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/sched/mm.h>
   7 #include <linux/proc_fs.h>
   8 #include <linux/smp.h>
   9 #include <linux/init.h>
  10 #include <linux/notifier.h>
  11 #include <linux/sched/signal.h>
  12 #include <linux/sched/hotplug.h>
  13 #include <linux/sched/isolation.h>
  14 #include <linux/sched/task.h>
  15 #include <linux/sched/smt.h>
  16 #include <linux/unistd.h>
  17 #include <linux/cpu.h>
  18 #include <linux/oom.h>
  19 #include <linux/rcupdate.h>
  20 #include <linux/export.h>
  21 #include <linux/bug.h>
  22 #include <linux/kthread.h>
  23 #include <linux/stop_machine.h>
  24 #include <linux/mutex.h>
  25 #include <linux/gfp.h>
  26 #include <linux/suspend.h>
  27 #include <linux/lockdep.h>
  28 #include <linux/tick.h>
  29 #include <linux/irq.h>
  30 #include <linux/nmi.h>
  31 #include <linux/smpboot.h>
  32 #include <linux/relay.h>
  33 #include <linux/slab.h>
  34 #include <linux/percpu-rwsem.h>
  35
  36 #include <trace/events/power.h>
  37 #define CREATE_TRACE_POINTS
  38 #include <trace/events/cpuhp.h>
  39
  40 #include "smpboot.h"
  41
  42 /**
  43  * cpuhp_cpu_state - Per cpu hotplug state storage
  44  * @state:      The current cpu state
  45  * @target:     The target state
  46  * @thread:     Pointer to the hotplug thread
  47  * @should_run: Thread should execute
  48  * @rollback:   Perform a rollback
  49  * @single:     Single callback invocation
  50  * @bringup:    Single callback bringup or teardown selector
  51  * @cb_state:   The state for a single callback (install/uninstall)
  52  * @result:     Result of the operation
  53  * @done_up:    Signal completion to the issuer of the task for cpu-up
  54  * @done_down:  Signal completion to the issuer of the task for cpu-down
  55  */
  56 struct cpuhp_cpu_state {
  57         enum cpuhp_state        state;
  58         enum cpuhp_state        target;
  59         enum cpuhp_state        fail;
  60 #ifdef CONFIG_SMP
  61         struct task_struct      *thread;
  62         bool                    should_run;
  63         bool                    rollback;
  64         bool                    single;
  65         bool                    bringup;
  66         struct hlist_node       *node;
  67         struct hlist_node       *last;
  68         enum cpuhp_state        cb_state;
  69         int                     result;
  70         struct completion       done_up;
  71         struct completion       done_down;
  72 #endif
  73 };
  74
  75 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
  76         .fail = CPUHP_INVALID,
  77 };
  78
  79 #ifdef CONFIG_SMP
  80 cpumask_t cpus_booted_once_mask;
  81 #endif
  82
  83 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
  84 static struct lockdep_map cpuhp_state_up_map =
  85         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
  86 static struct lockdep_map cpuhp_state_down_map =
  87         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
  88
  89
  90 static inline void cpuhp_lock_acquire(bool bringup)
  91 {
  92         lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
  93 }
  94
  95 static inline void cpuhp_lock_release(bool bringup)
  96 {
  97         lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
  98 }
  99 #else
 100
 101 static inline void cpuhp_lock_acquire(bool bringup) { }
 102 static inline void cpuhp_lock_release(bool bringup) { }
 103
 104 #endif
 105
 106 /**
 107  * cpuhp_step - Hotplug state machine step
 108  * @name:       Name of the step
 109  * @startup:    Startup function of the step
 110  * @teardown:   Teardown function of the step
 111  * @cant_stop:  Bringup/teardown can't be stopped at this step
 112  */
 113 struct cpuhp_step {
 114         const char              *name;
 115         union {
 116                 int             (*single)(unsigned int cpu);
 117                 int             (*multi)(unsigned int cpu,
 118                                          struct hlist_node *node);
 119         } startup;
 120         union {
 121                 int             (*single)(unsigned int cpu);
 122                 int             (*multi)(unsigned int cpu,
 123                                          struct hlist_node *node);
 124         } teardown;
 125         struct hlist_head       list;
 126         bool                    cant_stop;
 127         bool                    multi_instance;
 128 };
 129
 130 static DEFINE_MUTEX(cpuhp_state_mutex);
 131 static struct cpuhp_step cpuhp_hp_states[];
 132
 133 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
 134 {
 135         return cpuhp_hp_states + state;
 136 }
 137
 138 /**
 139  * cpuhp_invoke_callback _ Invoke the callbacks for a given state
 140  * @cpu:        The cpu for which the callback should be invoked
 141  * @state:      The state to do callbacks for
 142  * @bringup:    True if the bringup callback should be invoked
 143  * @node:       For multi-instance, do a single entry callback for install/remove
 144  * @lastp:      For multi-instance rollback, remember how far we got
 145  *
 146  * Called from cpu hotplug and from the state register machinery.
 147  */
 148 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 149                                  bool bringup, struct hlist_node *node,
 150                                  struct hlist_node **lastp)
 151 {
 152         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 153         struct cpuhp_step *step = cpuhp_get_step(state);
 154         int (*cbm)(unsigned int cpu, struct hlist_node *node);
 155         int (*cb)(unsigned int cpu);
 156         int ret, cnt;
 157
 158         if (st->fail == state) {
 159                 st->fail = CPUHP_INVALID;
 160
 161                 if (!(bringup ? step->startup.single : step->teardown.single))
 162                         return 0;
 163
 164                 return -EAGAIN;
 165         }
 166
 167         if (!step->multi_instance) {
 168                 WARN_ON_ONCE(lastp && *lastp);
 169                 cb = bringup ? step->startup.single : step->teardown.single;
 170                 if (!cb)
 171                         return 0;
 172                 trace_cpuhp_enter(cpu, st->target, state, cb);
 173                 ret = cb(cpu);
 174                 trace_cpuhp_exit(cpu, st->state, state, ret);
 175                 return ret;
 176         }
 177         cbm = bringup ? step->startup.multi : step->teardown.multi;
 178         if (!cbm)
 179                 return 0;
 180
 181         /* Single invocation for instance add/remove */
 182         if (node) {
 183                 WARN_ON_ONCE(lastp && *lastp);
 184                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 185                 ret = cbm(cpu, node);
 186                 trace_cpuhp_exit(cpu, st->state, state, ret);
 187                 return ret;
 188         }
 189
 190         /* State transition. Invoke on all instances */
 191         cnt = 0;
 192         hlist_for_each(node, &step->list) {
 193                 if (lastp && node == *lastp)
 194                         break;
 195
 196                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 197                 ret = cbm(cpu, node);
 198                 trace_cpuhp_exit(cpu, st->state, state, ret);
 199                 if (ret) {
 200                         if (!lastp)
 201                                 goto err;
 202
 203                         *lastp = node;
 204                         return ret;
 205                 }
 206                 cnt++;
 207         }
 208         if (lastp)
 209                 *lastp = NULL;
 210         return 0;
 211 err:
 212         /* Rollback the instances if one failed */
 213         cbm = !bringup ? step->startup.multi : step->teardown.multi;
 214         if (!cbm)
 215                 return ret;
 216
 217         hlist_for_each(node, &step->list) {
 218                 if (!cnt--)
 219                         break;
 220
 221                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 222                 ret = cbm(cpu, node);
 223                 trace_cpuhp_exit(cpu, st->state, state, ret);
 224                 /*
 225                  * Rollback must not fail,
 226                  */
 227                 WARN_ON_ONCE(ret);
 228         }
 229         return ret;
 230 }
 231
 232 #ifdef CONFIG_SMP
 233 static bool cpuhp_is_ap_state(enum cpuhp_state state)
 234 {
 235         /*
 236          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
 237          * purposes as that state is handled explicitly in cpu_down.
 238          */
 239         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
 240 }
 241
 242 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
 243 {
 244         struct completion *done = bringup ? &st->done_up : &st->done_down;
 245         wait_for_completion(done);
 246 }
 247
 248 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
 249 {
 250         struct completion *done = bringup ? &st->done_up : &st->done_down;
 251         complete(done);
 252 }
 253
 254 /*
 255  * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
 256  */
 257 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
 258 {
 259         return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
 260 }
 261
 262 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
 263 static DEFINE_MUTEX(cpu_add_remove_lock);
 264 bool cpuhp_tasks_frozen;
 265 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 266
 267 /*
 268  * The following two APIs (cpu_maps_update_begin/done) must be used when
 269  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 270  */
 271 void cpu_maps_update_begin(void)
 272 {
 273         mutex_lock(&cpu_add_remove_lock);
 274 }
 275
 276 void cpu_maps_update_done(void)
 277 {
 278         mutex_unlock(&cpu_add_remove_lock);
 279 }
 280
 281 /*
 282  * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 283  * Should always be manipulated under cpu_add_remove_lock
 284  */
 285 static int cpu_hotplug_disabled;
 286
 287 #ifdef CONFIG_HOTPLUG_CPU
 288
 289 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
 290
 291 void cpus_read_lock(void)
 292 {
 293         percpu_down_read(&cpu_hotplug_lock);
 294 }
 295 EXPORT_SYMBOL_GPL(cpus_read_lock);
 296
 297 int cpus_read_trylock(void)
 298 {
 299         return percpu_down_read_trylock(&cpu_hotplug_lock);
 300 }
 301 EXPORT_SYMBOL_GPL(cpus_read_trylock);
 302
 303 void cpus_read_unlock(void)
 304 {
 305         percpu_up_read(&cpu_hotplug_lock);
 306 }
 307 EXPORT_SYMBOL_GPL(cpus_read_unlock);
 308
 309 void cpus_write_lock(void)
 310 {
 311         percpu_down_write(&cpu_hotplug_lock);
 312 }
 313
 314 void cpus_write_unlock(void)
 315 {
 316         percpu_up_write(&cpu_hotplug_lock);
 317 }
 318
 319 void lockdep_assert_cpus_held(void)
 320 {
 321         /*
 322          * We can't have hotplug operations before userspace starts running,
 323          * and some init codepaths will knowingly not take the hotplug lock.
