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