xref: /f-stack/freebsd/kern/subr_taskqueue.c (revision 9bd490e8)
1 /*-
2  * Copyright (c) 2000 Doug Rabson
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/systm.h>
32 #include <sys/bus.h>
33 #include <sys/cpuset.h>
34 #include <sys/interrupt.h>
35 #include <sys/kernel.h>
36 #include <sys/kthread.h>
37 #include <sys/libkern.h>
38 #include <sys/limits.h>
39 #include <sys/lock.h>
40 #include <sys/malloc.h>
41 #include <sys/mutex.h>
42 #include <sys/proc.h>
43 #include <sys/sched.h>
44 #include <sys/smp.h>
45 #include <sys/taskqueue.h>
46 #include <sys/unistd.h>
47 #include <machine/stdarg.h>
48 
49 static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
50 static void	*taskqueue_giant_ih;
51 static void	*taskqueue_ih;
52 static void	 taskqueue_fast_enqueue(void *);
53 static void	 taskqueue_swi_enqueue(void *);
54 static void	 taskqueue_swi_giant_enqueue(void *);
55 
56 struct taskqueue_busy {
57 	struct task	*tb_running;
58 	TAILQ_ENTRY(taskqueue_busy) tb_link;
59 };
60 
61 struct task * const TB_DRAIN_WAITER = (struct task *)0x1;
62 
63 struct taskqueue {
64 	STAILQ_HEAD(, task)	tq_queue;
65 	taskqueue_enqueue_fn	tq_enqueue;
66 	void			*tq_context;
67 	char			*tq_name;
68 	TAILQ_HEAD(, taskqueue_busy) tq_active;
69 	struct mtx		tq_mutex;
70 	struct thread		**tq_threads;
71 	int			tq_tcount;
72 	int			tq_spin;
73 	int			tq_flags;
74 	int			tq_callouts;
75 	taskqueue_callback_fn	tq_callbacks[TASKQUEUE_NUM_CALLBACKS];
76 	void			*tq_cb_contexts[TASKQUEUE_NUM_CALLBACKS];
77 };
78 
79 #define	TQ_FLAGS_ACTIVE		(1 << 0)
80 #define	TQ_FLAGS_BLOCKED	(1 << 1)
81 #define	TQ_FLAGS_UNLOCKED_ENQUEUE	(1 << 2)
82 
83 #define	DT_CALLOUT_ARMED	(1 << 0)
84 
85 #define	TQ_LOCK(tq)							\
86 	do {								\
87 		if ((tq)->tq_spin)					\
88 			mtx_lock_spin(&(tq)->tq_mutex);			\
89 		else							\
90 			mtx_lock(&(tq)->tq_mutex);			\
91 	} while (0)
92 #define	TQ_ASSERT_LOCKED(tq)	mtx_assert(&(tq)->tq_mutex, MA_OWNED)
93 
94 #define	TQ_UNLOCK(tq)							\
95 	do {								\
96 		if ((tq)->tq_spin)					\
97 			mtx_unlock_spin(&(tq)->tq_mutex);		\
98 		else							\
99 			mtx_unlock(&(tq)->tq_mutex);			\
100 	} while (0)
101 #define	TQ_ASSERT_UNLOCKED(tq)	mtx_assert(&(tq)->tq_mutex, MA_NOTOWNED)
102 
103 void
104 _timeout_task_init(struct taskqueue *queue, struct timeout_task *timeout_task,
105     int priority, task_fn_t func, void *context)
106 {
107 
108 	TASK_INIT(&timeout_task->t, priority, func, context);
109 	callout_init_mtx(&timeout_task->c, &queue->tq_mutex,
110 	    CALLOUT_RETURNUNLOCKED);
111 	timeout_task->q = queue;
112 	timeout_task->f = 0;
113 }
114 
115 #ifndef FSTACK
116 static __inline int
117 TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
118     int t)
119 {
120 	if (tq->tq_spin)
121 		return (msleep_spin(p, m, wm, t));
122 	return (msleep(p, m, pri, wm, t));
123 }
124 #else
125 #define TQ_SLEEP(a, b, c, d, e, f) break;
126 #endif
127 
128 static struct taskqueue *
129 _taskqueue_create(const char *name, int mflags,
130 		 taskqueue_enqueue_fn enqueue, void *context,
131 		 int mtxflags, const char *mtxname __unused)
132 {
133 	struct taskqueue *queue;