 324          * This is all valid, so mute lockdep until it makes sense to report
 325          * unheld locks.
 326          */
 327         if (system_state < SYSTEM_RUNNING)
 328                 return;
 329
 330         percpu_rwsem_assert_held(&cpu_hotplug_lock);
 331 }
 332
 333 static void lockdep_acquire_cpus_lock(void)
 334 {
 335         rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
 336 }
 337
 338 static void lockdep_release_cpus_lock(void)
 339 {
 340         rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
 341 }
 342
 343 /*
 344  * Wait for currently running CPU hotplug operations to complete (if any) and
 345  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 346  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 347  * hotplug path before performing hotplug operations. So acquiring that lock
 348  * guarantees mutual exclusion from any currently running hotplug operations.
 349  */
 350 void cpu_hotplug_disable(void)
 351 {
 352         cpu_maps_update_begin();
 353         cpu_hotplug_disabled++;
 354         cpu_maps_update_done();
 355 }
 356 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 357
 358 static void __cpu_hotplug_enable(void)
 359 {
 360         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
 361                 return;
 362         cpu_hotplug_disabled--;
 363 }
 364
 365 void cpu_hotplug_enable(void)
 366 {
 367         cpu_maps_update_begin();
 368         __cpu_hotplug_enable();
 369         cpu_maps_update_done();
 370 }
 371 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 372
 373 #else
 374
 375 static void lockdep_acquire_cpus_lock(void)
 376 {
 377 }
 378
 379 static void lockdep_release_cpus_lock(void)
 380 {
 381 }
 382
 383 #endif  /* CONFIG_HOTPLUG_CPU */
 384
 385 /*
 386  * Architectures that need SMT-specific errata handling during SMT hotplug
 387  * should override this.
 388  */
 389 void __weak arch_smt_update(void) { }
 390
 391 #ifdef CONFIG_HOTPLUG_SMT
 392 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
 393
 394 void __init cpu_smt_disable(bool force)
 395 {
 396         if (!cpu_smt_possible())
 397                 return;
 398
 399         if (force) {
 400                 pr_info("SMT: Force disabled\n");
 401                 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
 402         } else {
 403                 pr_info("SMT: disabled\n");
 404                 cpu_smt_control = CPU_SMT_DISABLED;
 405         }
 406 }
 407
 408 /*
 409  * The decision whether SMT is supported can only be done after the full
 410  * CPU identification. Called from architecture code.
 411  */
 412 void __init cpu_smt_check_topology(void)
 413 {
 414         if (!topology_smt_supported())
 415                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 416 }
 417
 418 static int __init smt_cmdline_disable(char *str)
 419 {
 420         cpu_smt_disable(str && !strcmp(str, "force"));
 421         return 0;
 422 }
 423 early_param("nosmt", smt_cmdline_disable);
 424
 425 static inline bool cpu_smt_allowed(unsigned int cpu)
 426 {
 427         if (cpu_smt_control == CPU_SMT_ENABLED)
 428                 return true;
 429
 430         if (topology_is_primary_thread(cpu))
 431                 return true;
 432
 433         /*
 434          * On x86 it's required to boot all logical CPUs at least once so
 435          * that the init code can get a chance to set CR4.MCE on each
 436          * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
 437          * core will shutdown the machine.
 438          */
 439         return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
 440 }
 441
 442 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
 443 bool cpu_smt_possible(void)
 444 {
 445         return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
 446                 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
 447 }
 448 EXPORT_SYMBOL_GPL(cpu_smt_possible);
 449 #else
 450 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
 451 #endif
 452
 453 static inline enum cpuhp_state
 454 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 455 {
 456         enum cpuhp_state prev_state = st->state;
 457
 458         st->rollback = false;
 459         st->last = NULL;
 460
 461         st->target = target;
 462         st->single = false;
 463         st->bringup = st->state < target;
 464
 465         return prev_state;
 466 }
 467
 468 static inline void
 469 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
 470 {
 471         st->rollback = true;
 472
 473         /*
 474          * If we have st->last we need to undo partial multi_instance of this
 475          * state first. Otherwise start undo at the previous state.
 476          */
 477         if (!st->last) {
 478                 if (st->bringup)
 479                         st->state--;
 480                 else
 481                         st->state++;
 482         }
 483
 484         st->target = prev_state;
 485         st->bringup = !st->bringup;
 486 }
 487
 488 /* Regular hotplug invocation of the AP hotplug thread */
 489 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
 490 {
 491         if (!st->single && st->state == st->target)
 492                 return;
 493
 494         st->result = 0;
 495         /*
 496          * Make sure the above stores are visible before should_run becomes
 497          * true. Paired with the mb() above in cpuhp_thread_fun()
 498          */
 499         smp_mb();
 500         st->should_run = true;
 501         wake_up_process(st->thread);
 502         wait_for_ap_thread(st, st->bringup);
 503 }
 504
 505 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 506 {
 507         enum cpuhp_state prev_state;
 508         int ret;
 509
 510         prev_state = cpuhp_set_state(st, target);
 511         __cpuhp_kick_ap(st);
 512         if ((ret = st->result)) {
 513                 cpuhp_reset_state(st, prev_state);
 514                 __cpuhp_kick_ap(st);
 515         }
 516
 517         return ret;
 518 }
 519
 520 static int bringup_wait_for_ap(unsigned int cpu)
 521 {
 522         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 523
 524         /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
 525         wait_for_ap_thread(st, true);
 526         if (WARN_ON_ONCE((!cpu_online(cpu))))
 527                 return -ECANCELED;
 528
 529         /* Unpark the hotplug thread of the target cpu */
 530         kthread_unpark(st->thread);
 531
 532         /*
 533          * SMT soft disabling on X86 requires to bring the CPU out of the
 534          * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
 535          * CPU marked itself as booted_once in notify_cpu_starting() so the
 536          * cpu_smt_allowed() check will now return false if this is not the
 537          * primary sibling.
 538          */
 539         if (!cpu_smt_allowed(cpu))
 540                 return -ECANCELED;
 541
 542         if (st->target <= CPUHP_AP_ONLINE_IDLE)
 543                 return 0;
 544
 545         return cpuhp_kick_ap(st, st->target);
 546 }
 547
 548 static int bringup_cpu(unsigned int cpu)
 549 {
 550         struct task_struct *idle = idle_thread_get(cpu);
 551         int ret;
 552
 553         /*
 554          * Some architectures have to walk the irq descriptors to
 555          * setup the vector space for the cpu which comes online.
 556          * Prevent irq alloc/free across the bringup.
 557          */
 558         irq_lock_sparse();
 559
 560         /* Arch-specific enabling code. */
 561         ret = __cpu_up(cpu, idle);
 562         irq_unlock_sparse();
 563         if (ret)
 564                 return ret;
 565         return bringup_wait_for_ap(cpu);
 566 }
 567
 568 static int finish_cpu(unsigned int cpu)
 569 {
 570         struct task_struct *idle = idle_thread_get(cpu);
 571         struct mm_struct *mm = idle->active_mm;
 572
 573         /*
 574          * idle_task_exit() will have switched to &init_mm, now
 575          * clean up any remaining active_mm state.
 576          */
 577         if (mm != &init_mm)
 578                 idle->active_mm = &init_mm;
 579         mmdrop(mm);
 580         return 0;
 581 }
 582
 583 /*
 584  * Hotplug state machine related functions
 585  */
 586
 587 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
 588 {
 589         for (st->state--; st->state > st->target; st->state--)
 590                 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 591 }
 592
 593 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
 594 {
 595         if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
 596                 return true;
 597         /*
 598          * When CPU hotplug is disabled, then taking the CPU down is not
 599          * possible because takedown_cpu() and the architecture and
 600          * subsystem specific mechanisms are not available. So the CPU
 601          * which would be completely unplugged again needs to stay around
 602          * in the current state.
 603          */
 604         return st->state <= CPUHP_BRINGUP_CPU;
 605 }
 606
 607 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 608                               enum cpuhp_state target)
 609 {
 610         enum cpuhp_state prev_state = st->state;
 611         int ret = 0;
 612
 613         while (st->state < target) {
 614                 st->state++;
 615                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
 616                 if (ret) {
 617                         if (can_rollback_cpu(st)) {
 618                                 st->target = prev_state;
 619                                 undo_cpu_up(cpu, st);
 620                         }
 621                         break;
 622                 }
 623         }
 624         return ret;
 625 }
 626
 627 /*
 628  * The cpu hotplug threads manage the bringup and teardown of the cpus
 629  */
 630 static void cpuhp_create(unsigned int cpu)
 631 {
 632         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 633
 634         init_completion(&st->done_up);
 635         init_completion(&st->done_down);
 636 }
 637
 638 static int cpuhp_should_run(unsigned int cpu)
 639 {
 640         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 641
 642         return st->should_run;
 643 }
 644
 645 /*
 646  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 647  * callbacks when a state gets [un]installed at runtime.
 648  *
 649  * Each invocation of this function by the smpboot thread does a single AP
 650  * state callback.
