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. */
42 int (*threadfn
)(void *data
);
46 /* Result passed back to kthread_create() from kthreadd. */
47 struct task_struct
*result
;
48 struct completion
*done
;
50 struct list_head list
;
57 int (*threadfn
)(void *);
59 struct completion parked
;
60 struct completion exited
;
61 #ifdef CONFIG_BLK_CGROUP
62 struct cgroup_subsys_state
*blkcg_css
;
64 /* To store the full name if task comm is truncated. */
69 KTHREAD_IS_PER_CPU
= 0,
74 static inline struct kthread
*to_kthread(struct task_struct
*k
)
76 WARN_ON(!(k
->flags
& PF_KTHREAD
));
77 return k
->worker_private
;
81 * Variant of to_kthread() that doesn't assume @p is a kthread.
83 * Per construction; when:
85 * (p->flags & PF_KTHREAD) && p->worker_private
87 * the task is both a kthread and struct kthread is persistent. However
88 * PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and
91 static inline struct kthread
*__to_kthread(struct task_struct
*p
)
93 void *kthread
= p
->worker_private
;
94 if (kthread
&& !(p
->flags
& PF_KTHREAD
))
99 void get_kthread_comm(char *buf
, size_t buf_size
, struct task_struct
*tsk
)
101 struct kthread
*kthread
= to_kthread(tsk
);
103 if (!kthread
|| !kthread
->full_name
) {
104 __get_task_comm(buf
, buf_size
, tsk
);
108 strscpy_pad(buf
, kthread
->full_name
, buf_size
);
111 bool set_kthread_struct(struct task_struct
*p
)
113 struct kthread
*kthread
;
115 if (WARN_ON_ONCE(to_kthread(p
)))
118 kthread
= kzalloc(sizeof(*kthread
), GFP_KERNEL
);
122 init_completion(&kthread
->exited
);
123 init_completion(&kthread
->parked
);
124 p
->vfork_done
= &kthread
->exited
;
126 p
->worker_private
= kthread
;
130 void free_kthread_struct(struct task_struct
*k
)
132 struct kthread
*kthread
;
135 * Can be NULL if kmalloc() in set_kthread_struct() failed.
137 kthread
= to_kthread(k
);
141 #ifdef CONFIG_BLK_CGROUP
142 WARN_ON_ONCE(kthread
->blkcg_css
);
144 k
->worker_private
= NULL
;
145 kfree(kthread
->full_name
);
150 * kthread_should_stop - should this kthread return now?
152 * When someone calls kthread_stop() on your kthread, it will be woken
153 * and this will return true. You should then return, and your return
154 * value will be passed through to kthread_stop().
156 bool kthread_should_stop(void)
158 return test_bit(KTHREAD_SHOULD_STOP
, &to_kthread(current
)->flags
);
160 EXPORT_SYMBOL(kthread_should_stop
);
162 static bool __kthread_should_park(struct task_struct
*k
)
164 return test_bit(KTHREAD_SHOULD_PARK
, &to_kthread(k
)->flags
);
168 * kthread_should_park - should this kthread park now?
170 * When someone calls kthread_park() on your kthread, it will be woken
171 * and this will return true. You should then do the necessary
172 * cleanup and call kthread_parkme()
174 * Similar to kthread_should_stop(), but this keeps the thread alive
175 * and in a park position. kthread_unpark() "restarts" the thread and
176 * calls the thread function again.
178 bool kthread_should_park(void)
180 return __kthread_should_park(current
);
182 EXPORT_SYMBOL_GPL(kthread_should_park
);
184 bool kthread_should_stop_or_park(void)
186 struct kthread
*kthread
= __to_kthread(current
);
191 return kthread
->flags
& (BIT(KTHREAD_SHOULD_STOP
) | BIT(KTHREAD_SHOULD_PARK
));
195 * kthread_freezable_should_stop - should this freezable kthread return now?
196 * @was_frozen: optional out parameter, indicates whether %current was frozen
198 * kthread_should_stop() for freezable kthreads, which will enter
199 * refrigerator if necessary. This function is safe from kthread_stop() /
200 * freezer deadlock and freezable kthreads should use this function instead
201 * of calling try_to_freeze() directly.
203 bool kthread_freezable_should_stop(bool *was_frozen
)
209 if (unlikely(freezing(current
)))
210 frozen
= __refrigerator(true);
213 *was_frozen
= frozen
;
215 return kthread_should_stop();
217 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop
);
220 * kthread_func - return the function specified on kthread creation
221 * @task: kthread task in question
223 * Returns NULL if the task is not a kthread.
225 void *kthread_func(struct task_struct
*task
)
227 struct kthread
*kthread
= __to_kthread(task
);
229 return kthread
->threadfn
;
232 EXPORT_SYMBOL_GPL(kthread_func
);
235 * kthread_data - return data value specified on kthread creation
236 * @task: kthread task in question
238 * Return the data value specified when kthread @task was created.
239 * The caller is responsible for ensuring the validity of @task when
240 * calling this function.
