linux/kernel/cpu.c
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   1/* CPU control.
   2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
   3 *
   4 * This code is licenced under the GPL.
   5 */
   6#include <linux/sched/mm.h>
   7#include <linux/proc_fs.h>
   8#include <linux/smp.h>
   9#include <linux/init.h>
  10#include <linux/notifier.h>
  11#include <linux/sched/signal.h>
  12#include <linux/sched/hotplug.h>
  13#include <linux/sched/isolation.h>
  14#include <linux/sched/task.h>
  15#include <linux/sched/smt.h>
  16#include <linux/unistd.h>
  17#include <linux/cpu.h>
  18#include <linux/oom.h>
  19#include <linux/rcupdate.h>
  20#include <linux/export.h>
  21#include <linux/bug.h>
  22#include <linux/kthread.h>
  23#include <linux/stop_machine.h>
  24#include <linux/mutex.h>
  25#include <linux/gfp.h>
  26#include <linux/suspend.h>
  27#include <linux/lockdep.h>
  28#include <linux/tick.h>
  29#include <linux/irq.h>
  30#include <linux/nmi.h>
  31#include <linux/smpboot.h>
  32#include <linux/relay.h>
  33#include <linux/slab.h>
  34#include <linux/percpu-rwsem.h>
  35#include <linux/cpuset.h>
  36
  37#include <trace/events/power.h>
  38#define CREATE_TRACE_POINTS
  39#include <trace/events/cpuhp.h>
  40
  41#include "smpboot.h"
  42
  43/**
  44 * cpuhp_cpu_state - Per cpu hotplug state storage
  45 * @state:      The current cpu state
  46 * @target:     The target state
  47 * @thread:     Pointer to the hotplug thread
  48 * @should_run: Thread should execute
  49 * @rollback:   Perform a rollback
  50 * @single:     Single callback invocation
  51 * @bringup:    Single callback bringup or teardown selector
  52 * @cb_state:   The state for a single callback (install/uninstall)
  53 * @result:     Result of the operation
  54 * @done_up:    Signal completion to the issuer of the task for cpu-up
  55 * @done_down:  Signal completion to the issuer of the task for cpu-down
  56 */
  57struct cpuhp_cpu_state {
  58        enum cpuhp_state        state;
  59        enum cpuhp_state        target;
  60        enum cpuhp_state        fail;
  61#ifdef CONFIG_SMP
  62        struct task_struct      *thread;
  63        bool                    should_run;
  64        bool                    rollback;
  65        bool                    single;
  66        bool                    bringup;
  67        int                     cpu;
  68        struct hlist_node       *node;
  69        struct hlist_node       *last;
  70        enum cpuhp_state        cb_state;
  71        int                     result;
  72        struct completion       done_up;
  73        struct completion       done_down;
  74#endif
  75};
  76
  77static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
  78        .fail = CPUHP_INVALID,
  79};
  80
  81#ifdef CONFIG_SMP
  82cpumask_t cpus_booted_once_mask;
  83#endif
  84
  85#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
  86static struct lockdep_map cpuhp_state_up_map =
  87        STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
  88static struct lockdep_map cpuhp_state_down_map =
  89        STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
  90
  91
  92static inline void cpuhp_lock_acquire(bool bringup)
  93{
  94        lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
  95}
  96
  97static inline void cpuhp_lock_release(bool bringup)
  98{
  99        lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
 100}
 101#else
 102
 103static inline void cpuhp_lock_acquire(bool bringup) { }
 104static inline void cpuhp_lock_release(bool bringup) { }
 105
 106#endif
 107
 108/**
 109 * cpuhp_step - Hotplug state machine step
 110 * @name:       Name of the step
 111 * @startup:    Startup function of the step
 112 * @teardown:   Teardown function of the step
 113 * @cant_stop:  Bringup/teardown can't be stopped at this step
 114 */
 115struct cpuhp_step {
 116        const char              *name;
 117        union {
 118                int             (*single)(unsigned int cpu);
 119                int             (*multi)(unsigned int cpu,
 120                                         struct hlist_node *node);
 121        } startup;
 122        union {
 123                int             (*single)(unsigned int cpu);
 124                int             (*multi)(unsigned int cpu,
 125                                         struct hlist_node *node);
 126        } teardown;
 127        struct hlist_head       list;
 128        bool                    cant_stop;
 129        bool                    multi_instance;
 130};
 131
 132static DEFINE_MUTEX(cpuhp_state_mutex);
 133static struct cpuhp_step cpuhp_hp_states[];
 134
 135static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
 136{
 137        return cpuhp_hp_states + state;
 138}
 139
 140static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
 141{
 142        return bringup ? !step->startup.single : !step->teardown.single;
 143}
 144
 145/**
 146 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
 147 * @cpu:        The cpu for which the callback should be invoked
 148 * @state:      The state to do callbacks for
 149 * @bringup:    True if the bringup callback should be invoked
 150 * @node:       For multi-instance, do a single entry callback for install/remove
 151 * @lastp:      For multi-instance rollback, remember how far we got
 152 *
 153 * Called from cpu hotplug and from the state register machinery.
 154 */
 155static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 156                                 bool bringup, struct hlist_node *node,
 157                                 struct hlist_node **lastp)
 158{
 159        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 160        struct cpuhp_step *step = cpuhp_get_step(state);
 161        int (*cbm)(unsigned int cpu, struct hlist_node *node);
 162        int (*cb)(unsigned int cpu);
 163        int ret, cnt;
 164
 165        if (st->fail == state) {
 166                st->fail = CPUHP_INVALID;
 167                return -EAGAIN;
 168        }
 169
 170        if (cpuhp_step_empty(bringup, step)) {
 171                WARN_ON_ONCE(1);
 172                return 0;
 173        }
 174
 175        if (!step->multi_instance) {
 176                WARN_ON_ONCE(lastp && *lastp);
 177                cb = bringup ? step->startup.single : step->teardown.single;
 178
 179                trace_cpuhp_enter(cpu, st->target, state, cb);
 180                ret = cb(cpu);
 181                trace_cpuhp_exit(cpu, st->state, state, ret);
 182                return ret;
 183        }
 184        cbm = bringup ? step->startup.multi : step->teardown.multi;
 185
 186        /* Single invocation for instance add/remove */
 187        if (node) {
 188                WARN_ON_ONCE(lastp && *lastp);
 189                trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 190                ret = cbm(cpu, node);
 191                trace_cpuhp_exit(cpu, st->state, state, ret);
 192                return ret;
 193        }
 194
 195        /* State transition. Invoke on all instances */
 196        cnt = 0;
 197        hlist_for_each(node, &step->list) {
 198                if (lastp && node == *lastp)
 199                        break;
 200
 201                trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 202                ret = cbm(cpu, node);
 203                trace_cpuhp_exit(cpu, st->state, state, ret);
 204                if (ret) {
 205                        if (!lastp)
 206                                goto err;
 207
 208                        *lastp = node;
 209                        return ret;
 210                }
 211                cnt++;
 212        }
 213        if (lastp)
 214                *lastp = NULL;
 215        return 0;
 216err:
 217        /* Rollback the instances if one failed */
 218        cbm = !bringup ? step->startup.multi : step->teardown.multi;
 219        if (!cbm)
 220                return ret;
 221
 222        hlist_for_each(node, &step->list) {
 223                if (!cnt--)
 224                        break;
 225
 226                trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 227                ret = cbm(cpu, node);
 228                trace_cpuhp_exit(cpu, st->state, state, ret);
 229                /*
 230                 * Rollback must not fail,
 231                 */
 232                WARN_ON_ONCE(ret);
 233        }
 234        return ret;
 235}
 236
 237#ifdef CONFIG_SMP
 238static bool cpuhp_is_ap_state(enum cpuhp_state state)
 239{
 240        /*
 241         * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
 242         * purposes as that state is handled explicitly in cpu_down.
 243         */
 244        return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
 245}
 246
 247static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
 248{
 249        struct completion *done = bringup ? &st->done_up : &st->done_down;
 250        wait_for_completion(done);
 251}
 252
 253static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
 254{
 255        struct completion *done = bringup ? &st->done_up : &st->done_down;
 256        complete(done);
 257}
 258
 259/*
 260 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
 261 */
 262static bool cpuhp_is_atomic_state(enum cpuhp_state state)
 263{
 264        return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
 265}
 266
 267/* Serializes the updates to cpu_online_mask, cpu_present_mask */
 268static DEFINE_MUTEX(cpu_add_remove_lock);
 269bool cpuhp_tasks_frozen;
 270EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 271
 272/*
 273 * The following two APIs (cpu_maps_update_begin/done) must be used when
 274 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 275 */
 276void cpu_maps_update_begin(void)
 277{
 278        mutex_lock(&cpu_add_remove_lock);
 279}
 280
 281void cpu_maps_update_done(void)
 282{
 283        mutex_unlock(&cpu_add_remove_lock);
 284}
 285
 286/*
 287 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 288 * Should always be manipulated under cpu_add_remove_lock
 289 */
 290static int cpu_hotplug_disabled;
 291
 292#ifdef CONFIG_HOTPLUG_CPU
 293
 294DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
 295
 296void cpus_read_lock(void)
 297{
 298        percpu_down_read(&cpu_hotplug_lock);
 299}
 300EXPORT_SYMBOL_GPL(cpus_read_lock);
 301
 302int cpus_read_trylock(void)
 303{
 304        return percpu_down_read_trylock(&cpu_hotplug_lock);
 305}
 306EXPORT_SYMBOL_GPL(cpus_read_trylock);
 307
 308void cpus_read_unlock(void)
 309{
 310        percpu_up_read(&cpu_hotplug_lock);
 311}
 312EXPORT_SYMBOL_GPL(cpus_read_unlock);
 313
 314void cpus_write_lock(void)
 315{
 316        percpu_down_write(&cpu_hotplug_lock);
 317}
 318
 319void cpus_write_unlock(void)
 320{
 321        percpu_up_write(&cpu_hotplug_lock);
 322}
 323
 324void lockdep_assert_cpus_held(void)
 325{
 326        /*
 327         * We can't have hotplug operations before userspace starts running,
 328         * and some init codepaths will knowingly not take the hotplug lock.