 651  *
 652  * It has 3 modes of operation:
 653  *  - single: runs st->cb_state
 654  *  - up:     runs ++st->state, while st->state < st->target
 655  *  - down:   runs st->state--, while st->state > st->target
 656  *
 657  * When complete or on error, should_run is cleared and the completion is fired.
 658  */
 659 static void cpuhp_thread_fun(unsigned int cpu)
 660 {
 661         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 662         bool bringup = st->bringup;
 663         enum cpuhp_state state;
 664
 665         if (WARN_ON_ONCE(!st->should_run))
 666                 return;
 667
 668         /*
 669          * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
 670          * that if we see ->should_run we also see the rest of the state.
 671          */
 672         smp_mb();
 673
 674         /*
 675          * The BP holds the hotplug lock, but we're now running on the AP,
 676          * ensure that anybody asserting the lock is held, will actually find
 677          * it so.
 678          */
 679         lockdep_acquire_cpus_lock();
 680         cpuhp_lock_acquire(bringup);
 681
 682         if (st->single) {
 683                 state = st->cb_state;
 684                 st->should_run = false;
 685         } else {
 686                 if (bringup) {
 687                         st->state++;
 688                         state = st->state;
 689                         st->should_run = (st->state < st->target);
 690                         WARN_ON_ONCE(st->state > st->target);
 691                 } else {
 692                         state = st->state;
 693                         st->state--;
 694                         st->should_run = (st->state > st->target);
 695                         WARN_ON_ONCE(st->state < st->target);
 696                 }
 697         }
 698
 699         WARN_ON_ONCE(!cpuhp_is_ap_state(state));
 700
 701         if (cpuhp_is_atomic_state(state)) {
 702                 local_irq_disable();
 703                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
 704                 local_irq_enable();
 705
 706                 /*
 707                  * STARTING/DYING must not fail!
 708                  */
 709                 WARN_ON_ONCE(st->result);
 710         } else {
 711                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
 712         }
 713
 714         if (st->result) {
 715                 /*
 716                  * If we fail on a rollback, we're up a creek without no
 717                  * paddle, no way forward, no way back. We loose, thanks for
 718                  * playing.
 719                  */
 720                 WARN_ON_ONCE(st->rollback);
 721                 st->should_run = false;
 722         }
 723
 724         cpuhp_lock_release(bringup);
 725         lockdep_release_cpus_lock();
 726
 727         if (!st->should_run)
 728                 complete_ap_thread(st, bringup);
 729 }
 730
 731 /* Invoke a single callback on a remote cpu */
 732 static int
 733 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
 734                          struct hlist_node *node)
 735 {
 736         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 737         int ret;
 738
 739         if (!cpu_online(cpu))
 740                 return 0;
 741
 742         cpuhp_lock_acquire(false);
 743         cpuhp_lock_release(false);
 744
 745         cpuhp_lock_acquire(true);
 746         cpuhp_lock_release(true);
 747
 748         /*
 749          * If we are up and running, use the hotplug thread. For early calls
 750          * we invoke the thread function directly.
 751          */
 752         if (!st->thread)
 753                 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
 754
 755         st->rollback = false;
 756         st->last = NULL;
 757
 758         st->node = node;
 759         st->bringup = bringup;
 760         st->cb_state = state;
 761         st->single = true;
 762
 763         __cpuhp_kick_ap(st);
 764
 765         /*
 766          * If we failed and did a partial, do a rollback.
 767          */
 768         if ((ret = st->result) && st->last) {
 769                 st->rollback = true;
 770                 st->bringup = !bringup;
 771
 772                 __cpuhp_kick_ap(st);
 773         }
 774
 775         /*
 776          * Clean up the leftovers so the next hotplug operation wont use stale
 777          * data.
 778          */
 779         st->node = st->last = NULL;
 780         return ret;
 781 }
 782
 783 static int cpuhp_kick_ap_work(unsigned int cpu)
 784 {
 785         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 786         enum cpuhp_state prev_state = st->state;
 787         int ret;
 788
 789         cpuhp_lock_acquire(false);
 790         cpuhp_lock_release(false);
 791
 792         cpuhp_lock_acquire(true);
 793         cpuhp_lock_release(true);
 794
 795         trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
 796         ret = cpuhp_kick_ap(st, st->target);
 797         trace_cpuhp_exit(cpu, st->state, prev_state, ret);
 798
 799         return ret;
 800 }
 801
 802 static struct smp_hotplug_thread cpuhp_threads = {
 803         .store                  = &cpuhp_state.thread,
 804         .create                 = &cpuhp_create,
 805         .thread_should_run      = cpuhp_should_run,
 806         .thread_fn              = cpuhp_thread_fun,
 807         .thread_comm            = "cpuhp/%u",
 808         .selfparking            = true,
 809 };
 810
 811 void __init cpuhp_threads_init(void)
 812 {
 813         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 814         kthread_unpark(this_cpu_read(cpuhp_state.thread));
 815 }
 816
 817 #ifdef CONFIG_HOTPLUG_CPU
 818 #ifndef arch_clear_mm_cpumask_cpu
 819 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
 820 #endif
 821
 822 /**
 823  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 824  * @cpu: a CPU id
 825  *
 826  * This function walks all processes, finds a valid mm struct for each one and
 827  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 828  * trivial, there are various non-obvious corner cases, which this function
 829  * tries to solve in a safe manner.
 830  *
 831  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 832  * be called only for an already offlined CPU.
 833  */
 834 void clear_tasks_mm_cpumask(int cpu)
 835 {
 836         struct task_struct *p;
 837
 838         /*
 839          * This function is called after the cpu is taken down and marked
 840          * offline, so its not like new tasks will ever get this cpu set in
 841          * their mm mask. -- Peter Zijlstra
 842          * Thus, we may use rcu_read_lock() here, instead of grabbing
 843          * full-fledged tasklist_lock.
 844          */
 845         WARN_ON(cpu_online(cpu));
 846         rcu_read_lock();
 847         for_each_process(p) {
 848                 struct task_struct *t;
 849
 850                 /*
 851                  * Main thread might exit, but other threads may still have
 852                  * a valid mm. Find one.
 853                  */
 854                 t = find_lock_task_mm(p);
 855                 if (!t)
 856                         continue;
 857                 arch_clear_mm_cpumask_cpu(cpu, t->mm);
 858                 task_unlock(t);
 859         }
 860         rcu_read_unlock();
 861 }
 862
 863 /* Take this CPU down. */
 864 static int take_cpu_down(void *_param)
 865 {
 866         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 867         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 868         int err, cpu = smp_processor_id();
 869         int ret;
 870
 871         /* Ensure this CPU doesn't handle any more interrupts. */
 872         err = __cpu_disable();
 873         if (err < 0)
 874                 return err;
 875
 876         /*
 877          * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
 878          * do this step again.
 879          */
 880         WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
 881         st->state--;
 882         /* Invoke the former CPU_DYING callbacks */
 883         for (; st->state > target; st->state--) {
 884                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 885                 /*
 886                  * DYING must not fail!
 887                  */
 888                 WARN_ON_ONCE(ret);
 889         }
 890
 891         /* Give up timekeeping duties */
 892         tick_handover_do_timer();
 893         /* Remove CPU from timer broadcasting */
 894         tick_offline_cpu(cpu);
 895         /* Park the stopper thread */
 896         stop_machine_park(cpu);
 897         return 0;
 898 }
 899
 900 static int takedown_cpu(unsigned int cpu)
 901 {
 902         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 903         int err;
 904
 905         /* Park the smpboot threads */
 906         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 907
 908         /*
 909          * Prevent irq alloc/free while the dying cpu reorganizes the
 910          * interrupt affinities.
 911          */
 912         irq_lock_sparse();
 913
 914         /*
 915          * So now all preempt/rcu users must observe !cpu_active().
 916          */
 917         err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
 918         if (err) {
 919                 /* CPU refused to die */
 920                 irq_unlock_sparse();
 921                 /* Unpark the hotplug thread so we can rollback there */
 922                 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 923                 return err;
 924         }
 925         BUG_ON(cpu_online(cpu));
 926
 927         /*
 928          * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
 929          * all runnable tasks from the CPU, there's only the idle task left now
 930          * that the migration thread is done doing the stop_machine thing.
 931          *
 932          * Wait for the stop thread to go away.
 933          */
 934         wait_for_ap_thread(st, false);
 935         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
 936
 937         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
 938         irq_unlock_sparse();
 939
 940         hotplug_cpu__broadcast_tick_pull(cpu);
 941         /* This actually kills the CPU. */
 942         __cpu_die(cpu);
 943
 944         tick_cleanup_dead_cpu(cpu);
 945         rcutree_migrate_callbacks(cpu);
 946         return 0;
 947 }
 948
 949 static void cpuhp_complete_idle_dead(void *arg)
 950 {
 951         struct cpuhp_cpu_state *st = arg;
 952
 953         complete_ap_thread(st, false);
 954 }
 955
 956 void cpuhp_report_idle_dead(void)
 957 {
 958         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 959
 960         BUG_ON(st->state != CPUHP_AP_OFFLINE);
 961         rcu_report_dead(smp_processor_id());
 962         st->state = CPUHP_AP_IDLE_DEAD;
 963         /*
 964          * We cannot call complete after rcu_report_dead() so we delegate it
 965          * to an online cpu.
