1 /* Kernel thread helper functions. 2 * Copyright (C) 2004 IBM Corporation, Rusty Russell. 3 * 4 * Creation is done via kthreadd, so that we get a clean environment 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> 12 #include <linux/cpuset.h> 13 #include <linux/unistd.h> 14 #include <linux/file.h> 15 #include <linux/export.h> 16 #include <linux/mutex.h> 17 #include <linux/slab.h> 18 #include <linux/freezer.h> 19 #include <linux/ptrace.h> 20 #include <linux/uaccess.h> 21 #include <trace/events/sched.h> 22 23 static DEFINE_SPINLOCK(kthread_create_lock); 24 static LIST_HEAD(kthread_create_list); 25 struct task_struct *kthreadd_task; 26 27 struct kthread_create_info 28 { 29 /* Information passed to kthread() from kthreadd. */ 30 int (*threadfn)(void *data); 31 void *data; 32 int node; 33 34 /* Result passed back to kthread_create() from kthreadd. */ 35 struct task_struct *result; 36 struct completion *done; 37 38 struct list_head list; 39 }; 40 41 struct kthread { 42 unsigned long flags; 43 unsigned int cpu; 44 void *data; 45 struct completion parked; 46 struct completion exited; 47 }; 48 49 enum KTHREAD_BITS { 50 KTHREAD_IS_PER_CPU = 0, 51 KTHREAD_SHOULD_STOP, 52 KTHREAD_SHOULD_PARK, 53 KTHREAD_IS_PARKED, 54 }; 55 56 #define __to_kthread(vfork) \ 57 container_of(vfork, struct kthread, exited) 58 59 static inline struct kthread *to_kthread(struct task_struct *k) 60 { 61 return __to_kthread(k->vfork_done); 62 } 63 64 static struct kthread *to_live_kthread(struct task_struct *k) 65 { 66 struct completion *vfork = ACCESS_ONCE(k->vfork_done); 67 if (likely(vfork)) 68 return __to_kthread(vfork); 69 return NULL; 70 } 71 72 /** 73 * kthread_should_stop - should this kthread return now? 74 * 75 * When someone calls kthread_stop() on your kthread, it will be woken 76 * and this will return true. You should then return, and your return 77 * value will be passed through to kthread_stop(). 78 */ 79 bool kthread_should_stop(void) 80 { 81 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags); 82 } 83 EXPORT_SYMBOL(kthread_should_stop); 84 85 /** 86 * kthread_should_park - should this kthread park now? 87 * 88 * When someone calls kthread_park() on your kthread, it will be woken 89 * and this will return true. You should then do the necessary 90 * cleanup and call kthread_parkme() 91 * 92 * Similar to kthread_should_stop(), but this keeps the thread alive 93 * and in a park position. kthread_unpark() "restarts" the thread and 94 * calls the thread function again. 95 */ 96 bool kthread_should_park(void) 97 { 98 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags); 99 } 100 EXPORT_SYMBOL_GPL(kthread_should_park); 101 102 /** 103 * kthread_freezable_should_stop - should this freezable kthread return now? 104 * @was_frozen: optional out parameter, indicates whether %current was frozen 105 * 106 * kthread_should_stop() for freezable kthreads, which will enter 107 * refrigerator if necessary. This function is safe from kthread_stop() / 108 * freezer deadlock and freezable kthreads should use this function instead 109 * of calling try_to_freeze() directly. 110 */ 111 bool kthread_freezable_should_stop(bool *was_frozen) 112 { 113 bool frozen = false; 114 115 might_sleep(); 116 117 if (unlikely(freezing(current))) 118 frozen = __refrigerator(true); 119 120 if (was_frozen) 121 *was_frozen = frozen; 122 123 return kthread_should_stop(); 124 } 125 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop); 126 127 /** 128 * kthread_data - return data value specified on kthread creation 129 * @task: kthread task in question 130 * 131 * Return the data value specified when kthread @task was created. 132 * The caller is responsible for ensuring the validity of @task when 133 * calling this function. 134 */ 135 void *kthread_data(struct task_struct *task) 136 { 137 return to_kthread(task)->data; 138 } 139 140 /** 141 * probe_kthread_data - speculative version of kthread_data() 142 * @task: possible kthread task in question 143 * 144 * @task could be a kthread task. Return the data value specified when it 145 * was created if accessible. If @task isn't a kthread task or its data is 146 * inaccessible for any reason, %NULL is returned. This function requires 147 * that @task itself is safe to dereference. 