Commit | Line | Data |
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1da177e4 LT |
1 | /* Kernel thread helper functions. |
2 | * Copyright (C) 2004 IBM Corporation, Rusty Russell. | |
3 | * | |
73c27992 | 4 | * Creation is done via kthreadd, so that we get a clean environment |
1da177e4 LT |
5 | * even if we're invoked from userspace (think modprobe, hotplug cpu, |
6 | * etc.). | |
7 | */ | |
8 | #include <linux/sched.h> | |
9 | #include <linux/kthread.h> | |
10 | #include <linux/completion.h> | |
11 | #include <linux/err.h> | |
58568d2a | 12 | #include <linux/cpuset.h> |
1da177e4 LT |
13 | #include <linux/unistd.h> |
14 | #include <linux/file.h> | |
15 | #include <linux/module.h> | |
97d1f15b | 16 | #include <linux/mutex.h> |
b56c0d89 TH |
17 | #include <linux/slab.h> |
18 | #include <linux/freezer.h> | |
ad8d75ff | 19 | #include <trace/events/sched.h> |
1da177e4 | 20 | |
73c27992 EB |
21 | static DEFINE_SPINLOCK(kthread_create_lock); |
22 | static LIST_HEAD(kthread_create_list); | |
23 | struct task_struct *kthreadd_task; | |
1da177e4 LT |
24 | |
25 | struct kthread_create_info | |
26 | { | |
73c27992 | 27 | /* Information passed to kthread() from kthreadd. */ |
1da177e4 LT |
28 | int (*threadfn)(void *data); |
29 | void *data; | |
1da177e4 | 30 | |
73c27992 | 31 | /* Result passed back to kthread_create() from kthreadd. */ |
1da177e4 LT |
32 | struct task_struct *result; |
33 | struct completion done; | |
65f27f38 | 34 | |
73c27992 | 35 | struct list_head list; |
1da177e4 LT |
36 | }; |
37 | ||
63706172 ON |
38 | struct kthread { |
39 | int should_stop; | |
40 | struct completion exited; | |
1da177e4 LT |
41 | }; |
42 | ||
63706172 ON |
43 | #define to_kthread(tsk) \ |
44 | container_of((tsk)->vfork_done, struct kthread, exited) | |
1da177e4 | 45 | |
9e37bd30 RD |
46 | /** |
47 | * kthread_should_stop - should this kthread return now? | |
48 | * | |
72fd4a35 | 49 | * When someone calls kthread_stop() on your kthread, it will be woken |
9e37bd30 RD |
50 | * and this will return true. You should then return, and your return |
51 | * value will be passed through to kthread_stop(). | |
52 | */ | |
1da177e4 LT |
53 | int kthread_should_stop(void) |
54 | { | |
63706172 | 55 | return to_kthread(current)->should_stop; |
1da177e4 LT |
56 | } |
57 | EXPORT_SYMBOL(kthread_should_stop); | |
58 | ||
1da177e4 LT |
59 | static int kthread(void *_create) |
60 | { | |
63706172 | 61 | /* Copy data: it's on kthread's stack */ |
1da177e4 | 62 | struct kthread_create_info *create = _create; |
63706172 ON |
63 | int (*threadfn)(void *data) = create->threadfn; |
64 | void *data = create->data; | |
65 | struct kthread self; | |
66 | int ret; | |
1da177e4 | 67 | |
63706172 ON |
68 | self.should_stop = 0; |
69 | init_completion(&self.exited); | |
70 | current->vfork_done = &self.exited; | |
1da177e4 | 71 | |
1da177e4 | 72 | /* OK, tell user we're spawned, wait for stop or wakeup */ |
a076e4bc | 73 | __set_current_state(TASK_UNINTERRUPTIBLE); |
3217ab97 | 74 | create->result = current; |
cdd140bd | 75 | complete(&create->done); |
1da177e4 LT |
76 | schedule(); |
77 | ||
63706172 ON |
78 | ret = -EINTR; |
79 | if (!self.should_stop) | |
1da177e4 LT |
80 | ret = threadfn(data); |
81 | ||
63706172 ON |
82 | /* we can't just return, we must preserve "self" on stack */ |
83 | do_exit(ret); | |
1da177e4 LT |
84 | } |
85 | ||
73c27992 | 86 | static void create_kthread(struct kthread_create_info *create) |
1da177e4 | 87 | { |
1da177e4 LT |
88 | int pid; |
89 | ||
90 | /* We want our own signal handler (we take no signals by default). */ | |
91 | pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); | |
cdd140bd | 92 | if (pid < 0) { |
1da177e4 | 93 | create->result = ERR_PTR(pid); |
cdd140bd ON |
94 | complete(&create->done); |
95 | } | |
1da177e4 LT |
96 | } |
97 | ||
9e37bd30 RD |
98 | /** |