 966          */
 967         smp_call_function_single(cpumask_first(cpu_online_mask),
 968                                  cpuhp_complete_idle_dead, st, 0);
 969 }
 970
 971 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
 972 {
 973         for (st->state++; st->state < st->target; st->state++)
 974                 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
 975 }
 976
 977 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 978                                 enum cpuhp_state target)
 979 {
 980         enum cpuhp_state prev_state = st->state;
 981         int ret = 0;
 982
 983         for (; st->state > target; st->state--) {
 984                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 985                 if (ret) {
 986                         st->target = prev_state;
 987                         if (st->state < prev_state)
 988                                 undo_cpu_down(cpu, st);
 989                         break;
 990                 }
 991         }
 992         return ret;
 993 }
 994
 995 /* Requires cpu_add_remove_lock to be held */
 996 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 997                            enum cpuhp_state target)
 998 {
 999         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1000         int prev_state, ret = 0;
1001
1002         if (num_online_cpus() == 1)
1003                 return -EBUSY;
1004
1005         if (!cpu_present(cpu))
1006                 return -EINVAL;
1007
1008         cpus_write_lock();
1009
1010         cpuhp_tasks_frozen = tasks_frozen;
1011
1012         prev_state = cpuhp_set_state(st, target);
1013         /*
1014          * If the current CPU state is in the range of the AP hotplug thread,
1015          * then we need to kick the thread.
1016          */
1017         if (st->state > CPUHP_TEARDOWN_CPU) {
1018                 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1019                 ret = cpuhp_kick_ap_work(cpu);
1020                 /*
1021                  * The AP side has done the error rollback already. Just
1022                  * return the error code..
1023                  */
1024                 if (ret)
1025                         goto out;
1026
1027                 /*
1028                  * We might have stopped still in the range of the AP hotplug
1029                  * thread. Nothing to do anymore.
1030                  */
1031                 if (st->state > CPUHP_TEARDOWN_CPU)
1032                         goto out;
1033
1034                 st->target = target;
1035         }
1036         /*
1037          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1038          * to do the further cleanups.
1039          */
1040         ret = cpuhp_down_callbacks(cpu, st, target);
1041         if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1042                 cpuhp_reset_state(st, prev_state);
1043                 __cpuhp_kick_ap(st);
1044         }
1045
1046 out:
1047         cpus_write_unlock();
1048         /*
1049          * Do post unplug cleanup. This is still protected against
1050          * concurrent CPU hotplug via cpu_add_remove_lock.
1051          */
1052         lockup_detector_cleanup();
1053         arch_smt_update();
1054         return ret;
1055 }
1056
1057 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1058 {
1059         if (cpu_hotplug_disabled)
1060                 return -EBUSY;
1061         return _cpu_down(cpu, 0, target);
1062 }
1063
1064 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1065 {
1066         int err;
1067
1068         cpu_maps_update_begin();
1069         err = cpu_down_maps_locked(cpu, target);
1070         cpu_maps_update_done();
1071         return err;
1072 }
1073
1074 /**
1075  * cpu_device_down - Bring down a cpu device
1076  * @dev: Pointer to the cpu device to offline
1077  *
1078  * This function is meant to be used by device core cpu subsystem only.
1079  *
1080  * Other subsystems should use remove_cpu() instead.
1081  */
1082 int cpu_device_down(struct device *dev)
1083 {
1084         return cpu_down(dev->id, CPUHP_OFFLINE);
1085 }
1086
1087 int remove_cpu(unsigned int cpu)
1088 {
1089         int ret;
1090
1091         lock_device_hotplug();
1092         ret = device_offline(get_cpu_device(cpu));
1093         unlock_device_hotplug();
1094
1095         return ret;
1096 }
1097 EXPORT_SYMBOL_GPL(remove_cpu);
1098
1099 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1100 {
1101         unsigned int cpu;
1102         int error;
1103
1104         cpu_maps_update_begin();
1105
1106         /*
1107          * Make certain the cpu I'm about to reboot on is online.
1108          *
1109          * This is inline to what migrate_to_reboot_cpu() already do.
1110          */
1111         if (!cpu_online(primary_cpu))
1112                 primary_cpu = cpumask_first(cpu_online_mask);
1113
1114         for_each_online_cpu(cpu) {
1115                 if (cpu == primary_cpu)
1116                         continue;
1117
1118                 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1119                 if (error) {
1120                         pr_err("Failed to offline CPU%d - error=%d",
1121                                 cpu, error);
1122                         break;
1123                 }
1124         }
1125
1126         /*
1127          * Ensure all but the reboot CPU are offline.
1128          */
1129         BUG_ON(num_online_cpus() > 1);
1130
1131         /*
1132          * Make sure the CPUs won't be enabled by someone else after this
1133          * point. Kexec will reboot to a new kernel shortly resetting
1134          * everything along the way.
1135          */
1136         cpu_hotplug_disabled++;
1137
1138         cpu_maps_update_done();
1139 }
1140
1141 #else
1142 #define takedown_cpu            NULL
1143 #endif /*CONFIG_HOTPLUG_CPU*/
1144
1145 /**
1146  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1147  * @cpu: cpu that just started
1148  *
1149  * It must be called by the arch code on the new cpu, before the new cpu
1150  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1151  */
1152 void notify_cpu_starting(unsigned int cpu)
1153 {
1154         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1155         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1156         int ret;
1157
1158         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1159         cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1160         while (st->state < target) {
1161                 st->state++;
1162                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1163                 /*
1164                  * STARTING must not fail!
1165                  */
1166                 WARN_ON_ONCE(ret);
1167         }
1168 }
1169
1170 /*
1171  * Called from the idle task. Wake up the controlling task which brings the
1172  * hotplug thread of the upcoming CPU up and then delegates the rest of the
1173  * online bringup to the hotplug thread.
1174  */
1175 void cpuhp_online_idle(enum cpuhp_state state)
1176 {
1177         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1178
1179         /* Happens for the boot cpu */
1180         if (state != CPUHP_AP_ONLINE_IDLE)
1181                 return;
1182
1183         /*
1184          * Unpart the stopper thread before we start the idle loop (and start
1185          * scheduling); this ensures the stopper task is always available.
1186          */
1187         stop_machine_unpark(smp_processor_id());
1188
1189         st->state = CPUHP_AP_ONLINE_IDLE;
1190         complete_ap_thread(st, true);
1191 }
1192
1193 /* Requires cpu_add_remove_lock to be held */
1194 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1195 {
1196         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1197         struct task_struct *idle;
1198         int ret = 0;
1199
1200         cpus_write_lock();
1201
1202         if (!cpu_present(cpu)) {
1203                 ret = -EINVAL;
1204                 goto out;
1205         }
1206
1207         /*
1208          * The caller of cpu_up() might have raced with another
1209          * caller. Nothing to do.
1210          */
1211         if (st->state >= target)
1212                 goto out;
1213
1214         if (st->state == CPUHP_OFFLINE) {
1215                 /* Let it fail before we try to bring the cpu up */
1216                 idle = idle_thread_get(cpu);
1217                 if (IS_ERR(idle)) {
1218                         ret = PTR_ERR(idle);
1219                         goto out;
1220                 }
1221         }
1222
1223         cpuhp_tasks_frozen = tasks_frozen;
1224
1225         cpuhp_set_state(st, target);
1226         /*
1227          * If the current CPU state is in the range of the AP hotplug thread,
1228          * then we need to kick the thread once more.
1229          */
1230         if (st->state > CPUHP_BRINGUP_CPU) {
1231                 ret = cpuhp_kick_ap_work(cpu);
1232                 /*
1233                  * The AP side has done the error rollback already. Just
1234                  * return the error code..
1235                  */
1236                 if (ret)
1237                         goto out;
1238         }
1239
1240         /*
1241          * Try to reach the target state. We max out on the BP at
1242          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1243          * responsible for bringing it up to the target state.
1244          */
1245         target = min((int)target, CPUHP_BRINGUP_CPU);
1246         ret = cpuhp_up_callbacks(cpu, st, target);
1247 out:
1248         cpus_write_unlock();
1249         arch_smt_update();
1250         return ret;
1251 }
1252
1253 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1254 {
1255         int err = 0;
1256
1257         if (!cpu_possible(cpu)) {
1258                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1259                        cpu);
1260 #if defined(CONFIG_IA64)
1261                 pr_err("please check additional_cpus= boot parameter\n");
1262 #endif
1263                 return -EINVAL;
1264         }
1265
1266         err = try_online_node(cpu_to_node(cpu));
1267         if (err)
1268                 return err;
1269
1270         cpu_maps_update_begin();
1271
1272         if (cpu_hotplug_disabled) {
1273                 err = -EBUSY;
1274                 goto out;
1275         }
1276         if (!cpu_smt_allowed(cpu)) {
1277                 err = -EPERM;
1278                 goto out;
1279         }
1280
1281         err = _cpu_up(cpu, 0, target);
1282 out:
1283         cpu_maps_update_done();
1284         return err;
1285 }
1286
1287 /**
1288  * cpu_device_up - Bring up a cpu device
1289  * @dev: Pointer to the cpu device to online
1290  *
1291  * This function is meant to be used by device core cpu subsystem only.
1292  *
1293  * Other subsystems should use add_cpu() instead.
1294  */
1295 int cpu_device_up(struct device *dev)
1296 {
1297         return cpu_up(dev->id, CPUHP_ONLINE);
1298 }
1299
1300 int add_cpu(unsigned int cpu)
1301 {
1302         int ret;
1303
1304         lock_device_hotplug();
1305         ret = device_online(get_cpu_device(cpu));
1306         unlock_device_hotplug();
1307
1308         return ret;
1309 }
1310 EXPORT_SYMBOL_GPL(add_cpu);
1311
1312 /**
1313  * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1314  * @sleep_cpu: The cpu we hibernated on and should be brought up.
1315  *
1316  * On some architectures like arm64, we can hibernate on any CPU, but on
1317  * wake up the CPU we hibernated on might be offline as a side effect of
1318  * using maxcpus= for example.
