1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel thread helper functions.
3 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
4 * Copyright (C) 2009 Red Hat, Inc.
6 * Creation is done via kthreadd, so that we get a clean environment
7 * even if we're invoked from userspace (think modprobe, hotplug cpu,
10 #include <uapi/linux/sched/types.h>
12 #include <linux/mmu_context.h>
13 #include <linux/sched.h>
14 #include <linux/sched/mm.h>
15 #include <linux/sched/task.h>
16 #include <linux/kthread.h>
17 #include <linux/completion.h>
18 #include <linux/err.h>
19 #include <linux/cgroup.h>
20 #include <linux/cpuset.h>
21 #include <linux/unistd.h>
22 #include <linux/file.h>
23 #include <linux/export.h>
24 #include <linux/mutex.h>
25 #include <linux/slab.h>
26 #include <linux/freezer.h>
27 #include <linux/ptrace.h>
28 #include <linux/uaccess.h>
29 #include <linux/numa.h>
30 #include <linux/sched/isolation.h>
31 #include <trace/events/sched.h>
34 static DEFINE_SPINLOCK(kthread_create_lock
);
35 static LIST_HEAD(kthread_create_list
);
36 struct task_struct
*kthreadd_task
;
38 struct kthread_create_info
40 /* Information passed to kthread() from kthreadd. */
41 int (*threadfn
)(void *data
);
45 /* Result passed back to kthread_create() from kthreadd. */
46 struct task_struct
*result
;
47 struct completion
*done
;
49 struct list_head list
;
55 int (*threadfn
)(void *);
58 struct completion parked
;
59 struct completion exited
;
60 #ifdef CONFIG_BLK_CGROUP
61 struct cgroup_subsys_state
*blkcg_css
;
66 KTHREAD_IS_PER_CPU
= 0,
71 static inline void set_kthread_struct(void *kthread
)
74 * We abuse ->set_child_tid to avoid the new member and because it
75 * can't be wrongly copied by copy_process(). We also rely on fact
76 * that the caller can't exec, so PF_KTHREAD can't be cleared.
78 current
->set_child_tid
= (__force
void __user
*)kthread
;
81 static inline struct kthread
*to_kthread(struct task_struct
*k
)
83 WARN_ON(!(k
->flags
& PF_KTHREAD
));
84 return (__force
void *)k
->set_child_tid
;
87 void free_kthread_struct(struct task_struct
*k
)
89 struct kthread
*kthread
;
92 * Can be NULL if this kthread was created by kernel_thread()
93 * or if kmalloc() in kthread() failed.
95 kthread
= to_kthread(k
);
96 #ifdef CONFIG_BLK_CGROUP
97 WARN_ON_ONCE(kthread
&& kthread
->blkcg_css
);
103 * kthread_should_stop - should this kthread return now?
105 * When someone calls kthread_stop() on your kthread, it will be woken
106 * and this will return true. You should then return, and your return
107 * value will be passed through to kthread_stop().
109 bool kthread_should_stop(void)
111 return test_bit(KTHREAD_SHOULD_STOP
, &to_kthread(current
)->flags
);
113 EXPORT_SYMBOL(kthread_should_stop
);
115 bool __kthread_should_park(struct task_struct
*k
)
117 return test_bit(KTHREAD_SHOULD_PARK
, &to_kthread(k
)->flags
);
119 EXPORT_SYMBOL_GPL(__kthread_should_park
);
122 * kthread_should_park - should this kthread park now?
124 * When someone calls kthread_park() on your kthread, it will be woken
125 * and this will return true. You should then do the necessary
126 * cleanup and call kthread_parkme()
128 * Similar to kthread_should_stop(), but this keeps the thread alive
129 * and in a park position. kthread_unpark() "restarts" the thread and
130 * calls the thread function again.
132 bool kthread_should_park(void)
134 return __kthread_should_park(current
);
136 EXPORT_SYMBOL_GPL(kthread_should_park
);
139 * kthread_freezable_should_stop - should this freezable kthread return now?
140 * @was_frozen: optional out parameter, indicates whether %current was frozen
142 * kthread_should_stop() for freezable kthreads, which will enter
143 * refrigerator if necessary. This function is safe from kthread_stop() /
144 * freezer deadlock and freezable kthreads should use this function instead
145 * of calling try_to_freeze() directly.
147 bool kthread_freezable_should_stop(bool *was_frozen
)
153 if (unlikely(freezing(current
)))
154 frozen
= __refrigerator(true);
157 *was_frozen
= frozen
;
159 return kthread_should_stop();
161 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop
);
164 * kthread_func - return the function specified on kthread creation
165 * @task: kthread task in question
167 * Returns NULL if the task is not a kthread.
169 void *kthread_func(struct task_struct
*task
)
171 if (task
->flags
& PF_KTHREAD
)
172 return to_kthread(task
)->threadfn
;
175 EXPORT_SYMBOL_GPL(kthread_func
);
178 * kthread_data - return data value specified on kthread creation
179 * @task: kthread task in question
181 * Return the data value specified when kthread @task was created.