 329         * This is all valid, so mute lockdep until it makes sense to report
 330         * unheld locks.
 331         */
 332        if (system_state < SYSTEM_RUNNING)
 333                return;
 334
 335        percpu_rwsem_assert_held(&cpu_hotplug_lock);
 336}
 337
 338#ifdef CONFIG_LOCKDEP
 339int lockdep_is_cpus_held(void)
 340{
 341        return percpu_rwsem_is_held(&cpu_hotplug_lock);
 342}
 343#endif
 344
 345static void lockdep_acquire_cpus_lock(void)
 346{
 347        rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
 348}
 349
 350static void lockdep_release_cpus_lock(void)
 351{
 352        rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
 353}
 354
 355/*
 356 * Wait for currently running CPU hotplug operations to complete (if any) and
 357 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 358 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 359 * hotplug path before performing hotplug operations. So acquiring that lock
 360 * guarantees mutual exclusion from any currently running hotplug operations.
 361 */
 362void cpu_hotplug_disable(void)
 363{
 364        cpu_maps_update_begin();
 365        cpu_hotplug_disabled++;
 366        cpu_maps_update_done();
 367}
 368EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 369
 370static void __cpu_hotplug_enable(void)
 371{
 372        if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
 373                return;
 374        cpu_hotplug_disabled--;
 375}
 376
 377void cpu_hotplug_enable(void)
 378{
 379        cpu_maps_update_begin();
 380        __cpu_hotplug_enable();
 381        cpu_maps_update_done();
 382}
 383EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 384
 385#else
 386
 387static void lockdep_acquire_cpus_lock(void)
 388{
 389}
 390
 391static void lockdep_release_cpus_lock(void)
 392{
 393}
 394
 395#endif  /* CONFIG_HOTPLUG_CPU */
 396
 397/*
 398 * Architectures that need SMT-specific errata handling during SMT hotplug
 399 * should override this.
 400 */
 401void __weak arch_smt_update(void) { }
 402
 403#ifdef CONFIG_HOTPLUG_SMT
 404enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
 405
 406void __init cpu_smt_disable(bool force)
 407{
 408        if (!cpu_smt_possible())
 409                return;
 410
 411        if (force) {
 412                pr_info("SMT: Force disabled\n");
 413                cpu_smt_control = CPU_SMT_FORCE_DISABLED;
 414        } else {
 415                pr_info("SMT: disabled\n");
 416                cpu_smt_control = CPU_SMT_DISABLED;
 417        }
 418}
 419
 420/*
 421 * The decision whether SMT is supported can only be done after the full
 422 * CPU identification. Called from architecture code.
 423 */
 424void __init cpu_smt_check_topology(void)
 425{
 426        if (!topology_smt_supported())
 427                cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 428}
 429
 430static int __init smt_cmdline_disable(char *str)
 431{
 432        cpu_smt_disable(str && !strcmp(str, "force"));
 433        return 0;
 434}
 435early_param("nosmt", smt_cmdline_disable);
 436
 437static inline bool cpu_smt_allowed(unsigned int cpu)
 438{
 439        if (cpu_smt_control == CPU_SMT_ENABLED)
 440                return true;
 441
 442        if (topology_is_primary_thread(cpu))
 443                return true;
 444
 445        /*
 446         * On x86 it's required to boot all logical CPUs at least once so
 447         * that the init code can get a chance to set CR4.MCE on each
 448         * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
 449         * core will shutdown the machine.
 450         */
 451        return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
 452}
 453
 454/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
 455bool cpu_smt_possible(void)
 456{
 457        return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
 458                cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
 459}
 460EXPORT_SYMBOL_GPL(cpu_smt_possible);
 461#else
 462static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
 463#endif
 464
 465static inline enum cpuhp_state
 466cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 467{
 468        enum cpuhp_state prev_state = st->state;
 469        bool bringup = st->state < target;
 470
 471        st->rollback = false;
 472        st->last = NULL;
 473
 474        st->target = target;
 475        st->single = false;
 476        st->bringup = bringup;
 477        if (cpu_dying(st->cpu) != !bringup)
 478                set_cpu_dying(st->cpu, !bringup);
 479
 480        return prev_state;
 481}
 482
 483static inline void
 484cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
 485{
 486        bool bringup = !st->bringup;
 487
 488        st->target = prev_state;
 489
 490        /*
 491         * Already rolling back. No need invert the bringup value or to change
 492         * the current state.
 493         */
 494        if (st->rollback)
 495                return;
 496
 497        st->rollback = true;
 498
 499        /*
 500         * If we have st->last we need to undo partial multi_instance of this
 501         * state first. Otherwise start undo at the previous state.
 502         */
 503        if (!st->last) {
 504                if (st->bringup)
 505                        st->state--;
 506                else
 507                        st->state++;
 508        }
 509
 510        st->bringup = bringup;
 511        if (cpu_dying(st->cpu) != !bringup)
 512                set_cpu_dying(st->cpu, !bringup);
 513}
 514
 515/* Regular hotplug invocation of the AP hotplug thread */
 516static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
 517{
 518        if (!st->single && st->state == st->target)
 519                return;
 520
 521        st->result = 0;
 522        /*
 523         * Make sure the above stores are visible before should_run becomes
 524         * true. Paired with the mb() above in cpuhp_thread_fun()
 525         */
 526        smp_mb();
 527        st->should_run = true;
 528        wake_up_process(st->thread);
 529        wait_for_ap_thread(st, st->bringup);
 530}
 531
 532static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
 533{
 534        enum cpuhp_state prev_state;
 535        int ret;
 536
 537        prev_state = cpuhp_set_state(st, target);
 538        __cpuhp_kick_ap(st);
 539        if ((ret = st->result)) {
 540                cpuhp_reset_state(st, prev_state);
 541                __cpuhp_kick_ap(st);
 542        }
 543
 544        return ret;
 545}
 546
 547static int bringup_wait_for_ap(unsigned int cpu)
 548{
 549        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 550
 551        /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
 552        wait_for_ap_thread(st, true);
 553        if (WARN_ON_ONCE((!cpu_online(cpu))))
 554                return -ECANCELED;
 555
 556        /* Unpark the hotplug thread of the target cpu */
 557        kthread_unpark(st->thread);
 558
 559        /*
 560         * SMT soft disabling on X86 requires to bring the CPU out of the
 561         * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
 562         * CPU marked itself as booted_once in notify_cpu_starting() so the
 563         * cpu_smt_allowed() check will now return false if this is not the
 564         * primary sibling.
 565         */
 566        if (!cpu_smt_allowed(cpu))
 567                return -ECANCELED;
 568
 569        if (st->target <= CPUHP_AP_ONLINE_IDLE)
 570                return 0;
 571
 572        return cpuhp_kick_ap(st, st->target);
 573}
 574
 575static int bringup_cpu(unsigned int cpu)
 576{
 577        struct task_struct *idle = idle_thread_get(cpu);
 578        int ret;
 579
 580        /*
 581         * Some architectures have to walk the irq descriptors to
 582         * setup the vector space for the cpu which comes online.
 583         * Prevent irq alloc/free across the bringup.
 584         */
 585        irq_lock_sparse();
 586
 587        /* Arch-specific enabling code. */
 588        ret = __cpu_up(cpu, idle);
 589        irq_unlock_sparse();
 590        if (ret)
 591                return ret;
 592        return bringup_wait_for_ap(cpu);
 593}
 594
 595static int finish_cpu(unsigned int cpu)
 596{
 597        struct task_struct *idle = idle_thread_get(cpu);
 598        struct mm_struct *mm = idle->active_mm;
 599
 600        /*
 601         * idle_task_exit() will have switched to &init_mm, now
 602         * clean up any remaining active_mm state.
 603         */
 604        if (mm != &init_mm)
 605                idle->active_mm = &init_mm;
 606        mmdrop(mm);
 607        return 0;
 608}
 609
 610/*
 611 * Hotplug state machine related functions
 612 */
 613
 614/*
 615 * Get the next state to run. Empty ones will be skipped. Returns true if a
 616 * state must be run.
 617 *
 618 * st->state will be modified ahead of time, to match state_to_run, as if it
 619 * has already ran.
 620 */
 621static bool cpuhp_next_state(bool bringup,
 622                             enum cpuhp_state *state_to_run,
 623                             struct cpuhp_cpu_state *st,
 624                             enum cpuhp_state target)
 625{
 626        do {
 627                if (bringup) {
 628                        if (st->state >= target)
 629                                return false;
 630
 631                        *state_to_run = ++st->state;
 632                } else {
 633                        if (st->state <= target)
 634                                return false;
 635
 636                        *state_to_run = st->state--;
 637                }
 638
 639                if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
 640                        break;
 641        } while (true);
 642
 643        return true;
 644}
 645
 646static int cpuhp_invoke_callback_range(bool bringup,
 647                                       unsigned int cpu,
 648                                       struct cpuhp_cpu_state *st,
 649                                       enum cpuhp_state target)
 650{
 651        enum cpuhp_state state;
 652        int err = 0;
 653
 654        while (cpuhp_next_state(bringup, &state, st, target)) {
 655                err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
 656                if (err)
 657                        break;
 658        }
 659
 660        return err;
 661}
 662
 663static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
 664{
 665        if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
 666                return true;
 667        /*
 668         * When CPU hotplug is disabled, then taking the CPU down is not
 669         * possible because takedown_cpu() and the architecture and
 670         * subsystem specific mechanisms are not available. So the CPU
 671         * which would be completely unplugged again needs to stay around
 672         * in the current state.
