1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
4 * Creation is done via kthreadd, so that we get a clean environment
5 * even if we're invoked from userspace (think modprobe, hotplug cpu,
8 #include <linux/sched.h>
9 #include <linux/kthread.h>
10 #include <linux/completion.h>
11 #include <linux/err.h>
12 #include <linux/cpuset.h>
13 #include <linux/unistd.h>
14 #include <linux/file.h>
15 #include <linux/export.h>
16 #include <linux/mutex.h>
17 #include <linux/slab.h>
18 #include <linux/freezer.h>
19 #include <linux/ptrace.h>
20 #include <linux/uaccess.h>
21 #include <trace/events/sched.h>
23 static DEFINE_SPINLOCK(kthread_create_lock
);
24 static LIST_HEAD(kthread_create_list
);
25 struct task_struct
*kthreadd_task
;
27 struct kthread_create_info
29 /* Information passed to kthread() from kthreadd. */
30 int (*threadfn
)(void *data
);
34 /* Result passed back to kthread_create() from kthreadd. */
35 struct task_struct
*result
;
36 struct completion
*done
;
38 struct list_head list
;
45 struct completion parked
;
46 struct completion exited
;
50 KTHREAD_IS_PER_CPU
= 0,
56 #define __to_kthread(vfork) \
57 container_of(vfork, struct kthread, exited)
59 static inline struct kthread
*to_kthread(struct task_struct
*k
)
61 return __to_kthread(k
->vfork_done
);
64 static struct kthread
*to_live_kthread(struct task_struct
*k
)
66 struct completion
*vfork
= ACCESS_ONCE(k
->vfork_done
);
68 return __to_kthread(vfork
);
73 * kthread_should_stop - should this kthread return now?
75 * When someone calls kthread_stop() on your kthread, it will be woken
76 * and this will return true. You should then return, and your return
77 * value will be passed through to kthread_stop().
79 bool kthread_should_stop(void)
81 return test_bit(KTHREAD_SHOULD_STOP
, &to_kthread(current
)->flags
);
83 EXPORT_SYMBOL(kthread_should_stop
);
86 * kthread_should_park - should this kthread park now?
88 * When someone calls kthread_park() on your kthread, it will be woken
89 * and this will return true. You should then do the necessary
90 * cleanup and call kthread_parkme()
92 * Similar to kthread_should_stop(), but this keeps the thread alive
93 * and in a park position. kthread_unpark() "restarts" the thread and
94 * calls the thread function again.
96 bool kthread_should_park(void)
98 return test_bit(KTHREAD_SHOULD_PARK
, &to_kthread(current
)->flags
);
100 EXPORT_SYMBOL_GPL(kthread_should_park
);
103 * kthread_freezable_should_stop - should this freezable kthread return now?
104 * @was_frozen: optional out parameter, indicates whether %current was frozen
106 * kthread_should_stop() for freezable kthreads, which will enter
107 * refrigerator if necessary. This function is safe from kthread_stop() /
108 * freezer deadlock and freezable kthreads should use this function instead
109 * of calling try_to_freeze() directly.
111 bool kthread_freezable_should_stop(bool *was_frozen
)
117 if (unlikely(freezing(current
)))
118 frozen
= __refrigerator(true);
121 *was_frozen
= frozen
;
123 return kthread_should_stop();
125 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop
);
128 * kthread_data - return data value specified on kthread creation
129 * @task: kthread task in question
131 * Return the data value specified when kthread @task was created.
132 * The caller is responsible for ensuring the validity of @task when
133 * calling this function.
135 void *kthread_data(struct task_struct
*task
)
137 return to_kthread(task
)->data
;
141 * kthread_probe_data - speculative version of kthread_data()
142 * @task: possible kthread task in question
144 * @task could be a kthread task. Return the data value specified when it
145 * was created if accessible. If @task isn't a kthread task or its data is
146 * inaccessible for any reason, %NULL is returned. This function requires
147 * that @task itself is safe to dereference.