148 */ 149 void *probe_kthread_data(struct task_struct *task) 150 { 151 struct kthread *kthread = to_kthread(task); 152 void *data = NULL; 153 154 probe_kernel_read(&data, &kthread->data, sizeof(data)); 155 return data; 156 } 157 158 static void __kthread_parkme(struct kthread *self) 159 { 160 __set_current_state(TASK_PARKED); 161 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) { 162 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags)) 163 complete(&self->parked); 164 schedule(); 165 __set_current_state(TASK_PARKED); 166 } 167 clear_bit(KTHREAD_IS_PARKED, &self->flags); 168 __set_current_state(TASK_RUNNING); 169 } 170 171 void kthread_parkme(void) 172 { 173 __kthread_parkme(to_kthread(current)); 174 } 175 EXPORT_SYMBOL_GPL(kthread_parkme); 176 177 static int kthread(void *_create) 178 { 179 /* Copy data: it's on kthread's stack */ 180 struct kthread_create_info *create = _create; 181 int (*threadfn)(void *data) = create->threadfn; 182 void *data = create->data; 183 struct completion *done; 184 struct kthread self; 185 int ret; 186 187 self.flags = 0; 188 self.data = data; 189 init_completion(&self.exited); 190 init_completion(&self.parked); 191 current->vfork_done = &self.exited; 192 193 /* If user was SIGKILLed, I release the structure. */ 194 done = xchg(&create->done, NULL); 195 if (!done) { 196 kfree(create); 197 do_exit(-EINTR); 198 } 199 /* OK, tell user we're spawned, wait for stop or wakeup */ 200 __set_current_state(TASK_UNINTERRUPTIBLE); 201 create->result = current; 202 complete(done); 203 schedule(); 204 205 ret = -EINTR; 206 207 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) { 208 __kthread_parkme(&self); 209 ret = threadfn(data); 210 } 211 /* we can't just return, we must preserve "self" on stack */ 212 do_exit(ret); 213 } 214 215 /* called from do_fork() to get node information for about to be created task */ 216 int tsk_fork_get_node(struct task_struct *tsk) 217 { 218 #ifdef CONFIG_NUMA 219 if (tsk == kthreadd_task) 220 return tsk->pref_node_fork; 221 #endif 222 return NUMA_NO_NODE; 223 } 224 225 static void create_kthread(struct kthread_create_info *create) 226 { 227 int pid; 228 229 #ifdef CONFIG_NUMA 230 current->pref_node_fork = create->node; 231 #endif 232 /* We want our own signal handler (we take no signals by default). */ 233 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); 234 if (pid < 0) { 235 /* If user was SIGKILLed, I release the structure. */ 236 struct completion *done = xchg(&create->done, NULL); 237 238 if (!done) { 239 kfree(create); 240 return; 241 } 242 create->result = ERR_PTR(pid); 243 complete(done); 244 } 245 } 246 247 /** 248 * kthread_create_on_node - create a kthread. 249 * @threadfn: the function to run until signal_pending(current). 250 * @data: data ptr for @threadfn. 251 * @node: memory node number. 252 * @namefmt: printf-style name for the thread. 253 * 254 * Description: This helper function creates and names a kernel 255 * thread. The thread will be stopped: use wake_up_process() to start 256 * it. See also kthread_run(). 257 * 258 * If thread is going to be bound on a particular cpu, give its node 259 * in @node, to get NUMA affinity for kthread stack, or else give -1. 260 * When woken, the thread will run @threadfn() with @data as its 261 * argument. @threadfn() can either call do_exit() directly if it is a 262 * standalone thread for which no one will call kthread_stop(), or 263 * return when 'kthread_should_stop()' is true (which means 264 * kthread_stop() has been called). The return value should be zero 265 * or a negative error number; it will be passed to kthread_stop(). 266 * 267 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR). 268 */ 269 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), 270 void *data, int node, 271 const char namefmt[], 272 ...) 