kernel/cpu.c

   1 /* CPU control.
   2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
   3  *
   4  * This code is licenced under the GPL.
   5  */
   6 #include <linux/proc_fs.h>
   7 #include <linux/smp.h>
   8 #include <linux/init.h>
   9 #include <linux/notifier.h>
  10 #include <linux/sched.h>
  11 #include <linux/unistd.h>
  12 #include <linux/cpu.h>
  13 #include <linux/oom.h>
  14 #include <linux/rcupdate.h>
  15 #include <linux/export.h>
  16 #include <linux/bug.h>
  17 #include <linux/kthread.h>
  18 #include <linux/stop_machine.h>
  19 #include <linux/mutex.h>
  20 #include <linux/gfp.h>
  21 #include <linux/suspend.h>
  22 #include <linux/lockdep.h>
  23 #include <linux/tick.h>
  24 #include <linux/irq.h>
  25 #include <linux/smpboot.h>
  26 #include <linux/relay.h>
  27 #include <linux/slab.h>
  28
  29 #include <trace/events/power.h>
  30 #define CREATE_TRACE_POINTS
  31 #include <trace/events/cpuhp.h>
  32
  33 #include "smpboot.h"
  34
  35 /**
  36  * cpuhp_cpu_state - Per cpu hotplug state storage
  37  * @state:      The current cpu state
  38  * @target:     The target state
  39  * @thread:     Pointer to the hotplug thread
  40  * @should_run: Thread should execute
  41  * @rollback:   Perform a rollback
  42  * @single:     Single callback invocation
  43  * @bringup:    Single callback bringup or teardown selector
  44  * @cb_state:   The state for a single callback (install/uninstall)
  45  * @result:     Result of the operation
  46  * @done:       Signal completion to the issuer of the task
  47  */
  48 struct cpuhp_cpu_state {
  49         enum cpuhp_state        state;
  50         enum cpuhp_state        target;
  51 #ifdef CONFIG_SMP
  52         struct task_struct      *thread;
  53         bool                    should_run;
  54         bool                    rollback;
  55         bool                    single;
  56         bool                    bringup;
  57         bool                    booted_once;
  58         struct hlist_node       *node;
  59         enum cpuhp_state        cb_state;
  60         int                     result;
  61         struct completion       done;
  62 #endif
  63 };
  64
  65 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
  66
  67 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
  68 static struct lock_class_key cpuhp_state_key;
  69 static struct lockdep_map cpuhp_state_lock_map =
  70         STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key);
  71 #endif
  72
  73 /**
  74  * cpuhp_step - Hotplug state machine step
  75  * @name:       Name of the step
  76  * @startup:    Startup function of the step
  77  * @teardown:   Teardown function of the step
  78  * @skip_onerr: Do not invoke the functions on error rollback
  79  *              Will go away once the notifiers are gone
  80  * @cant_stop:  Bringup/teardown can't be stopped at this step
  81  */
  82 struct cpuhp_step {
  83         const char              *name;
  84         union {
  85                 int             (*single)(unsigned int cpu);
  86                 int             (*multi)(unsigned int cpu,
  87                                          struct hlist_node *node);
  88         } startup;
  89         union {
  90                 int             (*single)(unsigned int cpu);
  91                 int             (*multi)(unsigned int cpu,
  92                                          struct hlist_node *node);
  93         } teardown;
  94         struct hlist_head       list;
  95         bool                    skip_onerr;
  96         bool                    cant_stop;
  97         bool                    multi_instance;
  98 };
  99
 100 static DEFINE_MUTEX(cpuhp_state_mutex);
 101 static struct cpuhp_step cpuhp_bp_states[];
 102 static struct cpuhp_step cpuhp_ap_states[];
 103
 104 static bool cpuhp_is_ap_state(enum cpuhp_state state)
 105 {
 106         /*
 107          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
 108          * purposes as that state is handled explicitly in cpu_down.
 109          */
 110         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
 111 }
 112
 113 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
 114 {
 115         struct cpuhp_step *sp;
 116
 117         sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
 118         return sp + state;
 119 }
 120
 121 /**
 122  * cpuhp_invoke_callback _ Invoke the callbacks for a given state
 123  * @cpu:        The cpu for which the callback should be invoked
 124  * @step:       The step in the state machine
 125  * @bringup:    True if the bringup callback should be invoked
 126  *
 127  * Called from cpu hotplug and from the state register machinery.
 128  */
 129 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 130                                  bool bringup, struct hlist_node *node)
 131 {
 132         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 133         struct cpuhp_step *step = cpuhp_get_step(state);
 134         int (*cbm)(unsigned int cpu, struct hlist_node *node);
 135         int (*cb)(unsigned int cpu);
 136         int ret, cnt;
 137
 138         if (!step->multi_instance) {
 139                 cb = bringup ? step->startup.single : step->teardown.single;
 140                 if (!cb)
 141                         return 0;
 142                 trace_cpuhp_enter(cpu, st->target, state, cb);
 143                 ret = cb(cpu);
 144                 trace_cpuhp_exit(cpu, st->state, state, ret);
 145                 return ret;
 146         }
 147         cbm = bringup ? step->startup.multi : step->teardown.multi;
 148         if (!cbm)
 149                 return 0;
 150
 151         /* Single invocation for instance add/remove */
 152         if (node) {
 153                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 154                 ret = cbm(cpu, node);
 155                 trace_cpuhp_exit(cpu, st->state, state, ret);
 156                 return ret;
 157         }
 158
 159         /* State transition. Invoke on all instances */
 160         cnt = 0;
 161         hlist_for_each(node, &step->list) {
 162                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
 163                 ret = cbm(cpu, node);
 164                 trace_cpuhp_exit(cpu, st->state, state, ret);
 165                 if (ret)
 166                         goto err;
 167                 cnt++;
 168         }
 169         return 0;
 170 err:
 171         /* Rollback the instances if one failed */
 172         cbm = !bringup ? step->startup.multi : step->teardown.multi;
 173         if (!cbm)
 174                 return ret;
 175
 176         hlist_for_each(node, &step->list) {
 177                 if (!cnt--)
 178                         break;
 179                 cbm(cpu, node);
 180         }
 181         return ret;
 182 }
 183
 184 #ifdef CONFIG_SMP
 185 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
 186 static DEFINE_MUTEX(cpu_add_remove_lock);
 187 bool cpuhp_tasks_frozen;
 188 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 189
 190 /*
 191  * The following two APIs (cpu_maps_update_begin/done) must be used when
 192  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 193  * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
 194  * hotplug callback (un)registration performed using __register_cpu_notifier()
 195  * or __unregister_cpu_notifier().
 196  */
 197 void cpu_maps_update_begin(void)
 198 {
 199         mutex_lock(&cpu_add_remove_lock);
 200 }
 201 EXPORT_SYMBOL(cpu_notifier_register_begin);
 202
 203 void cpu_maps_update_done(void)
 204 {
 205         mutex_unlock(&cpu_add_remove_lock);
 206 }
 207 EXPORT_SYMBOL(cpu_notifier_register_done);
 208
 209 static RAW_NOTIFIER_HEAD(cpu_chain);
 210
 211 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 212  * Should always be manipulated under cpu_add_remove_lock
 213  */
 214 static int cpu_hotplug_disabled;
 215
 216 #ifdef CONFIG_HOTPLUG_CPU
 217
 218 static struct {
 219         struct task_struct *active_writer;
 220         /* wait queue to wake up the active_writer */
 221         wait_queue_head_t wq;
 222         /* verifies that no writer will get active while readers are active */
 223         struct mutex lock;
 224         /*
 225          * Also blocks the new readers during
 226          * an ongoing cpu hotplug operation.
 227          */
 228         atomic_t refcount;
 229
 230 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 231         struct lockdep_map dep_map;
 232 #endif
 233 } cpu_hotplug = {
 234         .active_writer = NULL,
 235         .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
 236         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
 237 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 238         .dep_map = STATIC_LOCKDEP_MAP_INIT("cpu_hotplug.dep_map", &cpu_hotplug.dep_map),
 239 #endif
 240 };
 241
 242 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
 243 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
 244 #define cpuhp_lock_acquire_tryread() \
 245                                   lock_map_acquire_tryread(&cpu_hotplug.dep_map)
 246 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 247 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 248
 249
 250 void get_online_cpus(void)
 251 {
 252         might_sleep();
 253         if (cpu_hotplug.active_writer == current)
 254                 return;
 255         cpuhp_lock_acquire_read();
 256         mutex_lock(&cpu_hotplug.lock);
 257         atomic_inc(&cpu_hotplug.refcount);
 258         mutex_unlock(&cpu_hotplug.lock);
 259 }
 260 EXPORT_SYMBOL_GPL(get_online_cpus);
 261
 262 void put_online_cpus(void)
 263 {
 264         int refcount;
 265
 266         if (cpu_hotplug.active_writer == current)
 267                 return;
 268
 269         refcount = atomic_dec_return(&cpu_hotplug.refcount);
 270         if (WARN_ON(refcount < 0)) /* try to fix things up */
 271                 atomic_inc(&cpu_hotplug.refcount);
 272
 273         if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 274                 wake_up(&cpu_hotplug.wq);
 275
 276         cpuhp_lock_release();
 277
 278 }
 279 EXPORT_SYMBOL_GPL(put_online_cpus);
 280
 281 /*
 282  * This ensures that the hotplug operation can begin only when the
 283  * refcount goes to zero.
