1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel thread helper functions.
3 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
5 * Creation is done via kthreadd, so that we get a clean environment
6 * even if we're invoked from userspace (think modprobe, hotplug cpu,
9 #include <uapi/linux/sched/types.h>
10 #include <linux/sched.h>
11 #include <linux/sched/task.h>
12 #include <linux/kthread.h>
13 #include <linux/completion.h>
14 #include <linux/err.h>
15 #include <linux/cgroup.h>
16 #include <linux/cpuset.h>
17 #include <linux/unistd.h>
18 #include <linux/file.h>
19 #include <linux/export.h>
20 #include <linux/mutex.h>
21 #include <linux/slab.h>
22 #include <linux/freezer.h>
23 #include <linux/ptrace.h>
24 #include <linux/uaccess.h>
25 #include <linux/numa.h>
26 #include <trace/events/sched.h>
28 static DEFINE_SPINLOCK(kthread_create_lock
);
29 static LIST_HEAD(kthread_create_list
);
30 struct task_struct
*kthreadd_task
;
32 struct kthread_create_info
34 /* Information passed to kthread() from kthreadd. */
35 int (*threadfn
)(void *data
);
39 /* Result passed back to kthread_create() from kthreadd. */
40 struct task_struct
*result
;
41 struct completion
*done
;
43 struct list_head list
;
50 struct completion parked
;
51 struct completion exited
;
52 #ifdef CONFIG_BLK_CGROUP
53 struct cgroup_subsys_state
*blkcg_css
;
58 KTHREAD_IS_PER_CPU
= 0,
63 static inline void set_kthread_struct(void *kthread
)
66 * We abuse ->set_child_tid to avoid the new member and because it
67 * can't be wrongly copied by copy_process(). We also rely on fact
68 * that the caller can't exec, so PF_KTHREAD can't be cleared.
70 current
->set_child_tid
= (__force
void __user
*)kthread
;
73 static inline struct kthread
*to_kthread(struct task_struct
*k
)
75 WARN_ON(!(k
->flags
& PF_KTHREAD
));
76 return (__force
void *)k
->set_child_tid
;
79 void free_kthread_struct(struct task_struct
*k
)
81 struct kthread
*kthread
;
84 * Can be NULL if this kthread was created by kernel_thread()
85 * or if kmalloc() in kthread() failed.
87 kthread
= to_kthread(k
);
88 #ifdef CONFIG_BLK_CGROUP
89 WARN_ON_ONCE(kthread
&& kthread
->blkcg_css
);
95 * kthread_should_stop - should this kthread return now?
97 * When someone calls kthread_stop() on your kthread, it will be woken
98 * and this will return true. You should then return, and your return
99 * value will be passed through to kthread_stop().
101 bool kthread_should_stop(void)
103 return test_bit(KTHREAD_SHOULD_STOP
, &to_kthread(current
)->flags
);
105 EXPORT_SYMBOL(kthread_should_stop
);
107 bool __kthread_should_park(struct task_struct
*k
)
109 return test_bit(KTHREAD_SHOULD_PARK
, &to_kthread(k
)->flags
);
111 EXPORT_SYMBOL_GPL(__kthread_should_park
);
114 * kthread_should_park - should this kthread park now?
116 * When someone calls kthread_park() on your kthread, it will be woken
117 * and this will return true. You should then do the necessary
118 * cleanup and call kthread_parkme()
120 * Similar to kthread_should_stop(), but this keeps the thread alive
121 * and in a park position. kthread_unpark() "restarts" the thread and
122 * calls the thread function again.
124 bool kthread_should_park(void)
126 return __kthread_should_park(current
);
128 EXPORT_SYMBOL_GPL(kthread_should_park
);
131 * kthread_freezable_should_stop - should this freezable kthread return now?
132 * @was_frozen: optional out parameter, indicates whether %current was frozen
134 * kthread_should_stop() for freezable kthreads, which will enter
135 * refrigerator if necessary. This function is safe from kthread_stop() /
136 * freezer deadlock and freezable kthreads should use this function instead
137 * of calling try_to_freeze() directly.
139 bool kthread_freezable_should_stop(bool *was_frozen
)
145 if (unlikely(freezing(current
)))
146 frozen
= __refrigerator(true);
149 *was_frozen
= frozen
;
151 return kthread_should_stop();
153 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop
);
156 * kthread_data - return data value specified on kthread creation
157 * @task: kthread task in question
159 * Return the data value specified when kthread @task was created.
