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
  27#include <trace/events/power.h>
  28#define CREATE_TRACE_POINTS
  29#include <trace/events/cpuhp.h>
  30
  31#include "smpboot.h"
  32
  33/**
  34 * cpuhp_cpu_state - Per cpu hotplug state storage
  35 * @state:	The current cpu state
  36 * @target:	The target state
  37 * @thread:	Pointer to the hotplug thread
  38 * @should_run:	Thread should execute
  39 * @rollback:	Perform a rollback
  40 * @cb_stat:	The state for a single callback (install/uninstall)
  41 * @cb:		Single callback function (install/uninstall)
  42 * @result:	Result of the operation
  43 * @done:	Signal completion to the issuer of the task
  44 */
  45struct cpuhp_cpu_state {
  46	enum cpuhp_state	state;
  47	enum cpuhp_state	target;
  48#ifdef CONFIG_SMP
  49	struct task_struct	*thread;
  50	bool			should_run;
  51	bool			rollback;
  52	enum cpuhp_state	cb_state;
  53	int			(*cb)(unsigned int cpu);
  54	int			result;
  55	struct completion	done;
  56#endif
  57};
  58
  59static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
  60
  61/**
  62 * cpuhp_step - Hotplug state machine step
  63 * @name:	Name of the step
  64 * @startup:	Startup function of the step
  65 * @teardown:	Teardown function of the step
  66 * @skip_onerr:	Do not invoke the functions on error rollback
  67 *		Will go away once the notifiers	are gone
  68 * @cant_stop:	Bringup/teardown can't be stopped at this step
  69 */
  70struct cpuhp_step {
  71	const char	*name;
  72	int		(*startup)(unsigned int cpu);
  73	int		(*teardown)(unsigned int cpu);
  74	bool		skip_onerr;
  75	bool		cant_stop;
  76};
  77
  78static DEFINE_MUTEX(cpuhp_state_mutex);
  79static struct cpuhp_step cpuhp_bp_states[];
  80static struct cpuhp_step cpuhp_ap_states[];
  81
  82/**
  83 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
  84 * @cpu:	The cpu for which the callback should be invoked
  85 * @step:	The step in the state machine
  86 * @cb:		The callback function to invoke
  87 *
  88 * Called from cpu hotplug and from the state register machinery
  89 */
  90static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
  91				 int (*cb)(unsigned int))
  92{
  93	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
  94	int ret = 0;
  95
  96	if (cb) {
  97		trace_cpuhp_enter(cpu, st->target, step, cb);
  98		ret = cb(cpu);
  99		trace_cpuhp_exit(cpu, st->state, step, ret);
 100	}
 101	return ret;
 102}
 103
 104#ifdef CONFIG_SMP
 105/* Serializes the updates to cpu_online_mask, cpu_present_mask */
 106static DEFINE_MUTEX(cpu_add_remove_lock);
 107bool cpuhp_tasks_frozen;
 108EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
 109
 110/*
 111 * The following two APIs (cpu_maps_update_begin/done) must be used when
 112 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 113 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
 114 * hotplug callback (un)registration performed using __register_cpu_notifier()
 115 * or __unregister_cpu_notifier().
 116 */
 117void cpu_maps_update_begin(void)
 118{
 119	mutex_lock(&cpu_add_remove_lock);
 120}
 121EXPORT_SYMBOL(cpu_notifier_register_begin);
 122
 123void cpu_maps_update_done(void)
 124{
 125	mutex_unlock(&cpu_add_remove_lock);
 126}
 127EXPORT_SYMBOL(cpu_notifier_register_done);
 128
 129static RAW_NOTIFIER_HEAD(cpu_chain);
 130
 131/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
 132 * Should always be manipulated under cpu_add_remove_lock
 133 */
 134static int cpu_hotplug_disabled;
 135
 136#ifdef CONFIG_HOTPLUG_CPU
 137
 138static struct {
 139	struct task_struct *active_writer;
 140	/* wait queue to wake up the active_writer */
 141	wait_queue_head_t wq;
 142	/* verifies that no writer will get active while readers are active */
 143	struct mutex lock;
 144	/*
 145	 * Also blocks the new readers during
 146	 * an ongoing cpu hotplug operation.
 147	 */
 148	atomic_t refcount;
 149
 150#ifdef CONFIG_DEBUG_LOCK_ALLOC
 151	struct lockdep_map dep_map;
 152#endif
 153} cpu_hotplug = {
 154	.active_writer = NULL,
 155	.wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
 156	.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
 157#ifdef CONFIG_DEBUG_LOCK_ALLOC
 158	.dep_map = {.name = "cpu_hotplug.lock" },
 159#endif
 160};
 161
 162/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
 163#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
 164#define cpuhp_lock_acquire_tryread() \
 165				  lock_map_acquire_tryread(&cpu_hotplug.dep_map)
 166#define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 167#define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 168
 169
 170void get_online_cpus(void)
 171{
 172	might_sleep();
 173	if (cpu_hotplug.active_writer == current)
 174		return;
 175	cpuhp_lock_acquire_read();
 176	mutex_lock(&cpu_hotplug.lock);
 177	atomic_inc(&cpu_hotplug.refcount);
 178	mutex_unlock(&cpu_hotplug.lock);
 