1319  */
1320 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1321 {
1322         int ret;
1323
1324         if (!cpu_online(sleep_cpu)) {
1325                 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1326                 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1327                 if (ret) {
1328                         pr_err("Failed to bring hibernate-CPU up!\n");
1329                         return ret;
1330                 }
1331         }
1332         return 0;
1333 }
1334
1335 void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1336 {
1337         unsigned int cpu;
1338
1339         for_each_present_cpu(cpu) {
1340                 if (num_online_cpus() >= setup_max_cpus)
1341                         break;
1342                 if (!cpu_online(cpu))
1343                         cpu_up(cpu, CPUHP_ONLINE);
1344         }
1345 }
1346
1347 #ifdef CONFIG_PM_SLEEP_SMP
1348 static cpumask_var_t frozen_cpus;
1349
1350 int freeze_secondary_cpus(int primary)
1351 {
1352         int cpu, error = 0;
1353
1354         cpu_maps_update_begin();
1355         if (primary == -1) {
1356                 primary = cpumask_first(cpu_online_mask);
1357                 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1358                         primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1359         } else {
1360                 if (!cpu_online(primary))
1361                         primary = cpumask_first(cpu_online_mask);
1362         }
1363
1364         /*
1365          * We take down all of the non-boot CPUs in one shot to avoid races
1366          * with the userspace trying to use the CPU hotplug at the same time
1367          */
1368         cpumask_clear(frozen_cpus);
1369
1370         pr_info("Disabling non-boot CPUs ...\n");
1371         for_each_online_cpu(cpu) {
1372                 if (cpu == primary)
1373                         continue;
1374
1375                 if (pm_wakeup_pending()) {
1376                         pr_info("Wakeup pending. Abort CPU freeze\n");
1377                         error = -EBUSY;
1378                         break;
1379                 }
1380
1381                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1382                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1383                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1384                 if (!error)
1385                         cpumask_set_cpu(cpu, frozen_cpus);
1386                 else {
1387                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1388                         break;
1389                 }
1390         }
1391
1392         if (!error)
1393                 BUG_ON(num_online_cpus() > 1);
1394         else
1395                 pr_err("Non-boot CPUs are not disabled\n");
1396
1397         /*
1398          * Make sure the CPUs won't be enabled by someone else. We need to do
1399          * this even in case of failure as all freeze_secondary_cpus() users are
1400          * supposed to do thaw_secondary_cpus() on the failure path.
1401          */
1402         cpu_hotplug_disabled++;
1403
1404         cpu_maps_update_done();
1405         return error;
1406 }
1407
1408 void __weak arch_thaw_secondary_cpus_begin(void)
1409 {
1410 }
1411
1412 void __weak arch_thaw_secondary_cpus_end(void)
1413 {
1414 }
1415
1416 void thaw_secondary_cpus(void)
1417 {
1418         int cpu, error;
1419
1420         /* Allow everyone to use the CPU hotplug again */
1421         cpu_maps_update_begin();
1422         __cpu_hotplug_enable();
1423         if (cpumask_empty(frozen_cpus))
1424                 goto out;
1425
1426         pr_info("Enabling non-boot CPUs ...\n");
1427
1428         arch_thaw_secondary_cpus_begin();
1429
1430         for_each_cpu(cpu, frozen_cpus) {
1431                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1432                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1433                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1434                 if (!error) {
1435                         pr_info("CPU%d is up\n", cpu);
1436                         continue;
1437                 }
1438                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1439         }
1440
1441         arch_thaw_secondary_cpus_end();
1442
1443         cpumask_clear(frozen_cpus);
1444 out:
1445         cpu_maps_update_done();
1446 }
1447
1448 static int __init alloc_frozen_cpus(void)
1449 {
1450         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1451                 return -ENOMEM;
1452         return 0;
1453 }
1454 core_initcall(alloc_frozen_cpus);
1455
1456 /*
1457  * When callbacks for CPU hotplug notifications are being executed, we must
1458  * ensure that the state of the system with respect to the tasks being frozen
1459  * or not, as reported by the notification, remains unchanged *throughout the
1460  * duration* of the execution of the callbacks.
1461  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1462  *
1463  * This synchronization is implemented by mutually excluding regular CPU
1464  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1465  * Hibernate notifications.
1466  */
1467 static int
1468 cpu_hotplug_pm_callback(struct notifier_block *nb,
1469                         unsigned long action, void *ptr)
1470 {
1471         switch (action) {
1472
1473         case PM_SUSPEND_PREPARE:
1474         case PM_HIBERNATION_PREPARE:
1475                 cpu_hotplug_disable();
1476                 break;
1477
1478         case PM_POST_SUSPEND:
1479         case PM_POST_HIBERNATION:
1480                 cpu_hotplug_enable();
1481                 break;
1482
1483         default:
1484                 return NOTIFY_DONE;
1485         }
1486
1487         return NOTIFY_OK;
1488 }
1489
1490
1491 static int __init cpu_hotplug_pm_sync_init(void)
1492 {
1493         /*
1494          * cpu_hotplug_pm_callback has higher priority than x86
1495          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1496          * to disable cpu hotplug to avoid cpu hotplug race.
1497          */
1498         pm_notifier(cpu_hotplug_pm_callback, 0);
1499         return 0;
1500 }
1501 core_initcall(cpu_hotplug_pm_sync_init);
1502
1503 #endif /* CONFIG_PM_SLEEP_SMP */
1504
1505 int __boot_cpu_id;
1506
1507 #endif /* CONFIG_SMP */
1508
1509 /* Boot processor state steps */
1510 static struct cpuhp_step cpuhp_hp_states[] = {
1511         [CPUHP_OFFLINE] = {
1512                 .name                   = "offline",
1513                 .startup.single         = NULL,
1514                 .teardown.single        = NULL,
1515         },
1516 #ifdef CONFIG_SMP
1517         [CPUHP_CREATE_THREADS]= {
1518                 .name                   = "threads:prepare",
1519                 .startup.single         = smpboot_create_threads,
1520                 .teardown.single        = NULL,
1521                 .cant_stop              = true,
1522         },
1523         [CPUHP_PERF_PREPARE] = {
1524                 .name                   = "perf:prepare",
1525                 .startup.single         = perf_event_init_cpu,
1526                 .teardown.single        = perf_event_exit_cpu,
1527         },
1528         [CPUHP_WORKQUEUE_PREP] = {
1529                 .name                   = "workqueue:prepare",
1530                 .startup.single         = workqueue_prepare_cpu,
1531                 .teardown.single        = NULL,
1532         },
1533         [CPUHP_HRTIMERS_PREPARE] = {
1534                 .name                   = "hrtimers:prepare",
1535                 .startup.single         = hrtimers_prepare_cpu,
1536                 .teardown.single        = hrtimers_dead_cpu,
1537         },
1538         [CPUHP_SMPCFD_PREPARE] = {
1539                 .name                   = "smpcfd:prepare",
1540                 .startup.single         = smpcfd_prepare_cpu,
1541                 .teardown.single        = smpcfd_dead_cpu,
1542         },
1543         [CPUHP_RELAY_PREPARE] = {
1544                 .name                   = "relay:prepare",
1545                 .startup.single         = relay_prepare_cpu,
1546                 .teardown.single        = NULL,
1547         },
1548         [CPUHP_SLAB_PREPARE] = {
1549                 .name                   = "slab:prepare",
1550                 .startup.single         = slab_prepare_cpu,
1551                 .teardown.single        = slab_dead_cpu,
1552         },
1553         [CPUHP_RCUTREE_PREP] = {
1554                 .name                   = "RCU/tree:prepare",
1555                 .startup.single         = rcutree_prepare_cpu,
1556                 .teardown.single        = rcutree_dead_cpu,
1557         },
1558         /*
1559          * On the tear-down path, timers_dead_cpu() must be invoked
1560          * before blk_mq_queue_reinit_notify() from notify_dead(),
1561          * otherwise a RCU stall occurs.
1562          */
1563         [CPUHP_TIMERS_PREPARE] = {
1564                 .name                   = "timers:prepare",
1565                 .startup.single         = timers_prepare_cpu,
1566                 .teardown.single        = timers_dead_cpu,
1567         },
1568         /* Kicks the plugged cpu into life */
1569         [CPUHP_BRINGUP_CPU] = {
1570                 .name                   = "cpu:bringup",
1571                 .startup.single         = bringup_cpu,
1572                 .teardown.single        = finish_cpu,
1573                 .cant_stop              = true,
1574         },
1575         /* Final state before CPU kills itself */
1576         [CPUHP_AP_IDLE_DEAD] = {
1577                 .name                   = "idle:dead",
1578         },
1579         /*
1580          * Last state before CPU enters the idle loop to die. Transient state
1581          * for synchronization.
1582          */
1583         [CPUHP_AP_OFFLINE] = {
1584                 .name                   = "ap:offline",
1585                 .cant_stop              = true,
1586         },
1587         /* First state is scheduler control. Interrupts are disabled */
1588         [CPUHP_AP_SCHED_STARTING] = {
1589                 .name                   = "sched:starting",
1590                 .startup.single         = sched_cpu_starting,
1591                 .teardown.single        = sched_cpu_dying,
1592         },
1593         [CPUHP_AP_RCUTREE_DYING] = {
1594                 .name                   = "RCU/tree:dying",
1595                 .startup.single         = NULL,
1596                 .teardown.single        = rcutree_dying_cpu,
1597         },
1598         [CPUHP_AP_SMPCFD_DYING] = {
1599                 .name                   = "smpcfd:dying",
1600                 .startup.single         = NULL,
1601                 .teardown.single        = smpcfd_dying_cpu,
1602         },
1603         /* Entry state on starting. Interrupts enabled from here on. Transient
1604          * state for synchronsization */
1605         [CPUHP_AP_ONLINE] = {
1606                 .name                   = "ap:online",
1607         },
1608         /*
1609          * Handled on controll processor until the plugged processor manages
1610          * this itself.