 284  *
 285  * Note that during a cpu-hotplug operation, the new readers, if any,
 286  * will be blocked by the cpu_hotplug.lock
 287  *
 288  * Since cpu_hotplug_begin() is always called after invoking
 289  * cpu_maps_update_begin(), we can be sure that only one writer is active.
 290  *
 291  * Note that theoretically, there is a possibility of a livelock:
 292  * - Refcount goes to zero, last reader wakes up the sleeping
 293  *   writer.
 294  * - Last reader unlocks the cpu_hotplug.lock.
 295  * - A new reader arrives at this moment, bumps up the refcount.
 296  * - The writer acquires the cpu_hotplug.lock finds the refcount
 297  *   non zero and goes to sleep again.
 298  *
 299  * However, this is very difficult to achieve in practice since
 300  * get_online_cpus() not an api which is called all that often.
 301  *
 302  */
 303 void cpu_hotplug_begin(void)
 304 {
 305         DEFINE_WAIT(wait);
 306
 307         cpu_hotplug.active_writer = current;
 308         cpuhp_lock_acquire();
 309
 310         for (;;) {
 311                 mutex_lock(&cpu_hotplug.lock);
 312                 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 313                 if (likely(!atomic_read(&cpu_hotplug.refcount)))
 314                                 break;
 315                 mutex_unlock(&cpu_hotplug.lock);
 316                 schedule();
 317         }
 318         finish_wait(&cpu_hotplug.wq, &wait);
 319 }
 320
 321 void cpu_hotplug_done(void)
 322 {
 323         cpu_hotplug.active_writer = NULL;
 324         mutex_unlock(&cpu_hotplug.lock);
 325         cpuhp_lock_release();
 326 }
 327
 328 /*
 329  * Wait for currently running CPU hotplug operations to complete (if any) and
 330  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 331  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 332  * hotplug path before performing hotplug operations. So acquiring that lock
 333  * guarantees mutual exclusion from any currently running hotplug operations.
 334  */
 335 void cpu_hotplug_disable(void)
 336 {
 337         cpu_maps_update_begin();
 338         cpu_hotplug_disabled++;
 339         cpu_maps_update_done();
 340 }
 341 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 342
 343 static void __cpu_hotplug_enable(void)
 344 {
 345         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
 346                 return;
 347         cpu_hotplug_disabled--;
 348 }
 349
 350 void cpu_hotplug_enable(void)
 351 {
 352         cpu_maps_update_begin();
 353         __cpu_hotplug_enable();
 354         cpu_maps_update_done();
 355 }
 356 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 357 #endif  /* CONFIG_HOTPLUG_CPU */
 358
 359 #ifdef CONFIG_HOTPLUG_SMT
 360 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
 361 EXPORT_SYMBOL_GPL(cpu_smt_control);
 362
 363 static bool cpu_smt_available __read_mostly;
 364
 365 void __init cpu_smt_disable(bool force)
 366 {
 367         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
 368                 cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
 369                 return;
 370
 371         if (force) {
 372                 pr_info("SMT: Force disabled\n");
 373                 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
 374         } else {
 375                 cpu_smt_control = CPU_SMT_DISABLED;
 376         }
 377 }
 378
 379 /*
 380  * The decision whether SMT is supported can only be done after the full
 381  * CPU identification. Called from architecture code before non boot CPUs
 382  * are brought up.
 383  */
 384 void __init cpu_smt_check_topology_early(void)
 385 {
 386         if (!topology_smt_supported())
 387                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 388 }
 389
 390 /*
 391  * If SMT was disabled by BIOS, detect it here, after the CPUs have been
 392  * brought online. This ensures the smt/l1tf sysfs entries are consistent
 393  * with reality. cpu_smt_available is set to true during the bringup of non
 394  * boot CPUs when a SMT sibling is detected. Note, this may overwrite
 395  * cpu_smt_control's previous setting.
 396  */
 397 void __init cpu_smt_check_topology(void)
 398 {
 399         if (!cpu_smt_available)
 400                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
 401 }
 402
 403 static int __init smt_cmdline_disable(char *str)
 404 {
 405         cpu_smt_disable(str && !strcmp(str, "force"));
 406         return 0;
 407 }
 408 early_param("nosmt", smt_cmdline_disable);
 409
 410 static inline bool cpu_smt_allowed(unsigned int cpu)
 411 {
 412         if (topology_is_primary_thread(cpu))
 413                 return true;
 414
 415         /*
 416          * If the CPU is not a 'primary' thread and the booted_once bit is
 417          * set then the processor has SMT support. Store this information
 418          * for the late check of SMT support in cpu_smt_check_topology().
 419          */
 420         if (per_cpu(cpuhp_state, cpu).booted_once)
 421                 cpu_smt_available = true;
 422
 423         if (cpu_smt_control == CPU_SMT_ENABLED)
 424                 return true;
 425
 426         /*
 427          * On x86 it's required to boot all logical CPUs at least once so
 428          * that the init code can get a chance to set CR4.MCE on each
 429          * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
 430          * core will shutdown the machine.
 431          */
 432         return !per_cpu(cpuhp_state, cpu).booted_once;
 433 }
 434 #else
 435 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
 436 #endif
 437
 438 /* Need to know about CPUs going up/down? */
 439 int register_cpu_notifier(struct notifier_block *nb)
 440 {
 441         int ret;
 442         cpu_maps_update_begin();
 443         ret = raw_notifier_chain_register(&cpu_chain, nb);
 444         cpu_maps_update_done();
 445         return ret;
 446 }
 447
 448 int __register_cpu_notifier(struct notifier_block *nb)
 449 {
 450         return raw_notifier_chain_register(&cpu_chain, nb);
 451 }
 452
 453 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 454                         int *nr_calls)
 455 {
 456         unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 457         void *hcpu = (void *)(long)cpu;
 458
 459         int ret;
 460
 461         ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 462                                         nr_calls);
 463
 464         return notifier_to_errno(ret);
 465 }
 466
 467 static int cpu_notify(unsigned long val, unsigned int cpu)
 468 {
 469         return __cpu_notify(val, cpu, -1, NULL);
 470 }
 471
 472 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 473 {
 474         BUG_ON(cpu_notify(val, cpu));
 475 }
 476
 477 /* Notifier wrappers for transitioning to state machine */
 478 static int notify_prepare(unsigned int cpu)
 479 {
 480         int nr_calls = 0;
 481         int ret;
 482
 483         ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 484         if (ret) {
 485                 nr_calls--;
 486                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 487                                 __func__, cpu);
 488                 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 489         }
 490         return ret;
 491 }
 492
 493 static int notify_online(unsigned int cpu)
 494 {
 495         cpu_notify(CPU_ONLINE, cpu);
 496         return 0;
 497 }
 498
 499 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st);
 500
 501 static int bringup_wait_for_ap(unsigned int cpu)
 502 {
 503         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 504
 505         /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
 506         wait_for_completion(&st->done);
 507         if (WARN_ON_ONCE((!cpu_online(cpu))))
 508                 return -ECANCELED;
 509
 510         /* Unpark the stopper thread and the hotplug thread of the target cpu */
 511         stop_machine_unpark(cpu);
 512         kthread_unpark(st->thread);
 513
 514         /*
 515          * SMT soft disabling on X86 requires to bring the CPU out of the
 516          * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
 517          * CPU marked itself as booted_once in cpu_notify_starting() so the
 518          * cpu_smt_allowed() check will now return false if this is not the
 519          * primary sibling.
 520          */
 521         if (!cpu_smt_allowed(cpu))
 522                 return -ECANCELED;
 523
 524         /* Should we go further up ? */
 525         if (st->target > CPUHP_AP_ONLINE_IDLE) {
 526                 __cpuhp_kick_ap_work(st);
 527                 wait_for_completion(&st->done);
 528         }
 529         return st->result;
 530 }
 531
 532 static int bringup_cpu(unsigned int cpu)
 533 {
 534         struct task_struct *idle = idle_thread_get(cpu);
 535         int ret;
 536
 537         /*
 538          * Some architectures have to walk the irq descriptors to
 539          * setup the vector space for the cpu which comes online.