 673         */
 674        return st->state <= CPUHP_BRINGUP_CPU;
 675}
 676
 677static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 678                              enum cpuhp_state target)
 679{
 680        enum cpuhp_state prev_state = st->state;
 681        int ret = 0;
 682
 683        ret = cpuhp_invoke_callback_range(true, cpu, st, target);
 684        if (ret) {
 685                cpuhp_reset_state(st, prev_state);
 686                if (can_rollback_cpu(st))
 687                        WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
 688                                                            prev_state));
 689        }
 690        return ret;
 691}
 692
 693/*
 694 * The cpu hotplug threads manage the bringup and teardown of the cpus
 695 */
 696static void cpuhp_create(unsigned int cpu)
 697{
 698        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 699
 700        init_completion(&st->done_up);
 701        init_completion(&st->done_down);
 702        st->cpu = cpu;
 703}
 704
 705static int cpuhp_should_run(unsigned int cpu)
 706{
 707        struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 708
 709        return st->should_run;
 710}
 711
 712/*
 713 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 714 * callbacks when a state gets [un]installed at runtime.
 715 *
 716 * Each invocation of this function by the smpboot thread does a single AP
 717 * state callback.
 718 *
 719 * It has 3 modes of operation:
 720 *  - single: runs st->cb_state
 721 *  - up:     runs ++st->state, while st->state < st->target
 722 *  - down:   runs st->state--, while st->state > st->target
 723 *
 724 * When complete or on error, should_run is cleared and the completion is fired.
 725 */
 726static void cpuhp_thread_fun(unsigned int cpu)
 727{
 728        struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 729        bool bringup = st->bringup;
 730        enum cpuhp_state state;
 731
 732        if (WARN_ON_ONCE(!st->should_run))
 733                return;
 734
 735        /*
 736         * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
 737         * that if we see ->should_run we also see the rest of the state.
 738         */
 739        smp_mb();
 740
 741        /*
 742         * The BP holds the hotplug lock, but we're now running on the AP,
 743         * ensure that anybody asserting the lock is held, will actually find
 744         * it so.
 745         */
 746        lockdep_acquire_cpus_lock();
 747        cpuhp_lock_acquire(bringup);
 748
 749        if (st->single) {
 750                state = st->cb_state;
 751                st->should_run = false;
 752        } else {
 753                st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
 754                if (!st->should_run)
 755                        goto end;
 756        }
 757
 758        WARN_ON_ONCE(!cpuhp_is_ap_state(state));
 759
 760        if (cpuhp_is_atomic_state(state)) {
 761                local_irq_disable();
 762                st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
 763                local_irq_enable();
 764
 765                /*
 766                 * STARTING/DYING must not fail!
 767                 */
 768                WARN_ON_ONCE(st->result);
 769        } else {
 770                st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
 771        }
 772
 773        if (st->result) {
 774                /*
 775                 * If we fail on a rollback, we're up a creek without no
 776                 * paddle, no way forward, no way back. We loose, thanks for
 777                 * playing.
 778                 */
 779                WARN_ON_ONCE(st->rollback);
 780                st->should_run = false;
 781        }
 782
 783end:
 784        cpuhp_lock_release(bringup);
 785        lockdep_release_cpus_lock();
 786
 787        if (!st->should_run)
 788                complete_ap_thread(st, bringup);
 789}
 790
 791/* Invoke a single callback on a remote cpu */
 792static int
 793cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
 794                         struct hlist_node *node)
 795{
 796        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 797        int ret;
 798
 799        if (!cpu_online(cpu))
 800                return 0;
 801
 802        cpuhp_lock_acquire(false);
 803        cpuhp_lock_release(false);
 804
 805        cpuhp_lock_acquire(true);
 806        cpuhp_lock_release(true);
 807
 808        /*
 809         * If we are up and running, use the hotplug thread. For early calls
 810         * we invoke the thread function directly.
 811         */
 812        if (!st->thread)
 813                return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
 814
 815        st->rollback = false;
 816        st->last = NULL;
 817
 818        st->node = node;
 819        st->bringup = bringup;
 820        st->cb_state = state;
 821        st->single = true;
 822
 823        __cpuhp_kick_ap(st);
 824
 825        /*
 826         * If we failed and did a partial, do a rollback.
 827         */
 828        if ((ret = st->result) && st->last) {
 829                st->rollback = true;
 830                st->bringup = !bringup;
 831
 832                __cpuhp_kick_ap(st);
 833        }
 834
 835        /*
 836         * Clean up the leftovers so the next hotplug operation wont use stale
 837         * data.
 838         */
 839        st->node = st->last = NULL;
 840        return ret;
 841}
 842
 843static int cpuhp_kick_ap_work(unsigned int cpu)
 844{
 845        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 846        enum cpuhp_state prev_state = st->state;
 847        int ret;
 848
 849        cpuhp_lock_acquire(false);
 850        cpuhp_lock_release(false);
 851
 852        cpuhp_lock_acquire(true);
 853        cpuhp_lock_release(true);
 854
 855        trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
 856        ret = cpuhp_kick_ap(st, st->target);
 857        trace_cpuhp_exit(cpu, st->state, prev_state, ret);
 858
 859        return ret;
 860}
 861
 862static struct smp_hotplug_thread cpuhp_threads = {
 863        .store                  = &cpuhp_state.thread,
 864        .create                 = &cpuhp_create,
 865        .thread_should_run      = cpuhp_should_run,
 866        .thread_fn              = cpuhp_thread_fun,
 867        .thread_comm            = "cpuhp/%u",
 868        .selfparking            = true,
 869};
 870
 871void __init cpuhp_threads_init(void)
 872{
 873        BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 874        kthread_unpark(this_cpu_read(cpuhp_state.thread));
 875}
 876
 877/*
 878 *
 879 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
 880 * protected region.
 881 *
 882 * The operation is still serialized against concurrent CPU hotplug via
 883 * cpu_add_remove_lock, i.e. CPU map protection.  But it is _not_
 884 * serialized against other hotplug related activity like adding or
 885 * removing of state callbacks and state instances, which invoke either the
 886 * startup or the teardown callback of the affected state.
 887 *
 888 * This is required for subsystems which are unfixable vs. CPU hotplug and
 889 * evade lock inversion problems by scheduling work which has to be
 890 * completed _before_ cpu_up()/_cpu_down() returns.
 891 *
 892 * Don't even think about adding anything to this for any new code or even
 893 * drivers. It's only purpose is to keep existing lock order trainwrecks
 894 * working.
 895 *
 896 * For cpu_down() there might be valid reasons to finish cleanups which are
 897 * not required to be done under cpu_hotplug_lock, but that's a different
 898 * story and would be not invoked via this.
 899 */
 900static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
 901{
 902        /*
 903         * cpusets delegate hotplug operations to a worker to "solve" the
 904         * lock order problems. Wait for the worker, but only if tasks are
 905         * _not_ frozen (suspend, hibernate) as that would wait forever.
 906         *
 907         * The wait is required because otherwise the hotplug operation
 908         * returns with inconsistent state, which could even be observed in
 909         * user space when a new CPU is brought up. The CPU plug uevent
 910         * would be delivered and user space reacting on it would fail to
 911         * move tasks to the newly plugged CPU up to the point where the
 912         * work has finished because up to that point the newly plugged CPU
 913         * is not assignable in cpusets/cgroups. On unplug that's not
 914         * necessarily a visible issue, but it is still inconsistent state,
 915         * which is the real problem which needs to be "fixed". This can't
 916         * prevent the transient state between scheduling the work and
 917         * returning from waiting for it.
 918         */
 919        if (!tasks_frozen)
 920                cpuset_wait_for_hotplug();
 921}
 922
 923#ifdef CONFIG_HOTPLUG_CPU
 924#ifndef arch_clear_mm_cpumask_cpu
 925#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
 926#endif
 927
 928/**
 929 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 930 * @cpu: a CPU id
 931 *
 932 * This function walks all processes, finds a valid mm struct for each one and
 933 * then clears a corresponding bit in mm's cpumask.  While this all sounds
 934 * trivial, there are various non-obvious corner cases, which this function
 935 * tries to solve in a safe manner.
 936 *
 937 * Also note that the function uses a somewhat relaxed locking scheme, so it may
 938 * be called only for an already offlined CPU.
 939 */
 940void clear_tasks_mm_cpumask(int cpu)
 941{
 942        struct task_struct *p;
 943
 944        /*
 945         * This function is called after the cpu is taken down and marked
 946         * offline, so its not like new tasks will ever get this cpu set in
 947         * their mm mask. -- Peter Zijlstra
 948         * Thus, we may use rcu_read_lock() here, instead of grabbing
 949         * full-fledged tasklist_lock.
 950         */
 951        WARN_ON(cpu_online(cpu));
 952        rcu_read_lock();
 953        for_each_process(p) {
 954                struct task_struct *t;
 955
 956                /*
 957                 * Main thread might exit, but other threads may still have
 958                 * a valid mm. Find one.
 959                 */
 960                t = find_lock_task_mm(p);
 961                if (!t)
 962                        continue;
 963                arch_clear_mm_cpumask_cpu(cpu, t->mm);
 964                task_unlock(t);
 965        }
 966        rcu_read_unlock();
 967}
 968
 969/* Take this CPU down. */
 970static int take_cpu_down(void *_param)
 971{
 972        struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 973        enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 974        int err, cpu = smp_processor_id();
 975        int ret;
 976
 977        /* Ensure this CPU doesn't handle any more interrupts. */
 978        err = __cpu_disable();
 979        if (err < 0)
 980                return err;
 981
 982        /*
 983         * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
 984         * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
 985         */
 986        WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
 987
 988        /* Invoke the former CPU_DYING callbacks */
 989        ret = cpuhp_invoke_callback_range(false, cpu, st, target);
 990
 991        /*
 992         * DYING must not fail!
 993         */
 994        WARN_ON_ONCE(ret);
 995
 996        /* Give up timekeeping duties */
 997        tick_handover_do_timer();
 998        /* Remove CPU from timer broadcasting */
 999        tick_offline_cpu(cpu);
1000        /* Park the stopper thread */
1001        stop_machine_park(cpu);
1002        return 0;
1003}
1004
1005static int takedown_cpu(unsigned int cpu)
1006{
1007        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1008        int err;
1009
1010        /* Park the smpboot threads */
1011        kthread_park(st->thread);
1012
1013        /*
1014         * Prevent irq alloc/free while the dying cpu reorganizes the
1015         * interrupt affinities.
