startup.single         = workqueue_online_cpu,
1709                 .teardown.single        = workqueue_offline_cpu,
1710         },
1711         [CPUHP_AP_RCUTREE_ONLINE] = {
1712                 .name                   = "RCU/tree:online",
1713                 .startup.single         = rcutree_online_cpu,
1714                 .teardown.single        = rcutree_offline_cpu,
1715         },
1716
1717         /*
1718          * Online/down_prepare notifiers. Will be removed once the notifiers
1719          * are converted to states.
1720          */
1721         [CPUHP_AP_NOTIFY_ONLINE] = {
1722                 .name                   = "notify:online",
1723                 .startup.single         = notify_online,
1724                 .teardown.single        = notify_down_prepare,
1725                 .skip_onerr             = true,
1726         },
1727 #endif
1728         /*
1729          * The dynamically registered state space is here
1730          */
1731
1732 #ifdef CONFIG_SMP
1733         /* Last state is scheduler control setting the cpu active */
1734         [CPUHP_AP_ACTIVE] = {
1735                 .name                   = "sched:active",
1736                 .startup.single         = sched_cpu_activate,
1737                 .teardown.single        = sched_cpu_deactivate,
1738         },
1739 #endif
1740
1741         /* CPU is fully up and running. */
1742         [CPUHP_ONLINE] = {
1743                 .name                   = "online",
1744                 .startup.single         = NULL,
1745                 .teardown.single        = NULL,
1746         },
1747 };
1748
1749 /* Sanity check for callbacks */
1750 static int cpuhp_cb_check(enum cpuhp_state state)
1751 {
1752         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1753                 return -EINVAL;
1754         return 0;
1755 }
1756
1757 static void cpuhp_store_callbacks(enum cpuhp_state state,
1758                                   const char *name,
1759                                   int (*startup)(unsigned int cpu),
1760                                   int (*teardown)(unsigned int cpu),
1761                                   bool multi_instance)
1762 {
1763         /* (Un)Install the callbacks for further cpu hotplug operations */
1764         struct cpuhp_step *sp;
1765
1766         mutex_lock(&cpuhp_state_mutex);
1767         sp = cpuhp_get_step(state);
1768         sp->startup.single = startup;
1769         sp->teardown.single = teardown;
1770         sp->name = name;
1771         sp->multi_instance = multi_instance;
1772         INIT_HLIST_HEAD(&sp->list);
1773         mutex_unlock(&cpuhp_state_mutex);
1774 }
1775
1776 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1777 {
1778         return cpuhp_get_step(state)->teardown.single;
1779 }
1780
1781 /*
1782  * Call the startup/teardown function for a step either on the AP or
1783  * on the current CPU.
1784  */
1785 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1786                             struct hlist_node *node)
1787 {
1788         struct cpuhp_step *sp = cpuhp_get_step(state);
1789         int ret;
1790
1791         if ((bringup && !sp->startup.single) ||
1792             (!bringup && !sp->teardown.single))
1793                 return 0;
1794         /*
1795          * The non AP bound callbacks can fail on bringup. On teardown
1796          * e.g. module removal we crash for now.
1797          */
1798 #ifdef CONFIG_SMP
1799         if (cpuhp_is_ap_state(state))
1800                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1801         else
1802                 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1803 #else
1804         ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1805 #endif
1806         BUG_ON(ret && !bringup);
1807         return ret;
1808 }
1809
1810 /*
1811  * Called from __cpuhp_setup_state on a recoverable failure.
1812  *
1813  * Note: The teardown callbacks for rollback are not allowed to fail!
1814  */
1815 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1816                                    struct hlist_node *node)
1817 {
1818         int cpu;
1819
1820         /* Roll back the already executed steps on the other cpus */
1821         for_each_present_cpu(cpu) {
1822                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1823                 int cpustate = st->state;
1824
1825                 if (cpu >= failedcpu)
1826                         break;
1827
1828                 /* Did we invoke the startup call on that cpu ? */
1829                 if (cpustate >= state)
1830                         cpuhp_issue_call(cpu, state, false, node);
1831         }
1832 }
1833
1834 /*
1835  * Returns a free for dynamic slot assignment of the Online state. The states
1836  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1837  * by having no name assigned.
