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 do_fork() 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
))) {
359 * If I was SIGKILLed before kthreadd (or new kernel thread)
360 * calls complete(), leave the cleanup of this structure to
363 if (xchg(&create
->done
, NULL
))
364 return ERR_PTR(-EINTR
);
366 * kthreadd (or new kernel thread) will call complete()
369 wait_for_completion(&done
);
371 task
= create
->result
;
373 static const struct sched_param param
= { .sched_priority
= 0 };
374 char name
[TASK_COMM_LEN
];
377 * task is already visible to other tasks, so updating
378 * COMM must be protected.
380 vsnprintf(name
, sizeof(name
), namefmt
, args
);
381 set_task_comm(task
, name
);
383 * root may have changed our (kthreadd's) priority or CPU mask.
384 * The kernel thread should not inherit these properties.
386 sched_setscheduler_nocheck(task
, SCHED_NORMAL
, ¶m
);
387 set_cpus_allowed_ptr(task
,
388 housekeeping_cpumask(HK_FLAG_KTHREAD
));
395 * kthread_create_on_node - create a kthread.
396 * @threadfn: the function to run until signal_pending(current).
397 * @data: data ptr for @threadfn.
398 * @node: task and thread structures for the thread are allocated on this node
399 * @namefmt: printf-style name for the thread.
401 * Description: This helper function creates and names a kernel
402 * thread. The thread will be stopped: use wake_up_process() to start
403 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
404 * is affine to all CPUs.
406 * If thread is going to be bound on a particular cpu, give its node
407 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
408 * When woken, the thread will run @threadfn() with @data as its
409 * argument. @threadfn() can either call do_exit() directly if it is a
410 * standalone thread for which no one will call kthread_stop(), or
411 * return when 'kthread_should_stop()' is true (which means
412 * kthread_stop() has been called). The return value should be zero
413 * or a negative error number; it will be passed to kthread_stop().
415 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
417 struct task_struct
*kthread_create_on_node(int (*threadfn
)(void *data
),
418 void *data
, int node
,
419 const char namefmt
[],
422 struct task_struct
*task
;
425 va_start(args
, namefmt
);
426 task
= __kthread_create_on_node(threadfn
, data
, node
, namefmt
, args
);
431 EXPORT_SYMBOL(kthread_create_on_node
);
433 static void __kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
, long state
)
437 if (!wait_task_inactive(p
, state
)) {
442 /* It's safe because the task is inactive. */
443 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
444 do_set_cpus_allowed(p
, mask
);
445 p
->flags
|= PF_NO_SETAFFINITY
;
446 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
449 static void __kthread_bind(struct task_struct
*p
, unsigned int cpu
, long state
)
451 __kthread_bind_mask(p
, cpumask_of(cpu
), state
);
454 void kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
)
456 __kthread_bind_mask(p
, mask
, TASK_UNINTERRUPTIBLE
);
460 * kthread_bind - bind a just-created kthread to a cpu.
461 * @p: thread created by kthread_create().
462 * @cpu: cpu (might not be online, must be possible) for @k to run on.
464 * Description: This function is equivalent to set_cpus_allowed(),
465 * except that @cpu doesn't need to be online, and the thread must be
466 * stopped (i.e., just returned from kthread_create()).
468 void kthread_bind(struct task_struct
*p
, unsigned int cpu
)
470 __kthread_bind(p
, cpu
, TASK_UNINTERRUPTIBLE
);
472 EXPORT_SYMBOL(kthread_bind
);
475 * kthread_create_on_cpu - Create a cpu bound kthread
476 * @threadfn: the function to run until signal_pending(current).
477 * @data: data ptr for @threadfn.
478 * @cpu: The cpu on which the thread should be bound,
479 * @namefmt: printf-style name for the thread. Format is restricted
480 * to "name.*%u". Code fills in cpu number.