1016         */
1017        irq_lock_sparse();
1018
1019        /*
1020         * So now all preempt/rcu users must observe !cpu_active().
1021         */
1022        err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1023        if (err) {
1024                /* CPU refused to die */
1025                irq_unlock_sparse();
1026                /* Unpark the hotplug thread so we can rollback there */
1027                kthread_unpark(st->thread);
1028                return err;
1029        }
1030        BUG_ON(cpu_online(cpu));
1031
1032        /*
1033         * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1034         * all runnable tasks from the CPU, there's only the idle task left now
1035         * that the migration thread is done doing the stop_machine thing.
1036         *
1037         * Wait for the stop thread to go away.
1038         */
1039        wait_for_ap_thread(st, false);
1040        BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1041
1042        /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1043        irq_unlock_sparse();
1044
1045        hotplug_cpu__broadcast_tick_pull(cpu);
1046        /* This actually kills the CPU. */
1047        __cpu_die(cpu);
1048
1049        tick_cleanup_dead_cpu(cpu);
1050        rcutree_migrate_callbacks(cpu);
1051        return 0;
1052}
1053
1054static void cpuhp_complete_idle_dead(void *arg)
1055{
1056        struct cpuhp_cpu_state *st = arg;
1057
1058        complete_ap_thread(st, false);
1059}
1060
1061void cpuhp_report_idle_dead(void)
1062{
1063        struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1064
1065        BUG_ON(st->state != CPUHP_AP_OFFLINE);
1066        rcu_report_dead(smp_processor_id());
1067        st->state = CPUHP_AP_IDLE_DEAD;
1068        /*
1069         * We cannot call complete after rcu_report_dead() so we delegate it
1070         * to an online cpu.
1071         */
1072        smp_call_function_single(cpumask_first(cpu_online_mask),
1073                                 cpuhp_complete_idle_dead, st, 0);
1074}
1075
1076static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1077                                enum cpuhp_state target)
1078{
1079        enum cpuhp_state prev_state = st->state;
1080        int ret = 0;
1081
1082        ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1083        if (ret) {
1084
1085                cpuhp_reset_state(st, prev_state);
1086
1087                if (st->state < prev_state)
1088                        WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1089                                                            prev_state));
1090        }
1091
1092        return ret;
1093}
1094
1095/* Requires cpu_add_remove_lock to be held */
1096static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1097                           enum cpuhp_state target)
1098{
1099        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1100        int prev_state, ret = 0;
1101
1102        if (num_online_cpus() == 1)
1103                return -EBUSY;
1104
1105        if (!cpu_present(cpu))
1106                return -EINVAL;
1107
1108        cpus_write_lock();
1109
1110        cpuhp_tasks_frozen = tasks_frozen;
1111
1112        prev_state = cpuhp_set_state(st, target);
1113        /*
1114         * If the current CPU state is in the range of the AP hotplug thread,
1115         * then we need to kick the thread.
1116         */
1117        if (st->state > CPUHP_TEARDOWN_CPU) {
1118                st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1119                ret = cpuhp_kick_ap_work(cpu);
1120                /*
1121                 * The AP side has done the error rollback already. Just
1122                 * return the error code..
1123                 */
1124                if (ret)
1125                        goto out;
1126
1127                /*
1128                 * We might have stopped still in the range of the AP hotplug
1129                 * thread. Nothing to do anymore.
1130                 */
1131                if (st->state > CPUHP_TEARDOWN_CPU)
1132                        goto out;
1133
1134                st->target = target;
1135        }
1136        /*
1137         * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1138         * to do the further cleanups.
1139         */
1140        ret = cpuhp_down_callbacks(cpu, st, target);
1141        if (ret && st->state < prev_state) {
1142                if (st->state == CPUHP_TEARDOWN_CPU) {
1143                        cpuhp_reset_state(st, prev_state);
1144                        __cpuhp_kick_ap(st);
1145                } else {
1146                        WARN(1, "DEAD callback error for CPU%d", cpu);
1147                }
1148        }
1149
1150out:
1151        cpus_write_unlock();
1152        /*
1153         * Do post unplug cleanup. This is still protected against
1154         * concurrent CPU hotplug via cpu_add_remove_lock.
1155         */
1156        lockup_detector_cleanup();
1157        arch_smt_update();
1158        cpu_up_down_serialize_trainwrecks(tasks_frozen);
1159        return ret;
1160}
1161
1162static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1163{
1164        if (cpu_hotplug_disabled)
1165                return -EBUSY;
1166        return _cpu_down(cpu, 0, target);
1167}
1168
1169static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1170{
1171        int err;
1172
1173        cpu_maps_update_begin();
1174        err = cpu_down_maps_locked(cpu, target);
1175        cpu_maps_update_done();
1176        return err;
1177}
1178
1179/**
1180 * cpu_device_down - Bring down a cpu device
1181 * @dev: Pointer to the cpu device to offline
1182 *
1183 * This function is meant to be used by device core cpu subsystem only.
1184 *
1185 * Other subsystems should use remove_cpu() instead.
1186 */
1187int cpu_device_down(struct device *dev)
1188{
1189        return cpu_down(dev->id, CPUHP_OFFLINE);
1190}
1191
1192int remove_cpu(unsigned int cpu)
1193{
1194        int ret;
1195
1196        lock_device_hotplug();
1197        ret = device_offline(get_cpu_device(cpu));
1198        unlock_device_hotplug();
1199
1200        return ret;
1201}
1202EXPORT_SYMBOL_GPL(remove_cpu);
1203
1204void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1205{
1206        unsigned int cpu;
1207        int error;
1208
1209        cpu_maps_update_begin();
1210
1211        /*
1212         * Make certain the cpu I'm about to reboot on is online.
1213         *
1214         * This is inline to what migrate_to_reboot_cpu() already do.
1215         */
1216        if (!cpu_online(primary_cpu))
1217                primary_cpu = cpumask_first(cpu_online_mask);
1218
1219        for_each_online_cpu(cpu) {
1220                if (cpu == primary_cpu)
1221                        continue;
1222
1223                error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1224                if (error) {
1225                        pr_err("Failed to offline CPU%d - error=%d",
1226                                cpu, error);
1227                        break;
1228                }
1229        }
1230
1231        /*
1232         * Ensure all but the reboot CPU are offline.
1233         */
1234        BUG_ON(num_online_cpus() > 1);
1235
1236        /*
1237         * Make sure the CPUs won't be enabled by someone else after this
1238         * point. Kexec will reboot to a new kernel shortly resetting
1239         * everything along the way.
1240         */
1241        cpu_hotplug_disabled++;
1242
1243        cpu_maps_update_done();
1244}
1245
1246#else
1247#define takedown_cpu            NULL
1248#endif /*CONFIG_HOTPLUG_CPU*/
1249
1250/**
1251 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1252 * @cpu: cpu that just started
1253 *
1254 * It must be called by the arch code on the new cpu, before the new cpu
1255 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1256 */
1257void notify_cpu_starting(unsigned int cpu)
1258{
1259        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1260        enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1261        int ret;
1262
1263        rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1264        cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1265        ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1266
1267        /*
1268         * STARTING must not fail!
1269         */
1270        WARN_ON_ONCE(ret);
1271}
1272
1273/*
1274 * Called from the idle task. Wake up the controlling task which brings the
1275 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1276 * online bringup to the hotplug thread.
1277 */
1278void cpuhp_online_idle(enum cpuhp_state state)
1279{
1280        struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1281
1282        /* Happens for the boot cpu */
1283        if (state != CPUHP_AP_ONLINE_IDLE)
1284                return;
1285
1286        /*
1287         * Unpart the stopper thread before we start the idle loop (and start
1288         * scheduling); this ensures the stopper task is always available.
1289         */
1290        stop_machine_unpark(smp_processor_id());
1291
1292        st->state = CPUHP_AP_ONLINE_IDLE;
1293        complete_ap_thread(st, true);
1294}
1295
1296/* Requires cpu_add_remove_lock to be held */
1297static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1298{
1299        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1300        struct task_struct *idle;
1301        int ret = 0;
1302
1303        cpus_write_lock();
1304
1305        if (!cpu_present(cpu)) {
1306                ret = -EINVAL;
1307                goto out;
1308        }
1309
1310        /*
1311         * The caller of cpu_up() might have raced with another
1312         * caller. Nothing to do.
1313         */
1314        if (st->state >= target)
1315                goto out;
1316
1317        if (st->state == CPUHP_OFFLINE) {
1318                /* Let it fail before we try to bring the cpu up */
1319                idle = idle_thread_get(cpu);
1320                if (IS_ERR(idle)) {
1321                        ret = PTR_ERR(idle);
1322                        goto out;
1323                }
1324        }
1325
1326        cpuhp_tasks_frozen = tasks_frozen;
1327
1328        cpuhp_set_state(st, target);
1329        /*
1330         * If the current CPU state is in the range of the AP hotplug thread,
1331         * then we need to kick the thread once more.
1332         */
1333        if (st->state > CPUHP_BRINGUP_CPU) {
1334                ret = cpuhp_kick_ap_work(cpu);
1335                /*
1336                 * The AP side has done the error rollback already. Just
1337                 * return the error code..
1338                 */
1339                if (ret)
1340                        goto out;
1341        }
1342
1343        /*
1344         * Try to reach the target state. We max out on the BP at
1345         * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1346         * responsible for bringing it up to the target state.