 179}
 180EXPORT_SYMBOL_GPL(get_online_cpus);
 181
 182void put_online_cpus(void)
 183{
 184	int refcount;
 185
 186	if (cpu_hotplug.active_writer == current)
 187		return;
 188
 189	refcount = atomic_dec_return(&cpu_hotplug.refcount);
 190	if (WARN_ON(refcount < 0)) /* try to fix things up */
 191		atomic_inc(&cpu_hotplug.refcount);
 192
 193	if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
 194		wake_up(&cpu_hotplug.wq);
 195
 196	cpuhp_lock_release();
 197
 198}
 199EXPORT_SYMBOL_GPL(put_online_cpus);
 200
 201/*
 202 * This ensures that the hotplug operation can begin only when the
 203 * refcount goes to zero.
 204 *
 205 * Note that during a cpu-hotplug operation, the new readers, if any,
 206 * will be blocked by the cpu_hotplug.lock
 207 *
 208 * Since cpu_hotplug_begin() is always called after invoking
 209 * cpu_maps_update_begin(), we can be sure that only one writer is active.
 210 *
 211 * Note that theoretically, there is a possibility of a livelock:
 212 * - Refcount goes to zero, last reader wakes up the sleeping
 213 *   writer.
 214 * - Last reader unlocks the cpu_hotplug.lock.
 215 * - A new reader arrives at this moment, bumps up the refcount.
 216 * - The writer acquires the cpu_hotplug.lock finds the refcount
 217 *   non zero and goes to sleep again.
 218 *
 219 * However, this is very difficult to achieve in practice since
 220 * get_online_cpus() not an api which is called all that often.
 221 *
 222 */
 223void cpu_hotplug_begin(void)
 224{
 225	DEFINE_WAIT(wait);
 226
 227	cpu_hotplug.active_writer = current;
 228	cpuhp_lock_acquire();
 229
 230	for (;;) {
 231		mutex_lock(&cpu_hotplug.lock);
 232		prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
 233		if (likely(!atomic_read(&cpu_hotplug.refcount)))
 234				break;
 235		mutex_unlock(&cpu_hotplug.lock);
 236		schedule();
 237	}
 238	finish_wait(&cpu_hotplug.wq, &wait);
 239}
 240
 241void cpu_hotplug_done(void)
 242{
 243	cpu_hotplug.active_writer = NULL;
 244	mutex_unlock(&cpu_hotplug.lock);
 245	cpuhp_lock_release();
 246}
 247
 248/*
 249 * Wait for currently running CPU hotplug operations to complete (if any) and
 250 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
 251 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
 252 * hotplug path before performing hotplug operations. So acquiring that lock
 253 * guarantees mutual exclusion from any currently running hotplug operations.
 254 */
 255void cpu_hotplug_disable(void)
 256{
 257	cpu_maps_update_begin();
 258	cpu_hotplug_disabled++;
 259	cpu_maps_update_done();
 260}
 261EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 262
 263void cpu_hotplug_enable(void)
 264{
 265	cpu_maps_update_begin();
 266	WARN_ON(--cpu_hotplug_disabled < 0);
 267	cpu_maps_update_done();
 268}
 269EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
 270#endif	/* CONFIG_HOTPLUG_CPU */
 271
 272/* Need to know about CPUs going up/down? */
 273int register_cpu_notifier(struct notifier_block *nb)
 274{
 275	int ret;
 276	cpu_maps_update_begin();
 277	ret = raw_notifier_chain_register(&cpu_chain, nb);
 278	cpu_maps_update_done();
 279	return ret;
 280}
 281
 282int __register_cpu_notifier(struct notifier_block *nb)
 283{
 284	return raw_notifier_chain_register(&cpu_chain, nb);
 285}
 286
 287static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
 288			int *nr_calls)
 289{
 290	unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
 291	void *hcpu = (void *)(long)cpu;
 292
 293	int ret;
 294
 295	ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
 296					nr_calls);
 297
 298	return notifier_to_errno(ret);
 299}
 300
 301static int cpu_notify(unsigned long val, unsigned int cpu)
 302{
 303	return __cpu_notify(val, cpu, -1, NULL);
 304}
 305
 306static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
 307{
 308	BUG_ON(cpu_notify(val, cpu));
 309}
 310
 311/* Notifier wrappers for transitioning to state machine */
 312static int notify_prepare(unsigned int cpu)
 313{
 314	int nr_calls = 0;
 315	int ret;
 316
 317	ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
 318	if (ret) {
 319		nr_calls--;
 320		printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 321				__func__, cpu);
 322		__cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
 323	}
 324	return ret;
 325}
 326
 327static int notify_online(unsigned int cpu)
 328{
 329	cpu_notify(CPU_ONLINE, cpu);
 330	return 0;
 331}
 332
 333static int notify_starting(unsigned int cpu)
 334{
 335	cpu_notify(CPU_STARTING, cpu);
 336	return 0;
 337}
 338
 339static int bringup_wait_for_ap(unsigned int cpu)
 340{
 341	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 342
 343	wait_for_completion(&st->done);
 344	return st->result;
 345}
 346
 347static int bringup_cpu(unsigned int cpu)
 348{
 349	struct task_struct *idle = idle_thread_get(cpu);
 350	int ret;
 351
 352	/* Arch-specific enabling code. */
 353	ret = __cpu_up(cpu, idle);
 354	if (ret) {
 355		cpu_notify(CPU_UP_CANCELED, cpu);
 356		return ret;
 357	}
 358	ret = bringup_wait_for_ap(cpu);
 359	BUG_ON(!cpu_online(cpu));
 360	return ret;
 361}
 362
 363/*
 364 * Hotplug state machine related functions
 365 */
 366static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st,
 367			  struct cpuhp_step *steps)
 368{
 369	for (st->state++; st->state < st->target; st->state++) {
 370		struct cpuhp_step *step = steps + st->state;
 371
 372		if (!step->skip_onerr)
 373			cpuhp_invoke_callback(cpu, st->state, step->startup);
 374	}
 375}
 376
 377static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 378				struct cpuhp_step *steps, enum cpuhp_state target)
 379{
 380	enum cpuhp_state prev_state = st->state;
 381	int ret = 0;
 382
 383	for (; st->state > target; st->state--) {
 384		struct cpuhp_step *step = steps + st->state;
 385
 386		ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
 387		if (ret) {
 388			st->target = prev_state;
 389			undo_cpu_down(cpu, st, steps);
 390			break;
 391		}
 392	}
 393	return ret;
 394}
 395
 396static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st,
 397			struct cpuhp_step *steps)
 398{
 399	for (st->state--; st->state > st->target; st->state--) {
 400		struct cpuhp_step *step = steps + st->state;
 401
 402		if (!step->skip_onerr)
 403			cpuhp_invoke_callback(cpu, st->state, step->teardown);
 404	}
 405}
 406
 407static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
 408			      struct cpuhp_step *steps, enum cpuhp_state target)
 409{
 410	enum cpuhp_state prev_state = st->state;
 411	int ret = 0;
 412
 413	while (st->state < target) {
 414		struct cpuhp_step *step;
 415
 416		st->state++;
 417		step = steps + st->state;
 418		ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
 419		if (ret) {
 420			st->target = prev_state;
 421			undo_cpu_up(cpu, st, steps);
 422			break;
 423		}
 424	}
 425	return ret;
 426}
 427
 428/*
 429 * The cpu hotplug threads manage the bringup and teardown of the cpus
 430 */
 431static void cpuhp_create(unsigned int cpu)
 432{
 433	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 434