 540          * Prevent irq alloc/free across the bringup.
 541          */
 542         irq_lock_sparse();
 543
 544         /* Arch-specific enabling code. */
 545         ret = __cpu_up(cpu, idle);
 546         irq_unlock_sparse();
 547         if (ret) {
 548                 cpu_notify(CPU_UP_CANCELED, cpu);
 549                 return ret;
 550         }
 551         return bringup_wait_for_ap(cpu);
 552 }
 553
 554 /*
 555  * Hotplug state machine related functions
 556  */
 557 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
 558 {
 559         for (st->state++; st->state < st->target; st->state++) {
 560                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 561
 562                 if (!step->skip_onerr)
 563                         cpuhp_invoke_callback(cpu, st->state, true, NULL);
 564         }
 565 }
 566
 567 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 568                                 enum cpuhp_state target)
 569 {
 570         enum cpuhp_state prev_state = st->state;
 571         int ret = 0;
 572
 573         for (; st->state > target; st->state--) {
 574                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL);
 575                 if (ret) {
 576                         st->target = prev_state;
 577                         undo_cpu_down(cpu, st);
 578                         break;
 579                 }
 580         }
 581         return ret;
 582 }
 583
 584 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
 585 {
 586         for (st->state--; st->state > st->target; st->state--) {
 587                 struct cpuhp_step *step = cpuhp_get_step(st->state);
 588
 589                 if (!step->skip_onerr)
 590                         cpuhp_invoke_callback(cpu, st->state, false, NULL);
 591         }
 592 }
 593
 594 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 595                               enum cpuhp_state target)
 596 {
 597         enum cpuhp_state prev_state = st->state;
 598         int ret = 0;
 599
 600         while (st->state < target) {
 601                 st->state++;
 602                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL);
 603                 if (ret) {
 604                         st->target = prev_state;
 605                         undo_cpu_up(cpu, st);
 606                         break;
 607                 }
 608         }
 609         return ret;
 610 }
 611
 612 /*
 613  * The cpu hotplug threads manage the bringup and teardown of the cpus
 614  */
 615 static void cpuhp_create(unsigned int cpu)
 616 {
 617         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 618
 619         init_completion(&st->done);
 620 }
 621
 622 static int cpuhp_should_run(unsigned int cpu)
 623 {
 624         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 625
 626         return st->should_run;
 627 }
 628
 629 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
 630 static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
 631 {
 632         enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
 633
 634         return cpuhp_down_callbacks(cpu, st, target);
 635 }
 636
 637 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
 638 static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
 639 {
 640         return cpuhp_up_callbacks(cpu, st, st->target);
 641 }
 642
 643 /*
 644  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 645  * callbacks when a state gets [un]installed at runtime.
 646  */
 647 static void cpuhp_thread_fun(unsigned int cpu)
 648 {
 649         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 650         int ret = 0;
 651
 652         /*
 653          * Paired with the mb() in cpuhp_kick_ap_work and
 654          * cpuhp_invoke_ap_callback, so the work set is consistent visible.
 655          */
 656         smp_mb();
 657         if (!st->should_run)
 658                 return;
 659
 660         st->should_run = false;
 661
 662         lock_map_acquire(&cpuhp_state_lock_map);
 663         /* Single callback invocation for [un]install ? */
 664         if (st->single) {
 665                 if (st->cb_state < CPUHP_AP_ONLINE) {
 666                         local_irq_disable();
 667                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 668                                                     st->bringup, st->node);
 669                         local_irq_enable();
 670                 } else {
 671                         ret = cpuhp_invoke_callback(cpu, st->cb_state,
 672                                                     st->bringup, st->node);
 673                 }
 674         } else if (st->rollback) {
 675                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 676
 677                 undo_cpu_down(cpu, st);
 678                 /*
 679                  * This is a momentary workaround to keep the notifier users
 680                  * happy. Will go away once we got rid of the notifiers.
 681                  */
 682                 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 683                 st->rollback = false;
 684         } else {
 685                 /* Cannot happen .... */
 686                 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 687
 688                 /* Regular hotplug work */
 689                 if (st->state < st->target)
 690                         ret = cpuhp_ap_online(cpu, st);
 691                 else if (st->state > st->target)
 692                         ret = cpuhp_ap_offline(cpu, st);
 693         }
 694         lock_map_release(&cpuhp_state_lock_map);
 695         st->result = ret;
 696         complete(&st->done);
 697 }
 698
 699 /* Invoke a single callback on a remote cpu */
 700 static int
 701 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
 702                          struct hlist_node *node)
 703 {
 704         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 705
 706         if (!cpu_online(cpu))
 707                 return 0;
 708
 709         lock_map_acquire(&cpuhp_state_lock_map);
 710         lock_map_release(&cpuhp_state_lock_map);
 711
 712         /*
 713          * If we are up and running, use the hotplug thread. For early calls
 714          * we invoke the thread function directly.
 715          */
 716         if (!st->thread)
 717                 return cpuhp_invoke_callback(cpu, state, bringup, node);
 718
 719         st->cb_state = state;
 720         st->single = true;
 721         st->bringup = bringup;
 722         st->node = node;
 723
 724         /*
 725          * Make sure the above stores are visible before should_run becomes
 726          * true. Paired with the mb() above in cpuhp_thread_fun()
 727          */
 728         smp_mb();
 729         st->should_run = true;
 730         wake_up_process(st->thread);
 731         wait_for_completion(&st->done);
 732         return st->result;
 733 }
 734
 735 /* Regular hotplug invocation of the AP hotplug thread */
 736 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
 737 {
 738         st->result = 0;
 739         st->single = false;
 740         /*
 741          * Make sure the above stores are visible before should_run becomes
 742          * true. Paired with the mb() above in cpuhp_thread_fun()
 743          */
 744         smp_mb();
 745         st->should_run = true;
 746         wake_up_process(st->thread);
 747 }
 748
 749 static int cpuhp_kick_ap_work(unsigned int cpu)
 750 {
 751         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 752         enum cpuhp_state state = st->state;
 753
 754         trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
 755         lock_map_acquire(&cpuhp_state_lock_map);
 756         lock_map_release(&cpuhp_state_lock_map);
 757         __cpuhp_kick_ap_work(st);
 758         wait_for_completion(&st->done);
 759         trace_cpuhp_exit(cpu, st->state, state, st->result);
 760         return st->result;
 761 }
 762
 763 static struct smp_hotplug_thread cpuhp_threads = {
 764         .store                  = &cpuhp_state.thread,
 765         .create                 = &cpuhp_create,
 766         .thread_should_run      = cpuhp_should_run,
 767         .thread_fn              = cpuhp_thread_fun,
 768         .thread_comm            = "cpuhp/%u",
 769         .selfparking            = true,
 770 };
 771
 772 void __init cpuhp_threads_init(void)
 773 {
 774         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 775         kthread_unpark(this_cpu_read(cpuhp_state.thread));
 776 }
 777
 778 EXPORT_SYMBOL(register_cpu_notifier);
 779 EXPORT_SYMBOL(__register_cpu_notifier);
 780 void unregister_cpu_notifier(struct notifier_block *nb)
 781 {
 782         cpu_maps_update_begin();
 783         raw_notifier_chain_unregister(&cpu_chain, nb);
 784         cpu_maps_update_done();
 785 }
 786 EXPORT_SYMBOL(unregister_cpu_notifier);
 787
 788 void __unregister_cpu_notifier(struct notifier_block *nb)
 789 {
 790         raw_notifier_chain_unregister(&cpu_chain, nb);
 791 }
 792 EXPORT_SYMBOL(__unregister_cpu_notifier);
 793
 794 #ifdef CONFIG_HOTPLUG_CPU
 795 /**
 796  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 797  * @cpu: a CPU id
 798  *
 799  * This function walks all processes, finds a valid mm struct for each one and
 800  * then clears a corresponding bit in mm's cpumask.  While this all sounds
 801  * trivial, there are various non-obvious corner cases, which this function
 802  * tries to solve in a safe manner.
 803  *
 804  * Also note that the function uses a somewhat relaxed locking scheme, so it may
 805  * be called only for an already offlined CPU.
 806  */
 807 void clear_tasks_mm_cpumask(int cpu)
 808 {
 809         struct task_struct *p;
 810
 811         /*
 812          * This function is called after the cpu is taken down and marked
 813          * offline, so its not like new tasks will ever get this cpu set in
 814          * their mm mask. -- Peter Zijlstra
 815          * Thus, we may use rcu_read_lock() here, instead of grabbing
 816          * full-fledged tasklist_lock.
