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