1838  */
1839 static int cpuhp_reserve_state(enum cpuhp_state state)
1840 {
1841         enum cpuhp_state i;
1842
1843         mutex_lock(&cpuhp_state_mutex);
1844         for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1845                 if (cpuhp_ap_states[i].name)
1846                         continue;
1847
1848                 cpuhp_ap_states[i].name = "Reserved";
1849                 mutex_unlock(&cpuhp_state_mutex);
1850                 return i;
1851         }
1852         mutex_unlock(&cpuhp_state_mutex);
1853         WARN(1, "No more dynamic states available for CPU hotplug\n");
1854         return -ENOSPC;
1855 }
1856
1857 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1858                                bool invoke)
1859 {
1860         struct cpuhp_step *sp;
1861         int cpu;
1862         int ret;
1863
1864         sp = cpuhp_get_step(state);
1865         if (sp->multi_instance == false)
1866                 return -EINVAL;
1867
1868         get_online_cpus();
1869
1870         if (!invoke || !sp->startup.multi)
1871                 goto add_node;
1872
1873         /*
1874          * Try to call the startup callback for each present cpu
1875          * depending on the hotplug state of the cpu.
1876          */
1877         for_each_present_cpu(cpu) {
1878                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1879                 int cpustate = st->state;
1880
1881                 if (cpustate < state)
1882                         continue;
1883
1884                 ret = cpuhp_issue_call(cpu, state, true, node);
1885                 if (ret) {
1886                         if (sp->teardown.multi)
1887                                 cpuhp_rollback_install(cpu, state, node);
1888                         goto err;
1889                 }
1890         }
1891 add_node:
1892         ret = 0;
1893         mutex_lock(&cpuhp_state_mutex);
1894         hlist_add_head(node, &sp->list);
1895         mutex_unlock(&cpuhp_state_mutex);
1896
1897 err:
1898         put_online_cpus();
1899         return ret;
1900 }
1901 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1902
1903 /**
1904  * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1905  * @state:      The state to setup
1906  * @invoke:     If true, the startup function is invoked for cpus where
1907  *              cpu state >= @state
1908  * @startup:    startup callback function
1909  * @teardown:   teardown callback function
1910  *
1911  * Returns 0 if successful, otherwise a proper error code
1912  */
1913 int __cpuhp_setup_state(enum cpuhp_state state,
1914                         const char *name, bool invoke,
1915                         int (*startup)(unsigned int cpu),
1916                         int (*teardown)(unsigned int cpu),
1917                         bool multi_instance)
1918 {
1919         int cpu, ret = 0;
1920         int dyn_state = 0;
1921
1922         if (cpuhp_cb_check(state) || !name)
1923                 return -EINVAL;
1924
1925         get_online_cpus();
1926
1927         /* currently assignments for the ONLINE state are possible */
1928         if (state == CPUHP_AP_ONLINE_DYN) {
1929                 dyn_state = 1;
1930                 ret = cpuhp_reserve_state(state);
1931                 if (ret < 0)
1932                         goto out;
1933                 state = ret;
1934         }
1935
1936         cpuhp_store_callbacks(state, name, startup, teardown, multi_instance);
1937
1938         if (!invoke || !startup)
1939                 goto out;
1940
1941         /*
1942          * Try to call the startup callback for each present cpu
1943          * depending on the hotplug state of the cpu.
1944          */
1945         for_each_present_cpu(cpu) {
1946                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1947                 int cpustate = st->state;
1948
1949                 if (cpustate < state)
1950                         continue;
1951
1952                 ret = cpuhp_issue_call(cpu, state, true, NULL);
1953                 if (ret) {
1954                         if (teardown)
1955                                 cpuhp_rollback_install(cpu, state, NULL);
1956                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1957                         goto out;
1958                 }
1959         }
1960 out:
1961         put_online_cpus();
1962         if (!ret && dyn_state)
1963                 return state;
1964         return ret;
1965 }
1966 EXPORT_SYMBOL(__cpuhp_setup_state);
1967
1968 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1969                                   struct hlist_node *node, bool invoke)
1970 {
1971         struct cpuhp_step *sp = cpuhp_get_step(state);
1972         int cpu;
1973
1974         BUG_ON(cpuhp_cb_check(state));
1975
1976         if (!sp->multi_instance)
1977                 return -EINVAL;
1978
1979         get_online_cpus();
1980         if (!invoke || !cpuhp_get_teardown_cb(state))
1981                 goto remove;
1982         /*
1983          * Call the teardown callback for each present cpu depending
1984          * on the hotplug state of the cpu. This function is not
1985          * allowed to fail currently!