 435	init_completion(&st->done);
 436}
 437
 438static int cpuhp_should_run(unsigned int cpu)
 439{
 440	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 441
 442	return st->should_run;
 443}
 444
 445/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
 446static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
 447{
 448	enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
 449
 450	return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
 451}
 452
 453/* Execute the online startup callbacks. Used to be CPU_ONLINE */
 454static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
 455{
 456	return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
 457}
 458
 459/*
 460 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
 461 * callbacks when a state gets [un]installed at runtime.
 462 */
 463static void cpuhp_thread_fun(unsigned int cpu)
 464{
 465	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 466	int ret = 0;
 467
 468	/*
 469	 * Paired with the mb() in cpuhp_kick_ap_work and
 470	 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
 471	 */
 472	smp_mb();
 473	if (!st->should_run)
 474		return;
 475
 476	st->should_run = false;
 477
 478	/* Single callback invocation for [un]install ? */
 479	if (st->cb) {
 480		if (st->cb_state < CPUHP_AP_ONLINE) {
 481			local_irq_disable();
 482			ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
 483			local_irq_enable();
 484		} else {
 485			ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
 486		}
 487	} else if (st->rollback) {
 488		BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 489
 490		undo_cpu_down(cpu, st, cpuhp_ap_states);
 491		/*
 492		 * This is a momentary workaround to keep the notifier users
 493		 * happy. Will go away once we got rid of the notifiers.
 494		 */
 495		cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
 496		st->rollback = false;
 497	} else {
 498		/* Cannot happen .... */
 499		BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
 500
 501		/* Regular hotplug work */
 502		if (st->state < st->target)
 503			ret = cpuhp_ap_online(cpu, st);
 504		else if (st->state > st->target)
 505			ret = cpuhp_ap_offline(cpu, st);
 506	}
 507	st->result = ret;
 508	complete(&st->done);
 509}
 510
 511/* Invoke a single callback on a remote cpu */
 512static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
 513				    int (*cb)(unsigned int))
 514{
 515	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 516
 517	if (!cpu_online(cpu))
 518		return 0;
 519
 520	st->cb_state = state;
 521	st->cb = cb;
 522	/*
 523	 * Make sure the above stores are visible before should_run becomes
 524	 * true. Paired with the mb() above in cpuhp_thread_fun()
 525	 */
 526	smp_mb();
 527	st->should_run = true;
 528	wake_up_process(st->thread);
 529	wait_for_completion(&st->done);
 530	return st->result;
 531}
 532
 533/* Regular hotplug invocation of the AP hotplug thread */
 534static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
 535{
 536	st->result = 0;
 537	st->cb = NULL;
 538	/*
 539	 * Make sure the above stores are visible before should_run becomes
 540	 * true. Paired with the mb() above in cpuhp_thread_fun()
 541	 */
 542	smp_mb();
 543	st->should_run = true;
 544	wake_up_process(st->thread);
 545}
 546
 547static int cpuhp_kick_ap_work(unsigned int cpu)
 548{
 549	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 550	enum cpuhp_state state = st->state;
 551
 552	trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
 553	__cpuhp_kick_ap_work(st);
 554	wait_for_completion(&st->done);
 555	trace_cpuhp_exit(cpu, st->state, state, st->result);
 556	return st->result;
 557}
 558
 559static struct smp_hotplug_thread cpuhp_threads = {
 560	.store			= &cpuhp_state.thread,
 561	.create			= &cpuhp_create,
 562	.thread_should_run	= cpuhp_should_run,
 563	.thread_fn		= cpuhp_thread_fun,
 564	.thread_comm		= "cpuhp/%u",
 565	.selfparking		= true,
 566};
 567
 568void __init cpuhp_threads_init(void)
 569{
 570	BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
 571	kthread_unpark(this_cpu_read(cpuhp_state.thread));
 572}
 573
 574#ifdef CONFIG_HOTPLUG_CPU
 575EXPORT_SYMBOL(register_cpu_notifier);
 576EXPORT_SYMBOL(__register_cpu_notifier);
 577void unregister_cpu_notifier(struct notifier_block *nb)
 578{
 579	cpu_maps_update_begin();
 580	raw_notifier_chain_unregister(&cpu_chain, nb);
 581	cpu_maps_update_done();
 582}
 583EXPORT_SYMBOL(unregister_cpu_notifier);
 584
 585void __unregister_cpu_notifier(struct notifier_block *nb)
 586{
 587	raw_notifier_chain_unregister(&cpu_chain, nb);
 588}
 589EXPORT_SYMBOL(__unregister_cpu_notifier);
 590
 591/**
 592 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
 593 * @cpu: a CPU id
 594 *
 595 * This function walks all processes, finds a valid mm struct for each one and
 596 * then clears a corresponding bit in mm's cpumask.  While this all sounds
 597 * trivial, there are various non-obvious corner cases, which this function
 598 * tries to solve in a safe manner.
 599 *
 600 * Also note that the function uses a somewhat relaxed locking scheme, so it may
 601 * be called only for an already offlined CPU.
 602 */
 603void clear_tasks_mm_cpumask(int cpu)
 604{
 605	struct task_struct *p;
 606
 607	/*
 608	 * This function is called after the cpu is taken down and marked
 609	 * offline, so its not like new tasks will ever get this cpu set in
 610	 * their mm mask. -- Peter Zijlstra
 611	 * Thus, we may use rcu_read_lock() here, instead of grabbing
 612	 * full-fledged tasklist_lock.
 613	 */
 614	WARN_ON(cpu_online(cpu));
 615	rcu_read_lock();
 616	for_each_process(p) {
 617		struct task_struct *t;
 618
 619		/*
 620		 * Main thread might exit, but other threads may still have
 621		 * a valid mm. Find one.
 622		 */
 623		t = find_lock_task_mm(p);
 624		if (!t)
 625			continue;
 626		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
 627		task_unlock(t);
 628	}
 629	rcu_read_unlock();
 630}
 631
 632static inline void check_for_tasks(int dead_cpu)
 633{
 634	struct task_struct *g, *p;
 635
 636	read_lock(&tasklist_lock);
 637	for_each_process_thread(g, p) {
 638		if (!p->on_rq)
 639			continue;
 640		/*
 641		 * We do the check with unlocked task_rq(p)->lock.
 642		 * Order the reading to do not warn about a task,
 643		 * which was running on this cpu in the past, and
 644		 * it's just been woken on another cpu.
 645		 */
 646		rmb();
 647		if (task_cpu(p) != dead_cpu)
 648			continue;
 649
 650		pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
 651			p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
 652	}
 653	read_unlock(&tasklist_lock);
 654}
 655
 656static int notify_down_prepare(unsigned int cpu)
 657{
 658	int err, nr_calls = 0;
 659
 660	err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
 661	if (err) {
 662		nr_calls--;
 663		__cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
 664		pr_warn("%s: attempt to take down CPU %u failed\n",
 665				__func__, cpu);
 666	}
 667	return err;
 