242 void *kthread_data(struct task_struct
*task
)
244 return to_kthread(task
)->data
;
246 EXPORT_SYMBOL_GPL(kthread_data
);
249 * kthread_probe_data - speculative version of kthread_data()
250 * @task: possible kthread task in question
252 * @task could be a kthread task. Return the data value specified when it
253 * was created if accessible. If @task isn't a kthread task or its data is
254 * inaccessible for any reason, %NULL is returned. This function requires
255 * that @task itself is safe to dereference.
257 void *kthread_probe_data(struct task_struct
*task
)
259 struct kthread
*kthread
= __to_kthread(task
);
263 copy_from_kernel_nofault(&data
, &kthread
->data
, sizeof(data
));
267 static void __kthread_parkme(struct kthread
*self
)
271 * TASK_PARKED is a special state; we must serialize against
272 * possible pending wakeups to avoid store-store collisions on
275 * Such a collision might possibly result in the task state
276 * changin from TASK_PARKED and us failing the
277 * wait_task_inactive() in kthread_park().
279 set_special_state(TASK_PARKED
);
280 if (!test_bit(KTHREAD_SHOULD_PARK
, &self
->flags
))
284 * Thread is going to call schedule(), do not preempt it,
285 * or the caller of kthread_park() may spend more time in
286 * wait_task_inactive().
289 complete(&self
->parked
);
290 schedule_preempt_disabled();
293 __set_current_state(TASK_RUNNING
);
296 void kthread_parkme(void)
298 __kthread_parkme(to_kthread(current
));
300 EXPORT_SYMBOL_GPL(kthread_parkme
);
303 * kthread_exit - Cause the current kthread return @result to kthread_stop().
304 * @result: The integer value to return to kthread_stop().
306 * While kthread_exit can be called directly, it exists so that
307 * functions which do some additional work in non-modular code such as
308 * module_put_and_kthread_exit can be implemented.
312 void __noreturn
kthread_exit(long result
)
314 struct kthread
*kthread
= to_kthread(current
);
315 kthread
->result
= result
;
320 * kthread_complete_and_exit - Exit the current kthread.
321 * @comp: Completion to complete
322 * @code: The integer value to return to kthread_stop().
324 * If present, complete @comp and then return code to kthread_stop().
326 * A kernel thread whose module may be removed after the completion of
327 * @comp can use this function to exit safely.
331 void __noreturn
kthread_complete_and_exit(struct completion
*comp
, long code
)
338 EXPORT_SYMBOL(kthread_complete_and_exit
);
340 static int kthread(void *_create
)
342 static const struct sched_param param
= { .sched_priority
= 0 };
343 /* Copy data: it's on kthread's stack */
344 struct kthread_create_info
*create
= _create
;
345 int (*threadfn
)(void *data
) = create
->threadfn
;
346 void *data
= create
->data
;
347 struct completion
*done
;
348 struct kthread
*self
;
351 self
= to_kthread(current
);
353 /* Release the structure when caller killed by a fatal signal. */
354 done
= xchg(&create
->done
, NULL
);
356 kfree(create
->full_name
);
358 kthread_exit(-EINTR
);
361 self
->full_name
= create
->full_name
;
362 self
->threadfn
= threadfn
;
366 * The new thread inherited kthreadd's priority and CPU mask. Reset
367 * back to default in case they have been changed.
369 sched_setscheduler_nocheck(current
, SCHED_NORMAL
, ¶m
);
370 set_cpus_allowed_ptr(current
, housekeeping_cpumask(HK_TYPE_KTHREAD
));
372 /* OK, tell user we're spawned, wait for stop or wakeup */
373 __set_current_state(TASK_UNINTERRUPTIBLE
);
374 create
->result
= current
;
376 * Thread is going to call schedule(), do not preempt it,
377 * or the creator may spend more time in wait_task_inactive().
381 schedule_preempt_disabled();
385 if (!test_bit(KTHREAD_SHOULD_STOP
, &self
->flags
)) {
386 cgroup_kthread_ready();
387 __kthread_parkme(self
);
388 ret
= threadfn(data
);
393 /* called from kernel_clone() to get node information for about to be created task */
394 int tsk_fork_get_node(struct task_struct
*tsk
)
397 if (tsk
== kthreadd_task
)
398 return tsk
->pref_node_fork
;
403 static void create_kthread(struct kthread_create_info
*create
)
408 current
->pref_node_fork
= create
->node
;
410 /* We want our own signal handler (we take no signals by default). */
411 pid
= kernel_thread(kthread
, create
, create
->full_name
,
412 CLONE_FS
| CLONE_FILES
| SIGCHLD
);
414 /* Release the structure when caller killed by a fatal signal. */
415 struct completion
*done
= xchg(&create
->done
, NULL
);
417 kfree(create
->full_name
);
422 create
->result
= ERR_PTR(pid
);
427 static __printf(4, 0)
428 struct task_struct
*__kthread_create_on_node(int (*threadfn
)(void *data
),
429 void *data
, int node
,
430 const char namefmt
[],
433 DECLARE_COMPLETION_ONSTACK(done
);
434 struct task_struct
*task
;
435 struct kthread_create_info
*create
= kmalloc(sizeof(*create
),
439 return ERR_PTR(-ENOMEM
);
440 create
->threadfn
= threadfn
;
443 create
->done
= &done
;
444 create
->full_name
= kvasprintf(GFP_KERNEL
, namefmt
, args
);
445 if (!create
->full_name
) {
446 task
= ERR_PTR(-ENOMEM
);
450 spin_lock(&kthread_create_lock
);
451 list_add_tail(&create
->list
, &kthread_create_list
);
452 spin_unlock(&kthread_create_lock
);
454 wake_up_process(kthreadd_task
);
456 * Wait for completion in killable state, for I might be chosen by
457 * the OOM killer while kthreadd is trying to allocate memory for
460 if (unlikely(wait_for_completion_killable(&done
))) {
462 * If I was killed by a fatal signal before kthreadd (or new
463 * kernel thread) calls complete(), leave the cleanup of this
464 * structure to that thread.