482 * Description: This helper function creates and names a kernel thread
484 struct task_struct
*kthread_create_on_cpu(int (*threadfn
)(void *data
),
485 void *data
, unsigned int cpu
,
488 struct task_struct
*p
;
490 p
= kthread_create_on_node(threadfn
, data
, cpu_to_node(cpu
), namefmt
,
494 kthread_bind(p
, cpu
);
495 /* CPU hotplug need to bind once again when unparking the thread. */
496 set_bit(KTHREAD_IS_PER_CPU
, &to_kthread(p
)->flags
);
497 to_kthread(p
)->cpu
= cpu
;
502 * kthread_unpark - unpark a thread created by kthread_create().
503 * @k: thread created by kthread_create().
505 * Sets kthread_should_park() for @k to return false, wakes it, and
506 * waits for it to return. If the thread is marked percpu then its
507 * bound to the cpu again.
509 void kthread_unpark(struct task_struct
*k
)
511 struct kthread
*kthread
= to_kthread(k
);
514 * Newly created kthread was parked when the CPU was offline.
515 * The binding was lost and we need to set it again.
517 if (test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
))
518 __kthread_bind(k
, kthread
->cpu
, TASK_PARKED
);
520 clear_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
522 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
524 wake_up_state(k
, TASK_PARKED
);
526 EXPORT_SYMBOL_GPL(kthread_unpark
);
529 * kthread_park - park a thread created by kthread_create().
530 * @k: thread created by kthread_create().
532 * Sets kthread_should_park() for @k to return true, wakes it, and
533 * waits for it to return. This can also be called after kthread_create()
534 * instead of calling wake_up_process(): the thread will park without
535 * calling threadfn().
537 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
538 * If called by the kthread itself just the park bit is set.
540 int kthread_park(struct task_struct
*k
)
542 struct kthread
*kthread
= to_kthread(k
);
544 if (WARN_ON(k
->flags
& PF_EXITING
))
547 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
)))
550 set_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
554 * Wait for __kthread_parkme() to complete(), this means we
555 * _will_ have TASK_PARKED and are about to call schedule().
557 wait_for_completion(&kthread
->parked
);
559 * Now wait for that schedule() to complete and the task to
562 WARN_ON_ONCE(!wait_task_inactive(k
, TASK_PARKED
));
567 EXPORT_SYMBOL_GPL(kthread_park
);
570 * kthread_stop - stop a thread created by kthread_create().
571 * @k: thread created by kthread_create().
573 * Sets kthread_should_stop() for @k to return true, wakes it, and
574 * waits for it to exit. This can also be called after kthread_create()
575 * instead of calling wake_up_process(): the thread will exit without
576 * calling threadfn().
578 * If threadfn() may call do_exit() itself, the caller must ensure
579 * task_struct can't go away.