 
 668}
 669
 670static int notify_dying(unsigned int cpu)
 671{
 672	cpu_notify(CPU_DYING, cpu);
 673	return 0;
 674}
 675
 676/* Take this CPU down. */
 677static int take_cpu_down(void *_param)
 678{
 679	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 680	enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
 681	int err, cpu = smp_processor_id();
 682
 683	/* Ensure this CPU doesn't handle any more interrupts. */
 684	err = __cpu_disable();
 685	if (err < 0)
 686		return err;
 687
 688	/* Invoke the former CPU_DYING callbacks */
 689	for (; st->state > target; st->state--) {
 690		struct cpuhp_step *step = cpuhp_ap_states + st->state;
 691
 692		cpuhp_invoke_callback(cpu, st->state, step->teardown);
 693	}
 694	/* Give up timekeeping duties */
 695	tick_handover_do_timer();
 696	/* Park the stopper thread */
 697	stop_machine_park(cpu);
 698	return 0;
 699}
 700
 701static int takedown_cpu(unsigned int cpu)
 
 702{
 703	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 704	int err;
 
 
 
 
 
 705
 706	/*
 707	 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
 708	 * and RCU users of this state to go away such that all new such users
 709	 * will observe it.
 710	 *
 711	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
 712	 * not imply sync_sched(), so wait for both.
 713	 *
 714	 * Do sync before park smpboot threads to take care the rcu boost case.
 715	 */
 716	if (IS_ENABLED(CONFIG_PREEMPT))
 717		synchronize_rcu_mult(call_rcu, call_rcu_sched);
 718	else
 719		synchronize_rcu();
 720
 721	/* Park the smpboot threads */
 722	kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 723	smpboot_park_threads(cpu);
 724
 725	/*
 726	 * Prevent irq alloc/free while the dying cpu reorganizes the
 727	 * interrupt affinities.
 728	 */
 729	irq_lock_sparse();
 730
 731	/*
 732	 * So now all preempt/rcu users must observe !cpu_active().
 733	 */
 734	err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
 735	if (err) {
 736		/* CPU refused to die */
 737		irq_unlock_sparse();
 738		/* Unpark the hotplug thread so we can rollback there */
 739		kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
 740		return err;
 
 
 
 
 
 
 
 
 741	}
 742	BUG_ON(cpu_online(cpu));
 743
 744	/*
 745	 * The migration_call() CPU_DYING callback will have removed all
 746	 * runnable tasks from the cpu, there's only the idle task left now
 747	 * that the migration thread is done doing the stop_machine thing.
 748	 *
 749	 * Wait for the stop thread to go away.
 750	 */
 751	wait_for_completion(&st->done);
 752	BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
 753
 754	/* Interrupts are moved away from the dying cpu, reenable alloc/free */
 755	irq_unlock_sparse();
 756
 757	hotplug_cpu__broadcast_tick_pull(cpu);
 758	/* This actually kills the CPU. */
 759	__cpu_die(cpu);
 760
 761	tick_cleanup_dead_cpu(cpu);
 762	return 0;
 763}
 764
 765static int notify_dead(unsigned int cpu)
 766{
 767	cpu_notify_nofail(CPU_DEAD, cpu);
 768	check_for_tasks(cpu);
 769	return 0;
 770}
 771
 772static void cpuhp_complete_idle_dead(void *arg)
 773{
 774	struct cpuhp_cpu_state *st = arg;
 775
 776	complete(&st->done);
 777}
 778
 779void cpuhp_report_idle_dead(void)
 780{
 781	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 782
 783	BUG_ON(st->state != CPUHP_AP_OFFLINE);
 784	rcu_report_dead(smp_processor_id());
 785	st->state = CPUHP_AP_IDLE_DEAD;
 786	/*
 787	 * We cannot call complete after rcu_report_dead() so we delegate it
 788	 * to an online cpu.
 789	 */
 790	smp_call_function_single(cpumask_first(cpu_online_mask),
 791				 cpuhp_complete_idle_dead, st, 0);
 792}
 793
 794#else
 795#define notify_down_prepare	NULL
 796#define takedown_cpu		NULL
 797#define notify_dead		NULL
 798#define notify_dying		NULL
 799#endif
 800
 801#ifdef CONFIG_HOTPLUG_CPU
 802
 803/* Requires cpu_add_remove_lock to be held */
 804static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
 805			   enum cpuhp_state target)
 806{
 807	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 808	int prev_state, ret = 0;
 809	bool hasdied = false;
 810
 811	if (num_online_cpus() == 1)
 812		return -EBUSY;
 813
 814	if (!cpu_present(cpu))
 815		return -EINVAL;
 816
 817	cpu_hotplug_begin();
 818
 819	cpuhp_tasks_frozen = tasks_frozen;
 820
 821	prev_state = st->state;
 822	st->target = target;
 823	/*
 824	 * If the current CPU state is in the range of the AP hotplug thread,
 825	 * then we need to kick the thread.
 826	 */
 827	if (st->state > CPUHP_TEARDOWN_CPU) {
 828		ret = cpuhp_kick_ap_work(cpu);
 829		/*
 830		 * The AP side has done the error rollback already. Just
 831		 * return the error code..
 832		 */
 833		if (ret)
 834			goto out;
 835
 836		/*
 837		 * We might have stopped still in the range of the AP hotplug
 838		 * thread. Nothing to do anymore.
 839		 */
 840		if (st->state > CPUHP_TEARDOWN_CPU)
 841			goto out;
 842	}
 843	/*
 844	 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
 845	 * to do the further cleanups.
 846	 */
 847	ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
 848	if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
 849		st->target = prev_state;
 850		st->rollback = true;
 851		cpuhp_kick_ap_work(cpu);
 852	}
 853
 854	hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
 855out:
 856	cpu_hotplug_done();
 857	/* This post dead nonsense must die */
 858	if (!ret && hasdied)
 859		cpu_notify_nofail(CPU_POST_DEAD, cpu);
 860	return ret;
 861}
 862
 863static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
 864{
 865	int err;
 866
 867	cpu_maps_update_begin();
 868
 869	if (cpu_hotplug_disabled) {
 870		err = -EBUSY;
 871		goto out;
 872	}
 873
 874	err = _cpu_down(cpu, 0, target);
 875
 876out:
 877	cpu_maps_update_done();
 878	return err;
 879}
 880int cpu_down(unsigned int cpu)
 881{
 882	return do_cpu_down(cpu, CPUHP_OFFLINE);
 883}
 884EXPORT_SYMBOL(cpu_down);
 885#endif /*CONFIG_HOTPLUG_CPU*/
 886
 887/**
 888 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 889 * @cpu: cpu that just started
 890 *
 891 * This function calls the cpu_chain notifiers with CPU_STARTING.
 892 * It must be called by the arch code on the new cpu, before the new cpu
 893 * enables interrupts and before the "boot" cpu returns from __cpu_up().
 894 */
 895void notify_cpu_starting(unsigned int cpu)
 896{
 897	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 898	enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
 899
 900	while (st->state < target) {
 901		struct cpuhp_step *step;
 902
 903		st->state++;
 904		step = cpuhp_ap_states + st->state;
 905		cpuhp_invoke_callback(cpu, st->state, step->startup);
 906	}
 907}
 908
 909/*
 910 * Called from the idle task. We need to set active here, so we can kick off
 911 * the stopper thread and unpark the smpboot threads. If the target state is
 912 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
 913 * cpu further.
 914 */
 915void cpuhp_online_idle(enum cpuhp_state state)
 916{
 917	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 918	unsigned int cpu = smp_processor_id();
 919
 920	/* Happens for the boot cpu */
 921	if (state != CPUHP_AP_ONLINE_IDLE)
 922		return;
 923
 924	st->state = CPUHP_AP_ONLINE_IDLE;
 925
 926	/* The cpu is marked online, set it active now */
 927	set_cpu_active(cpu, true);
 928	/* Unpark the stopper thread and the hotplug thread of this cpu */
 929	stop_machine_unpark(cpu);
 930	kthread_unpark(st->thread);
 931
 932	/* Should we go further up ? */
 933	if (st->target > CPUHP_AP_ONLINE_IDLE)
 934		__cpuhp_kick_ap_work(st);
 935	else
 936		complete(&st->done);
 937}
 938
 939/* Requires cpu_add_remove_lock to be held */
 940static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
 941{
 942	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 
 