182 * The caller is responsible for ensuring the validity of @task when
183 * calling this function.
185 void *kthread_data(struct task_struct
*task
)
187 return to_kthread(task
)->data
;
189 EXPORT_SYMBOL_GPL(kthread_data
);
192 * kthread_probe_data - speculative version of kthread_data()
193 * @task: possible kthread task in question
195 * @task could be a kthread task. Return the data value specified when it
196 * was created if accessible. If @task isn't a kthread task or its data is
197 * inaccessible for any reason, %NULL is returned. This function requires
198 * that @task itself is safe to dereference.
200 void *kthread_probe_data(struct task_struct
*task
)
202 struct kthread
*kthread
= to_kthread(task
);
205 copy_from_kernel_nofault(&data
, &kthread
->data
, sizeof(data
));
209 static void __kthread_parkme(struct kthread
*self
)
213 * TASK_PARKED is a special state; we must serialize against
214 * possible pending wakeups to avoid store-store collisions on
217 * Such a collision might possibly result in the task state
218 * changin from TASK_PARKED and us failing the
219 * wait_task_inactive() in kthread_park().
221 set_special_state(TASK_PARKED
);
222 if (!test_bit(KTHREAD_SHOULD_PARK
, &self
->flags
))
226 * Thread is going to call schedule(), do not preempt it,
227 * or the caller of kthread_park() may spend more time in
228 * wait_task_inactive().
231 complete(&self
->parked
);
232 schedule_preempt_disabled();
235 __set_current_state(TASK_RUNNING
);
238 void kthread_parkme(void)
240 __kthread_parkme(to_kthread(current
));
242 EXPORT_SYMBOL_GPL(kthread_parkme
);
244 static int kthread(void *_create
)
246 /* Copy data: it's on kthread's stack */
247 struct kthread_create_info
*create
= _create
;
248 int (*threadfn
)(void *data
) = create
->threadfn
;
249 void *data
= create
->data
;
250 struct completion
*done
;
251 struct kthread
*self
;
254 self
= kzalloc(sizeof(*self
), GFP_KERNEL
);
255 set_kthread_struct(self
);
257 /* If user was SIGKILLed, I release the structure. */
258 done
= xchg(&create
->done
, NULL
);
265 create
->result
= ERR_PTR(-ENOMEM
);
270 self
->threadfn
= threadfn
;
272 init_completion(&self
->exited
);
273 init_completion(&self
->parked
);
274 current
->vfork_done
= &self
->exited
;
276 /* OK, tell user we're spawned, wait for stop or wakeup */
277 __set_current_state(TASK_UNINTERRUPTIBLE
);
278 create
->result
= current
;
280 * Thread is going to call schedule(), do not preempt it,
281 * or the creator may spend more time in wait_task_inactive().
285 schedule_preempt_disabled();
289 if (!test_bit(KTHREAD_SHOULD_STOP
, &self
->flags
)) {
290 cgroup_kthread_ready();
291 __kthread_parkme(self
);
292 ret
= threadfn(data
);
297 /* called from kernel_clone() to get node information for about to be created task */
298 int tsk_fork_get_node(struct task_struct
*tsk
)
301 if (tsk
== kthreadd_task
)
302 return tsk
->pref_node_fork
;
307 static void create_kthread(struct kthread_create_info
*create
)
312 current
->pref_node_fork
= create
->node
;
314 /* We want our own signal handler (we take no signals by default). */
315 pid
= kernel_thread(kthread
, create
, CLONE_FS
| CLONE_FILES
| SIGCHLD
);
317 /* If user was SIGKILLed, I release the structure. */
318 struct completion
*done
= xchg(&create
->done
, NULL
);
324 create
->result
= ERR_PTR(pid
);
329 static __printf(4, 0)
330 struct task_struct
*__kthread_create_on_node(int (*threadfn
)(void *data
),
331 void *data
, int node
,
332 const char namefmt
[],
335 DECLARE_COMPLETION_ONSTACK(done
);
336 struct task_struct
*task
;
337 struct kthread_create_info
*create
= kmalloc(sizeof(*create
),
341 return ERR_PTR(-ENOMEM
);
342 create
->threadfn
= threadfn
;
345 create
->done
= &done
;
347 spin_lock(&kthread_create_lock
);
348 list_add_tail(&create
->list
, &kthread_create_list
);
349 spin_unlock(&kthread_create_lock
);
351 wake_up_process(kthreadd_task
);
353 * Wait for completion in killable state, for I might be chosen by
354 * the OOM killer while kthreadd is trying to allocate memory for
357 if (unlikely(wait_for_completion_killable(&done
))) {
361 * I got SIGKILL, but wait for 10 more seconds for completion
362 * unless chosen by the OOM killer. This delay is there as a
363 * workaround for boot failure caused by SIGKILL upon device
364 * driver initialization timeout.