581 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
584 int kthread_stop(struct task_struct
*k
)
586 struct kthread
*kthread
;
589 trace_sched_kthread_stop(k
);
592 kthread
= to_kthread(k
);
593 set_bit(KTHREAD_SHOULD_STOP
, &kthread
->flags
);
596 wait_for_completion(&kthread
->exited
);
600 trace_sched_kthread_stop_ret(ret
);
603 EXPORT_SYMBOL(kthread_stop
);
605 int kthreadd(void *unused
)
607 struct task_struct
*tsk
= current
;
609 /* Setup a clean context for our children to inherit. */
610 set_task_comm(tsk
, "kthreadd");
612 set_cpus_allowed_ptr(tsk
, housekeeping_cpumask(HK_FLAG_KTHREAD
));
613 set_mems_allowed(node_states
[N_MEMORY
]);
615 current
->flags
|= PF_NOFREEZE
;
616 cgroup_init_kthreadd();
619 set_current_state(TASK_INTERRUPTIBLE
);
620 if (list_empty(&kthread_create_list
))
622 __set_current_state(TASK_RUNNING
);
624 spin_lock(&kthread_create_lock
);
625 while (!list_empty(&kthread_create_list
)) {
626 struct kthread_create_info
*create
;
628 create
= list_entry(kthread_create_list
.next
,
629 struct kthread_create_info
, list
);
630 list_del_init(&create
->list
);
631 spin_unlock(&kthread_create_lock
);
633 create_kthread(create
);
635 spin_lock(&kthread_create_lock
);
637 spin_unlock(&kthread_create_lock
);
643 void __kthread_init_worker(struct kthread_worker
*worker
,
645 struct lock_class_key
*key
)
647 memset(worker
, 0, sizeof(struct kthread_worker
));
648 raw_spin_lock_init(&worker
->lock
);
649 lockdep_set_class_and_name(&worker
->lock
, key
, name
);
650 INIT_LIST_HEAD(&worker
->work_list
);
651 INIT_LIST_HEAD(&worker
->delayed_work_list
);
653 EXPORT_SYMBOL_GPL(__kthread_init_worker
);
656 * kthread_worker_fn - kthread function to process kthread_worker
657 * @worker_ptr: pointer to initialized kthread_worker
659 * This function implements the main cycle of kthread worker. It processes
660 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
663 * The works are not allowed to keep any locks, disable preemption or interrupts
664 * when they finish. There is defined a safe point for freezing when one work
665 * finishes and before a new one is started.
667 * Also the works must not be handled by more than one worker at the same time,
668 * see also kthread_queue_work().
670 int kthread_worker_fn(void *worker_ptr
)
672 struct kthread_worker
*worker
= worker_ptr
;
673 struct kthread_work
*work
;
676 * FIXME: Update the check and remove the assignment when all kthread
677 * worker users are created using kthread_create_worker*() functions.
679 WARN_ON(worker
->task
&& worker
->task
!= current
);
680 worker
->task
= current
;
682 if (worker
->flags
& KTW_FREEZABLE
)
686 set_current_state(TASK_INTERRUPTIBLE
); /* mb paired w/ kthread_stop */
688 if (kthread_should_stop()) {
689 __set_current_state(TASK_RUNNING
);
690 raw_spin_lock_irq(&worker
->lock
);
692 raw_spin_unlock_irq(&worker
->lock
);
697 raw_spin_lock_irq(&worker
->lock
);
698 if (!list_empty(&worker
->work_list
)) {
699 work
= list_first_entry(&worker
->work_list
,
700 struct kthread_work
, node
);
701 list_del_init(&work
->node
);
703 worker
->current_work
= work
;
704 raw_spin_unlock_irq(&worker
->lock
);
707 __set_current_state(TASK_RUNNING
);
709 } else if (!freezing(current
))
716 EXPORT_SYMBOL_GPL(kthread_worker_fn
);
718 static __printf(3, 0) struct kthread_worker
*
719 __kthread_create_worker(int cpu
, unsigned int flags
,
720 const char namefmt
[], va_list args
)
722 struct kthread_worker
*worker
;
723 struct task_struct
*task
;
724 int node
= NUMA_NO_NODE
;
726 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
728 return ERR_PTR(-ENOMEM
);
730 kthread_init_worker(worker
);
733 node
= cpu_to_node(cpu
);
735 task
= __kthread_create_on_node(kthread_worker_fn
, worker
,
736 node
, namefmt
, args
);
741 kthread_bind(task
, cpu
);
743 worker
->flags
= flags
;
745 wake_up_process(task
);
750 return ERR_CAST(task
);
754 * kthread_create_worker - create a kthread worker
755 * @flags: flags modifying the default behavior of the worker
756 * @namefmt: printf-style name for the kthread worker (task).
758 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
759 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
760 * when the worker was SIGKILLed.
762 struct kthread_worker
*
763 kthread_create_worker(unsigned int flags
, const char namefmt
[], ...)