273 { 274 DECLARE_COMPLETION_ONSTACK(done); 275 struct task_struct *task; 276 struct kthread_create_info *create = kmalloc(sizeof(*create), 277 GFP_KERNEL); 278 279 if (!create) 280 return ERR_PTR(-ENOMEM); 281 create->threadfn = threadfn; 282 create->data = data; 283 create->node = node; 284 create->done = &done; 285 286 spin_lock(&kthread_create_lock); 287 list_add_tail(&create->list, &kthread_create_list); 288 spin_unlock(&kthread_create_lock); 289 290 wake_up_process(kthreadd_task); 291 /* 292 * Wait for completion in killable state, for I might be chosen by 293 * the OOM killer while kthreadd is trying to allocate memory for 294 * new kernel thread. 295 */ 296 if (unlikely(wait_for_completion_killable(&done))) { 297 /* 298 * If I was SIGKILLed before kthreadd (or new kernel thread) 299 * calls complete(), leave the cleanup of this structure to 300 * that thread. 301 */ 302 if (xchg(&create->done, NULL)) 303 return ERR_PTR(-EINTR); 304 /* 305 * kthreadd (or new kernel thread) will call complete() 306 * shortly. 307 */ 308 wait_for_completion(&done); 309 } 310 task = create->result; 311 if (!IS_ERR(task)) { 312 static const struct sched_param param = { .sched_priority = 0 }; 313 va_list args; 314 315 va_start(args, namefmt); 316 vsnprintf(task->comm, sizeof(task->comm), namefmt, args); 317 va_end(args); 318 /* 319 * root may have changed our (kthreadd's) priority or CPU mask. 320 * The kernel thread should not inherit these properties. 321 */ 322 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m); 323 set_cpus_allowed_ptr(task, cpu_all_mask); 324 } 325 kfree(create); 326 return task; 327 } 328 EXPORT_SYMBOL(kthread_create_on_node); 329 330 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state) 331 { 332 /* Must have done schedule() in kthread() before we set_task_cpu */ 333 if (!wait_task_inactive(p, state)) { 334 WARN_ON(1); 335 return; 336 } 337 /* It's safe because the task is inactive. */ 338 do_set_cpus_allowed(p, cpumask_of(cpu)); 339 p->flags |= PF_NO_SETAFFINITY; 340 } 341 342 /** 343 * kthread_bind - bind a just-created kthread to a cpu. 344 * @p: thread created by kthread_create(). 345 * @cpu: cpu (might not be online, must be possible) for @k to run on. 346 * 347 * Description: This function is equivalent to set_cpus_allowed(), 348 * except that @cpu doesn't need to be online, and the thread must be 349 * stopped (i.e., just returned from kthread_create()). 350 */ 351 void kthread_bind(struct task_struct *p, unsigned int cpu) 352 { 353 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); 354 } 355 EXPORT_SYMBOL(kthread_bind); 356 357 /** 358 * kthread_create_on_cpu - Create a cpu bound kthread 359 * @threadfn: the function to run until signal_pending(current). 360 * @data: data ptr for @threadfn. 361 * @cpu: The cpu on which the thread should be bound, 362 * @namefmt: printf-style name for the thread. Format is restricted 363 * to "name.*%u". Code fills in cpu number. 364 * 365 * Description: This helper function creates and names a kernel thread 366 * The thread will be woken and put into park mode. 367 */ 368 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), 369 void *data, unsigned int cpu, 370 const char *namefmt) 371 { 372 struct task_struct *p; 373 374 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt, 375 cpu); 376 if (IS_ERR(p)) 377 return p; 378 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags); 379 to_kthread(p)->cpu = cpu; 380 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */ 381 kthread_park(p); 382 return p; 383 } 384 385 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) 386 { 387 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags); 388 /* 389 * We clear the IS_PARKED bit here as we don't wait 390 * until the task has left the park code. So if we'd 391 * park before that happens we'd see the IS_PARKED bit 392 * which might be about to be cleared. 393 */ 394 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) { 395 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags)) 396 __kthread_bind(k, kthread->cpu, TASK_PARKED); 397 wake_up_state(k, TASK_PARKED); 398 } 399 } 400 401 /** 402 * kthread_unpark - unpark a thread created by kthread_create(). 403 * @k: thread created by kthread_create(). 404 * 405 * Sets kthread_should_park() for @k to return false, wakes it, and 406 * waits for it to return. If the thread is marked percpu then its 407 * bound to the cpu again. 