160 * The caller is responsible for ensuring the validity of @task when
161 * calling this function.
163 void *kthread_data(struct task_struct
*task
)
165 return to_kthread(task
)->data
;
169 * kthread_probe_data - speculative version of kthread_data()
170 * @task: possible kthread task in question
172 * @task could be a kthread task. Return the data value specified when it
173 * was created if accessible. If @task isn't a kthread task or its data is
174 * inaccessible for any reason, %NULL is returned. This function requires
175 * that @task itself is safe to dereference.
177 void *kthread_probe_data(struct task_struct
*task
)
179 struct kthread
*kthread
= to_kthread(task
);
182 probe_kernel_read(&data
, &kthread
->data
, sizeof(data
));
186 static void __kthread_parkme(struct kthread
*self
)
190 * TASK_PARKED is a special state; we must serialize against
191 * possible pending wakeups to avoid store-store collisions on
194 * Such a collision might possibly result in the task state
195 * changin from TASK_PARKED and us failing the
196 * wait_task_inactive() in kthread_park().
198 set_special_state(TASK_PARKED
);
199 if (!test_bit(KTHREAD_SHOULD_PARK
, &self
->flags
))
203 * Thread is going to call schedule(), do not preempt it,
204 * or the caller of kthread_park() may spend more time in
205 * wait_task_inactive().
208 complete(&self
->parked
);
209 schedule_preempt_disabled();
212 __set_current_state(TASK_RUNNING
);
215 void kthread_parkme(void)
217 __kthread_parkme(to_kthread(current
));
219 EXPORT_SYMBOL_GPL(kthread_parkme
);
221 static int kthread(void *_create
)
223 /* Copy data: it's on kthread's stack */
224 struct kthread_create_info
*create
= _create
;
225 int (*threadfn
)(void *data
) = create
->threadfn
;
226 void *data
= create
->data
;
227 struct completion
*done
;
228 struct kthread
*self
;
231 self
= kzalloc(sizeof(*self
), GFP_KERNEL
);
232 set_kthread_struct(self
);
234 /* If user was SIGKILLed, I release the structure. */
235 done
= xchg(&create
->done
, NULL
);
242 create
->result
= ERR_PTR(-ENOMEM
);
248 init_completion(&self
->exited
);
249 init_completion(&self
->parked
);
250 current
->vfork_done
= &self
->exited
;
252 /* OK, tell user we're spawned, wait for stop or wakeup */
253 __set_current_state(TASK_UNINTERRUPTIBLE
);
254 create
->result
= current
;
256 * Thread is going to call schedule(), do not preempt it,
257 * or the creator may spend more time in wait_task_inactive().
261 schedule_preempt_disabled();
265 if (!test_bit(KTHREAD_SHOULD_STOP
, &self
->flags
)) {
266 cgroup_kthread_ready();
267 __kthread_parkme(self
);
268 ret
= threadfn(data
);
273 /* called from do_fork() to get node information for about to be created task */
274 int tsk_fork_get_node(struct task_struct
*tsk
)
277 if (tsk
== kthreadd_task
)
278 return tsk
->pref_node_fork
;
283 static void create_kthread(struct kthread_create_info
*create
)
288 current
->pref_node_fork
= create
->node
;
290 /* We want our own signal handler (we take no signals by default). */
291 pid
= kernel_thread(kthread
, create
, CLONE_FS
| CLONE_FILES
| SIGCHLD
);
293 /* If user was SIGKILLed, I release the structure. */
294 struct completion
*done
= xchg(&create
->done
, NULL
);
300 create
->result
= ERR_PTR(pid
);
305 static __printf(4, 0)
306 struct task_struct
*__kthread_create_on_node(int (*threadfn
)(void *data
),
307 void *data
, int node
,
308 const char namefmt
[],
311 DECLARE_COMPLETION_ONSTACK(done
);
312 struct task_struct
*task
;
313 struct kthread_create_info
*create
= kmalloc(sizeof(*create
),
317 return ERR_PTR(-ENOMEM
);
318 create
->threadfn
= threadfn
;
321 create
->done
= &done
;
323 spin_lock(&kthread_create_lock
);
324 list_add_tail(&create
->list
, &kthread_create_list
);
325 spin_unlock(&kthread_create_lock
);
327 wake_up_process(kthreadd_task
);
329 * Wait for completion in killable state, for I might be chosen by
330 * the OOM killer while kthreadd is trying to allocate memory for
333 if (unlikely(wait_for_completion_killable(&done
))) {
337 * I got SIGKILL, but wait for 10 more seconds for completion
338 * unless chosen by the OOM killer. This delay is there as a
339 * workaround for boot failure caused by SIGKILL upon device
340 * driver initialization timeout.