366 while (i
++ < 10 && !test_tsk_thread_flag(current
, TIF_MEMDIE
))
367 if (wait_for_completion_timeout(&done
, HZ
))
370 * If I was SIGKILLed before kthreadd (or new kernel thread)
371 * calls complete(), leave the cleanup of this structure to
374 if (xchg(&create
->done
, NULL
))
375 return ERR_PTR(-EINTR
);
377 * kthreadd (or new kernel thread) will call complete()
380 wait_for_completion(&done
);
383 task
= create
->result
;
385 static const struct sched_param param
= { .sched_priority
= 0 };
386 char name
[TASK_COMM_LEN
];
389 * task is already visible to other tasks, so updating
390 * COMM must be protected.
392 vsnprintf(name
, sizeof(name
), namefmt
, args
);
393 set_task_comm(task
, name
);
395 * root may have changed our (kthreadd's) priority or CPU mask.
396 * The kernel thread should not inherit these properties.
398 sched_setscheduler_nocheck(task
, SCHED_NORMAL
, ¶m
);
399 set_cpus_allowed_ptr(task
,
400 housekeeping_cpumask(HK_FLAG_KTHREAD
));
407 * kthread_create_on_node - create a kthread.
408 * @threadfn: the function to run until signal_pending(current).
409 * @data: data ptr for @threadfn.
410 * @node: task and thread structures for the thread are allocated on this node
411 * @namefmt: printf-style name for the thread.
413 * Description: This helper function creates and names a kernel
414 * thread. The thread will be stopped: use wake_up_process() to start
415 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
416 * is affine to all CPUs.
418 * If thread is going to be bound on a particular cpu, give its node
419 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
420 * When woken, the thread will run @threadfn() with @data as its
421 * argument. @threadfn() can either call do_exit() directly if it is a
422 * standalone thread for which no one will call kthread_stop(), or
423 * return when 'kthread_should_stop()' is true (which means
424 * kthread_stop() has been called). The return value should be zero
425 * or a negative error number; it will be passed to kthread_stop().
427 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
429 struct task_struct
*kthread_create_on_node(int (*threadfn
)(void *data
),
430 void *data
, int node
,
431 const char namefmt
[],
434 struct task_struct
*task
;
437 va_start(args
, namefmt
);
438 task
= __kthread_create_on_node(threadfn
, data
, node
, namefmt
, args
);
443 EXPORT_SYMBOL(kthread_create_on_node
);
445 static void __kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
, long state
)
449 if (!wait_task_inactive(p
, state
)) {
454 /* It's safe because the task is inactive. */
455 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
456 do_set_cpus_allowed(p
, mask
);
457 p
->flags
|= PF_NO_SETAFFINITY
;
458 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
461 static void __kthread_bind(struct task_struct
*p
, unsigned int cpu
, long state
)
463 __kthread_bind_mask(p
, cpumask_of(cpu
), state
);
466 void kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
)
468 __kthread_bind_mask(p
, mask
, TASK_UNINTERRUPTIBLE
);
472 * kthread_bind - bind a just-created kthread to a cpu.
473 * @p: thread created by kthread_create().
474 * @cpu: cpu (might not be online, must be possible) for @k to run on.
476 * Description: This function is equivalent to set_cpus_allowed(),
477 * except that @cpu doesn't need to be online, and the thread must be
478 * stopped (i.e., just returned from kthread_create()).
480 void kthread_bind(struct task_struct
*p
, unsigned int cpu
)
482 __kthread_bind(p
, cpu
, TASK_UNINTERRUPTIBLE
);
484 EXPORT_SYMBOL(kthread_bind
);
487 * kthread_create_on_cpu - Create a cpu bound kthread
488 * @threadfn: the function to run until signal_pending(current).
489 * @data: data ptr for @threadfn.
490 * @cpu: The cpu on which the thread should be bound,
491 * @namefmt: printf-style name for the thread. Format is restricted
492 * to "name.*%u". Code fills in cpu number.
494 * Description: This helper function creates and names a kernel thread
496 struct task_struct
*kthread_create_on_cpu(int (*threadfn
)(void *data
),
497 void *data
, unsigned int cpu
,
500 struct task_struct
*p
;
502 p
= kthread_create_on_node(threadfn
, data
, cpu_to_node(cpu
), namefmt
,
506 kthread_bind(p
, cpu
);
507 /* CPU hotplug need to bind once again when unparking the thread. */
508 to_kthread(p
)->cpu
= cpu
;
512 void kthread_set_per_cpu(struct task_struct
*k
, int cpu
)
514 struct kthread
*kthread
= to_kthread(k
);
518 WARN_ON_ONCE(!(k
->flags
& PF_NO_SETAFFINITY
));
521 clear_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
526 set_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
529 bool kthread_is_per_cpu(struct task_struct
*k
)
531 struct kthread
*kthread
= to_kthread(k
);
535 return test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
539 * kthread_unpark - unpark a thread created by kthread_create().