466 if (xchg(&create
->done
, NULL
))
467 return ERR_PTR(-EINTR
);
469 * kthreadd (or new kernel thread) will call complete()
472 wait_for_completion(&done
);
474 task
= create
->result
;
481 * kthread_create_on_node - create a kthread.
482 * @threadfn: the function to run until signal_pending(current).
483 * @data: data ptr for @threadfn.
484 * @node: task and thread structures for the thread are allocated on this node
485 * @namefmt: printf-style name for the thread.
487 * Description: This helper function creates and names a kernel
488 * thread. The thread will be stopped: use wake_up_process() to start
489 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
490 * is affine to all CPUs.
492 * If thread is going to be bound on a particular cpu, give its node
493 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
494 * When woken, the thread will run @threadfn() with @data as its
495 * argument. @threadfn() can either return directly if it is a
496 * standalone thread for which no one will call kthread_stop(), or
497 * return when 'kthread_should_stop()' is true (which means
498 * kthread_stop() has been called). The return value should be zero
499 * or a negative error number; it will be passed to kthread_stop().
501 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
503 struct task_struct
*kthread_create_on_node(int (*threadfn
)(void *data
),
504 void *data
, int node
,
505 const char namefmt
[],
508 struct task_struct
*task
;
511 va_start(args
, namefmt
);
512 task
= __kthread_create_on_node(threadfn
, data
, node
, namefmt
, args
);
517 EXPORT_SYMBOL(kthread_create_on_node
);
519 static void __kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
, unsigned int state
)
523 if (!wait_task_inactive(p
, state
)) {
528 /* It's safe because the task is inactive. */
529 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
530 do_set_cpus_allowed(p
, mask
);
531 p
->flags
|= PF_NO_SETAFFINITY
;
532 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
535 static void __kthread_bind(struct task_struct
*p
, unsigned int cpu
, unsigned int state
)
537 __kthread_bind_mask(p
, cpumask_of(cpu
), state
);
540 void kthread_bind_mask(struct task_struct
*p
, const struct cpumask
*mask
)
542 __kthread_bind_mask(p
, mask
, TASK_UNINTERRUPTIBLE
);
546 * kthread_bind - bind a just-created kthread to a cpu.
547 * @p: thread created by kthread_create().
548 * @cpu: cpu (might not be online, must be possible) for @k to run on.
550 * Description: This function is equivalent to set_cpus_allowed(),
551 * except that @cpu doesn't need to be online, and the thread must be
552 * stopped (i.e., just returned from kthread_create()).
554 void kthread_bind(struct task_struct
*p
, unsigned int cpu
)
556 __kthread_bind(p
, cpu
, TASK_UNINTERRUPTIBLE
);
558 EXPORT_SYMBOL(kthread_bind
);
561 * kthread_create_on_cpu - Create a cpu bound kthread
562 * @threadfn: the function to run until signal_pending(current).
563 * @data: data ptr for @threadfn.
564 * @cpu: The cpu on which the thread should be bound,
565 * @namefmt: printf-style name for the thread. Format is restricted
566 * to "name.*%u". Code fills in cpu number.
568 * Description: This helper function creates and names a kernel thread
570 struct task_struct
*kthread_create_on_cpu(int (*threadfn
)(void *data
),
571 void *data
, unsigned int cpu
,
574 struct task_struct
*p
;
576 p
= kthread_create_on_node(threadfn
, data
, cpu_to_node(cpu
), namefmt
,
580 kthread_bind(p
, cpu
);
581 /* CPU hotplug need to bind once again when unparking the thread. */
582 to_kthread(p
)->cpu
= cpu
;
585 EXPORT_SYMBOL(kthread_create_on_cpu
);
587 void kthread_set_per_cpu(struct task_struct
*k
, int cpu
)
589 struct kthread
*kthread
= to_kthread(k
);
593 WARN_ON_ONCE(!(k
->flags
& PF_NO_SETAFFINITY
));
596 clear_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
601 set_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
604 bool kthread_is_per_cpu(struct task_struct
*p
)
606 struct kthread
*kthread
= __to_kthread(p
);
610 return test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
);
614 * kthread_unpark - unpark a thread created by kthread_create().
615 * @k: thread created by kthread_create().
617 * Sets kthread_should_park() for @k to return false, wakes it, and
618 * waits for it to return. If the thread is marked percpu then its
619 * bound to the cpu again.
621 void kthread_unpark(struct task_struct
*k
)
623 struct kthread
*kthread
= to_kthread(k
);
626 * Newly created kthread was parked when the CPU was offline.
627 * The binding was lost and we need to set it again.
