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v4.17
 
  1/*
  2 * Common SMP CPU bringup/teardown functions
  3 */
  4#include <linux/cpu.h>
  5#include <linux/err.h>
  6#include <linux/smp.h>
  7#include <linux/delay.h>
  8#include <linux/init.h>
  9#include <linux/list.h>
 10#include <linux/slab.h>
 11#include <linux/sched.h>
 12#include <linux/sched/task.h>
 13#include <linux/export.h>
 14#include <linux/percpu.h>
 15#include <linux/kthread.h>
 16#include <linux/smpboot.h>
 17
 18#include "smpboot.h"
 19
 20#ifdef CONFIG_SMP
 21
 22#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
 23/*
 24 * For the hotplug case we keep the task structs around and reuse
 25 * them.
 26 */
 27static DEFINE_PER_CPU(struct task_struct *, idle_threads);
 28
 29struct task_struct *idle_thread_get(unsigned int cpu)
 30{
 31	struct task_struct *tsk = per_cpu(idle_threads, cpu);
 32
 33	if (!tsk)
 34		return ERR_PTR(-ENOMEM);
 35	init_idle(tsk, cpu);
 36	return tsk;
 37}
 38
 39void __init idle_thread_set_boot_cpu(void)
 40{
 41	per_cpu(idle_threads, smp_processor_id()) = current;
 42}
 43
 44/**
 45 * idle_init - Initialize the idle thread for a cpu
 46 * @cpu:	The cpu for which the idle thread should be initialized
 47 *
 48 * Creates the thread if it does not exist.
 49 */
 50static inline void idle_init(unsigned int cpu)
 51{
 52	struct task_struct *tsk = per_cpu(idle_threads, cpu);
 53
 54	if (!tsk) {
 55		tsk = fork_idle(cpu);
 56		if (IS_ERR(tsk))
 57			pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
 58		else
 59			per_cpu(idle_threads, cpu) = tsk;
 60	}
 61}
 62
 63/**
 64 * idle_threads_init - Initialize idle threads for all cpus
 65 */
 66void __init idle_threads_init(void)
 67{
 68	unsigned int cpu, boot_cpu;
 69
 70	boot_cpu = smp_processor_id();
 71
 72	for_each_possible_cpu(cpu) {
 73		if (cpu != boot_cpu)
 74			idle_init(cpu);
 75	}
 76}
 77#endif
 78
 79#endif /* #ifdef CONFIG_SMP */
 80
 81static LIST_HEAD(hotplug_threads);
 82static DEFINE_MUTEX(smpboot_threads_lock);
 83
 84struct smpboot_thread_data {
 85	unsigned int			cpu;
 86	unsigned int			status;
 87	struct smp_hotplug_thread	*ht;
 88};
 89
 90enum {
 91	HP_THREAD_NONE = 0,
 92	HP_THREAD_ACTIVE,
 93	HP_THREAD_PARKED,
 94};
 95
 96/**
 97 * smpboot_thread_fn - percpu hotplug thread loop function
 98 * @data:	thread data pointer
 99 *
100 * Checks for thread stop and park conditions. Calls the necessary
101 * setup, cleanup, park and unpark functions for the registered
102 * thread.
103 *
104 * Returns 1 when the thread should exit, 0 otherwise.
105 */
106static int smpboot_thread_fn(void *data)
107{
108	struct smpboot_thread_data *td = data;
109	struct smp_hotplug_thread *ht = td->ht;
110
111	while (1) {
112		set_current_state(TASK_INTERRUPTIBLE);
113		preempt_disable();
114		if (kthread_should_stop()) {
115			__set_current_state(TASK_RUNNING);
116			preempt_enable();
117			/* cleanup must mirror setup */
118			if (ht->cleanup && td->status != HP_THREAD_NONE)
119				ht->cleanup(td->cpu, cpu_online(td->cpu));
120			kfree(td);
121			return 0;
122		}
123
124		if (kthread_should_park()) {
125			__set_current_state(TASK_RUNNING);
126			preempt_enable();
127			if (ht->park && td->status == HP_THREAD_ACTIVE) {
128				BUG_ON(td->cpu != smp_processor_id());
129				ht->park(td->cpu);
130				td->status = HP_THREAD_PARKED;
131			}
132			kthread_parkme();
133			/* We might have been woken for stop */
134			continue;
135		}
136
137		BUG_ON(td->cpu != smp_processor_id());
138
139		/* Check for state change setup */
140		switch (td->status) {
141		case HP_THREAD_NONE:
142			__set_current_state(TASK_RUNNING);
143			preempt_enable();
144			if (ht->setup)
145				ht->setup(td->cpu);
146			td->status = HP_THREAD_ACTIVE;
147			continue;
148
149		case HP_THREAD_PARKED:
150			__set_current_state(TASK_RUNNING);
151			preempt_enable();
152			if (ht->unpark)
153				ht->unpark(td->cpu);
154			td->status = HP_THREAD_ACTIVE;
155			continue;
156		}
157
158		if (!ht->thread_should_run(td->cpu)) {
159			preempt_enable_no_resched();
160			schedule();
161		} else {
162			__set_current_state(TASK_RUNNING);
163			preempt_enable();
164			ht->thread_fn(td->cpu);
165		}
166	}
167}
168
169static int
170__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
171{
172	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
173	struct smpboot_thread_data *td;
174
175	if (tsk)
176		return 0;
177
178	td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
179	if (!td)
180		return -ENOMEM;
181	td->cpu = cpu;
182	td->ht = ht;
183
184	tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
185				    ht->thread_comm);
186	if (IS_ERR(tsk)) {
187		kfree(td);
188		return PTR_ERR(tsk);
189	}
 