540 * @k: thread created by kthread_create().
542 * Sets kthread_should_park() for @k to return false, wakes it, and
543 * waits for it to return. If the thread is marked percpu then its
544 * bound to the cpu again.
546 void kthread_unpark(struct task_struct
*k
)
548 struct kthread
*kthread
= to_kthread(k
);
551 * Newly created kthread was parked when the CPU was offline.
552 * The binding was lost and we need to set it again.
554 if (test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
))
555 __kthread_bind(k
, kthread
->cpu
, TASK_PARKED
);
557 clear_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
559 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
561 wake_up_state(k
, TASK_PARKED
);
563 EXPORT_SYMBOL_GPL(kthread_unpark
);
566 * kthread_park - park a thread created by kthread_create().
567 * @k: thread created by kthread_create().
569 * Sets kthread_should_park() for @k to return true, wakes it, and
570 * waits for it to return. This can also be called after kthread_create()
571 * instead of calling wake_up_process(): the thread will park without
572 * calling threadfn().
574 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
575 * If called by the kthread itself just the park bit is set.
577 int kthread_park(struct task_struct
*k
)
579 struct kthread
*kthread
= to_kthread(k
);
581 if (WARN_ON(k
->flags
& PF_EXITING
))
584 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
)))
587 set_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
591 * Wait for __kthread_parkme() to complete(), this means we
592 * _will_ have TASK_PARKED and are about to call schedule().
594 wait_for_completion(&kthread
->parked
);
596 * Now wait for that schedule() to complete and the task to
599 WARN_ON_ONCE(!wait_task_inactive(k
, TASK_PARKED
));
604 EXPORT_SYMBOL_GPL(kthread_park
);
607 * kthread_stop - stop a thread created by kthread_create().
608 * @k: thread created by kthread_create().
610 * Sets kthread_should_stop() for @k to return true, wakes it, and
611 * waits for it to exit. This can also be called after kthread_create()
612 * instead of calling wake_up_process(): the thread will exit without
613 * calling threadfn().
615 * If threadfn() may call do_exit() itself, the caller must ensure
616 * task_struct can't go away.
618 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
621 int kthread_stop(struct task_struct
*k
)
623 struct kthread
*kthread
;
626 trace_sched_kthread_stop(k
);
629 kthread
= to_kthread(k
);
630 set_bit(KTHREAD_SHOULD_STOP
, &kthread
->flags
);
633 wait_for_completion(&kthread
->exited
);
637 trace_sched_kthread_stop_ret(ret
);
640 EXPORT_SYMBOL(kthread_stop
);
642 int kthreadd(void *unused
)
644 struct task_struct
*tsk
= current
;
646 /* Setup a clean context for our children to inherit. */
647 set_task_comm(tsk
, "kthreadd");
649 set_cpus_allowed_ptr(tsk
, housekeeping_cpumask(HK_FLAG_KTHREAD
));
650 set_mems_allowed(node_states
[N_MEMORY
]);
652 current
->flags
|= PF_NOFREEZE
;
653 cgroup_init_kthreadd();
656 set_current_state(TASK_INTERRUPTIBLE
);
657 if (list_empty(&kthread_create_list
))
659 __set_current_state(TASK_RUNNING
);
661 spin_lock(&kthread_create_lock
);
662 while (!list_empty(&kthread_create_list
)) {
663 struct kthread_create_info
*create
;
665 create
= list_entry(kthread_create_list
.next
,
666 struct kthread_create_info
, list
);
667 list_del_init(&create
->list
);
668 spin_unlock(&kthread_create_lock
);
670 create_kthread(create
);
672 spin_lock(&kthread_create_lock
);
674 spin_unlock(&kthread_create_lock
);
680 void __kthread_init_worker(struct kthread_worker
*worker
,
682 struct lock_class_key
*key
)
684 memset(worker
, 0, sizeof(struct kthread_worker
));
685 raw_spin_lock_init(&worker
->lock
);
686 lockdep_set_class_and_name(&worker
->lock
, key
, name
);
687 INIT_LIST_HEAD(&worker
->work_list
);
688 INIT_LIST_HEAD(&worker
->delayed_work_list
);
690 EXPORT_SYMBOL_GPL(__kthread_init_worker
);
693 * kthread_worker_fn - kthread function to process kthread_worker
694 * @worker_ptr: pointer to initialized kthread_worker
696 * This function implements the main cycle of kthread worker. It processes
697 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
700 * The works are not allowed to keep any locks, disable preemption or interrupts
701 * when they finish. There is defined a safe point for freezing when one work
702 * finishes and before a new one is started.
704 * Also the works must not be handled by more than one worker at the same time,
705 * see also kthread_queue_work().