342 while (i
++ < 10 && !test_tsk_thread_flag(current
, TIF_MEMDIE
))
343 if (wait_for_completion_timeout(&done
, HZ
))
346 * If I was SIGKILLed before kthreadd (or new kernel thread)
347 * calls complete(), leave the cleanup of this structure to
350 if (xchg(&create
->done
, NULL
))
351 return ERR_PTR(-EINTR
);
353 * kthreadd (or new kernel thread) will call complete()
356 wait_for_completion(&done
);
359 task
= create
->result
;
361 static const struct sched_param param
= { .sched_priority
= 0 };
362 char name
[TASK_COMM_LEN
];
365 * task is already visible to other tasks, so updating
366 * COMM must be protected.
368 vsnprintf(name
, sizeof(name
), namefmt
, args
);
369 set_task_comm(task
, name
);
371 * root may have changed our (kthreadd's) priority or CPU mask.
372 * The kernel thread should not inherit these properties.
374 sched_setscheduler_nocheck(task
, SCHED_NORMAL
, ¶m
);
375 set_cpus_allowed_ptr(task
, cpu_all_mask
);
382 * kthread_create_on_node - create a kthread.
383 * @threadfn: the function to run until signal_pending(current).
384 * @data: data ptr for @threadfn.
385 * @node: task and thread structures for the thread are allocated on this node
386 * @namefmt: printf-style name for the thread.
388 * Description: This helper function creates and names a kernel
389 * thread. The thread will be stopped: use wake_up_process() to start
390 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
391 * is affine to all CPUs.
393 * If thread is going to be bound on a particular cpu, give its node
394 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
395 * When woken, the thread will run @threadfn() with @data as its
396 * argument. @threadfn() can either call do_exit() directly if it is a
397 * standalone thread for which no one will call kthread_stop(), or
398 * return when 'kthread_should_stop()' is true (which means
399 * kthread_stop() has been called). The return value should be zero
400 * or a negative error number; it will be passed to kthread_stop().
402 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
404 struct task_struct
*kthread_create_on_node(int (*threadfn
)(void *data
),
405 void *data
, int node
,
406 const char namefmt
[],
409 struct task_struct
*task
;
412 va_start(args
, namefmt
);
413 task
= __kthread_create_on_node(threadfn
, data
, node
, namefmt
, args
);
418 EXPORT_SYMBOL(kthread_create_on_node
);
420 static void __kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
, long state
)
424 if (!wait_task_inactive(p
, state
)) {
429 /* It's safe because the task is inactive. */
430 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
431 do_set_cpus_allowed(p
, mask
);
432 p
->flags
|= PF_NO_SETAFFINITY
;
433 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
436 static void __kthread_bind(struct task_struct
*p
, unsigned int cpu
, long state
)
438 __kthread_bind_mask(p
, cpumask_of(cpu
), state
);
441 void kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
)
443 __kthread_bind_mask(p
, mask
, TASK_UNINTERRUPTIBLE
);
447 * kthread_bind - bind a just-created kthread to a cpu.
448 * @p: thread created by kthread_create().
449 * @cpu: cpu (might not be online, must be possible) for @k to run on.
451 * Description: This function is equivalent to set_cpus_allowed(),
452 * except that @cpu doesn't need to be online, and the thread must be
453 * stopped (i.e., just returned from kthread_create()).
455 void kthread_bind(struct task_struct
*p
, unsigned int cpu
)
457 __kthread_bind(p
, cpu
, TASK_UNINTERRUPTIBLE
);
459 EXPORT_SYMBOL(kthread_bind
);
462 * kthread_create_on_cpu - Create a cpu bound kthread
463 * @threadfn: the function to run until signal_pending(current).
464 * @data: data ptr for @threadfn.
465 * @cpu: The cpu on which the thread should be bound,
466 * @namefmt: printf-style name for the thread. Format is restricted
467 * to "name.*%u". Code fills in cpu number.
469 * Description: This helper function creates and names a kernel thread
470 * The thread will be woken and put into park mode.
