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