190	/*
191	 * Park the thread so that it could start right on the CPU
192	 * when it is available.
193	 */
194	kthread_park(tsk);
195	get_task_struct(tsk);
196	*per_cpu_ptr(ht->store, cpu) = tsk;
197	if (ht->create) {
198		/*
199		 * Make sure that the task has actually scheduled out
200		 * into park position, before calling the create
201		 * callback. At least the migration thread callback
202		 * requires that the task is off the runqueue.
203		 */
204		if (!wait_task_inactive(tsk, TASK_PARKED))
205			WARN_ON(1);
206		else
207			ht->create(cpu);
208	}
209	return 0;
210}
211
212int smpboot_create_threads(unsigned int cpu)
213{
214	struct smp_hotplug_thread *cur;
215	int ret = 0;
216
217	mutex_lock(&smpboot_threads_lock);
218	list_for_each_entry(cur, &hotplug_threads, list) {
219		ret = __smpboot_create_thread(cur, cpu);
220		if (ret)
221			break;
222	}
223	mutex_unlock(&smpboot_threads_lock);
224	return ret;
225}
226
227static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
228{
229	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
230
231	if (!ht->selfparking)
232		kthread_unpark(tsk);
233}
234
235int smpboot_unpark_threads(unsigned int cpu)
236{
237	struct smp_hotplug_thread *cur;
238
239	mutex_lock(&smpboot_threads_lock);
240	list_for_each_entry(cur, &hotplug_threads, list)
241		if (cpumask_test_cpu(cpu, cur->cpumask))
242			smpboot_unpark_thread(cur, cpu);
243	mutex_unlock(&smpboot_threads_lock);
244	return 0;
245}
246
247static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
248{
249	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
250
251	if (tsk && !ht->selfparking)
252		kthread_park(tsk);
253}
254
255int smpboot_park_threads(unsigned int cpu)
256{
257	struct smp_hotplug_thread *cur;
258
259	mutex_lock(&smpboot_threads_lock);
260	list_for_each_entry_reverse(cur, &hotplug_threads, list)
261		smpboot_park_thread(cur, cpu);
262	mutex_unlock(&smpboot_threads_lock);
263	return 0;
264}
265
266static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
267{
268	unsigned int cpu;
269
270	/* We need to destroy also the parked threads of offline cpus */
271	for_each_possible_cpu(cpu) {
272		struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
273
274		if (tsk) {
275			kthread_stop(tsk);
276			put_task_struct(tsk);
277			*per_cpu_ptr(ht->store, cpu) = NULL;
278		}
279	}
280}
281
282/**
283 * smpboot_register_percpu_thread_cpumask - Register a per_cpu thread related
284 * 					    to hotplug
285 * @plug_thread:	Hotplug thread descriptor
286 * @cpumask:		The cpumask where threads run
287 *
288 * Creates and starts the threads on all online cpus.
289 */
290int smpboot_register_percpu_thread_cpumask(struct smp_hotplug_thread *plug_thread,
291					   const struct cpumask *cpumask)
292{
293	unsigned int cpu;
294	int ret = 0;
295
296	if (!alloc_cpumask_var(&plug_thread->cpumask, GFP_KERNEL))
297		return -ENOMEM;
298	cpumask_copy(plug_thread->cpumask, cpumask);
299
300	get_online_cpus();
301	mutex_lock(&smpboot_threads_lock);
302	for_each_online_cpu(cpu) {
303		ret = __smpboot_create_thread(plug_thread, cpu);
304		if (ret) {
305			smpboot_destroy_threads(plug_thread);
306			free_cpumask_var(plug_thread->cpumask);
307			goto out;
308		}
309		if (cpumask_test_cpu(cpu, cpumask))
310			smpboot_unpark_thread(plug_thread, cpu);
311	}
312	list_add(&plug_thread->list, &hotplug_threads);
313out:
314	mutex_unlock(&smpboot_threads_lock);
315	put_online_cpus();
316	return ret;
317}
318EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread_cpumask);
319
320/**
321 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
322 * @plug_thread:	Hotplug thread descriptor
323 *
324 * Stops all threads on all possible cpus.
325 */