629 if (test_bit(KTHREAD_IS_PER_CPU
, &kthread
->flags
))
630 __kthread_bind(k
, kthread
->cpu
, TASK_PARKED
);
632 clear_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
634 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
636 wake_up_state(k
, TASK_PARKED
);
638 EXPORT_SYMBOL_GPL(kthread_unpark
);
641 * kthread_park - park a thread created by kthread_create().
642 * @k: thread created by kthread_create().
644 * Sets kthread_should_park() for @k to return true, wakes it, and
645 * waits for it to return. This can also be called after kthread_create()
646 * instead of calling wake_up_process(): the thread will park without
647 * calling threadfn().
649 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
650 * If called by the kthread itself just the park bit is set.
652 int kthread_park(struct task_struct
*k
)
654 struct kthread
*kthread
= to_kthread(k
);
656 if (WARN_ON(k
->flags
& PF_EXITING
))
659 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
)))
662 set_bit(KTHREAD_SHOULD_PARK
, &kthread
->flags
);
666 * Wait for __kthread_parkme() to complete(), this means we
667 * _will_ have TASK_PARKED and are about to call schedule().
669 wait_for_completion(&kthread
->parked
);
671 * Now wait for that schedule() to complete and the task to
674 WARN_ON_ONCE(!wait_task_inactive(k
, TASK_PARKED
));
679 EXPORT_SYMBOL_GPL(kthread_park
);
682 * kthread_stop - stop a thread created by kthread_create().
683 * @k: thread created by kthread_create().
685 * Sets kthread_should_stop() for @k to return true, wakes it, and
686 * waits for it to exit. This can also be called after kthread_create()
687 * instead of calling wake_up_process(): the thread will exit without
688 * calling threadfn().
690 * If threadfn() may call kthread_exit() itself, the caller must ensure
691 * task_struct can't go away.
693 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
696 int kthread_stop(struct task_struct
*k
)
698 struct kthread
*kthread
;
701 trace_sched_kthread_stop(k
);
704 kthread
= to_kthread(k
);
705 set_bit(KTHREAD_SHOULD_STOP
, &kthread
->flags
);
707 set_tsk_thread_flag(k
, TIF_NOTIFY_SIGNAL
);
709 wait_for_completion(&kthread
->exited
);
710 ret
= kthread
->result
;
713 trace_sched_kthread_stop_ret(ret
);
716 EXPORT_SYMBOL(kthread_stop
);
719 * kthread_stop_put - stop a thread and put its task struct
720 * @k: thread created by kthread_create().
722 * Stops a thread created by kthread_create() and put its task_struct.
723 * Only use when holding an extra task struct reference obtained by
724 * calling get_task_struct().
726 int kthread_stop_put(struct task_struct
*k
)
730 ret
= kthread_stop(k
);
734 EXPORT_SYMBOL(kthread_stop_put
);
736 int kthreadd(void *unused
)
738 struct task_struct
*tsk
= current
;
740 /* Setup a clean context for our children to inherit. */
741 set_task_comm(tsk
, "kthreadd");
743 set_cpus_allowed_ptr(tsk
, housekeeping_cpumask(HK_TYPE_KTHREAD
));
744 set_mems_allowed(node_states
[N_MEMORY
]);
746 current
->flags
|= PF_NOFREEZE
;
747 cgroup_init_kthreadd();
750 set_current_state(TASK_INTERRUPTIBLE
);
751 if (list_empty(&kthread_create_list
))
753 __set_current_state(TASK_RUNNING
);
755 spin_lock(&kthread_create_lock
);
756 while (!list_empty(&kthread_create_list
)) {
757 struct kthread_create_info
*create
;
759 create
= list_entry(kthread_create_list
.next
,
760 struct kthread_create_info
, list
);
761 list_del_init(&create
->list
);
762 spin_unlock(&kthread_create_lock
);
764 create_kthread(create
);
766 spin_lock(&kthread_create_lock
);
768 spin_unlock(&kthread_create_lock
);
774 void __kthread_init_worker(struct kthread_worker
*worker
,
776 struct lock_class_key
*key
)
778 memset(worker
, 0, sizeof(struct kthread_worker
));
779 raw_spin_lock_init(&worker
->lock
);
780 lockdep_set_class_and_name(&worker
->lock
, key
, name
);
781 INIT_LIST_HEAD(&worker
->work_list
);
782 INIT_LIST_HEAD(&worker
->delayed_work_list
);
784 EXPORT_SYMBOL_GPL(__kthread_init_worker
);
787 * kthread_worker_fn - kthread function to process kthread_worker
788 * @worker_ptr: pointer to initialized kthread_worker
790 * This function implements the main cycle of kthread worker. It processes
791 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
794 * The works are not allowed to keep any locks, disable preemption or interrupts
795 * when they finish. There is defined a safe point for freezing when one work
796 * finishes and before a new one is started.
798 * Also the works must not be handled by more than one worker at the same time,
799 * see also kthread_queue_work().
801 int kthread_worker_fn(void *worker_ptr
)
803 struct kthread_worker
*worker
= worker_ptr
;
804 struct kthread_work
*work
;
807 * FIXME: Update the check and remove the assignment when all kthread
808 * worker users are created using kthread_create_worker*() functions.