707 int kthread_worker_fn(void *worker_ptr
)
709 struct kthread_worker
*worker
= worker_ptr
;
710 struct kthread_work
*work
;
713 * FIXME: Update the check and remove the assignment when all kthread
714 * worker users are created using kthread_create_worker*() functions.
716 WARN_ON(worker
->task
&& worker
->task
!= current
);
717 worker
->task
= current
;
719 if (worker
->flags
& KTW_FREEZABLE
)
723 set_current_state(TASK_INTERRUPTIBLE
); /* mb paired w/ kthread_stop */
725 if (kthread_should_stop()) {
726 __set_current_state(TASK_RUNNING
);
727 raw_spin_lock_irq(&worker
->lock
);
729 raw_spin_unlock_irq(&worker
->lock
);
734 raw_spin_lock_irq(&worker
->lock
);
735 if (!list_empty(&worker
->work_list
)) {
736 work
= list_first_entry(&worker
->work_list
,
737 struct kthread_work
, node
);
738 list_del_init(&work
->node
);
740 worker
->current_work
= work
;
741 raw_spin_unlock_irq(&worker
->lock
);
744 kthread_work_func_t func
= work
->func
;
745 __set_current_state(TASK_RUNNING
);
746 trace_sched_kthread_work_execute_start(work
);
749 * Avoid dereferencing work after this point. The trace
750 * event only cares about the address.
752 trace_sched_kthread_work_execute_end(work
, func
);
753 } else if (!freezing(current
))
760 EXPORT_SYMBOL_GPL(kthread_worker_fn
);
762 static __printf(3, 0) struct kthread_worker
*
763 __kthread_create_worker(int cpu
, unsigned int flags
,
764 const char namefmt
[], va_list args
)
766 struct kthread_worker
*worker
;
767 struct task_struct
*task
;
768 int node
= NUMA_NO_NODE
;
770 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
772 return ERR_PTR(-ENOMEM
);
774 kthread_init_worker(worker
);
777 node
= cpu_to_node(cpu
);
779 task
= __kthread_create_on_node(kthread_worker_fn
, worker
,
780 node
, namefmt
, args
);
785 kthread_bind(task
, cpu
);
787 worker
->flags
= flags
;
789 wake_up_process(task
);
794 return ERR_CAST(task
);
798 * kthread_create_worker - create a kthread worker
799 * @flags: flags modifying the default behavior of the worker
800 * @namefmt: printf-style name for the kthread worker (task).
802 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
803 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
804 * when the worker was SIGKILLed.
806 struct kthread_worker
*
807 kthread_create_worker(unsigned int flags
, const char namefmt
[], ...)
809 struct kthread_worker
*worker
;
812 va_start(args
, namefmt
);
813 worker
= __kthread_create_worker(-1, flags
, namefmt
, args
);
818 EXPORT_SYMBOL(kthread_create_worker
);
821 * kthread_create_worker_on_cpu - create a kthread worker and bind it
822 * to a given CPU and the associated NUMA node.
824 * @flags: flags modifying the default behavior of the worker
825 * @namefmt: printf-style name for the kthread worker (task).
827 * Use a valid CPU number if you want to bind the kthread worker
828 * to the given CPU and the associated NUMA node.
830 * A good practice is to add the cpu number also into the worker name.
831 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
834 * The kthread worker API is simple and generic. It just provides a way
835 * to create, use, and destroy workers.
837 * It is up to the API user how to handle CPU hotplug. They have to decide
838 * how to handle pending work items, prevent queuing new ones, and
839 * restore the functionality when the CPU goes off and on. There are a
842 * - CPU affinity gets lost when it is scheduled on an offline CPU.
844 * - The worker might not exist when the CPU was off when the user
845 * created the workers.
847 * Good practice is to implement two CPU hotplug callbacks and to
848 * destroy/create the worker when the CPU goes down/up.
851 * The pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
852 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
853 * when the worker was SIGKILLed.
855 struct kthread_worker
*
856 kthread_create_worker_on_cpu(int cpu
, unsigned int flags
,
857 const char namefmt
[], ...)
859 struct kthread_worker
*worker
;
862 va_start(args
, namefmt
);
863 worker
= __kthread_create_worker(cpu
, flags
, namefmt
, args
);
868 EXPORT_SYMBOL(kthread_create_worker_on_cpu
);
871 * Returns true when the work could not be queued at the moment.
872 * It happens when it is already pending in a worker list
873 * or when it is being cancelled.