326void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
327{
328	get_online_cpus();
329	mutex_lock(&smpboot_threads_lock);
330	list_del(&plug_thread->list);
331	smpboot_destroy_threads(plug_thread);
332	mutex_unlock(&smpboot_threads_lock);
333	put_online_cpus();
334	free_cpumask_var(plug_thread->cpumask);
335}
336EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
337
338/**
339 * smpboot_update_cpumask_percpu_thread - Adjust which per_cpu hotplug threads stay parked
340 * @plug_thread:	Hotplug thread descriptor
341 * @new:		Revised mask to use
342 *
343 * The cpumask field in the smp_hotplug_thread must not be updated directly
344 * by the client, but only by calling this function.
345 * This function can only be called on a registered smp_hotplug_thread.
346 */
347void smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
348					  const struct cpumask *new)
349{
350	struct cpumask *old = plug_thread->cpumask;
351	static struct cpumask tmp;
352	unsigned int cpu;
353
354	lockdep_assert_cpus_held();
355	mutex_lock(&smpboot_threads_lock);
356
357	/* Park threads that were exclusively enabled on the old mask. */
358	cpumask_andnot(&tmp, old, new);
359	for_each_cpu_and(cpu, &tmp, cpu_online_mask)
360		smpboot_park_thread(plug_thread, cpu);
361
362	/* Unpark threads that are exclusively enabled on the new mask. */
363	cpumask_andnot(&tmp, new, old);
364	for_each_cpu_and(cpu, &tmp, cpu_online_mask)
365		smpboot_unpark_thread(plug_thread, cpu);
366
367	cpumask_copy(old, new);
368
369	mutex_unlock(&smpboot_threads_lock);
370}
371
372static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
373
374/*
375 * Called to poll specified CPU's state, for example, when waiting for
376 * a CPU to come online.
377 */
378int cpu_report_state(int cpu)
379{
380	return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
381}
382
383/*
384 * If CPU has died properly, set its state to CPU_UP_PREPARE and
385 * return success.  Otherwise, return -EBUSY if the CPU died after
386 * cpu_wait_death() timed out.  And yet otherwise again, return -EAGAIN
387 * if cpu_wait_death() timed out and the CPU still hasn't gotten around
388 * to dying.  In the latter two cases, the CPU might not be set up
389 * properly, but it is up to the arch-specific code to decide.
390 * Finally, -EIO indicates an unanticipated problem.
391 *
392 * Note that it is permissible to omit this call entirely, as is
393 * done in architectures that do no CPU-hotplug error checking.
394 */
395int cpu_check_up_prepare(int cpu)
396{
397	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
398		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
399		return 0;
400	}
401
402	switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
403
404	case CPU_POST_DEAD:
405
406		/* The CPU died properly, so just start it up again. */
407		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
408		return 0;
409
410	case CPU_DEAD_FROZEN:
411
412		/*
413		 * Timeout during CPU death, so let caller know.
414		 * The outgoing CPU completed its processing, but after
415		 * cpu_wait_death() timed out and reported the error. The
416		 * caller is free to proceed, in which case the state
417		 * will be reset properly by cpu_set_state_online().
418		 * Proceeding despite this -EBUSY return makes sense
419		 * for systems where the outgoing CPUs take themselves
420		 * offline, with no post-death manipulation required from
421		 * a surviving CPU.
422		 */
423		return -EBUSY;
424
425	case CPU_BROKEN:
426
427		/*
428		 * The most likely reason we got here is that there was
429		 * a timeout during CPU death, and the outgoing CPU never
430		 * did complete its processing.  This could happen on
431		 * a virtualized system if the outgoing VCPU gets preempted