472 struct task_struct
*kthread_create_on_cpu(int (*threadfn
)(void *data
),
473 void *data
, unsigned int cpu
,
476 struct task_struct
*p
;
478 p
= kthread_create_on_node(threadfn
, data
, cpu_to_node(cpu
), namefmt
,
482 kthread_bind(p
, cpu
);
483 /* CPU hotplug need to bind once again when unparking the thread. */
484 to_kthread(p
)->cpu
= cpu
;
488 void kthread_set_per_cpu(struct task_struct
*k
, int cpu
)
490 struct kthread
*kthread
= to_kthread(k
);
494 WARN_ON_ONCE(!(k
->flags
& PF_NO_SETAFFINITY
));
497 clear_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
502 set_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
505 bool kthread_is_per_cpu(struct task_struct
*k
)
507 struct kthread
*kthread
= to_kthread(k
);
511 return test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
515 * kthread_unpark - unpark a thread created by kthread_create().
516 * @k: thread created by kthread_create().
518 * Sets kthread_should_park() for @k to return false, wakes it, and
519 * waits for it to return. If the thread is marked percpu then its
520 * bound to the cpu again.
522 void kthread_unpark(struct task_struct
*k
)
524 struct kthread
*kthread
= to_kthread(k
);
527 * Newly created kthread was parked when the CPU was offline.
528 * The binding was lost and we need to set it again.
530 if (test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
))
531 __kthread_bind(k
, kthread
->cpu
, TASK_PARKED
);
533 clear_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
535 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
537 wake_up_state(k
, TASK_PARKED
);
539 EXPORT_SYMBOL_GPL(kthread_unpark
);
542 * kthread_park - park a thread created by kthread_create().
543 * @k: thread created by kthread_create().
545 * Sets kthread_should_park() for @k to return true, wakes it, and
546 * waits for it to return. This can also be called after kthread_create()
547 * instead of calling wake_up_process(): the thread will park without
548 * calling threadfn().
550 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
551 * If called by the kthread itself just the park bit is set.
553 int kthread_park(struct task_struct
*k
)
555 struct kthread
*kthread
= to_kthread(k
);
557 if (WARN_ON(k
->flags
& PF_EXITING
))
560 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
)))
563 set_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
567 * Wait for __kthread_parkme() to complete(), this means we
568 * _will_ have TASK_PARKED and are about to call schedule().
570 wait_for_completion(&kthread
->parked
);
572 * Now wait for that schedule() to complete and the task to
575 WARN_ON_ONCE(!wait_task_inactive(k
, TASK_PARKED
));
580 EXPORT_SYMBOL_GPL(kthread_park
);
583 * kthread_stop - stop a thread created by kthread_create().
584 * @k: thread created by kthread_create().
586 * Sets kthread_should_stop() for @k to return true, wakes it, and
587 * waits for it to exit. This can also be called after kthread_create()
588 * instead of calling wake_up_process(): the thread will exit without
589 * calling threadfn().
591 * If threadfn() may call do_exit() itself, the caller must ensure
592 * task_struct can't go away.
594 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
597 int kthread_stop(struct task_struct
*k
)
599 struct kthread
*kthread
;
602 trace_sched_kthread_stop(k
);
605 kthread
= to_kthread(k
);
606 set_bit(KTHREAD_SHOULD_STOP
, &kthread
->flags
);
609 wait_for_completion(&kthread
->exited
);
613 trace_sched_kthread_stop_ret(ret
);
616 EXPORT_SYMBOL(kthread_stop
);
618 int kthreadd(void *unused
)
620 struct task_struct
*tsk
= current
;
622 /* Setup a clean context for our children to inherit. */
623 set_task_comm(tsk
, "kthreadd");
625 set_cpus_allowed_ptr(tsk
, cpu_all_mask
);
626 set_mems_allowed(node_states
[N_MEMORY
]);
628 current
->flags
|= PF_NOFREEZE
;
629 cgroup_init_kthreadd();
632 set_current_state(TASK_INTERRUPTIBLE
);
633 if (list_empty(&kthread_create_list
))
635 __set_current_state(TASK_RUNNING
);
637 spin_lock(&kthread_create_lock
);
638 while (!list_empty(&kthread_create_list
)) {
639 struct kthread_create_info
*create
;
641 create
= list_entry(kthread_create_list
.next
,
642 struct kthread_create_info
, list
);
643 list_del_init(&create
->list
);
644 spin_unlock(&kthread_create_lock
);
646 create_kthread(create
);
648 spin_lock(&kthread_create_lock
);
650 spin_unlock(&kthread_create_lock
);
656 void __kthread_init_worker(struct kthread_worker
*worker
,
658 struct lock_class_key
*key
)
660 memset(worker
, 0, sizeof(struct kthread_worker
));
661 raw_spin_lock_init(&worker
->lock
);
662 lockdep_set_class_and_name(&worker
->lock
, key
, name
);
663 INIT_LIST_HEAD(&worker
->work_list
);
664 INIT_LIST_HEAD(&worker
->delayed_work_list
);
666 EXPORT_SYMBOL_GPL(__kthread_init_worker
);
669 * kthread_worker_fn - kthread function to process kthread_worker
670 * @worker_ptr: pointer to initialized kthread_worker
672 * This function implements the main cycle of kthread worker. It processes
673 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
676 * The works are not allowed to keep any locks, disable preemption or interrupts
677 * when they finish. There is defined a safe point for freezing when one work
678 * finishes and before a new one is started.