765 struct kthread_worker
*worker
;
768 va_start(args
, namefmt
);
769 worker
= __kthread_create_worker(-1, flags
, namefmt
, args
);
774 EXPORT_SYMBOL(kthread_create_worker
);
777 * kthread_create_worker_on_cpu - create a kthread worker and bind it
778 * it to a given CPU and the associated NUMA node.
780 * @flags: flags modifying the default behavior of the worker
781 * @namefmt: printf-style name for the kthread worker (task).
783 * Use a valid CPU number if you want to bind the kthread worker
784 * to the given CPU and the associated NUMA node.
786 * A good practice is to add the cpu number also into the worker name.
787 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
789 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
790 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
791 * when the worker was SIGKILLed.
793 struct kthread_worker
*
794 kthread_create_worker_on_cpu(int cpu
, unsigned int flags
,
795 const char namefmt
[], ...)
797 struct kthread_worker
*worker
;
800 va_start(args
, namefmt
);
801 worker
= __kthread_create_worker(cpu
, flags
, namefmt
, args
);
806 EXPORT_SYMBOL(kthread_create_worker_on_cpu
);
809 * Returns true when the work could not be queued at the moment.
810 * It happens when it is already pending in a worker list
811 * or when it is being cancelled.
813 static inline bool queuing_blocked(struct kthread_worker
*worker
,
814 struct kthread_work
*work
)
816 lockdep_assert_held(&worker
->lock
);
818 return !list_empty(&work
->node
) || work
->canceling
;
821 static void kthread_insert_work_sanity_check(struct kthread_worker
*worker
,
822 struct kthread_work
*work
)
824 lockdep_assert_held(&worker
->lock
);
825 WARN_ON_ONCE(!list_empty(&work
->node
));
826 /* Do not use a work with >1 worker, see kthread_queue_work() */
827 WARN_ON_ONCE(work
->worker
&& work
->worker
!= worker
);
830 /* insert @work before @pos in @worker */
831 static void kthread_insert_work(struct kthread_worker
*worker
,
832 struct kthread_work
*work
,
833 struct list_head
*pos
)
835 kthread_insert_work_sanity_check(worker
, work
);
837 list_add_tail(&work
->node
, pos
);
838 work
->worker
= worker
;
839 if (!worker
->current_work
&& likely(worker
->task
))
840 wake_up_process(worker
->task
);
844 * kthread_queue_work - queue a kthread_work
845 * @worker: target kthread_worker
846 * @work: kthread_work to queue
848 * Queue @work to work processor @task for async execution. @task
849 * must have been created with kthread_worker_create(). Returns %true
850 * if @work was successfully queued, %false if it was already pending.
852 * Reinitialize the work if it needs to be used by another worker.
853 * For example, when the worker was stopped and started again.
855 bool kthread_queue_work(struct kthread_worker
*worker
,
856 struct kthread_work
*work
)
861 raw_spin_lock_irqsave(&worker
->lock
, flags
);
862 if (!queuing_blocked(worker
, work
)) {
863 kthread_insert_work(worker
, work
, &worker
->work_list
);
866 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
869 EXPORT_SYMBOL_GPL(kthread_queue_work
);
872 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
873 * delayed work when the timer expires.
874 * @t: pointer to the expired timer
876 * The format of the function is defined by struct timer_list.
877 * It should have been called from irqsafe timer with irq already off.
879 void kthread_delayed_work_timer_fn(struct timer_list
*t
)
881 struct kthread_delayed_work
*dwork
= from_timer(dwork
, t
, timer
);
882 struct kthread_work
*work
= &dwork
->work
;
883 struct kthread_worker
*worker
= work
->worker
;
887 * This might happen when a pending work is reinitialized.
888 * It means that it is used a wrong way.