 817          */
 818         WARN_ON(cpu_online(cpu));
 819         rcu_read_lock();
 820         for_each_process(p) {
 821                 struct task_struct *t;
 822
 823                 /*
 824                  * Main thread might exit, but other threads may still have
 825                  * a valid mm. Find one.
 826                  */
 827                 t = find_lock_task_mm(p);
 828                 if (!t)
 829                         continue;
 830                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 831                 task_unlock(t);
 832         }
 833         rcu_read_unlock();
 834 }
 835
 836 static inline void check_for_tasks(int dead_cpu)
 837 {
 838         struct task_struct *g, *p;
 839
 840         read_lock(&tasklist_lock);
 841         for_each_process_thread(g, p) {
 842                 if (!p->on_rq)
 843                         continue;
 844                 /*
 845                  * We do the check with unlocked task_rq(p)->lock.
 846                  * Order the reading to do not warn about a task,
 847                  * which was running on this cpu in the past, and
 848                  * it's just been woken on another cpu.
 849                  */
 850                 rmb();
 851                 if (task_cpu(p) != dead_cpu)
 852                         continue;
 853
 854                 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
 855                         p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
 856         }
 857         read_unlock(&tasklist_lock);
 858 }
 859
 860 static int notify_down_prepare(unsigned int cpu)
 861 {
 862         int err, nr_calls = 0;
 863
 864         err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
 865         if (err) {
 866                 nr_calls--;
 867                 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
 868                 pr_warn("%s: attempt to take down CPU %u failed\n",
 869                                 __func__, cpu);
 870         }
 871         return err;
 872 }
 873
 874 /* Take this CPU down. */
 875 static int take_cpu_down(void *_param)
 876 {
 877         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 878         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 879         int err, cpu = smp_processor_id();
 880
 881         /* Ensure this CPU doesn't handle any more interrupts. */
 882         err = __cpu_disable();
 883         if (err < 0)
 884                 return err;
 885
 886         /*
 887          * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
 888          * do this step again.
 889          */
 890         WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
 891         st->state--;
 892         /* Invoke the former CPU_DYING callbacks */
 893         for (; st->state > target; st->state--)
 894                 cpuhp_invoke_callback(cpu, st->state, false, NULL);
 895
 896         /* Give up timekeeping duties */
 897         tick_handover_do_timer();
 898         /* Park the stopper thread */
 899         stop_machine_park(cpu);
 900         return 0;
 901 }
 902
 903 static int takedown_cpu(unsigned int cpu)
 904 {
 905         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 906         int err;
 907
 908         /* Park the smpboot threads */
 909         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 910
 911         /*
 912          * Prevent irq alloc/free while the dying cpu reorganizes the
 913          * interrupt affinities.
 914          */
 915         irq_lock_sparse();
 916
 917         /*
 918          * So now all preempt/rcu users must observe !cpu_active().
 919          */
 920         err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
 921         if (err) {
 922                 /* CPU refused to die */
 923                 irq_unlock_sparse();
 924                 /* Unpark the hotplug thread so we can rollback there */
 925                 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 926                 return err;
 927         }
 928         BUG_ON(cpu_online(cpu));
 929
 930         /*
 931          * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
 932          * runnable tasks from the cpu, there's only the idle task left now
 933          * that the migration thread is done doing the stop_machine thing.
 934          *
 935          * Wait for the stop thread to go away.
 936          */
 937         wait_for_completion(&st->done);
 938         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
 939
 940         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
 941         irq_unlock_sparse();
 942
 943         hotplug_cpu__broadcast_tick_pull(cpu);
 944         /* This actually kills the CPU. */
 945         __cpu_die(cpu);
 946
 947         tick_cleanup_dead_cpu(cpu);
 948         return 0;
 949 }
 950
 951 static int notify_dead(unsigned int cpu)
 952 {
 953         cpu_notify_nofail(CPU_DEAD, cpu);
 954         check_for_tasks(cpu);
 955         return 0;
 956 }
 957
 958 static void cpuhp_complete_idle_dead(void *arg)
 959 {
 960         struct cpuhp_cpu_state *st = arg;
 961
 962         complete(&st->done);
 963 }
 964
 965 void cpuhp_report_idle_dead(void)
 966 {
 967         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 968
 969         BUG_ON(st->state != CPUHP_AP_OFFLINE);
 970         rcu_report_dead(smp_processor_id());
 971         st->state = CPUHP_AP_IDLE_DEAD;
 972         /*
 973          * We cannot call complete after rcu_report_dead() so we delegate it
 974          * to an online cpu.
 975          */
 976         smp_call_function_single(cpumask_first(cpu_online_mask),
 977                                  cpuhp_complete_idle_dead, st, 0);
 978 }
 979
 980 #else
 981 #define notify_down_prepare     NULL
 982 #define takedown_cpu            NULL
 983 #define notify_dead             NULL
 984 #endif
 985
 986 #ifdef CONFIG_HOTPLUG_CPU
 987
 988 /* Requires cpu_add_remove_lock to be held */
 989 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 990                            enum cpuhp_state target)
 991 {
 992         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 993         int prev_state, ret = 0;
 994         bool hasdied = false;
 995
 996         if (num_online_cpus() == 1)
 997                 return -EBUSY;
 998
 999         if (!cpu_present(cpu))
1000                 return -EINVAL;
1001
1002         cpu_hotplug_begin();
1003
1004         cpuhp_tasks_frozen = tasks_frozen;
1005
1006         prev_state = st->state;
1007         st->target = target;
1008         /*
1009          * If the current CPU state is in the range of the AP hotplug thread,
1010          * then we need to kick the thread.
1011          */
1012         if (st->state > CPUHP_TEARDOWN_CPU) {
1013                 ret = cpuhp_kick_ap_work(cpu);
1014                 /*
1015                  * The AP side has done the error rollback already. Just
1016                  * return the error code..
1017                  */
1018                 if (ret)
1019                         goto out;
1020
1021                 /*
1022                  * We might have stopped still in the range of the AP hotplug
1023                  * thread. Nothing to do anymore.
1024                  */
1025                 if (st->state > CPUHP_TEARDOWN_CPU)
1026                         goto out;
1027         }
1028         /*
1029          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1030          * to do the further cleanups.
1031          */
1032         ret = cpuhp_down_callbacks(cpu, st, target);
1033         if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1034                 st->target = prev_state;
1035                 st->rollback = true;
1036                 cpuhp_kick_ap_work(cpu);
1037         }
1038
1039         hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
1040 out:
1041         cpu_hotplug_done();
1042         /* This post dead nonsense must die */
1043         if (!ret && hasdied)
1044                 cpu_notify_nofail(CPU_POST_DEAD, cpu);
1045         return ret;
1046 }
1047
1048 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1049 {
1050         if (cpu_hotplug_disabled)
1051                 return -EBUSY;
1052         return _cpu_down(cpu, 0, target);
1053 }
1054
1055 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
1056 {
1057         int err;
1058
1059         cpu_maps_update_begin();
1060         err = cpu_down_maps_locked(cpu, target);
1061         cpu_maps_update_done();
1062         return err;
1063 }
1064 int cpu_down(unsigned int cpu)
1065 {
1066         return do_cpu_down(cpu, CPUHP_OFFLINE);
1067 }
1068 EXPORT_SYMBOL(cpu_down);
1069 #endif /*CONFIG_HOTPLUG_CPU*/
1070
1071 /**
1072  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1073  * @cpu: cpu that just started
1074  *
1075  * It must be called by the arch code on the new cpu, before the new cpu
1076  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1077  */
1078 void notify_cpu_starting(unsigned int cpu)
1079 {
1080         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1081         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1082
1083         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1084         st->booted_once = true;
1085         while (st->state < target) {
1086                 st->state++;
1087                 cpuhp_invoke_callback(cpu, st->state, true, NULL);
1088         }
1089 }
1090
1091 /*
1092  * Called from the idle task. Wake up the controlling task which brings the
1093  * stopper and the hotplug thread of the upcoming CPU up and then delegates
1094  * the rest of the online bringup to the hotplug thread.
1095  */
1096 void cpuhp_online_idle(enum cpuhp_state state)
1097 {
1098         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1099
1100         /* Happens for the boot cpu */
1101         if (state != CPUHP_AP_ONLINE_IDLE)
1102                 return;
1103
1104         st->state = CPUHP_AP_ONLINE_IDLE;
1105         complete(&st->done);
1106 }
1107
1108 /* Requires cpu_add_remove_lock to be held */
1109 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1110 {
1111         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1112         struct task_struct *idle;
1113         int ret = 0;
1114
1115         cpu_hotplug_begin();
1116
1117         if (!cpu_present(cpu)) {
1118                 ret = -EINVAL;
1119                 goto out;
1120         }
1121
1122         /*
1123          * The caller of do_cpu_up might have raced with another
1124          * caller. Ignore it for now.