 943	struct task_struct *idle;
 944	int ret = 0;
 
 
 945
 946	cpu_hotplug_begin();
 947
 948	if (!cpu_present(cpu)) {
 949		ret = -EINVAL;
 
 950		goto out;
 951	}
 952
 953	/*
 954	 * The caller of do_cpu_up might have raced with another
 955	 * caller. Ignore it for now.
 956	 */
 957	if (st->state >= target)
 958		goto out;
 959
 960	if (st->state == CPUHP_OFFLINE) {
 961		/* Let it fail before we try to bring the cpu up */
 962		idle = idle_thread_get(cpu);
 963		if (IS_ERR(idle)) {
 964			ret = PTR_ERR(idle);
 965			goto out;
 966		}
 967	}
 968
 969	cpuhp_tasks_frozen = tasks_frozen;
 
 
 
 
 970
 971	st->target = target;
 972	/*
 973	 * If the current CPU state is in the range of the AP hotplug thread,
 974	 * then we need to kick the thread once more.
 975	 */
 976	if (st->state > CPUHP_BRINGUP_CPU) {
 977		ret = cpuhp_kick_ap_work(cpu);
 978		/*
 979		 * The AP side has done the error rollback already. Just
 980		 * return the error code..
 981		 */
 982		if (ret)
 983			goto out;
 984	}
 985
 986	/*
 987	 * Try to reach the target state. We max out on the BP at
 988	 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
 989	 * responsible for bringing it up to the target state.
 990	 */
 991	target = min((int)target, CPUHP_BRINGUP_CPU);
 992	ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
 993out:
 994	cpu_hotplug_done();
 
 995	return ret;
 996}
 997
 998static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
 999{
1000	int err = 0;
1001
 
 
 
 
 
1002	if (!cpu_possible(cpu)) {
1003		pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1004		       cpu);
1005#if defined(CONFIG_IA64)
1006		pr_err("please check additional_cpus= boot parameter\n");
 
1007#endif
1008		return -EINVAL;
1009	}
1010
1011	err = try_online_node(cpu_to_node(cpu));
1012	if (err)
1013		return err;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1014
1015	cpu_maps_update_begin();
1016
1017	if (cpu_hotplug_disabled) {
1018		err = -EBUSY;
1019		goto out;
1020	}
1021
1022	err = _cpu_up(cpu, 0, target);
 
1023out:
1024	cpu_maps_update_done();
1025	return err;
1026}
1027
1028int cpu_up(unsigned int cpu)
1029{
1030	return do_cpu_up(cpu, CPUHP_ONLINE);
1031}
1032EXPORT_SYMBOL_GPL(cpu_up);
1033
1034#ifdef CONFIG_PM_SLEEP_SMP
1035static cpumask_var_t frozen_cpus;
1036
 
 
 
 
 
 
 
 
1037int disable_nonboot_cpus(void)
1038{
1039	int cpu, first_cpu, error = 0;
1040
1041	cpu_maps_update_begin();
1042	first_cpu = cpumask_first(cpu_online_mask);
1043	/*
1044	 * We take down all of the non-boot CPUs in one shot to avoid races
1045	 * with the userspace trying to use the CPU hotplug at the same time
1046	 */
1047	cpumask_clear(frozen_cpus);
 
1048
1049	pr_info("Disabling non-boot CPUs ...\n");
1050	for_each_online_cpu(cpu) {
1051		if (cpu == first_cpu)
1052			continue;
1053		trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1054		error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1055		trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1056		if (!error)
1057			cpumask_set_cpu(cpu, frozen_cpus);
1058		else {
1059			pr_err("Error taking CPU%d down: %d\n", cpu, error);
 
1060			break;
1061		}
1062	}
1063
1064	if (!error)
1065		BUG_ON(num_online_cpus() > 1);
1066	else
1067		pr_err("Non-boot CPUs are not disabled\n");
1068
1069	/*
1070	 * Make sure the CPUs won't be enabled by someone else. We need to do
1071	 * this even in case of failure as all disable_nonboot_cpus() users are
1072	 * supposed to do enable_nonboot_cpus() on the failure path.
1073	 */
1074	cpu_hotplug_disabled++;
1075
 
 
 
 
 
 
 