890 if (WARN_ON_ONCE(!worker
))
893 raw_spin_lock_irqsave(&worker
->lock
, flags
);
894 /* Work must not be used with >1 worker, see kthread_queue_work(). */
895 WARN_ON_ONCE(work
->worker
!= worker
);
897 /* Move the work from worker->delayed_work_list. */
898 WARN_ON_ONCE(list_empty(&work
->node
));
899 list_del_init(&work
->node
);
900 kthread_insert_work(worker
, work
, &worker
->work_list
);
902 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
904 EXPORT_SYMBOL(kthread_delayed_work_timer_fn
);
906 static void __kthread_queue_delayed_work(struct kthread_worker
*worker
,
907 struct kthread_delayed_work
*dwork
,
910 struct timer_list
*timer
= &dwork
->timer
;
911 struct kthread_work
*work
= &dwork
->work
;
913 WARN_ON_ONCE(timer
->function
!= kthread_delayed_work_timer_fn
);
916 * If @delay is 0, queue @dwork->work immediately. This is for
917 * both optimization and correctness. The earliest @timer can
918 * expire is on the closest next tick and delayed_work users depend
919 * on that there's no such delay when @delay is 0.
922 kthread_insert_work(worker
, work
, &worker
->work_list
);
926 /* Be paranoid and try to detect possible races already now. */
927 kthread_insert_work_sanity_check(worker
, work
);
929 list_add(&work
->node
, &worker
->delayed_work_list
);
930 work
->worker
= worker
;
931 timer
->expires
= jiffies
+ delay
;
936 * kthread_queue_delayed_work - queue the associated kthread work
938 * @worker: target kthread_worker
939 * @dwork: kthread_delayed_work to queue
940 * @delay: number of jiffies to wait before queuing
942 * If the work has not been pending it starts a timer that will queue
943 * the work after the given @delay. If @delay is zero, it queues the
946 * Return: %false if the @work has already been pending. It means that
947 * either the timer was running or the work was queued. It returns %true
950 bool kthread_queue_delayed_work(struct kthread_worker
*worker
,
951 struct kthread_delayed_work
*dwork
,
954 struct kthread_work
*work
= &dwork
->work
;
958 raw_spin_lock_irqsave(&worker
->lock
, flags
);
960 if (!queuing_blocked(worker
, work
)) {
961 __kthread_queue_delayed_work(worker
, dwork
, delay
);
965 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
968 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work
);
970 struct kthread_flush_work
{
971 struct kthread_work work
;
972 struct completion done
;
975 static void kthread_flush_work_fn(struct kthread_work
*work
)
977 struct kthread_flush_work
*fwork
=
978 container_of(work
, struct kthread_flush_work
, work
);
979 complete(&fwork
->done
);
983 * kthread_flush_work - flush a kthread_work
984 * @work: work to flush
986 * If @work is queued or executing, wait for it to finish execution.
988 void kthread_flush_work(struct kthread_work
*work
)
990 struct kthread_flush_work fwork
= {
991 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
992 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
994 struct kthread_worker
*worker
;
997 worker
= work
->worker
;
1001 raw_spin_lock_irq(&worker
->lock
);
1002 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1003 WARN_ON_ONCE(work
->worker
!= worker
);
1005 if (!list_empty(&work
->node
))
1006 kthread_insert_work(worker
, &fwork
.work
, work
->node
.next
);
1007 else if (worker
->current_work
== work
)
1008 kthread_insert_work(worker
, &fwork
.work
,
1009 worker
->work_list
.next
);
1013 raw_spin_unlock_irq(&worker
->lock
);
1016 wait_for_completion(&fwork
.done
);
1018 EXPORT_SYMBOL_GPL(kthread_flush_work
);
1021 * This function removes the work from the worker queue. Also it makes sure
1022 * that it won't get queued later via the delayed work's timer.
1024 * The work might still be in use when this function finishes. See the
1025 * current_work proceed by the worker.