1125          */
1126         if (st->state >= target)
1127                 goto out;
1128
1129         if (st->state == CPUHP_OFFLINE) {
1130                 /* Let it fail before we try to bring the cpu up */
1131                 idle = idle_thread_get(cpu);
1132                 if (IS_ERR(idle)) {
1133                         ret = PTR_ERR(idle);
1134                         goto out;
1135                 }
1136         }
1137
1138         cpuhp_tasks_frozen = tasks_frozen;
1139
1140         st->target = target;
1141         /*
1142          * If the current CPU state is in the range of the AP hotplug thread,
1143          * then we need to kick the thread once more.
1144          */
1145         if (st->state > CPUHP_BRINGUP_CPU) {
1146                 ret = cpuhp_kick_ap_work(cpu);
1147                 /*
1148                  * The AP side has done the error rollback already. Just
1149                  * return the error code..
1150                  */
1151                 if (ret)
1152                         goto out;
1153         }
1154
1155         /*
1156          * Try to reach the target state. We max out on the BP at
1157          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1158          * responsible for bringing it up to the target state.
1159          */
1160         target = min((int)target, CPUHP_BRINGUP_CPU);
1161         ret = cpuhp_up_callbacks(cpu, st, target);
1162 out:
1163         cpu_hotplug_done();
1164         return ret;
1165 }
1166
1167 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1168 {
1169         int err = 0;
1170
1171         if (!cpu_possible(cpu)) {
1172                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1173                        cpu);
1174 #if defined(CONFIG_IA64)
1175                 pr_err("please check additional_cpus= boot parameter\n");
1176 #endif
1177                 return -EINVAL;
1178         }
1179
1180         err = try_online_node(cpu_to_node(cpu));
1181         if (err)
1182                 return err;
1183
1184         cpu_maps_update_begin();
1185
1186         if (cpu_hotplug_disabled) {
1187                 err = -EBUSY;
1188                 goto out;
1189         }
1190         if (!cpu_smt_allowed(cpu)) {
1191                 err = -EPERM;
1192                 goto out;
1193         }
1194
1195         err = _cpu_up(cpu, 0, target);
1196 out:
1197         cpu_maps_update_done();
1198         return err;
1199 }
1200
1201 int cpu_up(unsigned int cpu)
1202 {
1203         return do_cpu_up(cpu, CPUHP_ONLINE);
1204 }
1205 EXPORT_SYMBOL_GPL(cpu_up);
1206
1207 #ifdef CONFIG_PM_SLEEP_SMP
1208 static cpumask_var_t frozen_cpus;
1209
1210 int freeze_secondary_cpus(int primary)
1211 {
1212         int cpu, error = 0;
1213
1214         cpu_maps_update_begin();
1215         if (!cpu_online(primary))
1216                 primary = cpumask_first(cpu_online_mask);
1217         /*
1218          * We take down all of the non-boot CPUs in one shot to avoid races
1219          * with the userspace trying to use the CPU hotplug at the same time
1220          */
1221         cpumask_clear(frozen_cpus);
1222
1223         pr_info("Disabling non-boot CPUs ...\n");
1224         for_each_online_cpu(cpu) {
1225                 if (cpu == primary)
1226                         continue;
1227                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1228                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1229                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1230                 if (!error)
1231                         cpumask_set_cpu(cpu, frozen_cpus);
1232                 else {
1233                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1234                         break;
1235                 }
1236         }
1237
1238         if (!error)
1239                 BUG_ON(num_online_cpus() > 1);
1240         else
1241                 pr_err("Non-boot CPUs are not disabled\n");
1242
1243         /*
1244          * Make sure the CPUs won't be enabled by someone else. We need to do
1245          * this even in case of failure as all disable_nonboot_cpus() users are
1246          * supposed to do enable_nonboot_cpus() on the failure path.
1247          */
1248         cpu_hotplug_disabled++;
1249
1250         cpu_maps_update_done();
1251         return error;
1252 }
1253
1254 void __weak arch_enable_nonboot_cpus_begin(void)
1255 {
1256 }
1257
1258 void __weak arch_enable_nonboot_cpus_end(void)
1259 {
1260 }
1261
1262 void enable_nonboot_cpus(void)
1263 {
1264         int cpu, error;
1265
1266         /* Allow everyone to use the CPU hotplug again */
1267         cpu_maps_update_begin();
1268         __cpu_hotplug_enable();
1269         if (cpumask_empty(frozen_cpus))
1270                 goto out;
1271
1272         pr_info("Enabling non-boot CPUs ...\n");
1273
1274         arch_enable_nonboot_cpus_begin();
1275
1276         for_each_cpu(cpu, frozen_cpus) {
1277                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1278                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1279                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1280                 if (!error) {
1281                         pr_info("CPU%d is up\n", cpu);
1282                         continue;
1283                 }
1284                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1285         }
1286
1287         arch_enable_nonboot_cpus_end();
1288
1289         cpumask_clear(frozen_cpus);
1290 out:
1291         cpu_maps_update_done();
1292 }
1293
1294 static int __init alloc_frozen_cpus(void)
1295 {
1296         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1297                 return -ENOMEM;
1298         return 0;
1299 }
1300 core_initcall(alloc_frozen_cpus);
1301
1302 /*
1303  * When callbacks for CPU hotplug notifications are being executed, we must
1304  * ensure that the state of the system with respect to the tasks being frozen
1305  * or not, as reported by the notification, remains unchanged *throughout the
1306  * duration* of the execution of the callbacks.
1307  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1308  *
1309  * This synchronization is implemented by mutually excluding regular CPU
1310  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1311  * Hibernate notifications.
1312  */
1313 static int
1314 cpu_hotplug_pm_callback(struct notifier_block *nb,
1315                         unsigned long action, void *ptr)
1316 {
1317         switch (action) {
1318
1319         case PM_SUSPEND_PREPARE:
1320         case PM_HIBERNATION_PREPARE:
1321                 cpu_hotplug_disable();
1322                 break;
1323
1324         case PM_POST_SUSPEND:
1325         case PM_POST_HIBERNATION:
1326                 cpu_hotplug_enable();
1327                 break;
1328
1329         default:
1330                 return NOTIFY_DONE;
1331         }
1332
1333         return NOTIFY_OK;
1334 }
1335
1336
1337 static int __init cpu_hotplug_pm_sync_init(void)
1338 {
1339         /*
1340          * cpu_hotplug_pm_callback has higher priority than x86
1341          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1342          * to disable cpu hotplug to avoid cpu hotplug race.
1343          */
1344         pm_notifier(cpu_hotplug_pm_callback, 0);
1345         return 0;
1346 }
1347 core_initcall(cpu_hotplug_pm_sync_init);
1348
1349 #endif /* CONFIG_PM_SLEEP_SMP */
1350
1351 #endif /* CONFIG_SMP */
1352
1353 /* Boot processor state steps */
1354 static struct cpuhp_step cpuhp_bp_states[] = {
1355         [CPUHP_OFFLINE] = {
1356                 .name                   = "offline",
1357                 .startup.single         = NULL,
1358                 .teardown.single        = NULL,
1359         },
1360 #ifdef CONFIG_SMP
1361         [CPUHP_CREATE_THREADS]= {
1362                 .name                   = "threads:prepare",
1363                 .startup.single         = smpboot_create_threads,
1364                 .teardown.single        = NULL,
1365                 .cant_stop              = true,
1366         },
1367         [CPUHP_PERF_PREPARE] = {
1368                 .name                   = "perf:prepare",
1369                 .startup.single         = perf_event_init_cpu,
1370                 .teardown.single        = perf_event_exit_cpu,
1371         },
1372         [CPUHP_WORKQUEUE_PREP] = {
1373                 .name                   = "workqueue:prepare",
1374                 .startup.single         = workqueue_prepare_cpu,
1375                 .teardown.single        = NULL,
1376         },
1377         [CPUHP_HRTIMERS_PREPARE] = {
1378                 .name                   = "hrtimers:prepare",
1379                 .startup.single         = hrtimers_prepare_cpu,
1380                 .teardown.single        = hrtimers_dead_cpu,
1381         },
1382         [CPUHP_SMPCFD_PREPARE] = {
1383                 .name                   = "smpcfd:prepare",
1384                 .startup.single         = smpcfd_prepare_cpu,
1385                 .teardown.single        = smpcfd_dead_cpu,
1386         },
1387         [CPUHP_RELAY_PREPARE] = {
1388                 .name                   = "relay:prepare",
1389                 .startup.single         = relay_prepare_cpu,
1390                 .teardown.single        = NULL,
1391         },
1392         [CPUHP_SLAB_PREPARE] = {
1393                 .name                   = "slab:prepare",
1394                 .startup.single         = slab_prepare_cpu,
1395                 .teardown.single        = slab_dead_cpu,
1396         },
1397         [CPUHP_RCUTREE_PREP] = {
1398                 .name                   = "RCU/tree:prepare",
1399                 .startup.single         = rcutree_prepare_cpu,
1400                 .teardown.single        = rcutree_dead_cpu,
1401         },
1402         /*
1403          * Preparatory and dead notifiers. Will be replaced once the notifiers
1404          * are converted to states.