810 WARN_ON(worker
->task
&& worker
->task
!= current
);
811 worker
->task
= current
;
813 if (worker
->flags
& KTW_FREEZABLE
)
817 set_current_state(TASK_INTERRUPTIBLE
); /* mb paired w/ kthread_stop */
819 if (kthread_should_stop()) {
820 __set_current_state(TASK_RUNNING
);
821 raw_spin_lock_irq(&worker
->lock
);
823 raw_spin_unlock_irq(&worker
->lock
);
828 raw_spin_lock_irq(&worker
->lock
);
829 if (!list_empty(&worker
->work_list
)) {
830 work
= list_first_entry(&worker
->work_list
,
831 struct kthread_work
, node
);
832 list_del_init(&work
->node
);
834 worker
->current_work
= work
;
835 raw_spin_unlock_irq(&worker
->lock
);
838 kthread_work_func_t func
= work
->func
;
839 __set_current_state(TASK_RUNNING
);
840 trace_sched_kthread_work_execute_start(work
);
843 * Avoid dereferencing work after this point. The trace
844 * event only cares about the address.
846 trace_sched_kthread_work_execute_end(work
, func
);
847 } else if (!freezing(current
))
854 EXPORT_SYMBOL_GPL(kthread_worker_fn
);
856 static __printf(3, 0) struct kthread_worker
*
857 __kthread_create_worker(int cpu
, unsigned int flags
,
858 const char namefmt
[], va_list args
)
860 struct kthread_worker
*worker
;
861 struct task_struct
*task
;
862 int node
= NUMA_NO_NODE
;
864 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
866 return ERR_PTR(-ENOMEM
);
868 kthread_init_worker(worker
);
871 node
= cpu_to_node(cpu
);
873 task
= __kthread_create_on_node(kthread_worker_fn
, worker
,
874 node
, namefmt
, args
);
879 kthread_bind(task
, cpu
);
881 worker
->flags
= flags
;
883 wake_up_process(task
);
888 return ERR_CAST(task
);
892 * kthread_create_worker - create a kthread worker
893 * @flags: flags modifying the default behavior of the worker
894 * @namefmt: printf-style name for the kthread worker (task).
896 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
897 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
898 * when the caller was killed by a fatal signal.
900 struct kthread_worker
*
901 kthread_create_worker(unsigned int flags
, const char namefmt
[], ...)
903 struct kthread_worker
*worker
;
906 va_start(args
, namefmt
);
907 worker
= __kthread_create_worker(-1, flags
, namefmt
, args
);
912 EXPORT_SYMBOL(kthread_create_worker
);
915 * kthread_create_worker_on_cpu - create a kthread worker and bind it
916 * to a given CPU and the associated NUMA node.
918 * @flags: flags modifying the default behavior of the worker
919 * @namefmt: printf-style name for the kthread worker (task).
921 * Use a valid CPU number if you want to bind the kthread worker
922 * to the given CPU and the associated NUMA node.
924 * A good practice is to add the cpu number also into the worker name.
925 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
928 * The kthread worker API is simple and generic. It just provides a way
929 * to create, use, and destroy workers.
931 * It is up to the API user how to handle CPU hotplug. They have to decide
932 * how to handle pending work items, prevent queuing new ones, and
933 * restore the functionality when the CPU goes off and on. There are a
936 * - CPU affinity gets lost when it is scheduled on an offline CPU.
938 * - The worker might not exist when the CPU was off when the user
939 * created the workers.
941 * Good practice is to implement two CPU hotplug callbacks and to
942 * destroy/create the worker when the CPU goes down/up.
945 * The pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
946 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
947 * when the caller was killed by a fatal signal.
949 struct kthread_worker
*
950 kthread_create_worker_on_cpu(int cpu
, unsigned int flags
,
951 const char namefmt
[], ...)
953 struct kthread_worker
*worker
;
956 va_start(args
, namefmt
);
957 worker
= __kthread_create_worker(cpu
, flags
, namefmt
, args
);
962 EXPORT_SYMBOL(kthread_create_worker_on_cpu
);
965 * Returns true when the work could not be queued at the moment.
966 * It happens when it is already pending in a worker list
967 * or when it is being cancelled.
969 static inline bool queuing_blocked(struct kthread_worker
*worker
,
970 struct kthread_work
*work
)
972 lockdep_assert_held(&worker
->lock
);
974 return !list_empty(&work
->node
) || work
->canceling
;
977 static void kthread_insert_work_sanity_check(struct kthread_worker
*worker
,
978 struct kthread_work
*work
)
980 lockdep_assert_held(&worker
->lock
);
981 WARN_ON_ONCE(!list_empty(&work
->node
));
982 /* Do not use a work with >1 worker, see kthread_queue_work() */
983 WARN_ON_ONCE(work
->worker
&& work
->worker
!= worker
);
986 /* insert @work before @pos in @worker */
987 static void kthread_insert_work(struct kthread_worker
*worker
,
988 struct kthread_work
*work
,
989 struct list_head
*pos
)
991 kthread_insert_work_sanity_check(worker
, work
);
993 trace_sched_kthread_work_queue_work(worker
, work
);
995 list_add_tail(&work
->node
, pos
);
996 work
->worker
= worker
;
997 if (!worker
->current_work
&& likely(worker
->task
))
998 wake_up_process(worker
->task
);
1002 * kthread_queue_work - queue a kthread_work
1003 * @worker: target kthread_worker
1004 * @work: kthread_work to queue
1006 * Queue @work to work processor @task for async execution. @task
1007 * must have been created with kthread_worker_create(). Returns %true
1008 * if @work was successfully queued, %false if it was already pending.