1986          */
1987         for_each_present_cpu(cpu) {
1988                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1989                 int cpustate = st->state;
1990
1991                 if (cpustate >= state)
1992                         cpuhp_issue_call(cpu, state, false, node);
1993         }
1994
1995 remove:
1996         mutex_lock(&cpuhp_state_mutex);
1997         hlist_del(node);
1998         mutex_unlock(&cpuhp_state_mutex);
1999         put_online_cpus();
2000
2001         return 0;
2002 }
2003 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2004 /**
2005  * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
2006  * @state:      The state to remove
2007  * @invoke:     If true, the teardown function is invoked for cpus where
2008  *              cpu state >= @state
2009  *
2010  * The teardown callback is currently not allowed to fail. Think
2011  * about module removal!
2012  */
2013 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2014 {
2015         struct cpuhp_step *sp = cpuhp_get_step(state);
2016         int cpu;
2017
2018         BUG_ON(cpuhp_cb_check(state));
2019
2020         get_online_cpus();
2021
2022         if (sp->multi_instance) {
2023                 WARN(!hlist_empty(&sp->list),
2024                      "Error: Removing state %d which has instances left.\n",
2025                      state);
2026                 goto remove;
2027         }
2028
2029         if (!invoke || !cpuhp_get_teardown_cb(state))
2030                 goto remove;
2031
2032         /*
2033          * Call the teardown callback for each present cpu depending
2034          * on the hotplug state of the cpu. This function is not
2035          * allowed to fail currently!
2036          */
2037         for_each_present_cpu(cpu) {
2038                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2039                 int cpustate = st->state;
2040
2041                 if (cpustate >= state)
2042                         cpuhp_issue_call(cpu, state, false, NULL);
2043         }
2044 remove:
2045         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2046         put_online_cpus();
2047 }
2048 EXPORT_SYMBOL(__cpuhp_remove_state);
2049
2050 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2051 static ssize_t show_cpuhp_state(struct device *dev,
2052                                 struct device_attribute *attr, char *buf)
2053 {
2054         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2055
2056         return sprintf(buf, "%d\n", st->state);
2057 }
2058 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
2059
2060 static ssize_t write_cpuhp_target(struct device *dev,
2061                                   struct device_attribute *attr,
2062                                   const char *buf, size_t count)
2063 {
2064         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2065         struct cpuhp_step *sp;
2066         int target, ret;
2067
2068         ret = kstrtoint(buf, 10, &target);
2069         if (ret)
2070                 return ret;
2071
2072 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2073         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2074                 return -EINVAL;
2075 #else
2076         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2077                 return -EINVAL;
2078 #endif
2079
2080         ret = lock_device_hotplug_sysfs();
2081         if (ret)
2082                 return ret;
2083
2084         mutex_lock(&cpuhp_state_mutex);
2085         sp = cpuhp_get_step(target);
2086         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2087         mutex_unlock(&cpuhp_state_mutex);
2088         if (ret)
2089                 return ret;
2090
2091         if (st->state < target)
2092                 ret = do_cpu_up(dev->id, target);
2093         else
2094                 ret = do_cpu_down(dev->id, target);
2095
2096         unlock_device_hotplug();
2097         return ret ? ret : count;
2098 }
2099
2100 static ssize_t show_cpuhp_target(struct device *dev,
2101                                  struct device_attribute *attr, char *buf)
2102 {
2103         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2104
2105         return sprintf(buf, "%d\n", st->target);
2106 }
2107 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2108
2109 static struct attribute *cpuhp_cpu_attrs[] = {
2110         &dev_attr_state.attr,
2111         &dev_attr_target.attr,
2112         NULL
2113 };
2114
2115 static struct attribute_group cpuhp_cpu_attr_group = {