1347         */
1348        target = min((int)target, CPUHP_BRINGUP_CPU);
1349        ret = cpuhp_up_callbacks(cpu, st, target);
1350out:
1351        cpus_write_unlock();
1352        arch_smt_update();
1353        cpu_up_down_serialize_trainwrecks(tasks_frozen);
1354        return ret;
1355}
1356
1357static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1358{
1359        int err = 0;
1360
1361        if (!cpu_possible(cpu)) {
1362                pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1363                       cpu);
1364#if defined(CONFIG_IA64)
1365                pr_err("please check additional_cpus= boot parameter\n");
1366#endif
1367                return -EINVAL;
1368        }
1369
1370        err = try_online_node(cpu_to_node(cpu));
1371        if (err)
1372                return err;
1373
1374        cpu_maps_update_begin();
1375
1376        if (cpu_hotplug_disabled) {
1377                err = -EBUSY;
1378                goto out;
1379        }
1380        if (!cpu_smt_allowed(cpu)) {
1381                err = -EPERM;
1382                goto out;
1383        }
1384
1385        err = _cpu_up(cpu, 0, target);
1386out:
1387        cpu_maps_update_done();
1388        return err;
1389}
1390
1391/**
1392 * cpu_device_up - Bring up a cpu device
1393 * @dev: Pointer to the cpu device to online
1394 *
1395 * This function is meant to be used by device core cpu subsystem only.
1396 *
1397 * Other subsystems should use add_cpu() instead.
1398 */
1399int cpu_device_up(struct device *dev)
1400{
1401        return cpu_up(dev->id, CPUHP_ONLINE);
1402}
1403
1404int add_cpu(unsigned int cpu)
1405{
1406        int ret;
1407
1408        lock_device_hotplug();
1409        ret = device_online(get_cpu_device(cpu));
1410        unlock_device_hotplug();
1411
1412        return ret;
1413}
1414EXPORT_SYMBOL_GPL(add_cpu);
1415
1416/**
1417 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1418 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1419 *
1420 * On some architectures like arm64, we can hibernate on any CPU, but on
1421 * wake up the CPU we hibernated on might be offline as a side effect of
1422 * using maxcpus= for example.
1423 */
1424int bringup_hibernate_cpu(unsigned int sleep_cpu)
1425{
1426        int ret;
1427
1428        if (!cpu_online(sleep_cpu)) {
1429                pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1430                ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1431                if (ret) {
1432                        pr_err("Failed to bring hibernate-CPU up!\n");
1433                        return ret;
1434                }
1435        }
1436        return 0;
1437}
1438
1439void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1440{
1441        unsigned int cpu;
1442
1443        for_each_present_cpu(cpu) {
1444                if (num_online_cpus() >= setup_max_cpus)
1445                        break;
1446                if (!cpu_online(cpu))
1447                        cpu_up(cpu, CPUHP_ONLINE);
1448        }
1449}
1450
1451#ifdef CONFIG_PM_SLEEP_SMP
1452static cpumask_var_t frozen_cpus;
1453
1454int freeze_secondary_cpus(int primary)
1455{
1456        int cpu, error = 0;
1457
1458        cpu_maps_update_begin();
1459        if (primary == -1) {
1460                primary = cpumask_first(cpu_online_mask);
1461                if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1462                        primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1463        } else {
1464                if (!cpu_online(primary))
1465                        primary = cpumask_first(cpu_online_mask);
1466        }
1467
1468        /*
1469         * We take down all of the non-boot CPUs in one shot to avoid races
1470         * with the userspace trying to use the CPU hotplug at the same time
1471         */
1472        cpumask_clear(frozen_cpus);
1473
1474        pr_info("Disabling non-boot CPUs ...\n");
1475        for_each_online_cpu(cpu) {
1476                if (cpu == primary)
1477                        continue;
1478
1479                if (pm_wakeup_pending()) {
1480                        pr_info("Wakeup pending. Abort CPU freeze\n");
1481                        error = -EBUSY;
1482                        break;
1483                }
1484
1485                trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1486                error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1487                trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1488                if (!error)
1489                        cpumask_set_cpu(cpu, frozen_cpus);
1490                else {
1491                        pr_err("Error taking CPU%d down: %d\n", cpu, error);
1492                        break;
1493                }
1494        }
1495
1496        if (!error)
1497                BUG_ON(num_online_cpus() > 1);
1498        else
1499                pr_err("Non-boot CPUs are not disabled\n");
1500
1501        /*
1502         * Make sure the CPUs won't be enabled by someone else. We need to do
1503         * this even in case of failure as all freeze_secondary_cpus() users are
1504         * supposed to do thaw_secondary_cpus() on the failure path.
1505         */
1506        cpu_hotplug_disabled++;
1507
1508        cpu_maps_update_done();
1509        return error;
1510}
1511
1512void __weak arch_thaw_secondary_cpus_begin(void)
1513{
1514}
1515
1516void __weak arch_thaw_secondary_cpus_end(void)
1517{
1518}
1519
1520void thaw_secondary_cpus(void)
1521{
1522        int cpu, error;
1523
1524        /* Allow everyone to use the CPU hotplug again */
1525        cpu_maps_update_begin();
1526        __cpu_hotplug_enable();
1527        if (cpumask_empty(frozen_cpus))
1528                goto out;
1529
1530        pr_info("Enabling non-boot CPUs ...\n");
1531
1532        arch_thaw_secondary_cpus_begin();
1533
1534        for_each_cpu(cpu, frozen_cpus) {
1535                trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1536                error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1537                trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1538                if (!error) {
1539                        pr_info("CPU%d is up\n", cpu);
1540                        continue;
1541                }
1542                pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1543        }
1544
1545        arch_thaw_secondary_cpus_end();
1546
1547        cpumask_clear(frozen_cpus);
1548out:
1549        cpu_maps_update_done();
1550}
1551
1552static int __init alloc_frozen_cpus(void)
1553{
1554        if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1555                return -ENOMEM;
1556        return 0;
1557}
1558core_initcall(alloc_frozen_cpus);
1559
1560/*
1561 * When callbacks for CPU hotplug notifications are being executed, we must
1562 * ensure that the state of the system with respect to the tasks being frozen
1563 * or not, as reported by the notification, remains unchanged *throughout the
1564 * duration* of the execution of the callbacks.
1565 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1566 *
1567 * This synchronization is implemented by mutually excluding regular CPU
1568 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1569 * Hibernate notifications.
1570 */
1571static int
1572cpu_hotplug_pm_callback(struct notifier_block *nb,
1573                        unsigned long action, void *ptr)
1574{
1575        switch (action) {
1576
1577        case PM_SUSPEND_PREPARE:
1578        case PM_HIBERNATION_PREPARE:
1579                cpu_hotplug_disable();
1580                break;
1581
1582        case PM_POST_SUSPEND:
1583        case PM_POST_HIBERNATION:
1584                cpu_hotplug_enable();
1585                break;
1586
1587        default:
1588                return NOTIFY_DONE;
1589        }
1590
1591        return NOTIFY_OK;
1592}
1593
1594
1595static int __init cpu_hotplug_pm_sync_init(void)
1596{
1597        /*
1598         * cpu_hotplug_pm_callback has higher priority than x86
1599         * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1600         * to disable cpu hotplug to avoid cpu hotplug race.
1601         */
1602        pm_notifier(cpu_hotplug_pm_callback, 0);
1603        return 0;
1604}
1605core_initcall(cpu_hotplug_pm_sync_init);
1606
1607#endif /* CONFIG_PM_SLEEP_SMP */
1608
1609int __boot_cpu_id;
1610
1611#endif /* CONFIG_SMP */
1612
1613/* Boot processor state steps */
1614static struct cpuhp_step cpuhp_hp_states[] = {
1615        [CPUHP_OFFLINE] = {
1616                .name                   = "offline",
1617                .startup.single         = NULL,
1618                .teardown.single        = NULL,
1619        },
1620#ifdef CONFIG_SMP
1621        [CPUHP_CREATE_THREADS]= {
1622                .name                   = "threads:prepare",
1623                .startup.single         = smpboot_create_threads,
1624                .teardown.single        = NULL,
1625                .cant_stop              = true,
1626        },
1627        [CPUHP_PERF_PREPARE] = {
1628                .name                   = "perf:prepare",
1629                .startup.single         = perf_event_init_cpu,
1630                .teardown.single        = perf_event_exit_cpu,
1631        },
1632        [CPUHP_WORKQUEUE_PREP] = {
1633                .name                   = "workqueue:prepare",
1634                .startup.single         = workqueue_prepare_cpu,
1635                .teardown.single        = NULL,
1636        },
1637        [CPUHP_HRTIMERS_PREPARE] = {
1638                .name                   = "hrtimers:prepare",
1639                .startup.single         = hrtimers_prepare_cpu,
1640                .teardown.single        = hrtimers_dead_cpu,
1641        },
1642        [CPUHP_SMPCFD_PREPARE] = {
1643                .name                   = "smpcfd:prepare",
1644                .startup.single         = smpcfd_prepare_cpu,
1645                .teardown.single        = smpcfd_dead_cpu,
1646        },
1647        [CPUHP_RELAY_PREPARE] = {
1648                .name                   = "relay:prepare",
1649                .startup.single         = relay_prepare_cpu,
1650                .teardown.single        = NULL,
1651        },
1652        [CPUHP_SLAB_PREPARE] = {
1653                .name                   = "slab:prepare",
1654                .startup.single         = slab_prepare_cpu,
1655                .teardown.single        = slab_dead_cpu,
1656        },
1657        [CPUHP_RCUTREE_PREP] = {
1658                .name                   = "RCU/tree:prepare",
1659                .startup.single         = rcutree_prepare_cpu,
1660                .teardown.single        = rcutree_dead_cpu,
1661        },
1662        /*
1663         * On the tear-down path, timers_dead_cpu() must be invoked
1664         * before blk_mq_queue_reinit_notify() from notify_dead(),
1665         * otherwise a RCU stall occurs.
1666         */
1667        [CPUHP_TIMERS_PREPARE] = {
1668                .name                   = "timers:prepare",
1669                .startup.single         = timers_prepare_cpu,
1670                .teardown.single        = timers_dead_cpu,
1671        },
1672        /* Kicks the plugged cpu into life */
1673        [CPUHP_BRINGUP_CPU] = {
1674                .name                   = "cpu:bringup",
1675                .startup.single         = bringup_cpu,
1676                .teardown.single        = finish_cpu,
1677                .cant_stop              = true,
1678        },
1679        /* Final state before CPU kills itself */
1680        [CPUHP_AP_IDLE_DEAD] = {
1681                .name                   = "idle:dead",
1682        },
1683        /*
1684         * Last state before CPU enters the idle loop to die. Transient state
1685         * for synchronization.