99 | * kthread_create - create a kthread. | |
100 | * @threadfn: the function to run until signal_pending(current). | |
101 | * @data: data ptr for @threadfn. | |
102 | * @namefmt: printf-style name for the thread. | |
103 | * | |
104 | * Description: This helper function creates and names a kernel | |
105 | * thread. The thread will be stopped: use wake_up_process() to start | |
301ba045 | 106 | * it. See also kthread_run(). |
9e37bd30 RD |
107 | * |
108 | * When woken, the thread will run @threadfn() with @data as its | |
72fd4a35 | 109 | * argument. @threadfn() can either call do_exit() directly if it is a |
9e37bd30 RD |
110 | * standalone thread for which noone will call kthread_stop(), or |
111 | * return when 'kthread_should_stop()' is true (which means | |
112 | * kthread_stop() has been called). The return value should be zero | |
113 | * or a negative error number; it will be passed to kthread_stop(). | |
114 | * | |
115 | * Returns a task_struct or ERR_PTR(-ENOMEM). | |
116 | */ | |
1da177e4 LT |
117 | struct task_struct *kthread_create(int (*threadfn)(void *data), |
118 | void *data, | |
119 | const char namefmt[], | |
120 | ...) | |
121 | { | |
122 | struct kthread_create_info create; | |
1da177e4 LT |
123 | |
124 | create.threadfn = threadfn; | |
125 | create.data = data; | |
1da177e4 | 126 | init_completion(&create.done); |
73c27992 EB |
127 | |
128 | spin_lock(&kthread_create_lock); | |
129 | list_add_tail(&create.list, &kthread_create_list); | |
73c27992 EB |
130 | spin_unlock(&kthread_create_lock); |
131 | ||
cbd9b67b | 132 | wake_up_process(kthreadd_task); |
73c27992 EB |
133 | wait_for_completion(&create.done); |
134 | ||
1da177e4 | 135 | if (!IS_ERR(create.result)) { |
1c99315b | 136 | struct sched_param param = { .sched_priority = 0 }; |
1da177e4 | 137 | va_list args; |
1c99315b | 138 | |
1da177e4 LT |
139 | va_start(args, namefmt); |
140 | vsnprintf(create.result->comm, sizeof(create.result->comm), | |
141 | namefmt, args); | |
142 | va_end(args); | |
1c99315b ON |
143 | /* |
144 | * root may have changed our (kthreadd's) priority or CPU mask. | |
145 | * The kernel thread should not inherit these properties. | |
146 | */ | |
147 | sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m); | |
1c99315b | 148 | set_cpus_allowed_ptr(create.result, cpu_all_mask); |
1da177e4 | 149 | } |
1da177e4 LT |
150 | return create.result; |
151 | } | |
152 | EXPORT_SYMBOL(kthread_create); | |
153 | ||
881232b7 PZ |
154 | /** |
155 | * kthread_bind - bind a just-created kthread to a cpu. | |
156 | * @p: thread created by kthread_create(). | |
157 | * @cpu: cpu (might not be online, must be possible) for @k to run on. | |
158 | * | |
159 | * Description: This function is equivalent to set_cpus_allowed(), | |
160 | * except that @cpu doesn't need to be online, and the thread must be | |
161 | * stopped (i.e., just returned from kthread_create()). | |
162 | */ | |
163 | void kthread_bind(struct task_struct *p, unsigned int cpu) | |
164 | { | |
165 | /* Must have done schedule() in kthread() before we set_task_cpu */ | |
166 | if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { | |
167 | WARN_ON(1); | |
168 | return; | |
169 | } | |
170 | ||
171 | p->cpus_allowed = cpumask_of_cpu(cpu); | |
172 | p->rt.nr_cpus_allowed = 1; | |
173 | p->flags |= PF_THREAD_BOUND; | |
174 | } | |
175 | EXPORT_SYMBOL(kthread_bind); | |
176 | ||
9e37bd30 RD |
177 | /** |
178 | * kthread_stop - stop a thread created by kthread_create(). | |
179 | * @k: thread created by kthread_create(). | |
180 | * | |
181 | * Sets kthread_should_stop() for @k to return true, wakes it, and | |
9ae26027 ON |
182 | * waits for it to exit. This can also be called after kthread_create() |
183 | * instead of calling wake_up_process(): the thread will exit without | |
184 | * calling threadfn(). | |
185 | * | |