680 * Also the works must not be handled by more than one worker at the same time,
681 * see also kthread_queue_work().
683 int kthread_worker_fn(void *worker_ptr
)
685 struct kthread_worker
*worker
= worker_ptr
;
686 struct kthread_work
*work
;
689 * FIXME: Update the check and remove the assignment when all kthread
690 * worker users are created using kthread_create_worker*() functions.
692 WARN_ON(worker
->task
&& worker
->task
!= current
);
693 worker
->task
= current
;
695 if (worker
->flags
& KTW_FREEZABLE
)
699 set_current_state(TASK_INTERRUPTIBLE
); /* mb paired w/ kthread_stop */
701 if (kthread_should_stop()) {
702 __set_current_state(TASK_RUNNING
);
703 raw_spin_lock_irq(&worker
->lock
);
705 raw_spin_unlock_irq(&worker
->lock
);
710 raw_spin_lock_irq(&worker
->lock
);
711 if (!list_empty(&worker
->work_list
)) {
712 work
= list_first_entry(&worker
->work_list
,
713 struct kthread_work
, node
);
714 list_del_init(&work
->node
);
716 worker
->current_work
= work
;
717 raw_spin_unlock_irq(&worker
->lock
);
720 __set_current_state(TASK_RUNNING
);
722 } else if (!freezing(current
))
729 EXPORT_SYMBOL_GPL(kthread_worker_fn
);
731 static __printf(3, 0) struct kthread_worker
*
732 __kthread_create_worker(int cpu
, unsigned int flags
,
733 const char namefmt
[], va_list args
)
735 struct kthread_worker
*worker
;
736 struct task_struct
*task
;
737 int node
= NUMA_NO_NODE
;
739 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
741 return ERR_PTR(-ENOMEM
);
743 kthread_init_worker(worker
);
746 node
= cpu_to_node(cpu
);
748 task
= __kthread_create_on_node(kthread_worker_fn
, worker
,
749 node
, namefmt
, args
);
754 kthread_bind(task
, cpu
);
756 worker
->flags
= flags
;
758 wake_up_process(task
);
763 return ERR_CAST(task
);
767 * kthread_create_worker - create a kthread worker
768 * @flags: flags modifying the default behavior of the worker
769 * @namefmt: printf-style name for the kthread worker (task).
771 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
772 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
773 * when the worker was SIGKILLed.
775 struct kthread_worker
*
776 kthread_create_worker(unsigned int flags
, const char namefmt
[], ...)
778 struct kthread_worker
*worker
;
781 va_start(args
, namefmt
);
782 worker
= __kthread_create_worker(-1, flags
, namefmt
, args
);
787 EXPORT_SYMBOL(kthread_create_worker
);
790 * kthread_create_worker_on_cpu - create a kthread worker and bind it
791 * it to a given CPU and the associated NUMA node.
793 * @flags: flags modifying the default behavior of the worker
794 * @namefmt: printf-style name for the kthread worker (task).
796 * Use a valid CPU number if you want to bind the kthread worker
797 * to the given CPU and the associated NUMA node.
799 * A good practice is to add the cpu number also into the worker name.
800 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
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_on_cpu(int cpu
, unsigned int flags
,
808 const char namefmt
[], ...)