1686         */
1687        [CPUHP_AP_OFFLINE] = {
1688                .name                   = "ap:offline",
1689                .cant_stop              = true,
1690        },
1691        /* First state is scheduler control. Interrupts are disabled */
1692        [CPUHP_AP_SCHED_STARTING] = {
1693                .name                   = "sched:starting",
1694                .startup.single         = sched_cpu_starting,
1695                .teardown.single        = sched_cpu_dying,
1696        },
1697        [CPUHP_AP_RCUTREE_DYING] = {
1698                .name                   = "RCU/tree:dying",
1699                .startup.single         = NULL,
1700                .teardown.single        = rcutree_dying_cpu,
1701        },
1702        [CPUHP_AP_SMPCFD_DYING] = {
1703                .name                   = "smpcfd:dying",
1704                .startup.single         = NULL,
1705                .teardown.single        = smpcfd_dying_cpu,
1706        },
1707        /* Entry state on starting. Interrupts enabled from here on. Transient
1708         * state for synchronsization */
1709        [CPUHP_AP_ONLINE] = {
1710                .name                   = "ap:online",
1711        },
1712        /*
1713         * Handled on control processor until the plugged processor manages
1714         * this itself.
1715         */
1716        [CPUHP_TEARDOWN_CPU] = {
1717                .name                   = "cpu:teardown",
1718                .startup.single         = NULL,
1719                .teardown.single        = takedown_cpu,
1720                .cant_stop              = true,
1721        },
1722
1723        [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1724                .name                   = "sched:waitempty",
1725                .startup.single         = NULL,
1726                .teardown.single        = sched_cpu_wait_empty,
1727        },
1728
1729        /* Handle smpboot threads park/unpark */
1730        [CPUHP_AP_SMPBOOT_THREADS] = {
1731                .name                   = "smpboot/threads:online",
1732                .startup.single         = smpboot_unpark_threads,
1733                .teardown.single        = smpboot_park_threads,
1734        },
1735        [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1736                .name                   = "irq/affinity:online",
1737                .startup.single         = irq_affinity_online_cpu,
1738                .teardown.single        = NULL,
1739        },
1740        [CPUHP_AP_PERF_ONLINE] = {
1741                .name                   = "perf:online",
1742                .startup.single         = perf_event_init_cpu,
1743                .teardown.single        = perf_event_exit_cpu,
1744        },
1745        [CPUHP_AP_WATCHDOG_ONLINE] = {
1746                .name                   = "lockup_detector:online",
1747                .startup.single         = lockup_detector_online_cpu,
1748                .teardown.single        = lockup_detector_offline_cpu,
1749        },
1750        [CPUHP_AP_WORKQUEUE_ONLINE] = {
1751                .name                   = "workqueue:online",
1752                .startup.single         = workqueue_online_cpu,
1753                .teardown.single        = workqueue_offline_cpu,
1754        },
1755        [CPUHP_AP_RCUTREE_ONLINE] = {
1756                .name                   = "RCU/tree:online",
1757                .startup.single         = rcutree_online_cpu,
1758                .teardown.single        = rcutree_offline_cpu,
1759        },
1760#endif
1761        /*
1762         * The dynamically registered state space is here
1763         */
1764
1765#ifdef CONFIG_SMP
1766        /* Last state is scheduler control setting the cpu active */
1767        [CPUHP_AP_ACTIVE] = {
1768                .name                   = "sched:active",
1769                .startup.single         = sched_cpu_activate,
1770                .teardown.single        = sched_cpu_deactivate,
1771        },
1772#endif
1773
1774        /* CPU is fully up and running. */
1775        [CPUHP_ONLINE] = {
1776                .name                   = "online",
1777                .startup.single         = NULL,
1778                .teardown.single        = NULL,
1779        },
1780};
1781
1782/* Sanity check for callbacks */
1783static int cpuhp_cb_check(enum cpuhp_state state)
1784{
1785        if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1786                return -EINVAL;
1787        return 0;
1788}
1789
1790/*
1791 * Returns a free for dynamic slot assignment of the Online state. The states
1792 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1793 * by having no name assigned.
1794 */
1795static int cpuhp_reserve_state(enum cpuhp_state state)
1796{
1797        enum cpuhp_state i, end;
1798        struct cpuhp_step *step;
1799
1800        switch (state) {
1801        case CPUHP_AP_ONLINE_DYN:
1802                step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1803                end = CPUHP_AP_ONLINE_DYN_END;
1804                break;
1805        case CPUHP_BP_PREPARE_DYN:
1806                step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1807                end = CPUHP_BP_PREPARE_DYN_END;
1808                break;
1809        default:
1810                return -EINVAL;
1811        }
1812
1813        for (i = state; i <= end; i++, step++) {
1814                if (!step->name)
1815                        return i;
1816        }
1817        WARN(1, "No more dynamic states available for CPU hotplug\n");
1818        return -ENOSPC;
1819}
1820
1821static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1822                                 int (*startup)(unsigned int cpu),
1823                                 int (*teardown)(unsigned int cpu),
1824                                 bool multi_instance)
1825{
1826        /* (Un)Install the callbacks for further cpu hotplug operations */
1827        struct cpuhp_step *sp;
1828        int ret = 0;
1829
1830        /*
1831         * If name is NULL, then the state gets removed.
1832         *
1833         * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1834         * the first allocation from these dynamic ranges, so the removal
1835         * would trigger a new allocation and clear the wrong (already
1836         * empty) state, leaving the callbacks of the to be cleared state
1837         * dangling, which causes wreckage on the next hotplug operation.
1838         */
1839        if (name && (state == CPUHP_AP_ONLINE_DYN ||
1840                     state == CPUHP_BP_PREPARE_DYN)) {
1841                ret = cpuhp_reserve_state(state);
1842                if (ret < 0)
1843                        return ret;
1844                state = ret;
1845        }
1846        sp = cpuhp_get_step(state);
1847        if (name && sp->name)
1848                return -EBUSY;
1849
1850        sp->startup.single = startup;
1851        sp->teardown.single = teardown;
1852        sp->name = name;
1853        sp->multi_instance = multi_instance;
1854        INIT_HLIST_HEAD(&sp->list);
1855        return ret;
1856}
1857
1858static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1859{
1860        return cpuhp_get_step(state)->teardown.single;
1861}
1862
1863/*
1864 * Call the startup/teardown function for a step either on the AP or
1865 * on the current CPU.
1866 */
1867static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1868                            struct hlist_node *node)
1869{
1870        struct cpuhp_step *sp = cpuhp_get_step(state);
1871        int ret;
1872
1873        /*
1874         * If there's nothing to do, we done.
1875         * Relies on the union for multi_instance.
1876         */
1877        if (cpuhp_step_empty(bringup, sp))
1878                return 0;
1879        /*
1880         * The non AP bound callbacks can fail on bringup. On teardown
1881         * e.g. module removal we crash for now.
1882         */
1883#ifdef CONFIG_SMP
1884        if (cpuhp_is_ap_state(state))
1885                ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1886        else
1887                ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1888#else
1889        ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1890#endif
1891        BUG_ON(ret && !bringup);
1892        return ret;
1893}
1894
1895/*
1896 * Called from __cpuhp_setup_state on a recoverable failure.
1897 *
1898 * Note: The teardown callbacks for rollback are not allowed to fail!
1899 */
1900static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1901                                   struct hlist_node *node)
1902{
1903        int cpu;
1904
1905        /* Roll back the already executed steps on the other cpus */
1906        for_each_present_cpu(cpu) {
1907                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1908                int cpustate = st->state;
1909
1910                if (cpu >= failedcpu)
1911                        break;
1912
1913                /* Did we invoke the startup call on that cpu ? */
1914                if (cpustate >= state)
1915                        cpuhp_issue_call(cpu, state, false, node);
1916        }
1917}
1918
1919int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1920                                          struct hlist_node *node,
1921                                          bool invoke)
1922{
1923        struct cpuhp_step *sp;
1924        int cpu;
1925        int ret;
1926
1927        lockdep_assert_cpus_held();
1928
1929        sp = cpuhp_get_step(state);
1930        if (sp->multi_instance == false)
1931                return -EINVAL;
1932
1933        mutex_lock(&cpuhp_state_mutex);
1934
1935        if (!invoke || !sp->startup.multi)
1936                goto add_node;
1937
1938        /*
1939         * Try to call the startup callback for each present cpu
1940         * depending on the hotplug state of the cpu.
1941         */
1942        for_each_present_cpu(cpu) {
1943                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1944                int cpustate = st->state;
1945
1946                if (cpustate < state)
1947                        continue;
1948
1949                ret = cpuhp_issue_call(cpu, state, true, node);
1950                if (ret) {
1951                        if (sp->teardown.multi)
1952                                cpuhp_rollback_install(cpu, state, node);
1953                        goto unlock;
1954                }
1955        }
1956add_node:
1957        ret = 0;
1958        hlist_add_head(node, &sp->list);
1959unlock:
1960        mutex_unlock(&cpuhp_state_mutex);
1961        return ret;
1962}
1963
1964int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1965                               bool invoke)
1966{
1967        int ret;
1968
1969        cpus_read_lock();
1970        ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1971        cpus_read_unlock();
1972        return ret;
1973}
1974EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1975
1976/**
1977 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1978 * @state:              The state to setup
1979 * @invoke:             If true, the startup function is invoked for cpus where
1980 *                      cpu state >= @state
1981 * @startup:            startup callback function
1982 * @teardown:           teardown callback function
1983 * @multi_instance:     State is set up for multiple instances which get
1984 *                      added afterwards.
1985 *
1986 * The caller needs to hold cpus read locked while calling this function.