134 	char *tq_name;
135 
136 	tq_name = malloc(TASKQUEUE_NAMELEN, M_TASKQUEUE, mflags | M_ZERO);
137 	if (tq_name == NULL)
138 		return (NULL);
139 
140 	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
141 	if (queue == NULL) {
142 		free(tq_name, M_TASKQUEUE);
143 		return (NULL);
144 	}
145 
146 	snprintf(tq_name, TASKQUEUE_NAMELEN, "%s", (name) ? name : "taskqueue");
147 
148 	STAILQ_INIT(&queue->tq_queue);
149 	TAILQ_INIT(&queue->tq_active);
150 	queue->tq_enqueue = enqueue;
151 	queue->tq_context = context;
152 	queue->tq_name = tq_name;
153 	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
154 	queue->tq_flags |= TQ_FLAGS_ACTIVE;
155 	if (enqueue == taskqueue_fast_enqueue ||
156 	    enqueue == taskqueue_swi_enqueue ||
157 	    enqueue == taskqueue_swi_giant_enqueue ||
158 	    enqueue == taskqueue_thread_enqueue)
159 		queue->tq_flags |= TQ_FLAGS_UNLOCKED_ENQUEUE;
160 	mtx_init(&queue->tq_mutex, tq_name, NULL, mtxflags);
161 
162 	return (queue);
163 }
164 
165 struct taskqueue *
166 taskqueue_create(const char *name, int mflags,
167 		 taskqueue_enqueue_fn enqueue, void *context)
168 {
169 
170 	return _taskqueue_create(name, mflags, enqueue, context,
171 			MTX_DEF, name);
172 }
173 
174 void
175 taskqueue_set_callback(struct taskqueue *queue,
176     enum taskqueue_callback_type cb_type, taskqueue_callback_fn callback,
177     void *context)
178 {
179 
180 	KASSERT(((cb_type >= TASKQUEUE_CALLBACK_TYPE_MIN) &&
181 	    (cb_type <= TASKQUEUE_CALLBACK_TYPE_MAX)),
182 	    ("Callback type %d not valid, must be %d-%d", cb_type,
183 	    TASKQUEUE_CALLBACK_TYPE_MIN, TASKQUEUE_CALLBACK_TYPE_MAX));
184 	KASSERT((queue->tq_callbacks[cb_type] == NULL),
185 	    ("Re-initialization of taskqueue callback?"));
186 
187 	queue->tq_callbacks[cb_type] = callback;
188 	queue->tq_cb_contexts[cb_type] = context;
189 }
190 
191 /*
192  * Signal a taskqueue thread to terminate.
193  */
194 static void
195 taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
196 {
197 
198 	while (tq->tq_tcount > 0 || tq->tq_callouts > 0) {
199 		wakeup(tq);
200 		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
201 	}
202 }
203 
204 void
205 taskqueue_free(struct taskqueue *queue)
206 {
207 
208 	TQ_LOCK(queue);
209 	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
210 	taskqueue_terminate(queue->tq_threads, queue);
211 	KASSERT(TAILQ_EMPTY(&queue->tq_active), ("Tasks still running?"));
212 	KASSERT(queue->tq_callouts == 0, ("Armed timeout tasks"));
213 	mtx_destroy(&queue->tq_mutex);
214 	free(queue->tq_threads, M_TASKQUEUE);
215 	free(queue->tq_name, M_TASKQUEUE);
216 	free(queue, M_TASKQUEUE);
217 }
218 
219 static int
220 taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
221 {
222 	struct task *ins;
223 	struct task *prev;
224 
225 	KASSERT(task->ta_func != NULL, ("enqueueing task with NULL func"));
226 	/*
227 	 * Count multiple enqueues.
228 	 */
229 	if (task->ta_pending) {
230 		if (task->ta_pending < USHRT_MAX)
231 			task->ta_pending++;
232 		TQ_UNLOCK(queue);
233 		return (0);
234 	}
235 
236 	/*
237 	 * Optimise the case when all tasks have the same priority.