810 struct kthread_worker
*worker
;
813 va_start(args
, namefmt
);
814 worker
= __kthread_create_worker(cpu
, flags
, namefmt
, args
);
819 EXPORT_SYMBOL(kthread_create_worker_on_cpu
);
822 * Returns true when the work could not be queued at the moment.
823 * It happens when it is already pending in a worker list
824 * or when it is being cancelled.
826 static inline bool queuing_blocked(struct kthread_worker
*worker
,
827 struct kthread_work
*work
)
829 lockdep_assert_held(&worker
->lock
);
831 return !list_empty(&work
->node
) || work
->canceling
;
834 static void kthread_insert_work_sanity_check(struct kthread_worker
*worker
,
835 struct kthread_work
*work
)
837 lockdep_assert_held(&worker
->lock
);
838 WARN_ON_ONCE(!list_empty(&work
->node
));
839 /* Do not use a work with >1 worker, see kthread_queue_work() */
840 WARN_ON_ONCE(work
->worker
&& work
->worker
!= worker
);
843 /* insert @work before @pos in @worker */
844 static void kthread_insert_work(struct kthread_worker
*worker
,
845 struct kthread_work
*work
,
846 struct list_head
*pos
)
848 kthread_insert_work_sanity_check(worker
, work
);
850 list_add_tail(&work
->node
, pos
);
851 work
->worker
= worker
;
852 if (!worker
->current_work
&& likely(worker
->task
))
853 wake_up_process(worker
->task
);
857 * kthread_queue_work - queue a kthread_work
858 * @worker: target kthread_worker
859 * @work: kthread_work to queue
861 * Queue @work to work processor @task for async execution. @task
862 * must have been created with kthread_worker_create(). Returns %true
863 * if @work was successfully queued, %false if it was already pending.
865 * Reinitialize the work if it needs to be used by another worker.
866 * For example, when the worker was stopped and started again.
868 bool kthread_queue_work(struct kthread_worker
*worker
,
869 struct kthread_work
*work
)
874 raw_spin_lock_irqsave(&worker
->lock
, flags
);
875 if (!queuing_blocked(worker
, work
)) {
876 kthread_insert_work(worker
, work
, &worker
->work_list
);
879 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
882 EXPORT_SYMBOL_GPL(kthread_queue_work
);
885 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
886 * delayed work when the timer expires.
887 * @t: pointer to the expired timer
889 * The format of the function is defined by struct timer_list.
890 * It should have been called from irqsafe timer with irq already off.
892 void kthread_delayed_work_timer_fn(struct timer_list
*t
)
894 struct kthread_delayed_work
*dwork
= from_timer(dwork
, t
, timer
);
895 struct kthread_work
*work
= &dwork
->work
;
896 struct kthread_worker
*worker
= work
->worker
;
900 * This might happen when a pending work is reinitialized.
901 * It means that it is used a wrong way.
903 if (WARN_ON_ONCE(!worker
))
906 raw_spin_lock_irqsave(&worker
->lock
, flags
);
907 /* Work must not be used with >1 worker, see kthread_queue_work(). */
908 WARN_ON_ONCE(work
->worker
!= worker
);
910 /* Move the work from worker->delayed_work_list. */
911 WARN_ON_ONCE(list_empty(&work
->node
));
912 list_del_init(&work
->node
);
913 if (!work
->canceling
)
914 kthread_insert_work(worker
, work
, &worker
->work_list
);
916 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
918 EXPORT_SYMBOL(kthread_delayed_work_timer_fn
);
920 static void __kthread_queue_delayed_work(struct kthread_worker
*worker
,
921 struct kthread_delayed_work
*dwork
,
924 struct timer_list
*timer
= &dwork
->timer
;
925 struct kthread_work
*work
= &dwork
->work
;
927 WARN_ON_ONCE(timer
->function
!= kthread_delayed_work_timer_fn
);
930 * If @delay is 0, queue @dwork->work immediately. This is for
931 * both optimization and correctness. The earliest @timer can
932 * expire is on the closest next tick and delayed_work users depend
933 * on that there's no such delay when @delay is 0.
