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