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