408 */ 409 void kthread_unpark(struct task_struct *k) 410 { 411 struct kthread *kthread = to_live_kthread(k); 412 413 if (kthread) 414 __kthread_unpark(k, kthread); 415 } 416 EXPORT_SYMBOL_GPL(kthread_unpark); 417 418 /** 419 * kthread_park - park a thread created by kthread_create(). 420 * @k: thread created by kthread_create(). 421 * 422 * Sets kthread_should_park() for @k to return true, wakes it, and 423 * waits for it to return. This can also be called after kthread_create() 424 * instead of calling wake_up_process(): the thread will park without 425 * calling threadfn(). 426 * 427 * Returns 0 if the thread is parked, -ENOSYS if the thread exited. 428 * If called by the kthread itself just the park bit is set. 429 */ 430 int kthread_park(struct task_struct *k) 431 { 432 struct kthread *kthread = to_live_kthread(k); 433 int ret = -ENOSYS; 434 435 if (kthread) { 436 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) { 437 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags); 438 if (k != current) { 439 wake_up_process(k); 440 wait_for_completion(&kthread->parked); 441 } 442 } 443 ret = 0; 444 } 445 return ret; 446 } 447 EXPORT_SYMBOL_GPL(kthread_park); 448 449 /** 450 * kthread_stop - stop a thread created by kthread_create(). 451 * @k: thread created by kthread_create(). 452 * 453 * Sets kthread_should_stop() for @k to return true, wakes it, and 454 * waits for it to exit. This can also be called after kthread_create() 455 * instead of calling wake_up_process(): the thread will exit without 456 * calling threadfn(). 457 * 458 * If threadfn() may call do_exit() itself, the caller must ensure 459 * task_struct can't go away. 460 * 461 * Returns the result of threadfn(), or %-EINTR if wake_up_process() 462 * was never called. 463 */ 464 int kthread_stop(struct task_struct *k) 465 { 466 struct kthread *kthread; 467 int ret; 468 469 trace_sched_kthread_stop(k); 470 471 get_task_struct(k); 472 kthread = to_live_kthread(k); 473 if (kthread) { 474 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); 475 __kthread_unpark(k, kthread); 476 wake_up_process(k); 477 wait_for_completion(&kthread->exited); 478 } 479 ret = k->exit_code; 480 put_task_struct(k); 481 482 trace_sched_kthread_stop_ret(ret); 483 return ret; 484 } 485 EXPORT_SYMBOL(kthread_stop); 486 487 int kthreadd(void *unused) 488 { 489 struct task_struct *tsk = current; 490 491 /* Setup a clean context for our children to inherit. */ 492 set_task_comm(tsk, "kthreadd"); 493 ignore_signals(tsk); 494 set_cpus_allowed_ptr(tsk, cpu_all_mask); 495 set_mems_allowed(node_states[N_MEMORY]); 496 497 current->flags |= PF_NOFREEZE; 498 499 for (;;) { 500 set_current_state(TASK_INTERRUPTIBLE); 501 if (list_empty(&kthread_create_list)) 502 schedule(); 503 __set_current_state(TASK_RUNNING); 504 505 spin_lock(&kthread_create_lock); 506 while (!list_empty(&kthread_create_list)) { 507 struct kthread_create_info *create; 508 509 create = list_entry(kthread_create_list.next, 510 struct kthread_create_info, list); 511 list_del_init(&create->list); 512 spin_unlock(&kthread_create_lock); 513 514 create_kthread(create); 515 516 spin_lock(&kthread_create_lock); 517 } 518 spin_unlock(&kthread_create_lock); 519 } 520 521 return 0; 522 } 523 524 void __init_kthread_worker(struct kthread_worker *worker, 525 const char *name, 526 struct lock_class_key *key) 527 { 528 spin_lock_init(&worker->lock); 529 lockdep_set_class_and_name(&worker->lock, key, name); 530 INIT_LIST_HEAD(&worker->work_list); 531 worker->task = NULL; 532 } 533 EXPORT_SYMBOL_GPL(__init_kthread_worker); 534 535 /** 536 * kthread_worker_fn - kthread function to process kthread_worker 537 * @worker_ptr: pointer to initialized kthread_worker 538 * 539 * This function can be used as @threadfn to kthread_create() or 540 * kthread_run() with @worker_ptr argument pointing to an initialized 541 * kthread_worker. The started kthread will process work_list until 542 * the it is stopped with kthread_stop(). A kthread can also call 543 * this function directly after extra initialization. 544 * 545 * Different kthreads can be used for the same kthread_worker as long 546 * as there's only one kthread attached to it at any given time. A 547 * kthread_worker without an attached kthread simply collects queued 548 * kthread_works. 