1611          */
1612         [CPUHP_TEARDOWN_CPU] = {
1613                 .name                   = "cpu:teardown",
1614                 .startup.single         = NULL,
1615                 .teardown.single        = takedown_cpu,
1616                 .cant_stop              = true,
1617         },
1618         /* Handle smpboot threads park/unpark */
1619         [CPUHP_AP_SMPBOOT_THREADS] = {
1620                 .name                   = "smpboot/threads:online",
1621                 .startup.single         = smpboot_unpark_threads,
1622                 .teardown.single        = smpboot_park_threads,
1623         },
1624         [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1625                 .name                   = "irq/affinity:online",
1626                 .startup.single         = irq_affinity_online_cpu,
1627                 .teardown.single        = NULL,
1628         },
1629         [CPUHP_AP_PERF_ONLINE] = {
1630                 .name                   = "perf:online",
1631                 .startup.single         = perf_event_init_cpu,
1632                 .teardown.single        = perf_event_exit_cpu,
1633         },
1634         [CPUHP_AP_WATCHDOG_ONLINE] = {
1635                 .name                   = "lockup_detector:online",
1636                 .startup.single         = lockup_detector_online_cpu,
1637                 .teardown.single        = lockup_detector_offline_cpu,
1638         },
1639         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1640                 .name                   = "workqueue:online",
1641                 .startup.single         = workqueue_online_cpu,
1642                 .teardown.single        = workqueue_offline_cpu,
1643         },
1644         [CPUHP_AP_RCUTREE_ONLINE] = {
1645                 .name                   = "RCU/tree:online",
1646                 .startup.single         = rcutree_online_cpu,
1647                 .teardown.single        = rcutree_offline_cpu,
1648         },
1649 #endif
1650         /*
1651          * The dynamically registered state space is here
1652          */
1653
1654 #ifdef CONFIG_SMP
1655         /* Last state is scheduler control setting the cpu active */
1656         [CPUHP_AP_ACTIVE] = {
1657                 .name                   = "sched:active",
1658                 .startup.single         = sched_cpu_activate,
1659                 .teardown.single        = sched_cpu_deactivate,
1660         },
1661 #endif
1662
1663         /* CPU is fully up and running. */
1664         [CPUHP_ONLINE] = {
1665                 .name                   = "online",
1666                 .startup.single         = NULL,
1667                 .teardown.single        = NULL,
1668         },
1669 };
1670
1671 /* Sanity check for callbacks */
1672 static int cpuhp_cb_check(enum cpuhp_state state)
1673 {
1674         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1675                 return -EINVAL;
1676         return 0;
1677 }
1678
1679 /*
1680  * Returns a free for dynamic slot assignment of the Online state. The states
1681  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1682  * by having no name assigned.
1683  */
1684 static int cpuhp_reserve_state(enum cpuhp_state state)
1685 {
1686         enum cpuhp_state i, end;
1687         struct cpuhp_step *step;
1688
1689         switch (state) {
1690         case CPUHP_AP_ONLINE_DYN:
1691                 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1692                 end = CPUHP_AP_ONLINE_DYN_END;
1693                 break;
1694         case CPUHP_BP_PREPARE_DYN:
1695                 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1696                 end = CPUHP_BP_PREPARE_DYN_END;
1697                 break;
1698         default:
1699                 return -EINVAL;
1700         }
1701
1702         for (i = state; i <= end; i++, step++) {
1703                 if (!step->name)
1704                         return i;
1705         }
1706         WARN(1, "No more dynamic states available for CPU hotplug\n");
1707         return -ENOSPC;
1708 }
1709
1710 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1711                                  int (*startup)(unsigned int cpu),
1712                                  int (*teardown)(unsigned int cpu),
1713                                  bool multi_instance)
1714 {
1715         /* (Un)Install the callbacks for further cpu hotplug operations */
1716         struct cpuhp_step *sp;
1717         int ret = 0;
1718
1719         /*
1720          * If name is NULL, then the state gets removed.
1721          *
1722          * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1723          * the first allocation from these dynamic ranges, so the removal
1724          * would trigger a new allocation and clear the wrong (already
1725          * empty) state, leaving the callbacks of the to be cleared state
1726          * dangling, which causes wreckage on the next hotplug operation.
1727          */
1728         if (name && (state == CPUHP_AP_ONLINE_DYN ||
1729                      state == CPUHP_BP_PREPARE_DYN)) {
1730                 ret = cpuhp_reserve_state(state);
1731                 if (ret < 0)
1732                         return ret;
1733                 state = ret;
1734         }
1735         sp = cpuhp_get_step(state);
1736         if (name && sp->name)
1737                 return -EBUSY;
1738
1739         sp->startup.single = startup;
1740         sp->teardown.single = teardown;
1741         sp->name = name;
1742         sp->multi_instance = multi_instance;
1743         INIT_HLIST_HEAD(&sp->list);
1744         return ret;
1745 }
1746
1747 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1748 {
1749         return cpuhp_get_step(state)->teardown.single;
1750 }
1751
1752 /*
1753  * Call the startup/teardown function for a step either on the AP or
1754  * on the current CPU.
1755  */
1756 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1757                             struct hlist_node *node)
1758 {
1759         struct cpuhp_step *sp = cpuhp_get_step(state);
1760         int ret;
1761
1762         /*
1763          * If there's nothing to do, we done.
1764          * Relies on the union for multi_instance.
1765          */
1766         if ((bringup && !sp->startup.single) ||
1767             (!bringup && !sp->teardown.single))
1768                 return 0;
1769         /*
1770          * The non AP bound callbacks can fail on bringup. On teardown
1771          * e.g. module removal we crash for now.
1772          */
1773 #ifdef CONFIG_SMP
1774         if (cpuhp_is_ap_state(state))
1775                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1776         else
1777                 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1778 #else
1779         ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1780 #endif
1781         BUG_ON(ret && !bringup);
1782         return ret;
1783 }
1784
1785 /*
1786  * Called from __cpuhp_setup_state on a recoverable failure.
1787  *
1788  * Note: The teardown callbacks for rollback are not allowed to fail!
1789  */
1790 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1791                                    struct hlist_node *node)
1792 {
1793         int cpu;
1794
1795         /* Roll back the already executed steps on the other cpus */
1796         for_each_present_cpu(cpu) {
1797                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1798                 int cpustate = st->state;
1799
1800                 if (cpu >= failedcpu)
1801                         break;
1802
1803                 /* Did we invoke the startup call on that cpu ? */
1804                 if (cpustate >= state)
1805                         cpuhp_issue_call(cpu, state, false, node);
1806         }
1807 }
1808
1809 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1810                                           struct hlist_node *node,
1811                                           bool invoke)
1812 {
1813         struct cpuhp_step *sp;
1814         int cpu;
1815         int ret;
1816
1817         lockdep_assert_cpus_held();
1818
1819         sp = cpuhp_get_step(state);
1820         if (sp->multi_instance == false)
1821                 return -EINVAL;
1822
1823         mutex_lock(&cpuhp_state_mutex);
1824
1825         if (!invoke || !sp->startup.multi)
1826                 goto add_node;
1827
1828         /*
1829          * Try to call the startup callback for each present cpu
1830          * depending on the hotplug state of the cpu.
1831          */
1832         for_each_present_cpu(cpu) {
1833                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1834                 int cpustate = st->state;
1835
1836                 if (cpustate < state)
1837                         continue;
1838
1839                 ret = cpuhp_issue_call(cpu, state, true, node);
1840                 if (ret) {
1841                         if (sp->teardown.multi)
1842                                 cpuhp_rollback_install(cpu, state, node);
1843                         goto unlock;
1844                 }
1845         }
1846 add_node:
1847         ret = 0;
1848         hlist_add_head(node, &sp->list);
1849 unlock:
1850         mutex_unlock(&cpuhp_state_mutex);
1851         return ret;
1852 }
1853
1854 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1855                                bool invoke)
1856 {
1857         int ret;
1858
1859         cpus_read_lock();
1860         ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1861         cpus_read_unlock();
1862         return ret;
1863 }
1864 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1865
1866 /**
1867  * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1868  * @state:              The state to setup
1869  * @invoke:             If true, the startup function is invoked for cpus where
1870  *                      cpu state >= @state
1871  * @startup:            startup callback function
1872  * @teardown:           teardown callback function
1873  * @multi_instance:     State is set up for multiple instances which get
1874  *                      added afterwards.
1875  *
1876  * The caller needs to hold cpus read locked while calling this function.
1877  * Returns:
1878  *   On success:
1879  *      Positive state number if @state is CPUHP_AP_ONLINE_DYN
1880  *      0 for all other states
1881  *   On failure: proper (negative) error code
1882  */
1883 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1884                                    const char *name, bool invoke,
1885                                    int (*startup)(unsigned int cpu),
1886                                    int (*teardown)(unsigned int cpu),
1887                                    bool multi_instance)
1888 {
1889         int cpu, ret = 0;
1890         bool dynstate;
1891
1892         lockdep_assert_cpus_held();
1893
1894         if (cpuhp_cb_check(state) || !name)
1895                 return -EINVAL;
1896
1897         mutex_lock(&cpuhp_state_mutex);
1898
1899         ret = cpuhp_store_callbacks(state, name, startup, teardown,
1900                                     multi_instance);
1901
1902         dynstate = state == CPUHP_AP_ONLINE_DYN;
1903         if (ret > 0 && dynstate) {
1904                 state = ret;
1905                 ret = 0;
1906         }
1907
1908         if (ret || !invoke || !startup)
1909                 goto out;
1910
1911         /*
1912          * Try to call the startup callback for each present cpu
1913          * depending on the hotplug state of the cpu.