432		 * for more than five seconds, and the user attempts to
433		 * immediately online that same CPU.  Trying again later
434		 * might return -EBUSY above, hence -EAGAIN.
435		 */
436		return -EAGAIN;
437
438	default:
439
440		/* Should not happen.  Famous last words. */
441		return -EIO;
442	}
443}
444
445/*
446 * Mark the specified CPU online.
447 *
448 * Note that it is permissible to omit this call entirely, as is
449 * done in architectures that do no CPU-hotplug error checking.
450 */
451void cpu_set_state_online(int cpu)
452{
453	(void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
454}
455
456#ifdef CONFIG_HOTPLUG_CPU
457
458/*
459 * Wait for the specified CPU to exit the idle loop and die.
460 */
461bool cpu_wait_death(unsigned int cpu, int seconds)
462{
463	int jf_left = seconds * HZ;
464	int oldstate;
465	bool ret = true;
466	int sleep_jf = 1;
467
468	might_sleep();
469
470	/* The outgoing CPU will normally get done quite quickly. */
471	if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
472		goto update_state;
473	udelay(5);
474
475	/* But if the outgoing CPU dawdles, wait increasingly long times. */
476	while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
477		schedule_timeout_uninterruptible(sleep_jf);
478		jf_left -= sleep_jf;
479		if (jf_left <= 0)
480			break;
481		sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
482	}
483update_state:
484	oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
485	if (oldstate == CPU_DEAD) {
486		/* Outgoing CPU died normally, update state. */
487		smp_mb(); /* atomic_read() before update. */
488		atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
489	} else {
490		/* Outgoing CPU still hasn't died, set state accordingly. */
491		if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
492				   oldstate, CPU_BROKEN) != oldstate)
493			goto update_state;
494		ret = false;
495	}
496	return ret;
497}
498
499/*
500 * Called by the outgoing CPU to report its successful death.  Return
501 * false if this report follows the surviving CPU's timing out.
502 *
503 * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
504 * timed out.  This approach allows architectures to omit calls to
505 * cpu_check_up_prepare() and cpu_set_state_online() without defeating
506 * the next cpu_wait_death()'s polling loop.
507 */
508bool cpu_report_death(void)
509{
510	int oldstate;
511	int newstate;
512	int cpu = smp_processor_id();
513
514	do {
515		oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
516		if (oldstate != CPU_BROKEN)
517			newstate = CPU_DEAD;
518		else
519			newstate = CPU_DEAD_FROZEN;
520	} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
521				oldstate, newstate) != oldstate);
522	return newstate == CPU_DEAD;
523}
524
525#endif /* #ifdef CONFIG_HOTPLUG_CPU */
v6.13.7
  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Common SMP CPU bringup/teardown functions
  4 */
  5#include <linux/cpu.h>
  6#include <linux/err.h>
  7#include <linux/smp.h>
  8#include <linux/delay.h>
  9#include <linux/init.h>
 10#include <linux/list.h>
 11#include <linux/slab.h>
 12#include <linux/sched.h>
 13#include <linux/sched/task.h>
 14#include <linux/export.h>
 15#include <linux/percpu.h>
 16#include <linux/kthread.h>
 17#include <linux/smpboot.h>
 18
 19#include "smpboot.h"
 20
 21#ifdef CONFIG_SMP
 22
 23#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
 24/*
 25 * For the hotplug case we keep the task structs around and reuse
 26 * them.
 27 */
 28static DEFINE_PER_CPU(struct task_struct *, idle_threads);
 29
 30struct task_struct *idle_thread_get(unsigned int cpu)
 31{
 32	struct task_struct *tsk = per_cpu(idle_threads, cpu);
 33
 34	if (!tsk)
 35		return ERR_PTR(-ENOMEM);
 