549 */ 550 int kthread_worker_fn(void *worker_ptr) 551 { 552 struct kthread_worker *worker = worker_ptr; 553 struct kthread_work *work; 554 555 WARN_ON(worker->task); 556 worker->task = current; 557 repeat: 558 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ 559 560 if (kthread_should_stop()) { 561 __set_current_state(TASK_RUNNING); 562 spin_lock_irq(&worker->lock); 563 worker->task = NULL; 564 spin_unlock_irq(&worker->lock); 565 return 0; 566 } 567 568 work = NULL; 569 spin_lock_irq(&worker->lock); 570 if (!list_empty(&worker->work_list)) { 571 work = list_first_entry(&worker->work_list, 572 struct kthread_work, node); 573 list_del_init(&work->node); 574 } 575 worker->current_work = work; 576 spin_unlock_irq(&worker->lock); 577 578 if (work) { 579 __set_current_state(TASK_RUNNING); 580 work->func(work); 581 } else if (!freezing(current)) 582 schedule(); 583 584 try_to_freeze(); 585 goto repeat; 586 } 587 EXPORT_SYMBOL_GPL(kthread_worker_fn); 588 589 /* insert @work before @pos in @worker */ 590 static void insert_kthread_work(struct kthread_worker *worker, 591 struct kthread_work *work, 592 struct list_head *pos) 593 { 594 lockdep_assert_held(&worker->lock); 595 596 list_add_tail(&work->node, pos); 597 work->worker = worker; 598 if (!worker->current_work && likely(worker->task)) 599 wake_up_process(worker->task); 600 } 601 602 /** 603 * queue_kthread_work - queue a kthread_work 604 * @worker: target kthread_worker 605 * @work: kthread_work to queue 606 * 607 * Queue @work to work processor @task for async execution. @task 608 * must have been created with kthread_worker_create(). Returns %true 609 * if @work was successfully queued, %false if it was already pending. 610 */ 611 bool queue_kthread_work(struct kthread_worker *worker, 612 struct kthread_work *work) 613 { 614 bool ret = false; 615 unsigned long flags; 616 617 spin_lock_irqsave(&worker->lock, flags); 618 if (list_empty(&work->node)) { 619 insert_kthread_work(worker, work, &worker->work_list); 620 ret = true; 621 } 622 spin_unlock_irqrestore(&worker->lock, flags); 623 return ret; 624 } 625 EXPORT_SYMBOL_GPL(queue_kthread_work); 626 627 struct kthread_flush_work { 628 struct kthread_work work; 629 struct completion done; 630 }; 631 632 static void kthread_flush_work_fn(struct kthread_work *work) 633 { 634 struct kthread_flush_work *fwork = 635 container_of(work, struct kthread_flush_work, work); 636 complete(&fwork->done); 637 } 638 639 /** 640 * flush_kthread_work - flush a kthread_work 641 * @work: work to flush 642 * 643 * If @work is queued or executing, wait for it to finish execution. 644 */ 645 void flush_kthread_work(struct kthread_work *work) 646 { 647 struct kthread_flush_work fwork = { 648 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), 649 COMPLETION_INITIALIZER_ONSTACK(fwork.done), 650 }; 651 struct kthread_worker *worker; 652 bool noop = false; 653 654 retry: 655 worker = work->worker; 656 if (!worker) 657 return; 658 659 spin_lock_irq(&worker->lock); 660 if (work->worker != worker) { 661 spin_unlock_irq(&worker->lock); 662 goto retry; 663 } 664 665 if (!list_empty(&work->node)) 666 insert_kthread_work(worker, &fwork.work, work->node.next); 667 else if (worker->current_work == work) 668 insert_kthread_work(worker, &fwork.work, worker->work_list.next); 669 else 670 noop = true; 671 672 spin_unlock_irq(&worker->lock); 673 674 if (!noop) 675 wait_for_completion(&fwork.done); 676 } 677 EXPORT_SYMBOL_GPL(flush_kthread_work); 678 679 /** 680 * flush_kthread_worker - flush all current works on a kthread_worker 681 * @worker: worker to flush 682 * 683 * Wait until all currently executing or pending works on @worker are 684 * finished. 685 */ 686 void flush_kthread_worker(struct kthread_worker *worker) 687 { 688 struct kthread_flush_work fwork = { 689 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn), 690 COMPLETION_INITIALIZER_ONSTACK(fwork.done), 691 }; 692 693 queue_kthread_work(worker, &fwork.work); 694 wait_for_completion(&fwork.done); 695 } 696 EXPORT_SYMBOL_GPL(flush_kthread_worker); 697