1914          */
1915         for_each_present_cpu(cpu) {
1916                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1917                 int cpustate = st->state;
1918
1919                 if (cpustate < state)
1920                         continue;
1921
1922                 ret = cpuhp_issue_call(cpu, state, true, NULL);
1923                 if (ret) {
1924                         if (teardown)
1925                                 cpuhp_rollback_install(cpu, state, NULL);
1926                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1927                         goto out;
1928                 }
1929         }
1930 out:
1931         mutex_unlock(&cpuhp_state_mutex);
1932         /*
1933          * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1934          * dynamically allocated state in case of success.
1935          */
1936         if (!ret && dynstate)
1937                 return state;
1938         return ret;
1939 }
1940 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1941
1942 int __cpuhp_setup_state(enum cpuhp_state state,
1943                         const char *name, bool invoke,
1944                         int (*startup)(unsigned int cpu),
1945                         int (*teardown)(unsigned int cpu),
1946                         bool multi_instance)
1947 {
1948         int ret;
1949
1950         cpus_read_lock();
1951         ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
1952                                              teardown, multi_instance);
1953         cpus_read_unlock();
1954         return ret;
1955 }
1956 EXPORT_SYMBOL(__cpuhp_setup_state);
1957
1958 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1959                                   struct hlist_node *node, bool invoke)
1960 {
1961         struct cpuhp_step *sp = cpuhp_get_step(state);
1962         int cpu;
1963
1964         BUG_ON(cpuhp_cb_check(state));
1965
1966         if (!sp->multi_instance)
1967                 return -EINVAL;
1968
1969         cpus_read_lock();
1970         mutex_lock(&cpuhp_state_mutex);
1971
1972         if (!invoke || !cpuhp_get_teardown_cb(state))
1973                 goto remove;
1974         /*
1975          * Call the teardown callback for each present cpu depending
1976          * on the hotplug state of the cpu. This function is not
1977          * allowed to fail currently!
1978          */
1979         for_each_present_cpu(cpu) {
1980                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1981                 int cpustate = st->state;
1982
1983                 if (cpustate >= state)
1984                         cpuhp_issue_call(cpu, state, false, node);
1985         }
1986
1987 remove:
1988         hlist_del(node);
1989         mutex_unlock(&cpuhp_state_mutex);
1990         cpus_read_unlock();
1991
1992         return 0;
1993 }
1994 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1995
1996 /**
1997  * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1998  * @state:      The state to remove
1999  * @invoke:     If true, the teardown function is invoked for cpus where
2000  *              cpu state >= @state
2001  *
2002  * The caller needs to hold cpus read locked while calling this function.
2003  * The teardown callback is currently not allowed to fail. Think
2004  * about module removal!
2005  */
2006 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2007 {
2008         struct cpuhp_step *sp = cpuhp_get_step(state);
2009         int cpu;
2010
2011         BUG_ON(cpuhp_cb_check(state));
2012
2013         lockdep_assert_cpus_held();
2014
2015         mutex_lock(&cpuhp_state_mutex);
2016         if (sp->multi_instance) {
2017                 WARN(!hlist_empty(&sp->list),
2018                      "Error: Removing state %d which has instances left.\n",
2019                      state);
2020                 goto remove;
2021         }
2022
2023         if (!invoke || !cpuhp_get_teardown_cb(state))
2024                 goto remove;
2025
2026         /*
2027          * Call the teardown callback for each present cpu depending
2028          * on the hotplug state of the cpu. This function is not
2029          * allowed to fail currently!
2030          */
2031         for_each_present_cpu(cpu) {
2032                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2033                 int cpustate = st->state;
2034
2035                 if (cpustate >= state)
2036                         cpuhp_issue_call(cpu, state, false, NULL);
2037         }
2038 remove:
2039         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2040         mutex_unlock(&cpuhp_state_mutex);
2041 }
2042 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2043
2044 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2045 {
2046         cpus_read_lock();
2047         __cpuhp_remove_state_cpuslocked(state, invoke);
2048         cpus_read_unlock();
2049 }
2050 EXPORT_SYMBOL(__cpuhp_remove_state);
2051
2052 #ifdef CONFIG_HOTPLUG_SMT
2053 static void cpuhp_offline_cpu_device(unsigned int cpu)
2054 {
2055         struct device *dev = get_cpu_device(cpu);
2056
2057         dev->offline = true;
2058         /* Tell user space about the state change */
2059         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2060 }
2061
2062 static void cpuhp_online_cpu_device(unsigned int cpu)
2063 {
2064         struct device *dev = get_cpu_device(cpu);
2065
2066         dev->offline = false;
2067         /* Tell user space about the state change */
2068         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2069 }
2070
2071 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2072 {
2073         int cpu, ret = 0;
2074
2075         cpu_maps_update_begin();
2076         for_each_online_cpu(cpu) {
2077                 if (topology_is_primary_thread(cpu))
2078                         continue;
2079                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2080                 if (ret)
2081                         break;
2082                 /*
2083                  * As this needs to hold the cpu maps lock it's impossible
2084                  * to call device_offline() because that ends up calling
2085                  * cpu_down() which takes cpu maps lock. cpu maps lock
2086                  * needs to be held as this might race against in kernel
2087                  * abusers of the hotplug machinery (thermal management).
2088                  *
2089                  * So nothing would update device:offline state. That would
2090                  * leave the sysfs entry stale and prevent onlining after
2091                  * smt control has been changed to 'off' again. This is
2092                  * called under the sysfs hotplug lock, so it is properly
2093                  * serialized against the regular offline usage.
2094                  */
2095                 cpuhp_offline_cpu_device(cpu);
2096         }
2097         if (!ret)
2098                 cpu_smt_control = ctrlval;
2099         cpu_maps_update_done();
2100         return ret;
2101 }
2102
2103 int cpuhp_smt_enable(void)
2104 {
2105         int cpu, ret = 0;
2106
2107         cpu_maps_update_begin();
2108         cpu_smt_control = CPU_SMT_ENABLED;
2109         for_each_present_cpu(cpu) {
2110                 /* Skip online CPUs and CPUs on offline nodes */
2111                 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2112                         continue;
2113                 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2114                 if (ret)
2115                         break;
2116                 /* See comment in cpuhp_smt_disable() */
2117                 cpuhp_online_cpu_device(cpu);
2118         }
2119         cpu_maps_update_done();
2120         return ret;
2121 }
2122 #endif
2123
2124 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2125 static ssize_t show_cpuhp_state(struct device *dev,
2126                                 struct device_attribute *attr, char *buf)
2127 {
2128         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2129
2130         return sprintf(buf, "%d\n", st->state);
2131 }
2132 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
2133
2134 static ssize_t write_cpuhp_target(struct device *dev,
2135                                   struct device_attribute *attr,
2136                                   const char *buf, size_t count)
2137 {
2138         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2139         struct cpuhp_step *sp;
2140         int target, ret;
2141
2142         ret = kstrtoint(buf, 10, &target);
2143         if (ret)
2144                 return ret;
2145
2146 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2147         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2148                 return -EINVAL;
2149 #else
2150         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2151                 return -EINVAL;
2152 #endif
2153
2154         ret = lock_device_hotplug_sysfs();
2155         if (ret)
2156                 return ret;
2157
2158         mutex_lock(&cpuhp_state_mutex);
2159         sp = cpuhp_get_step(target);
2160         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2161         mutex_unlock(&cpuhp_state_mutex);
2162         if (ret)
2163                 goto out;
2164
2165         if (st->state < target)
2166                 ret = cpu_up(dev->id, target);
2167         else
2168                 ret = cpu_down(dev->id, target);
2169 out:
2170         unlock_device_hotplug();
2171         return ret ? ret : count;
2172 }
2173
2174 static ssize_t show_cpuhp_target(struct device *dev,
2175                                  struct device_attribute *attr, char *buf)
2176 {
2177         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2178
2179         return sprintf(buf, "%d\n", st->target);
2180 }
2181 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2182
2183
2184 static ssize_t write_cpuhp_fail(struct device *dev,
2185                                 struct device_attribute *attr,
2186                                 const char *buf, size_t count)
2187 {
2188         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2189         struct cpuhp_step *sp;
2190         int fail, ret;
2191
2192         ret = kstrtoint(buf, 10, &fail);
2193         if (ret)
2194                 return ret;
2195
2196         if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2197                 return -EINVAL;
2198
2199         /*
2200          * Cannot fail STARTING/DYING callbacks.
2201          */
2202         if (cpuhp_is_atomic_state(fail))
2203                 return -EINVAL;
2204
2205         /*
2206          * Cannot fail anything that doesn't have callbacks.