1027 * Return: %true if @work was pending and successfully canceled,
1028 * %false if @work was not pending
1030 static bool __kthread_cancel_work(struct kthread_work
*work
, bool is_dwork
,
1031 unsigned long *flags
)
1033 /* Try to cancel the timer if exists. */
1035 struct kthread_delayed_work
*dwork
=
1036 container_of(work
, struct kthread_delayed_work
, work
);
1037 struct kthread_worker
*worker
= work
->worker
;
1040 * del_timer_sync() must be called to make sure that the timer
1041 * callback is not running. The lock must be temporary released
1042 * to avoid a deadlock with the callback. In the meantime,
1043 * any queuing is blocked by setting the canceling counter.
1046 raw_spin_unlock_irqrestore(&worker
->lock
, *flags
);
1047 del_timer_sync(&dwork
->timer
);
1048 raw_spin_lock_irqsave(&worker
->lock
, *flags
);
1053 * Try to remove the work from a worker list. It might either
1054 * be from worker->work_list or from worker->delayed_work_list.
1056 if (!list_empty(&work
->node
)) {
1057 list_del_init(&work
->node
);
1065 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1066 * @worker: kthread worker to use
1067 * @dwork: kthread delayed work to queue
1068 * @delay: number of jiffies to wait before queuing
1070 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1071 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1072 * @work is guaranteed to be queued immediately.
1074 * Return: %true if @dwork was pending and its timer was modified,
1077 * A special case is when the work is being canceled in parallel.
1078 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1079 * or yet another kthread_mod_delayed_work() call. We let the other command
1080 * win and return %false here. The caller is supposed to synchronize these
1081 * operations a reasonable way.
1083 * This function is safe to call from any context including IRQ handler.
1084 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1087 bool kthread_mod_delayed_work(struct kthread_worker
*worker
,
1088 struct kthread_delayed_work
*dwork
,
1089 unsigned long delay
)
1091 struct kthread_work
*work
= &dwork
->work
;
1092 unsigned long flags
;
1095 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1097 /* Do not bother with canceling when never queued. */
1101 /* Work must not be used with >1 worker, see kthread_queue_work() */
1102 WARN_ON_ONCE(work
->worker
!= worker
);
1104 /* Do not fight with another command that is canceling this work. */
1105 if (work
->canceling
)
1108 ret
= __kthread_cancel_work(work
, true, &flags
);
1110 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1112 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1115 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work
);
1117 static bool __kthread_cancel_work_sync(struct kthread_work
*work
, bool is_dwork
)
1119 struct kthread_worker
*worker
= work
->worker
;
1120 unsigned long flags
;
1126 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1127 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1128 WARN_ON_ONCE(work
->worker
!= worker
);
1130 ret
= __kthread_cancel_work(work
, is_dwork
, &flags
);
1132 if (worker
->current_work
!= work
)
1136 * The work is in progress and we need to wait with the lock released.
1137 * In the meantime, block any queuing by setting the canceling counter.
1140 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1141 kthread_flush_work(work
);
1142 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1146 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1152 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1153 * @work: the kthread work to cancel
1155 * Cancel @work and wait for its execution to finish. This function
1156 * can be used even if the work re-queues itself. On return from this
1157 * function, @work is guaranteed to be not pending or executing on any CPU.
1159 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1160 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1162 * The caller must ensure that the worker on which @work was last
1163 * queued can't be destroyed before this function returns.
1165 * Return: %true if @work was pending, %false otherwise.
1167 bool kthread_cancel_work_sync(struct kthread_work
*work
)
1169 return __kthread_cancel_work_sync(work
, false);
1171 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync
);
1174 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1175 * wait for it to finish.
1176 * @dwork: the kthread delayed work to cancel
1178 * This is kthread_cancel_work_sync() for delayed works.
1180 * Return: %true if @dwork was pending, %false otherwise.