936 kthread_insert_work(worker
, work
, &worker
->work_list
);
940 /* Be paranoid and try to detect possible races already now. */
941 kthread_insert_work_sanity_check(worker
, work
);
943 list_add(&work
->node
, &worker
->delayed_work_list
);
944 work
->worker
= worker
;
945 timer
->expires
= jiffies
+ delay
;
950 * kthread_queue_delayed_work - queue the associated kthread work
952 * @worker: target kthread_worker
953 * @dwork: kthread_delayed_work to queue
954 * @delay: number of jiffies to wait before queuing
956 * If the work has not been pending it starts a timer that will queue
957 * the work after the given @delay. If @delay is zero, it queues the
960 * Return: %false if the @work has already been pending. It means that
961 * either the timer was running or the work was queued. It returns %true
964 bool kthread_queue_delayed_work(struct kthread_worker
*worker
,
965 struct kthread_delayed_work
*dwork
,
968 struct kthread_work
*work
= &dwork
->work
;
972 raw_spin_lock_irqsave(&worker
->lock
, flags
);
974 if (!queuing_blocked(worker
, work
)) {
975 __kthread_queue_delayed_work(worker
, dwork
, delay
);
979 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
982 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work
);
984 struct kthread_flush_work
{
985 struct kthread_work work
;
986 struct completion done
;
989 static void kthread_flush_work_fn(struct kthread_work
*work
)
991 struct kthread_flush_work
*fwork
=
992 container_of(work
, struct kthread_flush_work
, work
);
993 complete(&fwork
->done
);
997 * kthread_flush_work - flush a kthread_work
998 * @work: work to flush
1000 * If @work is queued or executing, wait for it to finish execution.
1002 void kthread_flush_work(struct kthread_work
*work
)
1004 struct kthread_flush_work fwork
= {
1005 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1006 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1008 struct kthread_worker
*worker
;
1011 worker
= work
->worker
;
1015 raw_spin_lock_irq(&worker
->lock
);
1016 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1017 WARN_ON_ONCE(work
->worker
!= worker
);
1019 if (!list_empty(&work
->node
))
1020 kthread_insert_work(worker
, &fwork
.work
, work
->node
.next
);
1021 else if (worker
->current_work
== work
)
1022 kthread_insert_work(worker
, &fwork
.work
,
1023 worker
->work_list
.next
);
1027 raw_spin_unlock_irq(&worker
->lock
);
1030 wait_for_completion(&fwork
.done
);
1032 EXPORT_SYMBOL_GPL(kthread_flush_work
);
1035 * This function removes the work from the worker queue. Also it makes sure
1036 * that it won't get queued later via the delayed work's timer.
1038 * The work might still be in use when this function finishes. See the
1039 * current_work proceed by the worker.
1041 * Return: %true if @work was pending and successfully canceled,
1042 * %false if @work was not pending
1044 static bool __kthread_cancel_work(struct kthread_work
*work
, bool is_dwork
,
1045 unsigned long *flags
)
1047 /* Try to cancel the timer if exists. */
1049 struct kthread_delayed_work
*dwork
=
1050 container_of(work
, struct kthread_delayed_work
, work
);
1051 struct kthread_worker
*worker
= work
->worker
;
1054 * del_timer_sync() must be called to make sure that the timer
1055 * callback is not running. The lock must be temporary released
1056 * to avoid a deadlock with the callback. In the meantime,
1057 * any queuing is blocked by setting the canceling counter.
1060 raw_spin_unlock_irqrestore(&worker
->lock
, *flags
);
1061 del_timer_sync(&dwork
->timer
);
1062 raw_spin_lock_irqsave(&worker
->lock
, *flags
);
1067 * Try to remove the work from a worker list. It might either
1068 * be from worker->work_list or from worker->delayed_work_list.
1070 if (!list_empty(&work
->node
)) {
1071 list_del_init(&work
->node
);
1079 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1080 * @worker: kthread worker to use
1081 * @dwork: kthread delayed work to queue
1082 * @delay: number of jiffies to wait before queuing
1084 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1085 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1086 * @work is guaranteed to be queued immediately.
1088 * Return: %true if @dwork was pending and its timer was modified,
1091 * A special case is when the work is being canceled in parallel.
1092 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1093 * or yet another kthread_mod_delayed_work() call. We let the other command
1094 * win and return %false here. The caller is supposed to synchronize these
1095 * operations a reasonable way.
1097 * This function is safe to call from any context including IRQ handler.