2207          */
2208         mutex_lock(&cpuhp_state_mutex);
2209         sp = cpuhp_get_step(fail);
2210         if (!sp->startup.single && !sp->teardown.single)
2211                 ret = -EINVAL;
2212         mutex_unlock(&cpuhp_state_mutex);
2213         if (ret)
2214                 return ret;
2215
2216         st->fail = fail;
2217
2218         return count;
2219 }
2220
2221 static ssize_t show_cpuhp_fail(struct device *dev,
2222                                struct device_attribute *attr, char *buf)
2223 {
2224         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2225
2226         return sprintf(buf, "%d\n", st->fail);
2227 }
2228
2229 static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2230
2231 static struct attribute *cpuhp_cpu_attrs[] = {
2232         &dev_attr_state.attr,
2233         &dev_attr_target.attr,
2234         &dev_attr_fail.attr,
2235         NULL
2236 };
2237
2238 static const struct attribute_group cpuhp_cpu_attr_group = {
2239         .attrs = cpuhp_cpu_attrs,
2240         .name = "hotplug",
2241         NULL
2242 };
2243
2244 static ssize_t show_cpuhp_states(struct device *dev,
2245                                  struct device_attribute *attr, char *buf)
2246 {
2247         ssize_t cur, res = 0;
2248         int i;
2249
2250         mutex_lock(&cpuhp_state_mutex);
2251         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2252                 struct cpuhp_step *sp = cpuhp_get_step(i);
2253
2254                 if (sp->name) {
2255                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2256                         buf += cur;
2257                         res += cur;
2258                 }
2259         }
2260         mutex_unlock(&cpuhp_state_mutex);
2261         return res;
2262 }
2263 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2264
2265 static struct attribute *cpuhp_cpu_root_attrs[] = {
2266         &dev_attr_states.attr,
2267         NULL
2268 };
2269
2270 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2271         .attrs = cpuhp_cpu_root_attrs,
2272         .name = "hotplug",
2273         NULL
2274 };
2275
2276 #ifdef CONFIG_HOTPLUG_SMT
2277
2278 static ssize_t
2279 __store_smt_control(struct device *dev, struct device_attribute *attr,
2280                     const char *buf, size_t count)
2281 {
2282         int ctrlval, ret;
2283
2284         if (sysfs_streq(buf, "on"))
2285                 ctrlval = CPU_SMT_ENABLED;
2286         else if (sysfs_streq(buf, "off"))
2287                 ctrlval = CPU_SMT_DISABLED;
2288         else if (sysfs_streq(buf, "forceoff"))
2289                 ctrlval = CPU_SMT_FORCE_DISABLED;
2290         else
2291                 return -EINVAL;
2292
2293         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2294                 return -EPERM;
2295
2296         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2297                 return -ENODEV;
2298
2299         ret = lock_device_hotplug_sysfs();
2300         if (ret)
2301                 return ret;
2302
2303         if (ctrlval != cpu_smt_control) {
2304                 switch (ctrlval) {
2305                 case CPU_SMT_ENABLED:
2306                         ret = cpuhp_smt_enable();
2307                         break;
2308                 case CPU_SMT_DISABLED:
2309                 case CPU_SMT_FORCE_DISABLED:
2310                         ret = cpuhp_smt_disable(ctrlval);
2311                         break;
2312                 }
2313         }
2314
2315         unlock_device_hotplug();
2316         return ret ? ret : count;
2317 }
2318
2319 #else /* !CONFIG_HOTPLUG_SMT */
2320 static ssize_t
2321 __store_smt_control(struct device *dev, struct device_attribute *attr,
2322                     const char *buf, size_t count)
2323 {
2324         return -ENODEV;
2325 }
2326 #endif /* CONFIG_HOTPLUG_SMT */
2327
2328 static const char *smt_states[] = {
2329         [CPU_SMT_ENABLED]               = "on",
2330         [CPU_SMT_DISABLED]              = "off",
2331         [CPU_SMT_FORCE_DISABLED]        = "forceoff",
2332         [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
2333         [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
2334 };
2335
2336 static ssize_t
2337 show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2338 {
2339         const char *state = smt_states[cpu_smt_control];
2340
2341         return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2342 }
2343
2344 static ssize_t
2345 store_smt_control(struct device *dev, struct device_attribute *attr,
2346                   const char *buf, size_t count)
2347 {
2348         return __store_smt_control(dev, attr, buf, count);
2349 }
2350 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2351
2352 static ssize_t
2353 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2354 {
2355         return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2356 }
2357 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2358
2359 static struct attribute *cpuhp_smt_attrs[] = {
2360         &dev_attr_control.attr,
2361         &dev_attr_active.attr,
2362         NULL
2363 };
2364
2365 static const struct attribute_group cpuhp_smt_attr_group = {
2366         .attrs = cpuhp_smt_attrs,
2367         .name = "smt",
2368         NULL
2369 };
2370
2371 static int __init cpu_smt_sysfs_init(void)
2372 {
2373         return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2374                                   &cpuhp_smt_attr_group);
2375 }
2376
2377 static int __init cpuhp_sysfs_init(void)
2378 {
2379         int cpu, ret;
2380
2381         ret = cpu_smt_sysfs_init();
2382         if (ret)
2383                 return ret;
2384
2385         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2386                                  &cpuhp_cpu_root_attr_group);
2387         if (ret)
2388                 return ret;
2389
2390         for_each_possible_cpu(cpu) {
2391                 struct device *dev = get_cpu_device(cpu);
2392
2393                 if (!dev)
2394                         continue;
2395                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2396                 if (ret)
2397                         return ret;
2398         }
2399         return 0;
2400 }
2401 device_initcall(cpuhp_sysfs_init);
2402 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2403
2404 /*
2405  * cpu_bit_bitmap[] is a special, "compressed" data structure that
2406  * represents all NR_CPUS bits binary values of 1<<nr.
2407  *
2408  * It is used by cpumask_of() to get a constant address to a CPU
2409  * mask value that has a single bit set only.
2410  */
2411
2412 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2413 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2414 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2415 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2416 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2417
2418 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2419
2420         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2421         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2422 #if BITS_PER_LONG > 32
2423         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2424         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2425 #endif
2426 };
2427 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2428
2429 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2430 EXPORT_SYMBOL(cpu_all_bits);
2431
2432 #ifdef CONFIG_INIT_ALL_POSSIBLE
2433 struct cpumask __cpu_possible_mask __read_mostly
2434         = {CPU_BITS_ALL};
2435 #else
2436 struct cpumask __cpu_possible_mask __read_mostly;
2437 #endif
2438 EXPORT_SYMBOL(__cpu_possible_mask);
2439
2440 struct cpumask __cpu_online_mask __read_mostly;
2441 EXPORT_SYMBOL(__cpu_online_mask);
2442
2443 struct cpumask __cpu_present_mask __read_mostly;
2444 EXPORT_SYMBOL(__cpu_present_mask);
2445
2446 struct cpumask __cpu_active_mask __read_mostly;
2447 EXPORT_SYMBOL(__cpu_active_mask);
2448
2449 atomic_t __num_online_cpus __read_mostly;
2450 EXPORT_SYMBOL(__num_online_cpus);
2451
2452 void init_cpu_present(const struct cpumask *src)
2453 {
2454         cpumask_copy(&__cpu_present_mask, src);
2455 }
2456
2457 void init_cpu_possible(const struct cpumask *src)
2458 {
2459         cpumask_copy(&__cpu_possible_mask, src);
2460 }
2461
2462 void init_cpu_online(const struct cpumask *src)
2463 {
2464         cpumask_copy(&__cpu_online_mask, src);
2465 }
2466
2467 void set_cpu_online(unsigned int cpu, bool online)
2468 {
2469         /*
2470          * atomic_inc/dec() is required to handle the horrid abuse of this
2471          * function by the reboot and kexec code which invoke it from
2472          * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2473          * regular CPU hotplug is properly serialized.
2474          *
2475          * Note, that the fact that __num_online_cpus is of type atomic_t
2476          * does not protect readers which are not serialized against
2477          * concurrent hotplug operations.
2478          */
2479         if (online) {
2480                 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2481                         atomic_inc(&__num_online_cpus);
2482         } else {
2483                 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2484                         atomic_dec(&__num_online_cpus);
2485         }
2486 }
2487
2488 /*
2489  * Activate the first processor.
2490  */
2491 void __init boot_cpu_init(void)
2492 {
2493         int cpu = smp_processor_id();
2494
2495         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2496         set_cpu_online(cpu, true);
2497         set_cpu_active(cpu, true);
2498         set_cpu_present(cpu, true);
2499         set_cpu_possible(cpu, true);
2500
2501 #ifdef CONFIG_SMP
2502         __boot_cpu_id = cpu;
2503 #endif
2504 }
2505
2506 /*
2507  * Must be called _AFTER_ setting up the per_cpu areas
2508  */
2509 void __init boot_cpu_hotplug_init(void)
2510 {
2511 #ifdef CONFIG_SMP
2512         cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2513 #endif
2514         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2515 }
2516
2517 /*
2518  * These are used for a global "mitigations=" cmdline option for toggling
2519  * optional CPU mitigations.
2520  */
2521 enum cpu_mitigations {
2522         CPU_MITIGATIONS_OFF,
2523         CPU_MITIGATIONS_AUTO,
2524         CPU_MITIGATIONS_AUTO_NOSMT,
2525 };
2526
2527 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2528         CPU_MITIGATIONS_AUTO;
2529
2530 static int __init mitigations_parse_cmdline(char *arg)
2531 {
2532         if (!strcmp(arg, "off"))
2533                 cpu_mitigations = CPU_MITIGATIONS_OFF;
2534         else if (!strcmp(arg, "auto"))
2535                 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2536         else if (!strcmp(arg, "auto,nosmt"))
2537                 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2538         else
2539                 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2540                         arg);
2541
2542         return 0;
2543 }
2544 early_param("mitigations", mitigations_parse_cmdline);
2545
2546 /* mitigations=off */
2547 bool cpu_mitigations_off(void)
2548 {
2549         return cpu_mitigations == CPU_MITIGATIONS_OFF;
2550 }
2551 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2552
2553 /* mitigations=auto,nosmt */
2554 bool cpu_mitigations_auto_nosmt(void)
2555 {
2556         return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2557 }
2558 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);