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