875 static inline bool queuing_blocked(struct kthread_worker
*worker
,
876 struct kthread_work
*work
)
878 lockdep_assert_held(&worker
->lock
);
880 return !list_empty(&work
->node
) || work
->canceling
;
883 static void kthread_insert_work_sanity_check(struct kthread_worker
*worker
,
884 struct kthread_work
*work
)
886 lockdep_assert_held(&worker
->lock
);
887 WARN_ON_ONCE(!list_empty(&work
->node
));
888 /* Do not use a work with >1 worker, see kthread_queue_work() */
889 WARN_ON_ONCE(work
->worker
&& work
->worker
!= worker
);
892 /* insert @work before @pos in @worker */
893 static void kthread_insert_work(struct kthread_worker
*worker
,
894 struct kthread_work
*work
,
895 struct list_head
*pos
)
897 kthread_insert_work_sanity_check(worker
, work
);
899 trace_sched_kthread_work_queue_work(worker
, work
);
901 list_add_tail(&work
->node
, pos
);
902 work
->worker
= worker
;
903 if (!worker
->current_work
&& likely(worker
->task
))
904 wake_up_process(worker
->task
);
908 * kthread_queue_work - queue a kthread_work
909 * @worker: target kthread_worker
910 * @work: kthread_work to queue
912 * Queue @work to work processor @task for async execution. @task
913 * must have been created with kthread_worker_create(). Returns %true
914 * if @work was successfully queued, %false if it was already pending.
916 * Reinitialize the work if it needs to be used by another worker.
917 * For example, when the worker was stopped and started again.
919 bool kthread_queue_work(struct kthread_worker
*worker
,
920 struct kthread_work
*work
)
925 raw_spin_lock_irqsave(&worker
->lock
, flags
);
926 if (!queuing_blocked(worker
, work
)) {
927 kthread_insert_work(worker
, work
, &worker
->work_list
);
930 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
933 EXPORT_SYMBOL_GPL(kthread_queue_work
);
936 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
937 * delayed work when the timer expires.
938 * @t: pointer to the expired timer
940 * The format of the function is defined by struct timer_list.
941 * It should have been called from irqsafe timer with irq already off.
943 void kthread_delayed_work_timer_fn(struct timer_list
*t
)
945 struct kthread_delayed_work
*dwork
= from_timer(dwork
, t
, timer
);
946 struct kthread_work
*work
= &dwork
->work
;
947 struct kthread_worker
*worker
= work
->worker
;
951 * This might happen when a pending work is reinitialized.
952 * It means that it is used a wrong way.
954 if (WARN_ON_ONCE(!worker
))
957 raw_spin_lock_irqsave(&worker
->lock
, flags
);
958 /* Work must not be used with >1 worker, see kthread_queue_work(). */
959 WARN_ON_ONCE(work
->worker
!= worker
);
961 /* Move the work from worker->delayed_work_list. */
962 WARN_ON_ONCE(list_empty(&work
->node
));
963 list_del_init(&work
->node
);
964 if (!work
->canceling
)
965 kthread_insert_work(worker
, work
, &worker
->work_list
);
967 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
969 EXPORT_SYMBOL(kthread_delayed_work_timer_fn
);
971 static void __kthread_queue_delayed_work(struct kthread_worker
*worker
,
972 struct kthread_delayed_work
*dwork
,
975 struct timer_list
*timer
= &dwork
->timer
;
976 struct kthread_work
*work
= &dwork
->work
;
978 WARN_ON_ONCE(timer
->function
!= kthread_delayed_work_timer_fn
);
981 * If @delay is 0, queue @dwork->work immediately. This is for
982 * both optimization and correctness. The earliest @timer can
983 * expire is on the closest next tick and delayed_work users depend
984 * on that there's no such delay when @delay is 0.
987 kthread_insert_work(worker
, work
, &worker
->work_list
);
991 /* Be paranoid and try to detect possible races already now. */
992 kthread_insert_work_sanity_check(worker
, work
);
994 list_add(&work
->node
, &worker
->delayed_work_list
);
995 work
->worker
= worker
;
996 timer
->expires
= jiffies
+ delay
;
1001 * kthread_queue_delayed_work - queue the associated kthread work
1003 * @worker: target kthread_worker
1004 * @dwork: kthread_delayed_work to queue
1005 * @delay: number of jiffies to wait before queuing
1007 * If the work has not been pending it starts a timer that will queue
1008 * the work after the given @delay. If @delay is zero, it queues the
1011 * Return: %false if the @work has already been pending. It means that
1012 * either the timer was running or the work was queued. It returns %true
1015 bool kthread_queue_delayed_work(struct kthread_worker
*worker
,
1016 struct kthread_delayed_work
*dwork
,
1017 unsigned long delay
)
1019 struct kthread_work
*work
= &dwork
->work
;
1020 unsigned long flags
;
1023 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1025 if (!queuing_blocked(worker
, work
)) {
1026 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1030 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1033 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work
);
1035 struct kthread_flush_work
{
1036 struct kthread_work work
;
1037 struct completion done
;
1040 static void kthread_flush_work_fn(struct kthread_work
*work
)
1042 struct kthread_flush_work
*fwork
=
1043 container_of(work
, struct kthread_flush_work
, work
);
1044 complete(&fwork
->done
);
1048 * kthread_flush_work - flush a kthread_work
1049 * @work: work to flush
1051 * If @work is queued or executing, wait for it to finish execution.
