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