149 void *kthread_probe_data(struct task_struct
*task
)
151 struct kthread
*kthread
= to_kthread(task
);
154 probe_kernel_read(&data
, &kthread
->data
, sizeof(data
));
158 static void __kthread_parkme(struct kthread
*self
)
160 __set_current_state(TASK_PARKED
);
161 while (test_bit(KTHREAD_SHOULD_PARK
, &self
->flags
)) {
162 if (!test_and_set_bit(KTHREAD_IS_PARKED
, &self
->flags
))
163 complete(&self
->parked
);
165 __set_current_state(TASK_PARKED
);
167 clear_bit(KTHREAD_IS_PARKED
, &self
->flags
);
168 __set_current_state(TASK_RUNNING
);
171 void kthread_parkme(void)
173 __kthread_parkme(to_kthread(current
));
175 EXPORT_SYMBOL_GPL(kthread_parkme
);
177 static int kthread(void *_create
)
179 /* Copy data: it's on kthread's stack */
180 struct kthread_create_info
*create
= _create
;
181 int (*threadfn
)(void *data
) = create
->threadfn
;
182 void *data
= create
->data
;
183 struct completion
*done
;
189 init_completion(&self
.exited
);
190 init_completion(&self
.parked
);
191 current
->vfork_done
= &self
.exited
;
193 /* If user was SIGKILLed, I release the structure. */
194 done
= xchg(&create
->done
, NULL
);
199 /* OK, tell user we're spawned, wait for stop or wakeup */
200 __set_current_state(TASK_UNINTERRUPTIBLE
);
201 create
->result
= current
;
207 if (!test_bit(KTHREAD_SHOULD_STOP
, &self
.flags
)) {
208 __kthread_parkme(&self
);
209 ret
= threadfn(data
);
211 /* we can't just return, we must preserve "self" on stack */
215 /* called from do_fork() to get node information for about to be created task */
216 int tsk_fork_get_node(struct task_struct
*tsk
)
219 if (tsk
== kthreadd_task
)
220 return tsk
->pref_node_fork
;
225 static void create_kthread(struct kthread_create_info
*create
)
230 current
->pref_node_fork
= create
->node
;
232 /* We want our own signal handler (we take no signals by default). */
233 pid
= kernel_thread(kthread
, create
, CLONE_FS
| CLONE_FILES
| SIGCHLD
);
235 /* If user was SIGKILLed, I release the structure. */
236 struct completion
*done
= xchg(&create
->done
, NULL
);
242 create
->result
= ERR_PTR(pid
);
247 static struct task_struct
*__kthread_create_on_node(int (*threadfn
)(void *data
),
248 void *data
, int node
,
249 const char namefmt
[],
252 DECLARE_COMPLETION_ONSTACK(done
);
253 struct task_struct
*task
;
254 struct kthread_create_info
*create
= kmalloc(sizeof(*create
),
258 return ERR_PTR(-ENOMEM
);
259 create
->threadfn
= threadfn
;
262 create
->done
= &done
;
264 spin_lock(&kthread_create_lock
);
265 list_add_tail(&create
->list
, &kthread_create_list
);
266 spin_unlock(&kthread_create_lock
);
268 wake_up_process(kthreadd_task
);
270 * Wait for completion in killable state, for I might be chosen by
271 * the OOM killer while kthreadd is trying to allocate memory for
274 if (unlikely(wait_for_completion_killable(&done
))) {
276 * If I was SIGKILLed before kthreadd (or new kernel thread)
277 * calls complete(), leave the cleanup of this structure to
280 if (xchg(&create
->done
, NULL
))
281 return ERR_PTR(-EINTR
);
283 * kthreadd (or new kernel thread) will call complete()
286 wait_for_completion(&done
);
288 task
= create
->result
;
290 static const struct sched_param param
= { .sched_priority
= 0 };
292 vsnprintf(task
->comm
, sizeof(task
->comm
), namefmt
, args
);
294 * root may have changed our (kthreadd's) priority or CPU mask.
295 * The kernel thread should not inherit these properties.
297 sched_setscheduler_nocheck(task
, SCHED_NORMAL
, ¶m
);
298 set_cpus_allowed_ptr(task
, cpu_all_mask
);
305 * kthread_create_on_node - create a kthread.
306 * @threadfn: the function to run until signal_pending(current).
307 * @data: data ptr for @threadfn.
308 * @node: task and thread structures for the thread are allocated on this node
309 * @namefmt: printf-style name for the thread.
311 * Description: This helper function creates and names a kernel
312 * thread. The thread will be stopped: use wake_up_process() to start
313 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
314 * is affine to all CPUs.
316 * If thread is going to be bound on a particular cpu, give its node
317 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
318 * When woken, the thread will run @threadfn() with @data as its
319 * argument. @threadfn() can either call do_exit() directly if it is a
320 * standalone thread for which no one will call kthread_stop(), or
321 * return when 'kthread_should_stop()' is true (which means
322 * kthread_stop() has been called). The return value should be zero
323 * or a negative error number; it will be passed to kthread_stop().