1010 * Reinitialize the work if it needs to be used by another worker.
1011 * For example, when the worker was stopped and started again.
1013 bool kthread_queue_work(struct kthread_worker
*worker
,
1014 struct kthread_work
*work
)
1017 unsigned long flags
;
1019 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1020 if (!queuing_blocked(worker
, work
)) {
1021 kthread_insert_work(worker
, work
, &worker
->work_list
);
1024 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1027 EXPORT_SYMBOL_GPL(kthread_queue_work
);
1030 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
1031 * delayed work when the timer expires.
1032 * @t: pointer to the expired timer
1034 * The format of the function is defined by struct timer_list.
1035 * It should have been called from irqsafe timer with irq already off.
1037 void kthread_delayed_work_timer_fn(struct timer_list
*t
)
1039 struct kthread_delayed_work
*dwork
= from_timer(dwork
, t
, timer
);
1040 struct kthread_work
*work
= &dwork
->work
;
1041 struct kthread_worker
*worker
= work
->worker
;
1042 unsigned long flags
;
1045 * This might happen when a pending work is reinitialized.
1046 * It means that it is used a wrong way.
1048 if (WARN_ON_ONCE(!worker
))
1051 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1052 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1053 WARN_ON_ONCE(work
->worker
!= worker
);
1055 /* Move the work from worker->delayed_work_list. */
1056 WARN_ON_ONCE(list_empty(&work
->node
));
1057 list_del_init(&work
->node
);
1058 if (!work
->canceling
)
1059 kthread_insert_work(worker
, work
, &worker
->work_list
);
1061 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1063 EXPORT_SYMBOL(kthread_delayed_work_timer_fn
);
1065 static void __kthread_queue_delayed_work(struct kthread_worker
*worker
,
1066 struct kthread_delayed_work
*dwork
,
1067 unsigned long delay
)
1069 struct timer_list
*timer
= &dwork
->timer
;
1070 struct kthread_work
*work
= &dwork
->work
;
1072 WARN_ON_ONCE(timer
->function
!= kthread_delayed_work_timer_fn
);
1075 * If @delay is 0, queue @dwork->work immediately. This is for
1076 * both optimization and correctness. The earliest @timer can
1077 * expire is on the closest next tick and delayed_work users depend
1078 * on that there's no such delay when @delay is 0.
1081 kthread_insert_work(worker
, work
, &worker
->work_list
);
1085 /* Be paranoid and try to detect possible races already now. */
1086 kthread_insert_work_sanity_check(worker
, work
);
1088 list_add(&work
->node
, &worker
->delayed_work_list
);
1089 work
->worker
= worker
;
1090 timer
->expires
= jiffies
+ delay
;
1095 * kthread_queue_delayed_work - queue the associated kthread work
1097 * @worker: target kthread_worker
1098 * @dwork: kthread_delayed_work to queue
1099 * @delay: number of jiffies to wait before queuing
1101 * If the work has not been pending it starts a timer that will queue
1102 * the work after the given @delay. If @delay is zero, it queues the
1105 * Return: %false if the @work has already been pending. It means that
1106 * either the timer was running or the work was queued. It returns %true
1109 bool kthread_queue_delayed_work(struct kthread_worker
*worker
,
1110 struct kthread_delayed_work
*dwork
,
1111 unsigned long delay
)
1113 struct kthread_work
*work
= &dwork
->work
;
1114 unsigned long flags
;
1117 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1119 if (!queuing_blocked(worker
, work
)) {
1120 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1124 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1127 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work
);
1129 struct kthread_flush_work
{
1130 struct kthread_work work
;
1131 struct completion done
;
1134 static void kthread_flush_work_fn(struct kthread_work
*work
)
1136 struct kthread_flush_work
*fwork
=
1137 container_of(work
, struct kthread_flush_work
, work
);
1138 complete(&fwork
->done
);
1142 * kthread_flush_work - flush a kthread_work
1143 * @work: work to flush
1145 * If @work is queued or executing, wait for it to finish execution.
1147 void kthread_flush_work(struct kthread_work
*work
)
1149 struct kthread_flush_work fwork
= {
1150 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1151 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1153 struct kthread_worker
*worker
;
1156 worker
= work
->worker
;
1160 raw_spin_lock_irq(&worker
->lock
);
1161 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1162 WARN_ON_ONCE(work
->worker
!= worker
);
1164 if (!list_empty(&work
->node
))
1165 kthread_insert_work(worker
, &fwork
.work
, work
->node
.next
);
1166 else if (worker
->current_work
== work
)
1167 kthread_insert_work(worker
, &fwork
.work
,
1168 worker
->work_list
.next
);
1172 raw_spin_unlock_irq(&worker
->lock
);
1175 wait_for_completion(&fwork
.done
);
1177 EXPORT_SYMBOL_GPL(kthread_flush_work
);
1180 * Make sure that the timer is neither set nor running and could
1181 * not manipulate the work list_head any longer.