1076	cpu_maps_update_done();
1077	return error;
1078}
1079
1080void __weak arch_enable_nonboot_cpus_begin(void)
1081{
1082}
1083
1084void __weak arch_enable_nonboot_cpus_end(void)
1085{
1086}
1087
1088void enable_nonboot_cpus(void)
1089{
1090	int cpu, error;
1091
1092	/* Allow everyone to use the CPU hotplug again */
1093	cpu_maps_update_begin();
1094	WARN_ON(--cpu_hotplug_disabled < 0);
1095	if (cpumask_empty(frozen_cpus))
1096		goto out;
1097
1098	pr_info("Enabling non-boot CPUs ...\n");
1099
1100	arch_enable_nonboot_cpus_begin();
1101
1102	for_each_cpu(cpu, frozen_cpus) {
1103		trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1104		error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1105		trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1106		if (!error) {
1107			pr_info("CPU%d is up\n", cpu);
1108			continue;
1109		}
1110		pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1111	}
1112
1113	arch_enable_nonboot_cpus_end();
1114
1115	cpumask_clear(frozen_cpus);
1116out:
1117	cpu_maps_update_done();
1118}
1119
1120static int __init alloc_frozen_cpus(void)
1121{
1122	if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1123		return -ENOMEM;
1124	return 0;
1125}
1126core_initcall(alloc_frozen_cpus);
1127
1128/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1129 * When callbacks for CPU hotplug notifications are being executed, we must
1130 * ensure that the state of the system with respect to the tasks being frozen
1131 * or not, as reported by the notification, remains unchanged *throughout the
1132 * duration* of the execution of the callbacks.
1133 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1134 *
1135 * This synchronization is implemented by mutually excluding regular CPU
1136 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1137 * Hibernate notifications.
1138 */
1139static int
1140cpu_hotplug_pm_callback(struct notifier_block *nb,
1141			unsigned long action, void *ptr)
1142{
1143	switch (action) {
1144
1145	case PM_SUSPEND_PREPARE:
1146	case PM_HIBERNATION_PREPARE:
1147		cpu_hotplug_disable();
1148		break;
1149
1150	case PM_POST_SUSPEND:
1151	case PM_POST_HIBERNATION:
1152		cpu_hotplug_enable();
1153		break;
1154
1155	default:
1156		return NOTIFY_DONE;
1157	}
1158
1159	return NOTIFY_OK;
1160}
1161
1162
1163static int __init cpu_hotplug_pm_sync_init(void)
1164{
1165	/*
1166	 * cpu_hotplug_pm_callback has higher priority than x86
1167	 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1168	 * to disable cpu hotplug to avoid cpu hotplug race.
1169	 */
1170	pm_notifier(cpu_hotplug_pm_callback, 0);
1171	return 0;
1172}
1173core_initcall(cpu_hotplug_pm_sync_init);
1174
1175#endif /* CONFIG_PM_SLEEP_SMP */
1176
1177#endif /* CONFIG_SMP */
1178
1179/* Boot processor state steps */
1180static struct cpuhp_step cpuhp_bp_states[] = {
1181	[CPUHP_OFFLINE] = {
1182		.name			= "offline",
1183		.startup		= NULL,
1184		.teardown		= NULL,
1185	},
1186#ifdef CONFIG_SMP
1187	[CPUHP_CREATE_THREADS]= {
1188		.name			= "threads:create",
1189		.startup		= smpboot_create_threads,
1190		.teardown		= NULL,
1191		.cant_stop		= true,
1192	},
1193	/*
1194	 * Preparatory and dead notifiers. Will be replaced once the notifiers
1195	 * are converted to states.
1196	 */
1197	[CPUHP_NOTIFY_PREPARE] = {
1198		.name			= "notify:prepare",
1199		.startup		= notify_prepare,
1200		.teardown		= notify_dead,
1201		.skip_onerr		= true,
1202		.cant_stop		= true,
1203	},
1204	/* Kicks the plugged cpu into life */
1205	[CPUHP_BRINGUP_CPU] = {
1206		.name			= "cpu:bringup",
1207		.startup		= bringup_cpu,
1208		.teardown		= NULL,
1209		.cant_stop		= true,
1210	},
1211	/*
1212	 * Handled on controll processor until the plugged processor manages
1213	 * this itself.
1214	 */
1215	[CPUHP_TEARDOWN_CPU] = {
1216		.name			= "cpu:teardown",
1217		.startup		= NULL,
1218		.teardown		= takedown_cpu,
1219		.cant_stop		= true,
1220	},
1221#endif
1222};
1223
1224/* Application processor state steps */
1225static struct cpuhp_step cpuhp_ap_states[] = {
1226#ifdef CONFIG_SMP
1227	/* Final state before CPU kills itself */
1228	[CPUHP_AP_IDLE_DEAD] = {
1229		.name			= "idle:dead",
1230	},
1231	/*
1232	 * Last state before CPU enters the idle loop to die. Transient state
1233	 * for synchronization.
1234	 */
1235	[CPUHP_AP_OFFLINE] = {
1236		.name			= "ap:offline",
1237		.cant_stop		= true,
1238	},
1239	/*
1240	 * Low level startup/teardown notifiers. Run with interrupts
1241	 * disabled. Will be removed once the notifiers are converted to
1242	 * states.
1243	 */
1244	[CPUHP_AP_NOTIFY_STARTING] = {
1245		.name			= "notify:starting",
1246		.startup		= notify_starting,
1247		.teardown		= notify_dying,
1248		.skip_onerr		= true,
1249		.cant_stop		= true,
1250	},
1251	/* Entry state on starting. Interrupts enabled from here on. Transient
1252	 * state for synchronsization */
1253	[CPUHP_AP_ONLINE] = {
1254		.name			= "ap:online",
1255	},
1256	/* Handle smpboot threads park/unpark */
1257	[CPUHP_AP_SMPBOOT_THREADS] = {
1258		.name			= "smpboot:threads",
1259		.startup		= smpboot_unpark_threads,
1260		.teardown		= NULL,
1261	},
1262	/*
1263	 * Online/down_prepare notifiers. Will be removed once the notifiers
1264	 * are converted to states.
1265	 */
1266	[CPUHP_AP_NOTIFY_ONLINE] = {
1267		.name			= "notify:online",
1268		.startup		= notify_online,
1269		.teardown		= notify_down_prepare,
1270		.skip_onerr		= true,
1271	},
1272#endif
1273	/*
1274	 * The dynamically registered state space is here
1275	 */
1276
1277	/* CPU is fully up and running. */
1278	[CPUHP_ONLINE] = {
1279		.name			= "online",
1280		.startup		= NULL,
1281		.teardown		= NULL,
1282	},
1283};
1284
1285/* Sanity check for callbacks */
1286static int cpuhp_cb_check(enum cpuhp_state state)
1287{
1288	if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1289		return -EINVAL;
1290	return 0;
1291}
1292
1293static bool cpuhp_is_ap_state(enum cpuhp_state state)
1294{
1295	/*
1296	 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
1297	 * purposes as that state is handled explicitely in cpu_down.
1298	 */
1299	return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
1300}
1301
1302static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
1303{
1304	struct cpuhp_step *sp;
1305
1306	sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
1307	return sp + state;
1308}
1309
1310static void cpuhp_store_callbacks(enum cpuhp_state state,
1311				  const char *name,
1312				  int (*startup)(unsigned int cpu),
1313				  int (*teardown)(unsigned int cpu))
1314{
1315	/* (Un)Install the callbacks for further cpu hotplug operations */
1316	struct cpuhp_step *sp;
1317
1318	mutex_lock(&cpuhp_state_mutex);
1319	sp = cpuhp_get_step(state);
1320	sp->startup = startup;
1321	sp->teardown = teardown;
1322	sp->name = name;
1323	mutex_unlock(&cpuhp_state_mutex);
1324}
1325
1326static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1327{
1328	return cpuhp_get_step(state)->teardown;
1329}
1330
1331/*
1332 * Call the startup/teardown function for a step either on the AP or
1333 * on the current CPU.
1334 */
1335static int cpuhp_issue_call(int cpu, enum cpuhp_state state,
1336			    int (*cb)(unsigned int), bool bringup)
1337{
1338	int ret;
1339
1340	if (!cb)
1341		return 0;
1342	/*
1343	 * The non AP bound callbacks can fail on bringup. On teardown
1344	 * e.g. module removal we crash for now.
1345	 */
1346#ifdef CONFIG_SMP
1347	if (cpuhp_is_ap_state(state))
1348		ret = cpuhp_invoke_ap_callback(cpu, state, cb);
1349	else
1350		ret = cpuhp_invoke_callback(cpu, state, cb);
1351#else
1352	ret = cpuhp_invoke_callback(cpu, state, cb);
1353#endif
1354	BUG_ON(ret && !bringup);
1355	return ret;
1356}
1357
1358/*
1359 * Called from __cpuhp_setup_state on a recoverable failure.
1360 *
1361 * Note: The teardown callbacks for rollback are not allowed to fail!
1362 */
1363static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1364				   int (*teardown)(unsigned int cpu))
1365{
1366	int cpu;
1367
1368	if (!teardown)
1369		return;
1370
1371	/* Roll back the already executed steps on the other cpus */
1372	for_each_present_cpu(cpu) {
1373		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1374		int cpustate = st->state;
1375
1376		if (cpu >= failedcpu)
1377			break;
1378
1379		/* Did we invoke the startup call on that cpu ? */
1380		if (cpustate >= state)
1381			cpuhp_issue_call(cpu, state, teardown, false);
1382	}
1383}
1384
1385/*
1386 * Returns a free for dynamic slot assignment of the Online state. The states
1387 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1388 * by having no name assigned.
1389 */
1390static int cpuhp_reserve_state(enum cpuhp_state state)
1391{
1392	enum cpuhp_state i;
1393
1394	mutex_lock(&cpuhp_state_mutex);
1395	for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1396		if (cpuhp_ap_states[i].name)
1397			continue;
1398
1399		cpuhp_ap_states[i].name = "Reserved";
1400		mutex_unlock(&cpuhp_state_mutex);
1401		return i;
1402	}
1403	mutex_unlock(&cpuhp_state_mutex);
1404	WARN(1, "No more dynamic states available for CPU hotplug\n");
1405	return -ENOSPC;
1406}
1407
1408/**
1409 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1410 * @state:	The state to setup
1411 * @invoke:	If true, the startup function is invoked for cpus where
1412 *		cpu state >= @state
1413 * @startup:	startup callback function
1414 * @teardown:	teardown callback function
1415 *
1416 * Returns 0 if successful, otherwise a proper error code
1417 */
1418int __cpuhp_setup_state(enum cpuhp_state state,
1419			const char *name, bool invoke,
1420			int (*startup)(unsigned int cpu),
1421			int (*teardown)(unsigned int cpu))
1422{
1423	int cpu, ret = 0;
1424	int dyn_state = 0;
1425
1426	if (cpuhp_cb_check(state) || !name)
1427		return -EINVAL;
1428
1429	get_online_cpus();
1430
1431	/* currently assignments for the ONLINE state are possible */
1432	if (state == CPUHP_AP_ONLINE_DYN) {
1433		dyn_state = 1;
1434		ret = cpuhp_reserve_state(state);
1435		if (ret < 0)
1436			goto out;
1437		state = ret;
1438	}
1439
1440	cpuhp_store_callbacks(state, name, startup, teardown);
1441
1442	if (!invoke || !startup)
1443		goto out;
1444
1445	/*
1446	 * Try to call the startup callback for each present cpu
1447	 * depending on the hotplug state of the cpu.
1448	 */
1449	for_each_present_cpu(cpu) {
1450		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1451		int cpustate = st->state;
1452
1453		if (cpustate < state)
1454			continue;
1455
1456		ret = cpuhp_issue_call(cpu, state, startup, true);
1457		if (ret) {
1458			cpuhp_rollback_install(cpu, state, teardown);
1459			cpuhp_store_callbacks(state, NULL, NULL, NULL);
1460			goto out;
1461		}
1462	}
1463out:
1464	put_online_cpus();
1465	if (!ret && dyn_state)
1466		return state;
1467	return ret;
1468}
1469EXPORT_SYMBOL(__cpuhp_setup_state);
1470
1471/**
1472 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1473 * @state:	The state to remove
1474 * @invoke:	If true, the teardown function is invoked for cpus where
1475 *		cpu state >= @state
1476 *
1477 * The teardown callback is currently not allowed to fail. Think
1478 * about module removal!
 