325 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
327 struct task_struct
*kthread_create_on_node(int (*threadfn
)(void *data
),
328 void *data
, int node
,
329 const char namefmt
[],
332 struct task_struct
*task
;
335 va_start(args
, namefmt
);
336 task
= __kthread_create_on_node(threadfn
, data
, node
, namefmt
, args
);
341 EXPORT_SYMBOL(kthread_create_on_node
);
343 static void __kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
, long state
)
347 if (!wait_task_inactive(p
, state
)) {
352 /* It's safe because the task is inactive. */
353 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
354 do_set_cpus_allowed(p
, mask
);
355 p
->flags
|= PF_NO_SETAFFINITY
;
356 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
359 static void __kthread_bind(struct task_struct
*p
, unsigned int cpu
, long state
)
361 __kthread_bind_mask(p
, cpumask_of(cpu
), state
);
364 void kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
)
366 __kthread_bind_mask(p
, mask
, TASK_UNINTERRUPTIBLE
);
370 * kthread_bind - bind a just-created kthread to a cpu.
371 * @p: thread created by kthread_create().
372 * @cpu: cpu (might not be online, must be possible) for @k to run on.
374 * Description: This function is equivalent to set_cpus_allowed(),
375 * except that @cpu doesn't need to be online, and the thread must be
376 * stopped (i.e., just returned from kthread_create()).
378 void kthread_bind(struct task_struct
*p
, unsigned int cpu
)
380 __kthread_bind(p
, cpu
, TASK_UNINTERRUPTIBLE
);
382 EXPORT_SYMBOL(kthread_bind
);
385 * kthread_create_on_cpu - Create a cpu bound kthread
386 * @threadfn: the function to run until signal_pending(current).
387 * @data: data ptr for @threadfn.
388 * @cpu: The cpu on which the thread should be bound,
389 * @namefmt: printf-style name for the thread. Format is restricted
390 * to "name.*%u". Code fills in cpu number.
392 * Description: This helper function creates and names a kernel thread
393 * The thread will be woken and put into park mode.
395 struct task_struct
*kthread_create_on_cpu(int (*threadfn
)(void *data
),
396 void *data
, unsigned int cpu
,
399 struct task_struct
*p
;
401 p
= kthread_create_on_node(threadfn
, data
, cpu_to_node(cpu
), namefmt
,
405 kthread_bind(p
, cpu
);
406 /* CPU hotplug need to bind once again when unparking the thread. */
407 set_bit(KTHREAD_IS_PER_CPU
, &to_kthread(p
)->flags
);
408 to_kthread(p
)->cpu
= cpu
;
412 static void __kthread_unpark(struct task_struct
*k
, struct kthread
*kthread
)
414 clear_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
416 * We clear the IS_PARKED bit here as we don't wait
417 * until the task has left the park code. So if we'd
418 * park before that happens we'd see the IS_PARKED bit
419 * which might be about to be cleared.
421 if (test_and_clear_bit(KTHREAD_IS_PARKED
, &kthread
->flags
)) {
423 * Newly created kthread was parked when the CPU was offline.
424 * The binding was lost and we need to set it again.
426 if (test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
))
427 __kthread_bind(k
, kthread
->cpu
, TASK_PARKED
);
428 wake_up_state(k
, TASK_PARKED
);
433 * kthread_unpark - unpark a thread created by kthread_create().
434 * @k: thread created by kthread_create().
436 * Sets kthread_should_park() for @k to return false, wakes it, and
437 * waits for it to return. If the thread is marked percpu then its
438 * bound to the cpu again.
440 void kthread_unpark(struct task_struct
*k
)
442 struct kthread
*kthread
= to_live_kthread(k
);
445 __kthread_unpark(k
, kthread
);
447 EXPORT_SYMBOL_GPL(kthread_unpark
);
450 * kthread_park - park a thread created by kthread_create().
451 * @k: thread created by kthread_create().
453 * Sets kthread_should_park() for @k to return true, wakes it, and
454 * waits for it to return. This can also be called after kthread_create()
455 * instead of calling wake_up_process(): the thread will park without
456 * calling threadfn().
458 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
459 * If called by the kthread itself just the park bit is set.
461 int kthread_park(struct task_struct
*k
)
463 struct kthread
*kthread
= to_live_kthread(k
);
467 if (!test_bit(KTHREAD_IS_PARKED
, &kthread
->flags
)) {
468 set_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
471 wait_for_completion(&kthread
->parked
);
478 EXPORT_SYMBOL_GPL(kthread_park
);
481 * kthread_stop - stop a thread created by kthread_create().