1183 * The function is called under worker->lock. The lock is temporary
1184 * released but the timer can't be set again in the meantime.
1186 static void kthread_cancel_delayed_work_timer(struct kthread_work
*work
,
1187 unsigned long *flags
)
1189 struct kthread_delayed_work
*dwork
=
1190 container_of(work
, struct kthread_delayed_work
, work
);
1191 struct kthread_worker
*worker
= work
->worker
;
1194 * del_timer_sync() must be called to make sure that the timer
1195 * callback is not running. The lock must be temporary released
1196 * to avoid a deadlock with the callback. In the meantime,
1197 * any queuing is blocked by setting the canceling counter.
1200 raw_spin_unlock_irqrestore(&worker
->lock
, *flags
);
1201 del_timer_sync(&dwork
->timer
);
1202 raw_spin_lock_irqsave(&worker
->lock
, *flags
);
1207 * This function removes the work from the worker queue.
1209 * It is called under worker->lock. The caller must make sure that
1210 * the timer used by delayed work is not running, e.g. by calling
1211 * kthread_cancel_delayed_work_timer().
1213 * The work might still be in use when this function finishes. See the
1214 * current_work proceed by the worker.
1216 * Return: %true if @work was pending and successfully canceled,
1217 * %false if @work was not pending
1219 static bool __kthread_cancel_work(struct kthread_work
*work
)
1222 * Try to remove the work from a worker list. It might either
1223 * be from worker->work_list or from worker->delayed_work_list.
1225 if (!list_empty(&work
->node
)) {
1226 list_del_init(&work
->node
);
1234 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1235 * @worker: kthread worker to use
1236 * @dwork: kthread delayed work to queue
1237 * @delay: number of jiffies to wait before queuing
1239 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1240 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1241 * @work is guaranteed to be queued immediately.
1243 * Return: %false if @dwork was idle and queued, %true otherwise.
1245 * A special case is when the work is being canceled in parallel.
1246 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1247 * or yet another kthread_mod_delayed_work() call. We let the other command
1248 * win and return %true here. The return value can be used for reference
1249 * counting and the number of queued works stays the same. Anyway, the caller
1250 * is supposed to synchronize these operations a reasonable way.
1252 * This function is safe to call from any context including IRQ handler.
1253 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1256 bool kthread_mod_delayed_work(struct kthread_worker
*worker
,
1257 struct kthread_delayed_work
*dwork
,
1258 unsigned long delay
)
1260 struct kthread_work
*work
= &dwork
->work
;
1261 unsigned long flags
;
1264 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1266 /* Do not bother with canceling when never queued. */
1267 if (!work
->worker
) {
1272 /* Work must not be used with >1 worker, see kthread_queue_work() */
1273 WARN_ON_ONCE(work
->worker
!= worker
);
1276 * Temporary cancel the work but do not fight with another command
1277 * that is canceling the work as well.
1279 * It is a bit tricky because of possible races with another
1280 * mod_delayed_work() and cancel_delayed_work() callers.
1282 * The timer must be canceled first because worker->lock is released
1283 * when doing so. But the work can be removed from the queue (list)
1284 * only when it can be queued again so that the return value can
1285 * be used for reference counting.
1287 kthread_cancel_delayed_work_timer(work
, &flags
);
1288 if (work
->canceling
) {
1289 /* The number of works in the queue does not change. */
1293 ret
= __kthread_cancel_work(work
);
1296 __kthread_queue_delayed_work(worker
, dwork
, delay
);
1298 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1301 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work
);
1303 static bool __kthread_cancel_work_sync(struct kthread_work
*work
, bool is_dwork
)
1305 struct kthread_worker
*worker
= work
->worker
;
1306 unsigned long flags
;
1312 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1313 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1314 WARN_ON_ONCE(work
->worker
!= worker
);
1317 kthread_cancel_delayed_work_timer(work
, &flags
);
1319 ret
= __kthread_cancel_work(work
);
1321 if (worker
->current_work
!= work
)
1325 * The work is in progress and we need to wait with the lock released.
1326 * In the meantime, block any queuing by setting the canceling counter.
1329 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1330 kthread_flush_work(work
);
1331 raw_spin_lock_irqsave(&worker
->lock
, flags
);
1335 raw_spin_unlock_irqrestore(&worker
->lock
, flags
);
1341 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1342 * @work: the kthread work to cancel
1344 * Cancel @work and wait for its execution to finish. This function
1345 * can be used even if the work re-queues itself. On return from this
1346 * function, @work is guaranteed to be not pending or executing on any CPU.
1348 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1349 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1351 * The caller must ensure that the worker on which @work was last
1352 * queued can't be destroyed before this function returns.
1354 * Return: %true if @work was pending, %false otherwise.
1356 bool kthread_cancel_work_sync(struct kthread_work
*work
)
1358 return __kthread_cancel_work_sync(work
, false);
1360 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync
);
1363 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1364 * wait for it to finish.
1365 * @dwork: the kthread delayed work to cancel
1367 * This is kthread_cancel_work_sync() for delayed works.
1369 * Return: %true if @dwork was pending, %false otherwise.