1987 * Returns:
1988 *   On success:
1989 *      Positive state number if @state is CPUHP_AP_ONLINE_DYN
1990 *      0 for all other states
1991 *   On failure: proper (negative) error code
1992 */
1993int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1994                                   const char *name, bool invoke,
1995                                   int (*startup)(unsigned int cpu),
1996                                   int (*teardown)(unsigned int cpu),
1997                                   bool multi_instance)
1998{
1999        int cpu, ret = 0;
2000        bool dynstate;
2001
2002        lockdep_assert_cpus_held();
2003
2004        if (cpuhp_cb_check(state) || !name)
2005                return -EINVAL;
2006
2007        mutex_lock(&cpuhp_state_mutex);
2008
2009        ret = cpuhp_store_callbacks(state, name, startup, teardown,
2010                                    multi_instance);
2011
2012        dynstate = state == CPUHP_AP_ONLINE_DYN;
2013        if (ret > 0 && dynstate) {
2014                state = ret;
2015                ret = 0;
2016        }
2017
2018        if (ret || !invoke || !startup)
2019                goto out;
2020
2021        /*
2022         * Try to call the startup callback for each present cpu
2023         * depending on the hotplug state of the cpu.
2024         */
2025        for_each_present_cpu(cpu) {
2026                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2027                int cpustate = st->state;
2028
2029                if (cpustate < state)
2030                        continue;
2031
2032                ret = cpuhp_issue_call(cpu, state, true, NULL);
2033                if (ret) {
2034                        if (teardown)
2035                                cpuhp_rollback_install(cpu, state, NULL);
2036                        cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2037                        goto out;
2038                }
2039        }
2040out:
2041        mutex_unlock(&cpuhp_state_mutex);
2042        /*
2043         * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2044         * dynamically allocated state in case of success.
2045         */
2046        if (!ret && dynstate)
2047                return state;
2048        return ret;
2049}
2050EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2051
2052int __cpuhp_setup_state(enum cpuhp_state state,
2053                        const char *name, bool invoke,
2054                        int (*startup)(unsigned int cpu),
2055                        int (*teardown)(unsigned int cpu),
2056                        bool multi_instance)
2057{
2058        int ret;
2059
2060        cpus_read_lock();
2061        ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2062                                             teardown, multi_instance);
2063        cpus_read_unlock();
2064        return ret;
2065}
2066EXPORT_SYMBOL(__cpuhp_setup_state);
2067
2068int __cpuhp_state_remove_instance(enum cpuhp_state state,
2069                                  struct hlist_node *node, bool invoke)
2070{
2071        struct cpuhp_step *sp = cpuhp_get_step(state);
2072        int cpu;
2073
2074        BUG_ON(cpuhp_cb_check(state));
2075
2076        if (!sp->multi_instance)
2077                return -EINVAL;
2078
2079        cpus_read_lock();
2080        mutex_lock(&cpuhp_state_mutex);
2081
2082        if (!invoke || !cpuhp_get_teardown_cb(state))
2083                goto remove;
2084        /*
2085         * Call the teardown callback for each present cpu depending
2086         * on the hotplug state of the cpu. This function is not
2087         * allowed to fail currently!
2088         */
2089        for_each_present_cpu(cpu) {
2090                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2091                int cpustate = st->state;
2092
2093                if (cpustate >= state)
2094                        cpuhp_issue_call(cpu, state, false, node);
2095        }
2096
2097remove:
2098        hlist_del(node);
2099        mutex_unlock(&cpuhp_state_mutex);
2100        cpus_read_unlock();
2101
2102        return 0;
2103}
2104EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2105
2106/**
2107 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2108 * @state:      The state to remove
2109 * @invoke:     If true, the teardown function is invoked for cpus where
2110 *              cpu state >= @state
2111 *
2112 * The caller needs to hold cpus read locked while calling this function.
2113 * The teardown callback is currently not allowed to fail. Think
2114 * about module removal!
2115 */
2116void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2117{
2118        struct cpuhp_step *sp = cpuhp_get_step(state);
2119        int cpu;
2120
2121        BUG_ON(cpuhp_cb_check(state));
2122
2123        lockdep_assert_cpus_held();
2124
2125        mutex_lock(&cpuhp_state_mutex);
2126        if (sp->multi_instance) {
2127                WARN(!hlist_empty(&sp->list),
2128                     "Error: Removing state %d which has instances left.\n",
2129                     state);
2130                goto remove;
2131        }
2132
2133        if (!invoke || !cpuhp_get_teardown_cb(state))
2134                goto remove;
2135
2136        /*
2137         * Call the teardown callback for each present cpu depending
2138         * on the hotplug state of the cpu. This function is not
2139         * allowed to fail currently!
2140         */
2141        for_each_present_cpu(cpu) {
2142                struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2143                int cpustate = st->state;
2144
2145                if (cpustate >= state)
2146                        cpuhp_issue_call(cpu, state, false, NULL);
2147        }
2148remove:
2149        cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2150        mutex_unlock(&cpuhp_state_mutex);
2151}
2152EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2153
2154void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2155{
2156        cpus_read_lock();
2157        __cpuhp_remove_state_cpuslocked(state, invoke);
2158        cpus_read_unlock();
2159}
2160EXPORT_SYMBOL(__cpuhp_remove_state);
2161
2162#ifdef CONFIG_HOTPLUG_SMT
2163static void cpuhp_offline_cpu_device(unsigned int cpu)
2164{
2165        struct device *dev = get_cpu_device(cpu);
2166
2167        dev->offline = true;
2168        /* Tell user space about the state change */
2169        kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2170}
2171
2172static void cpuhp_online_cpu_device(unsigned int cpu)
2173{
2174        struct device *dev = get_cpu_device(cpu);
2175
2176        dev->offline = false;
2177        /* Tell user space about the state change */
2178        kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2179}
2180
2181int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2182{
2183        int cpu, ret = 0;
2184
2185        cpu_maps_update_begin();
2186        for_each_online_cpu(cpu) {
2187                if (topology_is_primary_thread(cpu))
2188                        continue;
2189                ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2190                if (ret)
2191                        break;
2192                /*
2193                 * As this needs to hold the cpu maps lock it's impossible
2194                 * to call device_offline() because that ends up calling
2195                 * cpu_down() which takes cpu maps lock. cpu maps lock
2196                 * needs to be held as this might race against in kernel
2197                 * abusers of the hotplug machinery (thermal management).
2198                 *
2199                 * So nothing would update device:offline state. That would
2200                 * leave the sysfs entry stale and prevent onlining after
2201                 * smt control has been changed to 'off' again. This is
2202                 * called under the sysfs hotplug lock, so it is properly
2203                 * serialized against the regular offline usage.
2204                 */
2205                cpuhp_offline_cpu_device(cpu);
2206        }
2207        if (!ret)
2208                cpu_smt_control = ctrlval;
2209        cpu_maps_update_done();
2210        return ret;
2211}
2212
2213int cpuhp_smt_enable(void)
2214{
2215        int cpu, ret = 0;
2216
2217        cpu_maps_update_begin();
2218        cpu_smt_control = CPU_SMT_ENABLED;
2219        for_each_present_cpu(cpu) {
2220                /* Skip online CPUs and CPUs on offline nodes */
2221                if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2222                        continue;
2223                ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2224                if (ret)
2225                        break;
2226                /* See comment in cpuhp_smt_disable() */
2227                cpuhp_online_cpu_device(cpu);
2228        }
2229        cpu_maps_update_done();
2230        return ret;
2231}
2232#endif
2233
2234#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2235static ssize_t show_cpuhp_state(struct device *dev,
2236                                struct device_attribute *attr, char *buf)
2237{
2238        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2239
2240        return sprintf(buf, "%d\n", st->state);
2241}
2242static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
2243
2244static ssize_t write_cpuhp_target(struct device *dev,
2245                                  struct device_attribute *attr,
2246                                  const char *buf, size_t count)
2247{
2248        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2249        struct cpuhp_step *sp;
2250        int target, ret;
2251
2252        ret = kstrtoint(buf, 10, &target);
2253        if (ret)
2254                return ret;
2255
2256#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2257        if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2258                return -EINVAL;
2259#else
2260        if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2261                return -EINVAL;
2262#endif
2263
2264        ret = lock_device_hotplug_sysfs();
2265        if (ret)
2266                return ret;
2267
2268        mutex_lock(&cpuhp_state_mutex);
2269        sp = cpuhp_get_step(target);
2270        ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2271        mutex_unlock(&cpuhp_state_mutex);
2272        if (ret)
2273                goto out;
2274
2275        if (st->state < target)
2276                ret = cpu_up(dev->id, target);
2277        else
2278                ret = cpu_down(dev->id, target);
2279out:
2280        unlock_device_hotplug();
2281        return ret ? ret : count;
2282}
2283
2284static ssize_t show_cpuhp_target(struct device *dev,
2285                                 struct device_attribute *attr, char *buf)
2286{
2287        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2288
2289        return sprintf(buf, "%d\n", st->target);
2290}
2291static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2292
2293
2294static ssize_t write_cpuhp_fail(struct device *dev,
2295                                struct device_attribute *attr,
2296                                const char *buf, size_t count)
2297{
2298        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2299        struct cpuhp_step *sp;
2300        int fail, ret;
2301
2302        ret = kstrtoint(buf, 10, &fail);
2303        if (ret)
2304                return ret;
2305
2306        if (fail == CPUHP_INVALID) {
2307                st->fail = fail;
2308                return count;
2309        }
2310
2311        if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2312                return -EINVAL;
2313
2314        /*
2315         * Cannot fail STARTING/DYING callbacks.
2316         */
2317        if (cpuhp_is_atomic_state(fail))
2318                return -EINVAL;
2319
2320        /*
2321         * DEAD callbacks cannot fail...
2322         * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2323         * triggering STARTING callbacks, a failure in this state would
2324         * hinder rollback.
2325         */
2326        if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2327                return -EINVAL;
2328
2329        /*
2330         * Cannot fail anything that doesn't have callbacks.