1405          */
1406         [CPUHP_NOTIFY_PREPARE] = {
1407                 .name                   = "notify:prepare",
1408                 .startup.single         = notify_prepare,
1409                 .teardown.single        = notify_dead,
1410                 .skip_onerr             = true,
1411                 .cant_stop              = true,
1412         },
1413         /*
1414          * On the tear-down path, timers_dead_cpu() must be invoked
1415          * before blk_mq_queue_reinit_notify() from notify_dead(),
1416          * otherwise a RCU stall occurs.
1417          */
1418         [CPUHP_TIMERS_PREPARE] = {
1419                 .name                   = "timers:dead",
1420                 .startup.single         = timers_prepare_cpu,
1421                 .teardown.single        = timers_dead_cpu,
1422         },
1423         /* Kicks the plugged cpu into life */
1424         [CPUHP_BRINGUP_CPU] = {
1425                 .name                   = "cpu:bringup",
1426                 .startup.single         = bringup_cpu,
1427                 .teardown.single        = NULL,
1428                 .cant_stop              = true,
1429         },
1430         /*
1431          * Handled on controll processor until the plugged processor manages
1432          * this itself.
1433          */
1434         [CPUHP_TEARDOWN_CPU] = {
1435                 .name                   = "cpu:teardown",
1436                 .startup.single         = NULL,
1437                 .teardown.single        = takedown_cpu,
1438                 .cant_stop              = true,
1439         },
1440 #else
1441         [CPUHP_BRINGUP_CPU] = { },
1442 #endif
1443 };
1444
1445 /* Application processor state steps */
1446 static struct cpuhp_step cpuhp_ap_states[] = {
1447 #ifdef CONFIG_SMP
1448         /* Final state before CPU kills itself */
1449         [CPUHP_AP_IDLE_DEAD] = {
1450                 .name                   = "idle:dead",
1451         },
1452         /*
1453          * Last state before CPU enters the idle loop to die. Transient state
1454          * for synchronization.
1455          */
1456         [CPUHP_AP_OFFLINE] = {
1457                 .name                   = "ap:offline",
1458                 .cant_stop              = true,
1459         },
1460         /* First state is scheduler control. Interrupts are disabled */
1461         [CPUHP_AP_SCHED_STARTING] = {
1462                 .name                   = "sched:starting",
1463                 .startup.single         = sched_cpu_starting,
1464                 .teardown.single        = sched_cpu_dying,
1465         },
1466         [CPUHP_AP_RCUTREE_DYING] = {
1467                 .name                   = "RCU/tree:dying",
1468                 .startup.single         = NULL,
1469                 .teardown.single        = rcutree_dying_cpu,
1470         },
1471         [CPUHP_AP_SMPCFD_DYING] = {
1472                 .name                   = "smpcfd:dying",
1473                 .startup.single         = NULL,
1474                 .teardown.single        = smpcfd_dying_cpu,
1475         },
1476         /* Entry state on starting. Interrupts enabled from here on. Transient
1477          * state for synchronsization */
1478         [CPUHP_AP_ONLINE] = {
1479                 .name                   = "ap:online",
1480         },
1481         /* Handle smpboot threads park/unpark */
1482         [CPUHP_AP_SMPBOOT_THREADS] = {
1483                 .name                   = "smpboot/threads:online",
1484                 .startup.single         = smpboot_unpark_threads,
1485                 .teardown.single        = smpboot_park_threads,
1486         },
1487         [CPUHP_AP_PERF_ONLINE] = {
1488                 .name                   = "perf:online",
1489                 .startup.single         = perf_event_init_cpu,
1490                 .teardown.single        = perf_event_exit_cpu,
1491         },
1492         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1493                 .name                   = "workqueue:online",
1494                 .startup.single         = workqueue_online_cpu,
1495                 .teardown.single        = workqueue_offline_cpu,
1496         },
1497         [CPUHP_AP_RCUTREE_ONLINE] = {
1498                 .name                   = "RCU/tree:online",
1499                 .startup.single         = rcutree_online_cpu,
1500                 .teardown.single        = rcutree_offline_cpu,
1501         },
1502
1503         /*
1504          * Online/down_prepare notifiers. Will be removed once the notifiers
1505          * are converted to states.
1506          */
1507         [CPUHP_AP_NOTIFY_ONLINE] = {
1508                 .name                   = "notify:online",
1509                 .startup.single         = notify_online,
1510                 .teardown.single        = notify_down_prepare,
1511                 .skip_onerr             = true,
1512         },
1513 #endif
1514         /*
1515          * The dynamically registered state space is here
1516          */
1517
1518 #ifdef CONFIG_SMP
1519         /* Last state is scheduler control setting the cpu active */
1520         [CPUHP_AP_ACTIVE] = {
1521                 .name                   = "sched:active",
1522                 .startup.single         = sched_cpu_activate,
1523                 .teardown.single        = sched_cpu_deactivate,
1524         },
1525 #endif
1526
1527         /* CPU is fully up and running. */
1528         [CPUHP_ONLINE] = {
1529                 .name                   = "online",
1530                 .startup.single         = NULL,
1531                 .teardown.single        = NULL,
1532         },
1533 };
1534
1535 /* Sanity check for callbacks */
1536 static int cpuhp_cb_check(enum cpuhp_state state)
1537 {
1538         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1539                 return -EINVAL;
1540         return 0;
1541 }
1542
1543 static void cpuhp_store_callbacks(enum cpuhp_state state,
1544                                   const char *name,
1545                                   int (*startup)(unsigned int cpu),
1546                                   int (*teardown)(unsigned int cpu),
1547                                   bool multi_instance)
1548 {
1549         /* (Un)Install the callbacks for further cpu hotplug operations */
1550         struct cpuhp_step *sp;
1551
1552         sp = cpuhp_get_step(state);
1553         sp->startup.single = startup;
1554         sp->teardown.single = teardown;
1555         sp->name = name;
1556         sp->multi_instance = multi_instance;
1557         INIT_HLIST_HEAD(&sp->list);
1558 }
1559
1560 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1561 {
1562         return cpuhp_get_step(state)->teardown.single;
1563 }
1564
1565 /*
1566  * Call the startup/teardown function for a step either on the AP or
1567  * on the current CPU.
1568  */
1569 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1570                             struct hlist_node *node)
1571 {
1572         struct cpuhp_step *sp = cpuhp_get_step(state);
1573         int ret;
1574
1575         if ((bringup && !sp->startup.single) ||
1576             (!bringup && !sp->teardown.single))
1577                 return 0;
1578         /*
1579          * The non AP bound callbacks can fail on bringup. On teardown
1580          * e.g. module removal we crash for now.
1581          */
1582 #ifdef CONFIG_SMP
1583         if (cpuhp_is_ap_state(state))
1584                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1585         else
1586                 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1587 #else
1588         ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1589 #endif
1590         BUG_ON(ret && !bringup);
1591         return ret;
1592 }
1593
1594 /*
1595  * Called from __cpuhp_setup_state on a recoverable failure.
1596  *
1597  * Note: The teardown callbacks for rollback are not allowed to fail!
1598  */
1599 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1600                                    struct hlist_node *node)
1601 {
1602         int cpu;
1603
1604         /* Roll back the already executed steps on the other cpus */
1605         for_each_present_cpu(cpu) {
1606                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1607                 int cpustate = st->state;
1608
1609                 if (cpu >= failedcpu)
1610                         break;
1611
1612                 /* Did we invoke the startup call on that cpu ? */
1613                 if (cpustate >= state)
1614                         cpuhp_issue_call(cpu, state, false, node);
1615         }
1616 }
1617
1618 /*
1619  * Returns a free for dynamic slot assignment of the Online state. The states
1620  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1621  * by having no name assigned.