1371 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work
*dwork
)
1373 return __kthread_cancel_work_sync(&dwork
->work
, true);
1375 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync
);
1378 * kthread_flush_worker - flush all current works on a kthread_worker
1379 * @worker: worker to flush
1381 * Wait until all currently executing or pending works on @worker are
1384 void kthread_flush_worker(struct kthread_worker
*worker
)
1386 struct kthread_flush_work fwork
= {
1387 KTHREAD_WORK_INIT(fwork
.work
, kthread_flush_work_fn
),
1388 COMPLETION_INITIALIZER_ONSTACK(fwork
.done
),
1391 kthread_queue_work(worker
, &fwork
.work
);
1392 wait_for_completion(&fwork
.done
);
1394 EXPORT_SYMBOL_GPL(kthread_flush_worker
);
1397 * kthread_destroy_worker - destroy a kthread worker
1398 * @worker: worker to be destroyed
1400 * Flush and destroy @worker. The simple flush is enough because the kthread
1401 * worker API is used only in trivial scenarios. There are no multi-step state
1404 * Note that this function is not responsible for handling delayed work, so
1405 * caller should be responsible for queuing or canceling all delayed work items
1406 * before invoke this function.
1408 void kthread_destroy_worker(struct kthread_worker
*worker
)
1410 struct task_struct
*task
;
1412 task
= worker
->task
;
1416 kthread_flush_worker(worker
);
1418 WARN_ON(!list_empty(&worker
->delayed_work_list
));
1419 WARN_ON(!list_empty(&worker
->work_list
));
1422 EXPORT_SYMBOL(kthread_destroy_worker
);
1425 * kthread_use_mm - make the calling kthread operate on an address space
1426 * @mm: address space to operate on
1428 void kthread_use_mm(struct mm_struct
*mm
)
1430 struct mm_struct
*active_mm
;
1431 struct task_struct
*tsk
= current
;
1433 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1434 WARN_ON_ONCE(tsk
->mm
);
1437 * It is possible for mm to be the same as tsk->active_mm, but
1438 * we must still mmgrab(mm) and mmdrop_lazy_tlb(active_mm),
1439 * because these references are not equivalent.
1444 /* Hold off tlb flush IPIs while switching mm's */
1445 local_irq_disable();
1446 active_mm
= tsk
->active_mm
;
1447 tsk
->active_mm
= mm
;
1449 membarrier_update_current_mm(mm
);
1450 switch_mm_irqs_off(active_mm
, mm
, tsk
);
1453 #ifdef finish_arch_post_lock_switch
1454 finish_arch_post_lock_switch();
1458 * When a kthread starts operating on an address space, the loop
1459 * in membarrier_{private,global}_expedited() may not observe
1460 * that tsk->mm, and not issue an IPI. Membarrier requires a
1461 * memory barrier after storing to tsk->mm, before accessing
1462 * user-space memory. A full memory barrier for membarrier
1463 * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
1464 * mmdrop_lazy_tlb().
1466 mmdrop_lazy_tlb(active_mm
);
1468 EXPORT_SYMBOL_GPL(kthread_use_mm
);
1471 * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1472 * @mm: address space to operate on
1474 void kthread_unuse_mm(struct mm_struct
*mm
)
1476 struct task_struct
*tsk
= current
;
1478 WARN_ON_ONCE(!(tsk
->flags
& PF_KTHREAD
));
1479 WARN_ON_ONCE(!tsk
->mm
);
1483 * When a kthread stops operating on an address space, the loop
1484 * in membarrier_{private,global}_expedited() may not observe
1485 * that tsk->mm, and not issue an IPI. Membarrier requires a
1486 * memory barrier after accessing user-space memory, before
1489 smp_mb__after_spinlock();
1490 local_irq_disable();
1492 membarrier_update_current_mm(NULL
);
1493 mmgrab_lazy_tlb(mm
);
1494 /* active_mm is still 'mm' */
1495 enter_lazy_tlb(mm
, tsk
);
1501 EXPORT_SYMBOL_GPL(kthread_unuse_mm
);
1503 #ifdef CONFIG_BLK_CGROUP
1505 * kthread_associate_blkcg - associate blkcg to current kthread
1506 * @css: the cgroup info
1508 * Current thread must be a kthread. The thread is running jobs on behalf of
1509 * other threads. In some cases, we expect the jobs attach cgroup info of
1510 * original threads instead of that of current thread. This function stores
1511 * original thread's cgroup info in current kthread context for later
1514 void kthread_associate_blkcg(struct cgroup_subsys_state
*css
)
1516 struct kthread
*kthread
;
1518 if (!(current
->flags
& PF_KTHREAD
))
1520 kthread
= to_kthread(current
);
1524 if (kthread
->blkcg_css
) {
1525 css_put(kthread
->blkcg_css
);
1526 kthread
->blkcg_css
= NULL
;
1530 kthread
->blkcg_css
= css
;
1533 EXPORT_SYMBOL(kthread_associate_blkcg
);
1536 * kthread_blkcg - get associated blkcg css of current kthread
1538 * Current thread must be a kthread.
1540 struct cgroup_subsys_state
*kthread_blkcg(void)
1542 struct kthread
*kthread
;
1544 if (current
->flags
& PF_KTHREAD
) {
1545 kthread
= to_kthread(current
);
1547 return kthread
->blkcg_css
;