2116         .attrs = cpuhp_cpu_attrs,
2117         .name = "hotplug",
2118         NULL
2119 };
2120
2121 static ssize_t show_cpuhp_states(struct device *dev,
2122                                  struct device_attribute *attr, char *buf)
2123 {
2124         ssize_t cur, res = 0;
2125         int i;
2126
2127         mutex_lock(&cpuhp_state_mutex);
2128         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2129                 struct cpuhp_step *sp = cpuhp_get_step(i);
2130
2131                 if (sp->name) {
2132                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2133                         buf += cur;
2134                         res += cur;
2135                 }
2136         }
2137         mutex_unlock(&cpuhp_state_mutex);
2138         return res;
2139 }
2140 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2141
2142 static struct attribute *cpuhp_cpu_root_attrs[] = {
2143         &dev_attr_states.attr,
2144         NULL
2145 };
2146
2147 static struct attribute_group cpuhp_cpu_root_attr_group = {
2148         .attrs = cpuhp_cpu_root_attrs,
2149         .name = "hotplug",
2150         NULL
2151 };
2152
2153 static int __init cpuhp_sysfs_init(void)
2154 {
2155         int cpu, ret;
2156
2157         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2158                                  &cpuhp_cpu_root_attr_group);
2159         if (ret)
2160                 return ret;
2161
2162         for_each_possible_cpu(cpu) {
2163                 struct device *dev = get_cpu_device(cpu);
2164
2165                 if (!dev)
2166                         continue;
2167                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2168                 if (ret)
2169                         return ret;
2170         }
2171         return 0;
2172 }
2173 device_initcall(cpuhp_sysfs_init);
2174 #endif
2175
2176 /*
2177  * cpu_bit_bitmap[] is a special, "compressed" data structure that
2178  * represents all NR_CPUS bits binary values of 1<<nr.
2179  *
2180  * It is used by cpumask_of() to get a constant address to a CPU
2181  * mask value that has a single bit set only.
2182  */
2183
2184 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2185 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2186 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2187 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2188 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2189
2190 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2191
2192         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2193         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2194 #if BITS_PER_LONG > 32
2195         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2196         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2197 #endif
2198 };
2199 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2200
2201 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2202 EXPORT_SYMBOL(cpu_all_bits);
2203
2204 #ifdef CONFIG_INIT_ALL_POSSIBLE
2205 struct cpumask __cpu_possible_mask __read_mostly
2206         = {CPU_BITS_ALL};
2207 #else
2208 struct cpumask __cpu_possible_mask __read_mostly;
2209 #endif
2210 EXPORT_SYMBOL(__cpu_possible_mask);
2211
2212 struct cpumask __cpu_online_mask __read_mostly;
2213 EXPORT_SYMBOL(__cpu_online_mask);
2214
2215 struct cpumask __cpu_present_mask __read_mostly;
2216 EXPORT_SYMBOL(__cpu_present_mask);
2217
2218 struct cpumask __cpu_active_mask __read_mostly;
2219 EXPORT_SYMBOL(__cpu_active_mask);
2220
2221 void init_cpu_present(const struct cpumask *src)
2222 {
2223         cpumask_copy(&__cpu_present_mask, src);
2224 }
2225
2226 void init_cpu_possible(const struct cpumask *src)
2227 {
2228         cpumask_copy(&__cpu_possible_mask, src);
2229 }
2230
2231 void init_cpu_online(const struct cpumask *src)
2232 {
2233         cpumask_copy(&__cpu_online_mask, src);
2234 }
2235
2236 /*
2237  * Activate the first processor.
2238  */
2239 void __init boot_cpu_init(void)
2240 {
2241         int cpu = smp_processor_id();
2242
2243         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2244         set_cpu_online(cpu, true);
2245         set_cpu_active(cpu, true);
2246         set_cpu_present(cpu, true);
2247         set_cpu_possible(cpu, true);
2248 }
2249
2250 /*
2251  * Must be called _AFTER_ setting up the per_cpu areas
2252  */
2253 void __init boot_cpu_state_init(void)
2254 {
2255         per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
2256 }