1622  */
1623 static int cpuhp_reserve_state(enum cpuhp_state state)
1624 {
1625         enum cpuhp_state i;
1626
1627         for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1628                 if (cpuhp_ap_states[i].name)
1629                         continue;
1630
1631                 cpuhp_ap_states[i].name = "Reserved";
1632                 return i;
1633         }
1634         WARN(1, "No more dynamic states available for CPU hotplug\n");
1635         return -ENOSPC;
1636 }
1637
1638 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1639                                bool invoke)
1640 {
1641         struct cpuhp_step *sp;
1642         int cpu;
1643         int ret;
1644
1645         sp = cpuhp_get_step(state);
1646         if (sp->multi_instance == false)
1647                 return -EINVAL;
1648
1649         get_online_cpus();
1650         mutex_lock(&cpuhp_state_mutex);
1651
1652         if (!invoke || !sp->startup.multi)
1653                 goto add_node;
1654
1655         /*
1656          * Try to call the startup callback for each present cpu
1657          * depending on the hotplug state of the cpu.
1658          */
1659         for_each_present_cpu(cpu) {
1660                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1661                 int cpustate = st->state;
1662
1663                 if (cpustate < state)
1664                         continue;
1665
1666                 ret = cpuhp_issue_call(cpu, state, true, node);
1667                 if (ret) {
1668                         if (sp->teardown.multi)
1669                                 cpuhp_rollback_install(cpu, state, node);
1670                         goto err;
1671                 }
1672         }
1673 add_node:
1674         ret = 0;
1675         hlist_add_head(node, &sp->list);
1676
1677 err:
1678         mutex_unlock(&cpuhp_state_mutex);
1679         put_online_cpus();
1680         return ret;
1681 }
1682 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1683
1684 /**
1685  * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1686  * @state:      The state to setup
1687  * @invoke:     If true, the startup function is invoked for cpus where
1688  *              cpu state >= @state
1689  * @startup:    startup callback function
1690  * @teardown:   teardown callback function
1691  *
1692  * Returns 0 if successful, otherwise a proper error code
1693  */
1694 int __cpuhp_setup_state(enum cpuhp_state state,
1695                         const char *name, bool invoke,
1696                         int (*startup)(unsigned int cpu),
1697                         int (*teardown)(unsigned int cpu),
1698                         bool multi_instance)
1699 {
1700         int cpu, ret = 0;
1701         int dyn_state = 0;
1702
1703         if (cpuhp_cb_check(state) || !name)
1704                 return -EINVAL;
1705
1706         get_online_cpus();
1707         mutex_lock(&cpuhp_state_mutex);
1708
1709         /* currently assignments for the ONLINE state are possible */
1710         if (state == CPUHP_AP_ONLINE_DYN) {
1711                 dyn_state = 1;
1712                 ret = cpuhp_reserve_state(state);
1713                 if (ret < 0)
1714                         goto out;
1715                 state = ret;
1716         }
1717
1718         cpuhp_store_callbacks(state, name, startup, teardown, multi_instance);
1719
1720         if (!invoke || !startup)
1721                 goto out;
1722
1723         /*
1724          * Try to call the startup callback for each present cpu
1725          * depending on the hotplug state of the cpu.
1726          */
1727         for_each_present_cpu(cpu) {
1728                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1729                 int cpustate = st->state;
1730
1731                 if (cpustate < state)
1732                         continue;
1733
1734                 ret = cpuhp_issue_call(cpu, state, true, NULL);
1735                 if (ret) {
1736                         if (teardown)
1737                                 cpuhp_rollback_install(cpu, state, NULL);
1738                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1739                         goto out;
1740                 }
1741         }
1742 out:
1743         mutex_unlock(&cpuhp_state_mutex);
1744
1745         put_online_cpus();
1746         if (!ret && dyn_state)
1747                 return state;
1748         return ret;
1749 }
1750 EXPORT_SYMBOL(__cpuhp_setup_state);
1751
1752 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1753                                   struct hlist_node *node, bool invoke)
1754 {
1755         struct cpuhp_step *sp = cpuhp_get_step(state);
1756         int cpu;
1757
1758         BUG_ON(cpuhp_cb_check(state));
1759
1760         if (!sp->multi_instance)
1761                 return -EINVAL;
1762
1763         get_online_cpus();
1764         mutex_lock(&cpuhp_state_mutex);
1765
1766         if (!invoke || !cpuhp_get_teardown_cb(state))
1767                 goto remove;
1768         /*
1769          * Call the teardown callback for each present cpu depending
1770          * on the hotplug state of the cpu. This function is not
1771          * allowed to fail currently!
1772          */
1773         for_each_present_cpu(cpu) {
1774                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1775                 int cpustate = st->state;
1776
1777                 if (cpustate >= state)
1778                         cpuhp_issue_call(cpu, state, false, node);
1779         }
1780
1781 remove:
1782         hlist_del(node);
1783         mutex_unlock(&cpuhp_state_mutex);
1784         put_online_cpus();
1785
1786         return 0;
1787 }
1788 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1789 /**
1790  * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1791  * @state:      The state to remove
1792  * @invoke:     If true, the teardown function is invoked for cpus where
1793  *              cpu state >= @state
1794  *
1795  * The teardown callback is currently not allowed to fail. Think
1796  * about module removal!
1797  */
1798 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1799 {
1800         struct cpuhp_step *sp = cpuhp_get_step(state);
1801         int cpu;
1802
1803         BUG_ON(cpuhp_cb_check(state));
1804
1805         get_online_cpus();
1806         mutex_lock(&cpuhp_state_mutex);
1807
1808         if (sp->multi_instance) {
1809                 WARN(!hlist_empty(&sp->list),
1810                      "Error: Removing state %d which has instances left.\n",
1811                      state);
1812                 goto remove;
1813         }
1814
1815         if (!invoke || !cpuhp_get_teardown_cb(state))
1816                 goto remove;
1817
1818         /*
1819          * Call the teardown callback for each present cpu depending
1820          * on the hotplug state of the cpu. This function is not
1821          * allowed to fail currently!
1822          */
1823         for_each_present_cpu(cpu) {
1824                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1825                 int cpustate = st->state;
1826
1827                 if (cpustate >= state)
1828                         cpuhp_issue_call(cpu, state, false, NULL);
1829         }
1830 remove:
1831         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1832         mutex_unlock(&cpuhp_state_mutex);
1833         put_online_cpus();
1834 }
1835 EXPORT_SYMBOL(__cpuhp_remove_state);
1836
1837 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1838 static ssize_t show_cpuhp_state(struct device *dev,
1839                                 struct device_attribute *attr, char *buf)
1840 {
1841         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1842
1843         return sprintf(buf, "%d\n", st->state);
1844 }
1845 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1846
1847 static ssize_t write_cpuhp_target(struct device *dev,
1848                                   struct device_attribute *attr,
1849                                   const char *buf, size_t count)
1850 {
1851         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1852         struct cpuhp_step *sp;
1853         int target, ret;
1854
1855         ret = kstrtoint(buf, 10, &target);
1856         if (ret)
1857                 return ret;
1858
1859 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1860         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1861                 return -EINVAL;
1862 #else
1863         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1864                 return -EINVAL;
1865 #endif
1866
1867         ret = lock_device_hotplug_sysfs();
1868         if (ret)
1869                 return ret;
1870
1871         mutex_lock(&cpuhp_state_mutex);
1872         sp = cpuhp_get_step(target);
1873         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1874         mutex_unlock(&cpuhp_state_mutex);
1875         if (ret)
1876                 goto out;
1877
1878         if (st->state < target)
1879                 ret = do_cpu_up(dev->id, target);
1880         else
1881                 ret = do_cpu_down(dev->id, target);
1882 out:
1883         unlock_device_hotplug();
1884         return ret ? ret : count;
1885 }
1886
1887 static ssize_t show_cpuhp_target(struct device *dev,
1888                                  struct device_attribute *attr, char *buf)
1889 {
1890         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1891
1892         return sprintf(buf, "%d\n", st->target);
1893 }
1894 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1895
1896 static struct attribute *cpuhp_cpu_attrs[] = {
1897         &dev_attr_state.attr,
1898         &dev_attr_target.attr,
1899         NULL
1900 };
1901
1902 static struct attribute_group cpuhp_cpu_attr_group = {
1903         .attrs = cpuhp_cpu_attrs,
1904         .name = "hotplug",
1905         NULL
1906 };
1907
1908 static ssize_t show_cpuhp_states(struct device *dev,
1909                                  struct device_attribute *attr, char *buf)
1910 {
1911         ssize_t cur, res = 0;
1912         int i;
1913
1914         mutex_lock(&cpuhp_state_mutex);
1915         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1916                 struct cpuhp_step *sp = cpuhp_get_step(i);
1917
1918                 if (sp->name) {
1919                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1920                         buf += cur;
1921                         res += cur;
1922                 }
1923         }
1924         mutex_unlock(&cpuhp_state_mutex);
1925         return res;
1926 }
1927 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1928
1929 static struct attribute *cpuhp_cpu_root_attrs[] = {
1930         &dev_attr_states.attr,
1931         NULL
1932 };
1933
1934 static struct attribute_group cpuhp_cpu_root_attr_group = {
1935         .attrs = cpuhp_cpu_root_attrs,
1936         .name = "hotplug",
1937         NULL
1938 };
1939
1940 #ifdef CONFIG_HOTPLUG_SMT
1941
1942 static const char *smt_states[] = {
1943         [CPU_SMT_ENABLED]               = "on",
1944         [CPU_SMT_DISABLED]              = "off",
1945         [CPU_SMT_FORCE_DISABLED]        = "forceoff",
1946         [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
1947 };
1948
1949 static ssize_t
1950 show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
1951 {
1952         return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]);
1953 }
1954
1955 static void cpuhp_offline_cpu_device(unsigned int cpu)
1956 {
1957         struct device *dev = get_cpu_device(cpu);
1958
1959         dev->offline = true;
1960         /* Tell user space about the state change */
1961         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
1962 }
1963
1964 static void cpuhp_online_cpu_device(unsigned int cpu)
1965 {
1966         struct device *dev = get_cpu_device(cpu);
1967
1968         dev->offline = false;
1969         /* Tell user space about the state change */
1970         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
1971 }
1972
1973 static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
1974 {
1975         int cpu, ret = 0;
1976
1977         cpu_maps_update_begin();
1978         for_each_online_cpu(cpu) {
1979                 if (topology_is_primary_thread(cpu))
1980                         continue;
1981                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1982                 if (ret)
1983                         break;
1984                 /*
1985                  * As this needs to hold the cpu maps lock it's impossible
1986                  * to call device_offline() because that ends up calling
1987                  * cpu_down() which takes cpu maps lock. cpu maps lock
1988                  * needs to be held as this might race against in kernel
1989                  * abusers of the hotplug machinery (thermal management).