2331         */
2332        mutex_lock(&cpuhp_state_mutex);
2333        sp = cpuhp_get_step(fail);
2334        if (!sp->startup.single && !sp->teardown.single)
2335                ret = -EINVAL;
2336        mutex_unlock(&cpuhp_state_mutex);
2337        if (ret)
2338                return ret;
2339
2340        st->fail = fail;
2341
2342        return count;
2343}
2344
2345static ssize_t show_cpuhp_fail(struct device *dev,
2346                               struct device_attribute *attr, char *buf)
2347{
2348        struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2349
2350        return sprintf(buf, "%d\n", st->fail);
2351}
2352
2353static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2354
2355static struct attribute *cpuhp_cpu_attrs[] = {
2356        &dev_attr_state.attr,
2357        &dev_attr_target.attr,
2358        &dev_attr_fail.attr,
2359        NULL
2360};
2361
2362static const struct attribute_group cpuhp_cpu_attr_group = {
2363        .attrs = cpuhp_cpu_attrs,
2364        .name = "hotplug",
2365        NULL
2366};
2367
2368static ssize_t show_cpuhp_states(struct device *dev,
2369                                 struct device_attribute *attr, char *buf)
2370{
2371        ssize_t cur, res = 0;
2372        int i;
2373
2374        mutex_lock(&cpuhp_state_mutex);
2375        for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2376                struct cpuhp_step *sp = cpuhp_get_step(i);
2377
2378                if (sp->name) {
2379                        cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2380                        buf += cur;
2381                        res += cur;
2382                }
2383        }
2384        mutex_unlock(&cpuhp_state_mutex);
2385        return res;
2386}
2387static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2388
2389static struct attribute *cpuhp_cpu_root_attrs[] = {
2390        &dev_attr_states.attr,
2391        NULL
2392};
2393
2394static const struct attribute_group cpuhp_cpu_root_attr_group = {
2395        .attrs = cpuhp_cpu_root_attrs,
2396        .name = "hotplug",
2397        NULL
2398};
2399
2400#ifdef CONFIG_HOTPLUG_SMT
2401
2402static ssize_t
2403__store_smt_control(struct device *dev, struct device_attribute *attr,
2404                    const char *buf, size_t count)
2405{
2406        int ctrlval, ret;
2407
2408        if (sysfs_streq(buf, "on"))
2409                ctrlval = CPU_SMT_ENABLED;
2410        else if (sysfs_streq(buf, "off"))
2411                ctrlval = CPU_SMT_DISABLED;
2412        else if (sysfs_streq(buf, "forceoff"))
2413                ctrlval = CPU_SMT_FORCE_DISABLED;
2414        else
2415                return -EINVAL;
2416
2417        if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2418                return -EPERM;
2419
2420        if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2421                return -ENODEV;
2422
2423        ret = lock_device_hotplug_sysfs();
2424        if (ret)
2425                return ret;
2426
2427        if (ctrlval != cpu_smt_control) {
2428                switch (ctrlval) {
2429                case CPU_SMT_ENABLED:
2430                        ret = cpuhp_smt_enable();
2431                        break;
2432                case CPU_SMT_DISABLED:
2433                case CPU_SMT_FORCE_DISABLED:
2434                        ret = cpuhp_smt_disable(ctrlval);
2435                        break;
2436                }
2437        }
2438
2439        unlock_device_hotplug();
2440        return ret ? ret : count;
2441}
2442
2443#else /* !CONFIG_HOTPLUG_SMT */
2444static ssize_t
2445__store_smt_control(struct device *dev, struct device_attribute *attr,
2446                    const char *buf, size_t count)
2447{
2448        return -ENODEV;
2449}
2450#endif /* CONFIG_HOTPLUG_SMT */
2451
2452static const char *smt_states[] = {
2453        [CPU_SMT_ENABLED]               = "on",
2454        [CPU_SMT_DISABLED]              = "off",
2455        [CPU_SMT_FORCE_DISABLED]        = "forceoff",
2456        [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
2457        [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
2458};
2459
2460static ssize_t
2461show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2462{
2463        const char *state = smt_states[cpu_smt_control];
2464
2465        return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2466}
2467
2468static ssize_t
2469store_smt_control(struct device *dev, struct device_attribute *attr,
2470                  const char *buf, size_t count)
2471{
2472        return __store_smt_control(dev, attr, buf, count);
2473}
2474static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2475
2476static ssize_t
2477show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2478{
2479        return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2480}
2481static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2482
2483static struct attribute *cpuhp_smt_attrs[] = {
2484        &dev_attr_control.attr,
2485        &dev_attr_active.attr,
2486        NULL
2487};
2488
2489static const struct attribute_group cpuhp_smt_attr_group = {
2490        .attrs = cpuhp_smt_attrs,
2491        .name = "smt",
2492        NULL
2493};
2494
2495static int __init cpu_smt_sysfs_init(void)
2496{
2497        return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2498                                  &cpuhp_smt_attr_group);
2499}
2500
2501static int __init cpuhp_sysfs_init(void)
2502{
2503        int cpu, ret;
2504
2505        ret = cpu_smt_sysfs_init();
2506        if (ret)
2507                return ret;
2508
2509        ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2510                                 &cpuhp_cpu_root_attr_group);
2511        if (ret)
2512                return ret;
2513
2514        for_each_possible_cpu(cpu) {
2515                struct device *dev = get_cpu_device(cpu);
2516
2517                if (!dev)
2518                        continue;
2519                ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2520                if (ret)
2521                        return ret;
2522        }
2523        return 0;
2524}
2525device_initcall(cpuhp_sysfs_init);
2526#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2527
2528/*
2529 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2530 * represents all NR_CPUS bits binary values of 1<<nr.
2531 *
2532 * It is used by cpumask_of() to get a constant address to a CPU
2533 * mask value that has a single bit set only.
2534 */
2535
2536/* cpu_bit_bitmap[0] is empty - so we can back into it */
2537#define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2538#define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2539#define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2540#define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2541
2542const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2543
2544        MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2545        MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2546#if BITS_PER_LONG > 32
2547        MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2548        MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2549#endif
2550};
2551EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2552
2553const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2554EXPORT_SYMBOL(cpu_all_bits);
2555
2556#ifdef CONFIG_INIT_ALL_POSSIBLE
2557struct cpumask __cpu_possible_mask __read_mostly
2558        = {CPU_BITS_ALL};
2559#else
2560struct cpumask __cpu_possible_mask __read_mostly;
2561#endif
2562EXPORT_SYMBOL(__cpu_possible_mask);
2563
2564struct cpumask __cpu_online_mask __read_mostly;
2565EXPORT_SYMBOL(__cpu_online_mask);
2566
2567struct cpumask __cpu_present_mask __read_mostly;
2568EXPORT_SYMBOL(__cpu_present_mask);
2569
2570struct cpumask __cpu_active_mask __read_mostly;
2571EXPORT_SYMBOL(__cpu_active_mask);
2572
2573struct cpumask __cpu_dying_mask __read_mostly;
2574EXPORT_SYMBOL(__cpu_dying_mask);
2575
2576atomic_t __num_online_cpus __read_mostly;
2577EXPORT_SYMBOL(__num_online_cpus);
2578
2579void init_cpu_present(const struct cpumask *src)
2580{
2581        cpumask_copy(&__cpu_present_mask, src);
2582}
2583
2584void init_cpu_possible(const struct cpumask *src)
2585{
2586        cpumask_copy(&__cpu_possible_mask, src);
2587}
2588
2589void init_cpu_online(const struct cpumask *src)
2590{
2591        cpumask_copy(&__cpu_online_mask, src);
2592}
2593
2594void set_cpu_online(unsigned int cpu, bool online)
2595{
2596        /*
2597         * atomic_inc/dec() is required to handle the horrid abuse of this
2598         * function by the reboot and kexec code which invoke it from
2599         * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2600         * regular CPU hotplug is properly serialized.
2601         *
2602         * Note, that the fact that __num_online_cpus is of type atomic_t
2603         * does not protect readers which are not serialized against
2604         * concurrent hotplug operations.
2605         */
2606        if (online) {
2607                if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2608                        atomic_inc(&__num_online_cpus);
2609        } else {
2610                if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2611                        atomic_dec(&__num_online_cpus);
2612        }
2613}
2614
2615/*
2616 * Activate the first processor.
2617 */
2618void __init boot_cpu_init(void)
2619{
2620        int cpu = smp_processor_id();
2621
2622        /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2623        set_cpu_online(cpu, true);
2624        set_cpu_active(cpu, true);
2625        set_cpu_present(cpu, true);
2626        set_cpu_possible(cpu, true);
2627
2628#ifdef CONFIG_SMP
2629        __boot_cpu_id = cpu;
2630#endif
2631}
2632
2633/*
2634 * Must be called _AFTER_ setting up the per_cpu areas
2635 */
2636void __init boot_cpu_hotplug_init(void)
2637{
2638#ifdef CONFIG_SMP
2639        cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2640#endif
2641        this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2642}
2643
2644/*
2645 * These are used for a global "mitigations=" cmdline option for toggling
2646 * optional CPU mitigations.
2647 */
2648enum cpu_mitigations {
2649        CPU_MITIGATIONS_OFF,
2650        CPU_MITIGATIONS_AUTO,
2651        CPU_MITIGATIONS_AUTO_NOSMT,
2652};
2653
2654static enum cpu_mitigations cpu_mitigations __ro_after_init =
2655        CPU_MITIGATIONS_AUTO;
2656
2657static int __init mitigations_parse_cmdline(char *arg)
2658{
2659        if (!strcmp(arg, "off"))
2660                cpu_mitigations = CPU_MITIGATIONS_OFF;
2661        else if (!strcmp(arg, "auto"))
2662                cpu_mitigations = CPU_MITIGATIONS_AUTO;
2663        else if (!strcmp(arg, "auto,nosmt"))
2664                cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2665        else
2666                pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2667                        arg);
2668
2669        return 0;
2670}
2671early_param("mitigations", mitigations_parse_cmdline);
2672
2673/* mitigations=off */
2674bool cpu_mitigations_off(void)
2675{
2676        return cpu_mitigations == CPU_MITIGATIONS_OFF;
2677}
2678EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2679
2680/* mitigations=auto,nosmt */
2681bool cpu_mitigations_auto_nosmt(void)
2682{
2683        return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2684}
2685EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
2686
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