482 * @k: thread created by kthread_create().
484 * Sets kthread_should_stop() for @k to return true, wakes it, and
485 * waits for it to exit. This can also be called after kthread_create()
486 * instead of calling wake_up_process(): the thread will exit without
487 * calling threadfn().
489 * If threadfn() may call do_exit() itself, the caller must ensure
490 * task_struct can't go away.
492 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
495 int kthread_stop(struct task_struct
*k
)
497 struct kthread
*kthread
;
500 trace_sched_kthread_stop(k
);
503 kthread
= to_live_kthread(k
);
505 set_bit(KTHREAD_SHOULD_STOP
, &kthread
->flags
);
506 __kthread_unpark(k
, kthread
);
508 wait_for_completion(&kthread
->exited
);
513 trace_sched_kthread_stop_ret(ret
);
516 EXPORT_SYMBOL(kthread_stop
);
518 int kthreadd(void *unused
)
520 struct task_struct
*tsk
= current
;
522 /* Setup a clean context for our children to inherit. */
523 set_task_comm(tsk
, "kthreadd");
525 set_cpus_allowed_ptr(tsk
, cpu_all_mask
);
526 set_mems_allowed(node_states
[N_MEMORY
]);
528 current
->flags
|= PF_NOFREEZE
;
531 set_current_state(TASK_INTERRUPTIBLE
);
532 if (list_empty(&kthread_create_list
))
534 __set_current_state(TASK_RUNNING
);
536 spin_lock(&kthread_create_lock
);
537 while (!list_empty(&kthread_create_list
)) {
538 struct kthread_create_info
*create
;
540 create
= list_entry(kthread_create_list
.next
,
541 struct kthread_create_info
, list
);
542 list_del_init(&create
->list
);
543 spin_unlock(&kthread_create_lock
);
545 create_kthread(create
);
547 spin_lock(&kthread_create_lock
);
549 spin_unlock(&kthread_create_lock
);
555 void __kthread_init_worker(struct kthread_worker
*worker
,
557 struct lock_class_key
*key
)
559 spin_lock_init(&worker
->lock
);
560 lockdep_set_class_and_name(&worker
->lock
, key
, name
);
561 INIT_LIST_HEAD(&worker
->work_list
);
564 EXPORT_SYMBOL_GPL(__kthread_init_worker
);
567 * kthread_worker_fn - kthread function to process kthread_worker
568 * @worker_ptr: pointer to initialized kthread_worker
570 * This function implements the main cycle of kthread worker. It processes
571 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
574 * The works are not allowed to keep any locks, disable preemption or interrupts
575 * when they finish. There is defined a safe point for freezing when one work
576 * finishes and before a new one is started.
578 int kthread_worker_fn(void *worker_ptr
)
580 struct kthread_worker
*worker
= worker_ptr
;
581 struct kthread_work
*work
;
584 * FIXME: Update the check and remove the assignment when all kthread
585 * worker users are created using kthread_create_worker*() functions.
587 WARN_ON(worker
->task
&& worker
->task
!= current
);
588 worker
->task
= current
;
590 set_current_state(TASK_INTERRUPTIBLE
); /* mb paired w/ kthread_stop */
592 if (kthread_should_stop()) {
593 __set_current_state(TASK_RUNNING
);
594 spin_lock_irq(&worker
->lock
);
596 spin_unlock_irq(&worker
->lock
);
601 spin_lock_irq(&worker
->lock
);
602 if (!list_empty(&worker
->work_list
)) {
603 work
= list_first_entry(&worker
->work_list
,
604 struct kthread_work
, node
);
605 list_del_init(&work
->node
);
607 worker
->current_work
= work
;
608 spin_unlock_irq(&worker
->lock
);
611 __set_current_state(TASK_RUNNING
);
613 } else if (!freezing(current
))
619 EXPORT_SYMBOL_GPL(kthread_worker_fn
);
621 static struct kthread_worker
*
622 __kthread_create_worker(int cpu
, const char namefmt
[], va_list args
)
624 struct kthread_worker
*worker
;
625 struct task_struct
*task
;
627 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
629 return ERR_PTR(-ENOMEM
);
631 kthread_init_worker(worker
);
634 char name
[TASK_COMM_LEN
];
637 * kthread_create_worker_on_cpu() allows to pass a generic
638 * namefmt in compare with kthread_create_on_cpu. We need
641 vsnprintf(name
, sizeof(name
), namefmt
, args
);
642 task
= kthread_create_on_cpu(kthread_worker_fn
, worker
,
645 task
= __kthread_create_on_node(kthread_worker_fn
, worker
,
653 wake_up_process(task
);
658 return ERR_CAST(task
);
662 * kthread_create_worker - create a kthread worker
663 * @namefmt: printf-style name for the kthread worker (task).