186 | * If threadfn() may call do_exit() itself, the caller must ensure | |
187 | * task_struct can't go away. | |
9e37bd30 RD |
188 | * |
189 | * Returns the result of threadfn(), or %-EINTR if wake_up_process() | |
190 | * was never called. | |
191 | */ | |
1da177e4 LT |
192 | int kthread_stop(struct task_struct *k) |
193 | { | |
63706172 | 194 | struct kthread *kthread; |
1da177e4 LT |
195 | int ret; |
196 | ||
0a16b607 | 197 | trace_sched_kthread_stop(k); |
63706172 | 198 | get_task_struct(k); |
0a16b607 | 199 | |
63706172 ON |
200 | kthread = to_kthread(k); |
201 | barrier(); /* it might have exited */ | |
202 | if (k->vfork_done != NULL) { | |
203 | kthread->should_stop = 1; | |
204 | wake_up_process(k); | |
205 | wait_for_completion(&kthread->exited); | |
206 | } | |
207 | ret = k->exit_code; | |
1da177e4 | 208 | |
1da177e4 | 209 | put_task_struct(k); |
0a16b607 MD |
210 | trace_sched_kthread_stop_ret(ret); |
211 | ||
1da177e4 LT |
212 | return ret; |
213 | } | |
52e92e57 | 214 | EXPORT_SYMBOL(kthread_stop); |
1da177e4 | 215 | |
e804a4a4 | 216 | int kthreadd(void *unused) |
1da177e4 | 217 | { |
73c27992 | 218 | struct task_struct *tsk = current; |
1da177e4 | 219 | |
e804a4a4 | 220 | /* Setup a clean context for our children to inherit. */ |
73c27992 | 221 | set_task_comm(tsk, "kthreadd"); |
10ab825b | 222 | ignore_signals(tsk); |
1a2142af | 223 | set_cpus_allowed_ptr(tsk, cpu_all_mask); |
5ab116c9 | 224 | set_mems_allowed(node_states[N_HIGH_MEMORY]); |
73c27992 | 225 | |
ebb12db5 | 226 | current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG; |
73c27992 EB |
227 | |
228 | for (;;) { | |
229 | set_current_state(TASK_INTERRUPTIBLE); | |
230 | if (list_empty(&kthread_create_list)) | |
231 | schedule(); | |
232 | __set_current_state(TASK_RUNNING); | |
233 | ||
234 | spin_lock(&kthread_create_lock); | |
235 | while (!list_empty(&kthread_create_list)) { | |
236 | struct kthread_create_info *create; | |
237 | ||
238 | create = list_entry(kthread_create_list.next, | |
239 | struct kthread_create_info, list); | |
240 | list_del_init(&create->list); | |
241 | spin_unlock(&kthread_create_lock); | |
242 | ||
243 | create_kthread(create); | |
244 | ||
245 | spin_lock(&kthread_create_lock); | |
246 | } | |
247 | spin_unlock(&kthread_create_lock); | |
248 | } | |
249 | ||
250 | return 0; | |
251 | } | |
b56c0d89 TH |
252 | |
253 | /** | |
254 | * kthread_worker_fn - kthread function to process kthread_worker | |
255 | * @worker_ptr: pointer to initialized kthread_worker | |
256 | * | |
257 | * This function can be used as @threadfn to kthread_create() or | |
258 | * kthread_run() with @worker_ptr argument pointing to an initialized | |
259 | * kthread_worker. The started kthread will process work_list until | |
260 | * the it is stopped with kthread_stop(). A kthread can also call | |
261 | * this function directly after extra initialization. | |
262 | * | |
263 | * Different kthreads can be used for the same kthread_worker as long | |
264 | * as there's only one kthread attached to it at any given time. A | |
265 | * kthread_worker without an attached kthread simply collects queued | |
266 | * kthread_works. | |
267 | */ | |
268 | int kthread_worker_fn(void *worker_ptr) | |
269 | { | |
270 | struct kthread_worker *worker = worker_ptr; | |
271 | struct kthread_work *work; | |
272 | ||
273 | WARN_ON(worker->task); | |
274 | worker->task = current; | |
275 | repeat: | |
276 | set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ | |
277 | ||
278 | if (kthread_should_stop()) { | |
279 | __set_current_state(TASK_RUNNING); | |
280 | spin_lock_irq(&worker->lock); | |
281 | worker->task = NULL; | |
282 | spin_unlock_irq(&worker->lock); | |
283 | return 0; | |
284 | } | |
285 | ||
286 | work = NULL; | |
287 | spin_lock_irq(&worker->lock); | |
288 | if (!list_empty(&worker->work_list)) { | |