1098 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1101 bool kthread_mod_delayed_work(struct kthread_worker
*worker
,
1102 struct kthread_delayed_work
*dwork
,
1103 unsigned long delay
)
1105 struct kthread_work
*work
= &dwork
->work
;
1106 unsigned long flags
;
1109 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1111 /* Do not bother with canceling when never queued. */
1115 /* Work must not be used with >1 worker, see kthread_queue_work() */
1116 WARN_ON_ONCE(work
->worker
!= worker
);
1118 /* Do not fight with another command that is canceling this work. */
1119 if (work
->canceling
)
1122 ret
= __kthread_cancel_work(work
, true, &flags
);
1124 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1126 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1129 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work
);
1131 static bool __kthread_cancel_work_sync(struct kthread_work
*work
, bool is_dwork
)
1133 struct kthread_worker
*worker
= work
->worker
;
1134 unsigned long flags
;
1140 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1141 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1142 WARN_ON_ONCE(work
->worker
!= worker
);
1144 ret
= __kthread_cancel_work(work
, is_dwork
, &flags
);
1146 if (worker
->current_work
!= work
)
1150 * The work is in progress and we need to wait with the lock released.
1151 * In the meantime, block any queuing by setting the canceling counter.
1154 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1155 kthread_flush_work(work
);
1156 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1160 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1166 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1167 * @work: the kthread work to cancel
1169 * Cancel @work and wait for its execution to finish. This function
1170 * can be used even if the work re-queues itself. On return from this
1171 * function, @work is guaranteed to be not pending or executing on any CPU.
1173 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1174 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1176 * The caller must ensure that the worker on which @work was last
1177 * queued can't be destroyed before this function returns.
1179 * Return: %true if @work was pending, %false otherwise.
1181 bool kthread_cancel_work_sync(struct kthread_work
*work
)
1183 return __kthread_cancel_work_sync(work
, false);
1185 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync
);
1188 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1189 * wait for it to finish.
1190 * @dwork: the kthread delayed work to cancel
1192 * This is kthread_cancel_work_sync() for delayed works.
1194 * Return: %true if @dwork was pending, %false otherwise.
1196 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work
*dwork
)
1198 return __kthread_cancel_work_sync(&dwork
->work
, true);
1200 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync
);
1203 * kthread_flush_worker - flush all current works on a kthread_worker
1204 * @worker: worker to flush
1206 * Wait until all currently executing or pending works on @worker are
1209 void kthread_flush_worker(struct kthread_worker
*worker
)
1211 struct kthread_flush_work fwork
= {
1212 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1213 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1216 kthread_queue_work(worker
, &fwork
.work
);
1217 wait_for_completion(&fwork
.done
);
1219 EXPORT_SYMBOL_GPL(kthread_flush_worker
);
1222 * kthread_destroy_worker - destroy a kthread worker
1223 * @worker: worker to be destroyed
1225 * Flush and destroy @worker. The simple flush is enough because the kthread
1226 * worker API is used only in trivial scenarios. There are no multi-step state
1229 void kthread_destroy_worker(struct kthread_worker
*worker
)
1231 struct task_struct
*task
;
1233 task
= worker
->task
;
1237 kthread_flush_worker(worker
);
1239 WARN_ON(!list_empty(&worker
->work_list
));
1242 EXPORT_SYMBOL(kthread_destroy_worker
);
1244 #ifdef CONFIG_BLK_CGROUP
1246 * kthread_associate_blkcg - associate blkcg to current kthread
1247 * @css: the cgroup info
1249 * Current thread must be a kthread. The thread is running jobs on behalf of
1250 * other threads. In some cases, we expect the jobs attach cgroup info of
1251 * original threads instead of that of current thread. This function stores
1252 * original thread's cgroup info in current kthread context for later
1255 void kthread_associate_blkcg(struct cgroup_subsys_state
*css
)
1257 struct kthread
*kthread
;
1259 if (!(current
->flags
& PF_KTHREAD
))
1261 kthread
= to_kthread(current
);
1265 if (kthread
->blkcg_css
) {
1266 css_put(kthread
->blkcg_css
);
1267 kthread
->blkcg_css
= NULL
;
1271 kthread
->blkcg_css
= css
;
1274 EXPORT_SYMBOL(kthread_associate_blkcg
);
1277 * kthread_blkcg - get associated blkcg css of current kthread
1279 * Current thread must be a kthread.
1281 struct cgroup_subsys_state
*kthread_blkcg(void)
1283 struct kthread
*kthread
;
1285 if (current
->flags
& PF_KTHREAD
) {
1286 kthread
= to_kthread(current
);
1288 return kthread
->blkcg_css
;
1292 EXPORT_SYMBOL(kthread_blkcg
);