 36	return tsk;
 37}
 38
 39void __init idle_thread_set_boot_cpu(void)
 40{
 41	per_cpu(idle_threads, smp_processor_id()) = current;
 42}
 43
 44/**
 45 * idle_init - Initialize the idle thread for a cpu
 46 * @cpu:	The cpu for which the idle thread should be initialized
 47 *
 48 * Creates the thread if it does not exist.
 49 */
 50static __always_inline void idle_init(unsigned int cpu)
 51{
 52	struct task_struct *tsk = per_cpu(idle_threads, cpu);
 53
 54	if (!tsk) {
 55		tsk = fork_idle(cpu);
 56		if (IS_ERR(tsk))
 57			pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
 58		else
 59			per_cpu(idle_threads, cpu) = tsk;
 60	}
 61}
 62
 63/**
 64 * idle_threads_init - Initialize idle threads for all cpus
 65 */
 66void __init idle_threads_init(void)
 67{
 68	unsigned int cpu, boot_cpu;
 69
 70	boot_cpu = smp_processor_id();
 71
 72	for_each_possible_cpu(cpu) {
 73		if (cpu != boot_cpu)
 74			idle_init(cpu);
 75	}
 76}
 77#endif
 78
 79#endif /* #ifdef CONFIG_SMP */
 80
 81static LIST_HEAD(hotplug_threads);
 82static DEFINE_MUTEX(smpboot_threads_lock);
 83
 84struct smpboot_thread_data {
 85	unsigned int			cpu;
 86	unsigned int			status;
 87	struct smp_hotplug_thread	*ht;
 88};
 89
 90enum {
 91	HP_THREAD_NONE = 0,
 92	HP_THREAD_ACTIVE,
 93	HP_THREAD_PARKED,
 94};
 95
 96/**
 97 * smpboot_thread_fn - percpu hotplug thread loop function
 98 * @data:	thread data pointer
 99 *
100 * Checks for thread stop and park conditions. Calls the necessary
101 * setup, cleanup, park and unpark functions for the registered
102 * thread.
103 *
104 * Returns 1 when the thread should exit, 0 otherwise.
105 */
106static int smpboot_thread_fn(void *data)
107{
108	struct smpboot_thread_data *td = data;
109	struct smp_hotplug_thread *ht = td->ht;
110
111	while (1) {
112		set_current_state(TASK_INTERRUPTIBLE);
113		preempt_disable();
114		if (kthread_should_stop()) {
115			__set_current_state(TASK_RUNNING);
116			preempt_enable();
117			/* cleanup must mirror setup */
118			if (ht->cleanup && td->status != HP_THREAD_NONE)
119				ht->cleanup(td->cpu, cpu_online(td->cpu));
120			kfree(td);
121			return 0;
122		}
123
124		if (kthread_should_park()) {
125			__set_current_state(TASK_RUNNING);
126			preempt_enable();
127			if (ht->park && td->status == HP_THREAD_ACTIVE) {
128				BUG_ON(td->cpu != smp_processor_id());
129				ht->park(td->cpu);
130				td->status = HP_THREAD_PARKED;
131			}
132			kthread_parkme();
133			/* We might have been woken for stop */
134			continue;
135		}
136
137		BUG_ON(td->cpu != smp_processor_id());
138
139		/* Check for state change setup */
140		switch (td->status) {
141		case HP_THREAD_NONE:
142			__set_current_state(TASK_RUNNING);
143			preempt_enable();
144			if (ht->setup)
145				ht->setup(td->cpu);
146			td->status = HP_THREAD_ACTIVE;
147			continue;
148
149		case HP_THREAD_PARKED:
150			__set_current_state(TASK_RUNNING);
151			preempt_enable();
152			if (ht->unpark)
153				ht->unpark(td->cpu);
154			td->status = HP_THREAD_ACTIVE;
155			continue;
156		}
157
158		if (!ht->thread_should_run(td->cpu)) {
159			preempt_enable_no_resched();
160			schedule();
161		} else {
162			__set_current_state(TASK_RUNNING);
163			preempt_enable();
164			ht->thread_fn(td->cpu);
165		}
166	}
167}
168
169static int
170__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
171{
172	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
173	struct smpboot_thread_data *td;
174
175	if (tsk)
176		return 0;
177
178	td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
179	if (!td)
180		return -ENOMEM;
181	td->cpu = cpu;
182	td->ht = ht;
183
184	tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
185				    ht->thread_comm);
186	if (IS_ERR(tsk)) {
187		kfree(td);
188		return PTR_ERR(tsk);
189	}
190	kthread_set_per_cpu(tsk, cpu);
191	/*
192	 * Park the thread so that it could start right on the CPU
193	 * when it is available.
194	 */
195	kthread_park(tsk);
196	get_task_struct(tsk);
197	*per_cpu_ptr(ht->store, cpu) = tsk;
198	if (ht->create) {
199		/*
200		 * Make sure that the task has actually scheduled out
201		 * into park position, before calling the create
202		 * callback. At least the migration thread callback
203		 * requires that the task is off the runqueue.
204		 */
205		if (!wait_task_inactive(tsk, TASK_PARKED))
206			WARN_ON(1);
207		else
208			ht->create(cpu);
209	}
210	return 0;
211}
212
213int smpboot_create_threads(unsigned int cpu)
214{
215	struct smp_hotplug_thread *cur;
216	int ret = 0;
217
218	mutex_lock(&smpboot_threads_lock);
219	list_for_each_entry(cur, &hotplug_threads, list) {
220		ret = __smpboot_create_thread(cur, cpu);
221		if (ret)
222			break;
223	}
224	mutex_unlock(&smpboot_threads_lock);
225	return ret;
226}
227
228static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
229{
230	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
231
232	if (!ht->selfparking)
233		kthread_unpark(tsk);
234}
235
236int smpboot_unpark_threads(unsigned int cpu)
237{
238	struct smp_hotplug_thread *cur;
239
240	mutex_lock(&smpboot_threads_lock);
241	list_for_each_entry(cur, &hotplug_threads, list)
242		smpboot_unpark_thread(cur, cpu);
 