1053 void kthread_flush_work(struct kthread_work
*work
)
1055 struct kthread_flush_work fwork
= {
1056 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1057 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1059 struct kthread_worker
*worker
;
1062 worker
= work
->worker
;
1066 raw_spin_lock_irq(&worker
->lock
);
1067 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1068 WARN_ON_ONCE(work
->worker
!= worker
);
1070 if (!list_empty(&work
->node
))
1071 kthread_insert_work(worker
, &fwork
.work
, work
->node
.next
);
1072 else if (worker
->current_work
== work
)
1073 kthread_insert_work(worker
, &fwork
.work
,
1074 worker
->work_list
.next
);
1078 raw_spin_unlock_irq(&worker
->lock
);
1081 wait_for_completion(&fwork
.done
);
1083 EXPORT_SYMBOL_GPL(kthread_flush_work
);
1086 * This function removes the work from the worker queue. Also it makes sure
1087 * that it won't get queued later via the delayed work's timer.
1089 * The work might still be in use when this function finishes. See the
1090 * current_work proceed by the worker.
1092 * Return: %true if @work was pending and successfully canceled,
1093 * %false if @work was not pending
1095 static bool __kthread_cancel_work(struct kthread_work
*work
, bool is_dwork
,
1096 unsigned long *flags
)
1098 /* Try to cancel the timer if exists. */
1100 struct kthread_delayed_work
*dwork
=
1101 container_of(work
, struct kthread_delayed_work
, work
);
1102 struct kthread_worker
*worker
= work
->worker
;
1105 * del_timer_sync() must be called to make sure that the timer
1106 * callback is not running. The lock must be temporary released
1107 * to avoid a deadlock with the callback. In the meantime,
1108 * any queuing is blocked by setting the canceling counter.
1111 raw_spin_unlock_irqrestore(&worker
->lock
, *flags
);
1112 del_timer_sync(&dwork
->timer
);
1113 raw_spin_lock_irqsave(&worker
->lock
, *flags
);
1118 * Try to remove the work from a worker list. It might either
1119 * be from worker->work_list or from worker->delayed_work_list.
1121 if (!list_empty(&work
->node
)) {
1122 list_del_init(&work
->node
);
1130 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1131 * @worker: kthread worker to use
1132 * @dwork: kthread delayed work to queue
1133 * @delay: number of jiffies to wait before queuing
1135 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1136 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1137 * @work is guaranteed to be queued immediately.
1139 * Return: %true if @dwork was pending and its timer was modified,
1142 * A special case is when the work is being canceled in parallel.
1143 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1144 * or yet another kthread_mod_delayed_work() call. We let the other command
1145 * win and return %false here. The caller is supposed to synchronize these
1146 * operations a reasonable way.
1148 * This function is safe to call from any context including IRQ handler.
1149 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1152 bool kthread_mod_delayed_work(struct kthread_worker
*worker
,
1153 struct kthread_delayed_work
*dwork
,
1154 unsigned long delay
)
1156 struct kthread_work
*work
= &dwork
->work
;
1157 unsigned long flags
;
1160 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1162 /* Do not bother with canceling when never queued. */
1166 /* Work must not be used with >1 worker, see kthread_queue_work() */
1167 WARN_ON_ONCE(work
->worker
!= worker
);
1169 /* Do not fight with another command that is canceling this work. */
1170 if (work
->canceling
)
1173 ret
= __kthread_cancel_work(work
, true, &flags
);
1175 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1177 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1180 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work
);
1182 static bool __kthread_cancel_work_sync(struct kthread_work
*work
, bool is_dwork
)
1184 struct kthread_worker
*worker
= work
->worker
;
1185 unsigned long flags
;
1191 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1192 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1193 WARN_ON_ONCE(work
->worker
!= worker
);
1195 ret
= __kthread_cancel_work(work
, is_dwork
, &flags
);
1197 if (worker
->current_work
!= work
)
1201 * The work is in progress and we need to wait with the lock released.
1202 * In the meantime, block any queuing by setting the canceling counter.
1205 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1206 kthread_flush_work(work
);
1207 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1211 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1217 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1218 * @work: the kthread work to cancel
1220 * Cancel @work and wait for its execution to finish. This function
1221 * can be used even if the work re-queues itself. On return from this
1222 * function, @work is guaranteed to be not pending or executing on any CPU.
1224 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1225 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1227 * The caller must ensure that the worker on which @work was last
1228 * queued can't be destroyed before this function returns.
1230 * Return: %true if @work was pending, %false otherwise.
1232 bool kthread_cancel_work_sync(struct kthread_work
*work
)
1234 return __kthread_cancel_work_sync(work
, false);
1236 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync
);
1239 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1240 * wait for it to finish.
1241 * @dwork: the kthread delayed work to cancel
1243 * This is kthread_cancel_work_sync() for delayed works.
1245 * Return: %true if @dwork was pending, %false otherwise.