1479 */
1480void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1481{
1482	int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state);
1483	int cpu;
1484
1485	BUG_ON(cpuhp_cb_check(state));
1486
1487	get_online_cpus();
1488
1489	if (!invoke || !teardown)
1490		goto remove;
1491
1492	/*
1493	 * Call the teardown callback for each present cpu depending
1494	 * on the hotplug state of the cpu. This function is not
1495	 * allowed to fail currently!
1496	 */
1497	for_each_present_cpu(cpu) {
1498		struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1499		int cpustate = st->state;
1500
1501		if (cpustate >= state)
1502			cpuhp_issue_call(cpu, state, teardown, false);
1503	}
1504remove:
1505	cpuhp_store_callbacks(state, NULL, NULL, NULL);
1506	put_online_cpus();
1507}
1508EXPORT_SYMBOL(__cpuhp_remove_state);
1509
1510#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1511static ssize_t show_cpuhp_state(struct device *dev,
1512				struct device_attribute *attr, char *buf)
1513{
1514	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1515
1516	return sprintf(buf, "%d\n", st->state);
1517}
1518static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1519
1520static ssize_t write_cpuhp_target(struct device *dev,
1521				  struct device_attribute *attr,
1522				  const char *buf, size_t count)
1523{
1524	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1525	struct cpuhp_step *sp;
1526	int target, ret;
1527
1528	ret = kstrtoint(buf, 10, &target);
1529	if (ret)
1530		return ret;
1531
1532#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1533	if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1534		return -EINVAL;
1535#else
1536	if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1537		return -EINVAL;
1538#endif
1539
1540	ret = lock_device_hotplug_sysfs();
1541	if (ret)
1542		return ret;
1543
1544	mutex_lock(&cpuhp_state_mutex);
1545	sp = cpuhp_get_step(target);
1546	ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1547	mutex_unlock(&cpuhp_state_mutex);
1548	if (ret)
1549		return ret;
1550
1551	if (st->state < target)
1552		ret = do_cpu_up(dev->id, target);
1553	else
1554		ret = do_cpu_down(dev->id, target);
1555
1556	unlock_device_hotplug();
1557	return ret ? ret : count;
1558}
1559
1560static ssize_t show_cpuhp_target(struct device *dev,
1561				 struct device_attribute *attr, char *buf)
1562{
1563	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1564
1565	return sprintf(buf, "%d\n", st->target);
1566}
1567static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1568
1569static struct attribute *cpuhp_cpu_attrs[] = {
1570	&dev_attr_state.attr,
1571	&dev_attr_target.attr,
1572	NULL
1573};
1574
1575static struct attribute_group cpuhp_cpu_attr_group = {
1576	.attrs = cpuhp_cpu_attrs,
1577	.name = "hotplug",
1578	NULL
1579};
1580
1581static ssize_t show_cpuhp_states(struct device *dev,
1582				 struct device_attribute *attr, char *buf)
1583{
1584	ssize_t cur, res = 0;
1585	int i;
1586
1587	mutex_lock(&cpuhp_state_mutex);
1588	for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1589		struct cpuhp_step *sp = cpuhp_get_step(i);
1590
1591		if (sp->name) {
1592			cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1593			buf += cur;
1594			res += cur;
1595		}
1596	}
1597	mutex_unlock(&cpuhp_state_mutex);
1598	return res;
1599}
1600static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1601
1602static struct attribute *cpuhp_cpu_root_attrs[] = {
1603	&dev_attr_states.attr,
1604	NULL
1605};
1606
1607static struct attribute_group cpuhp_cpu_root_attr_group = {
1608	.attrs = cpuhp_cpu_root_attrs,
1609	.name = "hotplug",
1610	NULL
1611};
1612
1613static int __init cpuhp_sysfs_init(void)
1614{
1615	int cpu, ret;
1616
1617	ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1618				 &cpuhp_cpu_root_attr_group);
1619	if (ret)
1620		return ret;
1621
1622	for_each_possible_cpu(cpu) {
1623		struct device *dev = get_cpu_device(cpu);
1624
1625		if (!dev)
1626			continue;
1627		ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1628		if (ret)
1629			return ret;
1630	}
1631	return 0;
1632}
1633device_initcall(cpuhp_sysfs_init);
1634#endif
1635
1636/*
1637 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1638 * represents all NR_CPUS bits binary values of 1<<nr.
1639 *
1640 * It is used by cpumask_of() to get a constant address to a CPU
1641 * mask value that has a single bit set only.
1642 */
1643
1644/* cpu_bit_bitmap[0] is empty - so we can back into it */
1645#define MASK_DECLARE_1(x)	[x+1][0] = (1UL << (x))
1646#define MASK_DECLARE_2(x)	MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1647#define MASK_DECLARE_4(x)	MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1648#define MASK_DECLARE_8(x)	MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1649
1650const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1651
1652	MASK_DECLARE_8(0),	MASK_DECLARE_8(8),
1653	MASK_DECLARE_8(16),	MASK_DECLARE_8(24),
1654#if BITS_PER_LONG > 32
1655	MASK_DECLARE_8(32),	MASK_DECLARE_8(40),
1656	MASK_DECLARE_8(48),	MASK_DECLARE_8(56),
1657#endif
1658};
1659EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1660
1661const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1662EXPORT_SYMBOL(cpu_all_bits);
1663
1664#ifdef CONFIG_INIT_ALL_POSSIBLE
1665struct cpumask __cpu_possible_mask __read_mostly
1666	= {CPU_BITS_ALL};
1667#else
1668struct cpumask __cpu_possible_mask __read_mostly;
1669#endif
1670EXPORT_SYMBOL(__cpu_possible_mask);
 
