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