1247 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work
*dwork
)
1249 return __kthread_cancel_work_sync(&dwork
->work
, true);
1251 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync
);
1254 * kthread_flush_worker - flush all current works on a kthread_worker
1255 * @worker: worker to flush
1257 * Wait until all currently executing or pending works on @worker are
1260 void kthread_flush_worker(struct kthread_worker
*worker
)
1262 struct kthread_flush_work fwork
= {
1263 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1264 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1267 kthread_queue_work(worker
, &fwork
.work
);
1268 wait_for_completion(&fwork
.done
);
1270 EXPORT_SYMBOL_GPL(kthread_flush_worker
);
1273 * kthread_destroy_worker - destroy a kthread worker
1274 * @worker: worker to be destroyed
1276 * Flush and destroy @worker. The simple flush is enough because the kthread
1277 * worker API is used only in trivial scenarios. There are no multi-step state
1280 void kthread_destroy_worker(struct kthread_worker
*worker
)
1282 struct task_struct
*task
;
1284 task
= worker
->task
;
1288 kthread_flush_worker(worker
);
1290 WARN_ON(!list_empty(&worker
->work_list
));
1293 EXPORT_SYMBOL(kthread_destroy_worker
);
1296 * kthread_use_mm - make the calling kthread operate on an address space
1297 * @mm: address space to operate on
1299 void kthread_use_mm(struct mm_struct
*mm
)
1301 struct mm_struct
*active_mm
;
1302 struct task_struct
*tsk
= current
;
1304 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1305 WARN_ON_ONCE(tsk
->mm
);
1308 /* Hold off tlb flush IPIs while switching mm's */
1309 local_irq_disable();
1310 active_mm
= tsk
->active_mm
;
1311 if (active_mm
!= mm
) {
1313 tsk
->active_mm
= mm
;
1316 membarrier_update_current_mm(mm
);
1317 switch_mm_irqs_off(active_mm
, mm
, tsk
);
1320 #ifdef finish_arch_post_lock_switch
1321 finish_arch_post_lock_switch();
1325 * When a kthread starts operating on an address space, the loop
1326 * in membarrier_{private,global}_expedited() may not observe
1327 * that tsk->mm, and not issue an IPI. Membarrier requires a
1328 * memory barrier after storing to tsk->mm, before accessing
1329 * user-space memory. A full memory barrier for membarrier
1330 * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
1331 * mmdrop(), or explicitly with smp_mb().
1333 if (active_mm
!= mm
)
1338 to_kthread(tsk
)->oldfs
= force_uaccess_begin();
1340 EXPORT_SYMBOL_GPL(kthread_use_mm
);
1343 * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1344 * @mm: address space to operate on
1346 void kthread_unuse_mm(struct mm_struct
*mm
)
1348 struct task_struct
*tsk
= current
;
1350 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1351 WARN_ON_ONCE(!tsk
->mm
);
1353 force_uaccess_end(to_kthread(tsk
)->oldfs
);
1357 * When a kthread stops operating on an address space, the loop
1358 * in membarrier_{private,global}_expedited() may not observe
1359 * that tsk->mm, and not issue an IPI. Membarrier requires a
1360 * memory barrier after accessing user-space memory, before
1363 smp_mb__after_spinlock();
1365 local_irq_disable();
1367 membarrier_update_current_mm(NULL
);
1368 /* active_mm is still 'mm' */
1369 enter_lazy_tlb(mm
, tsk
);
1373 EXPORT_SYMBOL_GPL(kthread_unuse_mm
);
1375 #ifdef CONFIG_BLK_CGROUP
1377 * kthread_associate_blkcg - associate blkcg to current kthread
1378 * @css: the cgroup info
1380 * Current thread must be a kthread. The thread is running jobs on behalf of
1381 * other threads. In some cases, we expect the jobs attach cgroup info of
1382 * original threads instead of that of current thread. This function stores
1383 * original thread's cgroup info in current kthread context for later
1386 void kthread_associate_blkcg(struct cgroup_subsys_state
*css
)
1388 struct kthread
*kthread
;
1390 if (!(current
->flags
& PF_KTHREAD
))
1392 kthread
= to_kthread(current
);
1396 if (kthread
->blkcg_css
) {
1397 css_put(kthread
->blkcg_css
);
1398 kthread
->blkcg_css
= NULL
;
1402 kthread
->blkcg_css
= css
;
1405 EXPORT_SYMBOL(kthread_associate_blkcg
);
1408 * kthread_blkcg - get associated blkcg css of current kthread
1410 * Current thread must be a kthread.
1412 struct cgroup_subsys_state
*kthread_blkcg(void)
1414 struct kthread
*kthread
;
1416 if (current
->flags
& PF_KTHREAD
) {
1417 kthread
= to_kthread(current
);
1419 return kthread
->blkcg_css
;
1423 EXPORT_SYMBOL(kthread_blkcg
);