1671
1672struct cpumask __cpu_online_mask __read_mostly;
1673EXPORT_SYMBOL(__cpu_online_mask);
 
1674
1675struct cpumask __cpu_present_mask __read_mostly;
1676EXPORT_SYMBOL(__cpu_present_mask);
 
1677
1678struct cpumask __cpu_active_mask __read_mostly;
1679EXPORT_SYMBOL(__cpu_active_mask);
 
1680
1681void init_cpu_present(const struct cpumask *src)
 
 
 
 
 
 
 
 
1682{
1683	cpumask_copy(&__cpu_present_mask, src);
 
 
 
1684}
1685
1686void init_cpu_possible(const struct cpumask *src)
1687{
1688	cpumask_copy(&__cpu_possible_mask, src);
 
 
 
1689}
1690
1691void init_cpu_online(const struct cpumask *src)
1692{
1693	cpumask_copy(&__cpu_online_mask, src);
 
 
 
1694}
1695
1696/*
1697 * Activate the first processor.
1698 */
1699void __init boot_cpu_init(void)
1700{
1701	int cpu = smp_processor_id();
 
1702
1703	/* Mark the boot cpu "present", "online" etc for SMP and UP case */
1704	set_cpu_online(cpu, true);
1705	set_cpu_active(cpu, true);
1706	set_cpu_present(cpu, true);
1707	set_cpu_possible(cpu, true);
1708}
1709
1710/*
1711 * Must be called _AFTER_ setting up the per_cpu areas
1712 */
1713void __init boot_cpu_state_init(void)
1714{
1715	per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1716}