289 | work = list_first_entry(&worker->work_list, | |
290 | struct kthread_work, node); | |
291 | list_del_init(&work->node); | |
292 | } | |
293 | spin_unlock_irq(&worker->lock); | |
294 | ||
295 | if (work) { | |
296 | __set_current_state(TASK_RUNNING); | |
297 | work->func(work); | |
298 | smp_wmb(); /* wmb worker-b0 paired with flush-b1 */ | |
299 | work->done_seq = work->queue_seq; | |
300 | smp_mb(); /* mb worker-b1 paired with flush-b0 */ | |
301 | if (atomic_read(&work->flushing)) | |
302 | wake_up_all(&work->done); | |
303 | } else if (!freezing(current)) | |
304 | schedule(); | |
305 | ||
306 | try_to_freeze(); | |
307 | goto repeat; | |
308 | } | |
309 | EXPORT_SYMBOL_GPL(kthread_worker_fn); | |
310 | ||
311 | /** | |
312 | * queue_kthread_work - queue a kthread_work | |
313 | * @worker: target kthread_worker | |
314 | * @work: kthread_work to queue | |
315 | * | |
316 | * Queue @work to work processor @task for async execution. @task | |
317 | * must have been created with kthread_worker_create(). Returns %true | |
318 | * if @work was successfully queued, %false if it was already pending. | |
319 | */ | |
320 | bool queue_kthread_work(struct kthread_worker *worker, | |
321 | struct kthread_work *work) | |
322 | { | |
323 | bool ret = false; | |
324 | unsigned long flags; | |
325 | ||
326 | spin_lock_irqsave(&worker->lock, flags); | |
327 | if (list_empty(&work->node)) { | |
328 | list_add_tail(&work->node, &worker->work_list); | |
329 | work->queue_seq++; | |
330 | if (likely(worker->task)) | |
331 | wake_up_process(worker->task); | |
332 | ret = true; | |
333 | } | |
334 | spin_unlock_irqrestore(&worker->lock, flags); | |
335 | return ret; | |
336 | } | |
337 | EXPORT_SYMBOL_GPL(queue_kthread_work); | |
338 | ||
339 | /** | |
340 | * flush_kthread_work - flush a kthread_work | |
341 | * @work: work to flush | |
342 | * | |
343 | * If @work is queued or executing, wait for it to finish execution. | |
344 | */ | |
345 | void flush_kthread_work(struct kthread_work *work) | |
346 | { | |
347 | int seq = work->queue_seq; | |
348 | ||
349 | atomic_inc(&work->flushing); | |
350 | ||
351 | /* | |
352 | * mb flush-b0 paired with worker-b1, to make sure either | |
353 | * worker sees the above increment or we see done_seq update. | |
354 | */ | |
355 | smp_mb__after_atomic_inc(); | |
356 | ||
357 | /* A - B <= 0 tests whether B is in front of A regardless of overflow */ | |
358 | wait_event(work->done, seq - work->done_seq <= 0); | |
359 | atomic_dec(&work->flushing); | |
360 | ||
361 | /* | |
362 | * rmb flush-b1 paired with worker-b0, to make sure our caller | |
363 | * sees every change made by work->func(). | |
364 | */ | |
365 | smp_mb__after_atomic_dec(); | |
366 | } | |
367 | EXPORT_SYMBOL_GPL(flush_kthread_work); | |
368 | ||
369 | struct kthread_flush_work { | |
370 | struct kthread_work work; | |
371 | struct completion done; | |
372 | }; | |
373 | ||
374 | static void kthread_flush_work_fn(struct kthread_work *work) | |
375 | { | |
376 | struct kthread_flush_work *fwork = | |
377 | container_of(work, struct kthread_flush_work, work); | |
378 | complete(&fwork->done); | |
379 | } | |
380 | ||
381 | /** | |
382 | * flush_kthread_worker - flush all current works on a kthread_worker | |
383 | * @worker: worker to flush | |
384 | * | |
385 | * Wait until all currently executing or pending works on @worker are | |
386 | * finished. | |
387 | */ | |
388 | void flush_kthread_worker(struct kthread_worker *worker) | |
389 | { | |
390 | struct kthread_flush_work fwork = { | |
391 | KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), | |
392 | COMPLETION_INITIALIZER_ONSTACK(fwork.done), | |
393 | }; | |
394 | ||
395 | queue_kthread_work(worker, &fwork.work); | |
396 | wait_for_completion(&fwork.done); | |
397 | } | |
398 | EXPORT_SYMBOL_GPL(flush_kthread_worker); |