665 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
666 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
667 * when the worker was SIGKILLed.
669 struct kthread_worker
*
670 kthread_create_worker(const char namefmt
[], ...)
672 struct kthread_worker
*worker
;
675 va_start(args
, namefmt
);
676 worker
= __kthread_create_worker(-1, namefmt
, args
);
681 EXPORT_SYMBOL(kthread_create_worker
);
684 * kthread_create_worker_on_cpu - create a kthread worker and bind it
685 * it to a given CPU and the associated NUMA node.
687 * @namefmt: printf-style name for the kthread worker (task).
689 * Use a valid CPU number if you want to bind the kthread worker
690 * to the given CPU and the associated NUMA node.
692 * A good practice is to add the cpu number also into the worker name.
693 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
695 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
696 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
697 * when the worker was SIGKILLed.
699 struct kthread_worker
*
700 kthread_create_worker_on_cpu(int cpu
, const char namefmt
[], ...)
702 struct kthread_worker
*worker
;
705 va_start(args
, namefmt
);
706 worker
= __kthread_create_worker(cpu
, namefmt
, args
);
711 EXPORT_SYMBOL(kthread_create_worker_on_cpu
);
713 /* insert @work before @pos in @worker */
714 static void kthread_insert_work(struct kthread_worker
*worker
,
715 struct kthread_work
*work
,
716 struct list_head
*pos
)
718 lockdep_assert_held(&worker
->lock
);
720 list_add_tail(&work
->node
, pos
);
721 work
->worker
= worker
;
722 if (!worker
->current_work
&& likely(worker
->task
))
723 wake_up_process(worker
->task
);
727 * kthread_queue_work - queue a kthread_work
728 * @worker: target kthread_worker
729 * @work: kthread_work to queue
731 * Queue @work to work processor @task for async execution. @task
732 * must have been created with kthread_worker_create(). Returns %true
733 * if @work was successfully queued, %false if it was already pending.
735 bool kthread_queue_work(struct kthread_worker
*worker
,
736 struct kthread_work
*work
)
741 spin_lock_irqsave(&worker
->lock
, flags
);
742 if (list_empty(&work
->node
)) {
743 kthread_insert_work(worker
, work
, &worker
->work_list
);
746 spin_unlock_irqrestore(&worker
->lock
, flags
);
749 EXPORT_SYMBOL_GPL(kthread_queue_work
);
751 struct kthread_flush_work
{
752 struct kthread_work work
;
753 struct completion done
;
756 static void kthread_flush_work_fn(struct kthread_work
*work
)
758 struct kthread_flush_work
*fwork
=
759 container_of(work
, struct kthread_flush_work
, work
);
760 complete(&fwork
->done
);
764 * kthread_flush_work - flush a kthread_work
765 * @work: work to flush
767 * If @work is queued or executing, wait for it to finish execution.
769 void kthread_flush_work(struct kthread_work
*work
)
771 struct kthread_flush_work fwork
= {
772 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
773 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
775 struct kthread_worker
*worker
;
779 worker
= work
->worker
;
783 spin_lock_irq(&worker
->lock
);
784 if (work
->worker
!= worker
) {
785 spin_unlock_irq(&worker
->lock
);
789 if (!list_empty(&work
->node
))
790 kthread_insert_work(worker
, &fwork
.work
, work
->node
.next
);
791 else if (worker
->current_work
== work
)
792 kthread_insert_work(worker
, &fwork
.work
,
793 worker
->work_list
.next
);
797 spin_unlock_irq(&worker
->lock
);
800 wait_for_completion(&fwork
.done
);
802 EXPORT_SYMBOL_GPL(kthread_flush_work
);
805 * kthread_flush_worker - flush all current works on a kthread_worker
806 * @worker: worker to flush
808 * Wait until all currently executing or pending works on @worker are
811 void kthread_flush_worker(struct kthread_worker
*worker
)
813 struct kthread_flush_work fwork
= {
814 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
815 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
818 kthread_queue_work(worker
, &fwork
.work
);
819 wait_for_completion(&fwork
.done
);
821 EXPORT_SYMBOL_GPL(kthread_flush_worker
);