1990                  *
1991                  * So nothing would update device:offline state. That would
1992                  * leave the sysfs entry stale and prevent onlining after
1993                  * smt control has been changed to 'off' again. This is
1994                  * called under the sysfs hotplug lock, so it is properly
1995                  * serialized against the regular offline usage.
1996                  */
1997                 cpuhp_offline_cpu_device(cpu);
1998         }
1999         if (!ret)
2000                 cpu_smt_control = ctrlval;
2001         cpu_maps_update_done();
2002         return ret;
2003 }
2004
2005 static int cpuhp_smt_enable(void)
2006 {
2007         int cpu, ret = 0;
2008
2009         cpu_maps_update_begin();
2010         cpu_smt_control = CPU_SMT_ENABLED;
2011         for_each_present_cpu(cpu) {
2012                 /* Skip online CPUs and CPUs on offline nodes */
2013                 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2014                         continue;
2015                 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2016                 if (ret)
2017                         break;
2018                 /* See comment in cpuhp_smt_disable() */
2019                 cpuhp_online_cpu_device(cpu);
2020         }
2021         cpu_maps_update_done();
2022         return ret;
2023 }
2024
2025 static ssize_t
2026 store_smt_control(struct device *dev, struct device_attribute *attr,
2027                   const char *buf, size_t count)
2028 {
2029         int ctrlval, ret;
2030
2031         if (sysfs_streq(buf, "on"))
2032                 ctrlval = CPU_SMT_ENABLED;
2033         else if (sysfs_streq(buf, "off"))
2034                 ctrlval = CPU_SMT_DISABLED;
2035         else if (sysfs_streq(buf, "forceoff"))
2036                 ctrlval = CPU_SMT_FORCE_DISABLED;
2037         else
2038                 return -EINVAL;
2039
2040         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2041                 return -EPERM;
2042
2043         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2044                 return -ENODEV;
2045
2046         ret = lock_device_hotplug_sysfs();
2047         if (ret)
2048                 return ret;
2049
2050         if (ctrlval != cpu_smt_control) {
2051                 switch (ctrlval) {
2052                 case CPU_SMT_ENABLED:
2053                         ret = cpuhp_smt_enable();
2054                         break;
2055                 case CPU_SMT_DISABLED:
2056                 case CPU_SMT_FORCE_DISABLED:
2057                         ret = cpuhp_smt_disable(ctrlval);
2058                         break;
2059                 }
2060         }
2061
2062         unlock_device_hotplug();
2063         return ret ? ret : count;
2064 }
2065 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2066
2067 static ssize_t
2068 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2069 {
2070         bool active = topology_max_smt_threads() > 1;
2071
2072         return snprintf(buf, PAGE_SIZE - 2, "%d\n", active);
2073 }
2074 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2075
2076 static struct attribute *cpuhp_smt_attrs[] = {
2077         &dev_attr_control.attr,
2078         &dev_attr_active.attr,
2079         NULL
2080 };
2081
2082 static const struct attribute_group cpuhp_smt_attr_group = {
2083         .attrs = cpuhp_smt_attrs,
2084         .name = "smt",
2085         NULL
2086 };
2087
2088 static int __init cpu_smt_state_init(void)
2089 {
2090         return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2091                                   &cpuhp_smt_attr_group);
2092 }
2093
2094 #else
2095 static inline int cpu_smt_state_init(void) { return 0; }
2096 #endif
2097
2098 static int __init cpuhp_sysfs_init(void)
2099 {
2100         int cpu, ret;
2101
2102         ret = cpu_smt_state_init();
2103         if (ret)
2104                 return ret;
2105
2106         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2107                                  &cpuhp_cpu_root_attr_group);
2108         if (ret)
2109                 return ret;
2110
2111         for_each_possible_cpu(cpu) {
2112                 struct device *dev = get_cpu_device(cpu);
2113
2114                 if (!dev)
2115                         continue;
2116                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2117                 if (ret)
2118                         return ret;
2119         }
2120         return 0;
2121 }
2122 device_initcall(cpuhp_sysfs_init);
2123 #endif
2124
2125 /*
2126  * cpu_bit_bitmap[] is a special, "compressed" data structure that
2127  * represents all NR_CPUS bits binary values of 1<<nr.
2128  *
2129  * It is used by cpumask_of() to get a constant address to a CPU
2130  * mask value that has a single bit set only.
2131  */
2132
2133 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2134 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2135 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2136 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2137 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2138
2139 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2140
2141         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2142         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2143 #if BITS_PER_LONG > 32
2144         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2145         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2146 #endif
2147 };
2148 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2149
2150 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2151 EXPORT_SYMBOL(cpu_all_bits);
2152
2153 #ifdef CONFIG_INIT_ALL_POSSIBLE
2154 struct cpumask __cpu_possible_mask __read_mostly
2155         = {CPU_BITS_ALL};
2156 #else
2157 struct cpumask __cpu_possible_mask __read_mostly;
2158 #endif
2159 EXPORT_SYMBOL(__cpu_possible_mask);
2160
2161 struct cpumask __cpu_online_mask __read_mostly;
2162 EXPORT_SYMBOL(__cpu_online_mask);
2163
2164 struct cpumask __cpu_present_mask __read_mostly;
2165 EXPORT_SYMBOL(__cpu_present_mask);
2166
2167 struct cpumask __cpu_active_mask __read_mostly;
2168 EXPORT_SYMBOL(__cpu_active_mask);
2169
2170 void init_cpu_present(const struct cpumask *src)
2171 {
2172         cpumask_copy(&__cpu_present_mask, src);
2173 }
2174
2175 void init_cpu_possible(const struct cpumask *src)
2176 {
2177         cpumask_copy(&__cpu_possible_mask, src);
2178 }
2179
2180 void init_cpu_online(const struct cpumask *src)
2181 {
2182         cpumask_copy(&__cpu_online_mask, src);
2183 }
2184
2185 /*
2186  * Activate the first processor.
2187  */
2188 void __init boot_cpu_init(void)
2189 {
2190         int cpu = smp_processor_id();
2191
2192         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2193         set_cpu_online(cpu, true);
2194         set_cpu_active(cpu, true);
2195         set_cpu_present(cpu, true);
2196         set_cpu_possible(cpu, true);
2197 }
2198
2199 /*
2200  * Must be called _AFTER_ setting up the per_cpu areas
2201  */
2202 void __init boot_cpu_hotplug_init(void)
2203 {
2204 #ifdef CONFIG_SMP
2205         this_cpu_write(cpuhp_state.booted_once, true);
2206 #endif
2207         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2208 }