243	mutex_unlock(&smpboot_threads_lock);
244	return 0;
245}
246
247static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
248{
249	struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
250
251	if (tsk && !ht->selfparking)
252		kthread_park(tsk);
253}
254
255int smpboot_park_threads(unsigned int cpu)
256{
257	struct smp_hotplug_thread *cur;
258
259	mutex_lock(&smpboot_threads_lock);
260	list_for_each_entry_reverse(cur, &hotplug_threads, list)
261		smpboot_park_thread(cur, cpu);
262	mutex_unlock(&smpboot_threads_lock);
263	return 0;
264}
265
266static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
267{
268	unsigned int cpu;
269
270	/* We need to destroy also the parked threads of offline cpus */
271	for_each_possible_cpu(cpu) {
272		struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
273
274		if (tsk) {
275			kthread_stop_put(tsk);
 
276			*per_cpu_ptr(ht->store, cpu) = NULL;
277		}
278	}
279}
280
281/**
282 * smpboot_register_percpu_thread - Register a per_cpu thread related
283 * 					    to hotplug
284 * @plug_thread:	Hotplug thread descriptor
 
285 *
286 * Creates and starts the threads on all online cpus.
287 */
288int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
 
289{
290	unsigned int cpu;
291	int ret = 0;
292
293	cpus_read_lock();
 
 
 
 
294	mutex_lock(&smpboot_threads_lock);
295	for_each_online_cpu(cpu) {
296		ret = __smpboot_create_thread(plug_thread, cpu);
297		if (ret) {
298			smpboot_destroy_threads(plug_thread);
 
299			goto out;
300		}
301		smpboot_unpark_thread(plug_thread, cpu);
 
302	}
303	list_add(&plug_thread->list, &hotplug_threads);
304out:
305	mutex_unlock(&smpboot_threads_lock);
306	cpus_read_unlock();
307	return ret;
308}
309EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
310
311/**
312 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
313 * @plug_thread:	Hotplug thread descriptor
314 *
315 * Stops all threads on all possible cpus.
316 */
317void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
318{
319	cpus_read_lock();
320	mutex_lock(&smpboot_threads_lock);
321	list_del(&plug_thread->list);
322	smpboot_destroy_threads(plug_thread);
323	mutex_unlock(&smpboot_threads_lock);
324	cpus_read_unlock();
 
325}
326EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);