1182 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work
*dwork
)
1184 return __kthread_cancel_work_sync(&dwork
->work
, true);
1186 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync
);
1189 * kthread_flush_worker - flush all current works on a kthread_worker
1190 * @worker: worker to flush
1192 * Wait until all currently executing or pending works on @worker are
1195 void kthread_flush_worker(struct kthread_worker
*worker
)
1197 struct kthread_flush_work fwork
= {
1198 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1199 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1202 kthread_queue_work(worker
, &fwork
.work
);
1203 wait_for_completion(&fwork
.done
);
1205 EXPORT_SYMBOL_GPL(kthread_flush_worker
);
1208 * kthread_destroy_worker - destroy a kthread worker
1209 * @worker: worker to be destroyed
1211 * Flush and destroy @worker. The simple flush is enough because the kthread
1212 * worker API is used only in trivial scenarios. There are no multi-step state
1215 void kthread_destroy_worker(struct kthread_worker
*worker
)
1217 struct task_struct
*task
;
1219 task
= worker
->task
;
1223 kthread_flush_worker(worker
);
1225 WARN_ON(!list_empty(&worker
->work_list
));
1228 EXPORT_SYMBOL(kthread_destroy_worker
);
1231 * kthread_use_mm - make the calling kthread operate on an address space
1232 * @mm: address space to operate on
1234 void kthread_use_mm(struct mm_struct
*mm
)
1236 struct mm_struct
*active_mm
;
1237 struct task_struct
*tsk
= current
;
1239 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1240 WARN_ON_ONCE(tsk
->mm
);
1243 /* Hold off tlb flush IPIs while switching mm's */
1244 local_irq_disable();
1245 active_mm
= tsk
->active_mm
;
1246 if (active_mm
!= mm
) {
1248 tsk
->active_mm
= mm
;
1251 switch_mm_irqs_off(active_mm
, mm
, tsk
);
1254 #ifdef finish_arch_post_lock_switch
1255 finish_arch_post_lock_switch();
1258 if (active_mm
!= mm
)
1261 to_kthread(tsk
)->oldfs
= force_uaccess_begin();
1263 EXPORT_SYMBOL_GPL(kthread_use_mm
);
1266 * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1267 * @mm: address space to operate on
1269 void kthread_unuse_mm(struct mm_struct
*mm
)
1271 struct task_struct
*tsk
= current
;
1273 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1274 WARN_ON_ONCE(!tsk
->mm
);
1276 force_uaccess_end(to_kthread(tsk
)->oldfs
);
1280 local_irq_disable();
1282 /* active_mm is still 'mm' */
1283 enter_lazy_tlb(mm
, tsk
);
1287 EXPORT_SYMBOL_GPL(kthread_unuse_mm
);
1289 #ifdef CONFIG_BLK_CGROUP
1291 * kthread_associate_blkcg - associate blkcg to current kthread
1292 * @css: the cgroup info
1294 * Current thread must be a kthread. The thread is running jobs on behalf of
1295 * other threads. In some cases, we expect the jobs attach cgroup info of
1296 * original threads instead of that of current thread. This function stores
1297 * original thread's cgroup info in current kthread context for later
1300 void kthread_associate_blkcg(struct cgroup_subsys_state
*css
)
1302 struct kthread
*kthread
;
1304 if (!(current
->flags
& PF_KTHREAD
))
1306 kthread
= to_kthread(current
);
1310 if (kthread
->blkcg_css
) {
1311 css_put(kthread
->blkcg_css
);
1312 kthread
->blkcg_css
= NULL
;
1316 kthread
->blkcg_css
= css
;
1319 EXPORT_SYMBOL(kthread_associate_blkcg
);
1322 * kthread_blkcg - get associated blkcg css of current kthread
1324 * Current thread must be a kthread.
1326 struct cgroup_subsys_state
*kthread_blkcg(void)
1328 struct kthread
*kthread
;
1330 if (current
->flags
& PF_KTHREAD
) {
1331 kthread
= to_kthread(current
);
1333 return kthread
->blkcg_css
;
1337 EXPORT_SYMBOL(kthread_blkcg
);