238 	 */
239 	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
240 	if (!prev || prev->ta_priority >= task->ta_priority) {
241 		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
242 	} else {
243 		prev = NULL;
244 		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
245 		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
246 			if (ins->ta_priority < task->ta_priority)
247 				break;
248 
249 		if (prev)
250 			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
251 		else
252 			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
253 	}
254 
255 	task->ta_pending = 1;
256 	if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) != 0)
257 		TQ_UNLOCK(queue);
258 	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
259 		queue->tq_enqueue(queue->tq_context);
260 	if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) == 0)
261 		TQ_UNLOCK(queue);
262 
263 	/* Return with lock released. */
264 	return (0);
265 }
266 
267 int
268 taskqueue_enqueue(struct taskqueue *queue, struct task *task)
269 {
270 	int res;
271 
272 	TQ_LOCK(queue);
273 	res = taskqueue_enqueue_locked(queue, task);
274 	/* The lock is released inside. */
275 
276 	return (res);
277 }
278 
279 static void
280 taskqueue_timeout_func(void *arg)
281 {
282 	struct taskqueue *queue;
283 	struct timeout_task *timeout_task;
284 
285 	timeout_task = arg;
286 	queue = timeout_task->q;
287 	KASSERT((timeout_task->f & DT_CALLOUT_ARMED) != 0, ("Stray timeout"));
288 	timeout_task->f &= ~DT_CALLOUT_ARMED;
289 	queue->tq_callouts--;
290 	taskqueue_enqueue_locked(timeout_task->q, &timeout_task->t);
291 	/* The lock is released inside. */
292 }
293 
294 int
295 taskqueue_enqueue_timeout(struct taskqueue *queue,
296     struct timeout_task *timeout_task, int ticks)
297 {
298 	int res;
299 
300 	TQ_LOCK(queue);
301 	KASSERT(timeout_task->q == NULL || timeout_task->q == queue,
302 	    ("Migrated queue"));
303 	KASSERT(!queue->tq_spin, ("Timeout for spin-queue"));
304 	timeout_task->q = queue;
305 	res = timeout_task->t.ta_pending;
306 	if (ticks == 0) {
307 		taskqueue_enqueue_locked(queue, &timeout_task->t);
308 		/* The lock is released inside. */
309 	} else {
310 		if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
311 			res++;
312 		} else {
313 			queue->tq_callouts++;
314 			timeout_task->f |= DT_CALLOUT_ARMED;
315 			if (ticks < 0)
316 				ticks = -ticks; /* Ignore overflow. */
317 		}
318 		if (ticks > 0) {
319 			callout_reset(&timeout_task->c, ticks,
320 			    taskqueue_timeout_func, timeout_task);
321 		}
322 		TQ_UNLOCK(queue);
323 	}
324 	return (res);
325 }
326 
327 static void
328 taskqueue_task_nop_fn(void *context, int pending)
329 {
330 }
331 
332 /*
333  * Block until all currently queued tasks in this taskqueue
334  * have begun execution.  Tasks queued during execution of
335  * this function are ignored.
336  */
337 static void
338 taskqueue_drain_tq_queue(struct taskqueue *queue)
339 {
340 	struct task t_barrier;
341 
342 	if (STAILQ_EMPTY(&queue->tq_queue))
343 		return;
344 
345 	/*
346 	 * Enqueue our barrier after all current tasks, but with
347 	 * the highest priority so that newly queued tasks cannot
348 	 * pass it.  Because of the high priority, we can not use
349 	 * taskqueue_enqueue_locked directly (which drops the lock
350 	 * anyway) so just insert it at tail while we have the
351 	 * queue lock.
352 	 */
353 	TASK_INIT(&t_barrier, USHRT_MAX, taskqueue_task_nop_fn, &t_barrier);
354 	STAILQ_INSERT_TAIL(&queue->tq_queue, &t_barrier, ta_link);
355 	t_barrier.ta_pending = 1;
356 
357 	/*
358 	 * Once the barrier has executed, all previously queued tasks
359 	 * have completed or are currently executing.
360 	 */
361 	while (t_barrier.ta_pending != 0)
362 		TQ_SLEEP(queue, &t_barrier, &queue->tq_mutex, PWAIT, "-", 0);
363 }
364 
365 /*
366  * Block until all currently executing tasks for this taskqueue
367  * complete.  Tasks that begin execution during the execution
368  * of this function are ignored.
369  */
370 static void
371 taskqueue_drain_tq_active(struct taskqueue *queue)
372 {
373 	struct taskqueue_busy tb_marker, *tb_first;
374 
375 	if (TAILQ_EMPTY(&queue->tq_active))
376 		return;
377 
378 	/* Block taskq_terminate().*/
379 	queue->tq_callouts++;
380 
381 	/*
382 	 * Wait for all currently executing taskqueue threads
383 	 * to go idle.
384 	 */
385 	tb_marker.tb_running = TB_DRAIN_WAITER;
386 	TAILQ_INSERT_TAIL(&queue->tq_active, &tb_marker, tb_link);
387 	while (TAILQ_FIRST(&queue->tq_active) != &tb_marker)
388 		TQ_SLEEP(queue, &tb_marker, &queue->tq_mutex, PWAIT, "-", 0);
389 	TAILQ_REMOVE(&queue->tq_active, &tb_marker, tb_link);
390 
391 	/*
392 	 * Wakeup any other drain waiter that happened to queue up
393 	 * without any intervening active thread.
394 	 */
395 	tb_first = TAILQ_FIRST(&queue->tq_active);
396 	if (tb_first != NULL && tb_first->tb_running == TB_DRAIN_WAITER)
397 		wakeup(tb_first);
398 
399 	/* Release taskqueue_terminate(). */
400 	queue->tq_callouts--;
401 	if ((queue->tq_flags & TQ_FLAGS_ACTIVE) == 0)
402 		wakeup_one(queue->tq_threads);
403 }
404 
405 void
406 taskqueue_block(struct taskqueue *queue)
407 {
408 
409 	TQ_LOCK(queue);
410 	queue->tq_flags |= TQ_FLAGS_BLOCKED;
411 	TQ_UNLOCK(queue);
412 }
413 
414 void
415 taskqueue_unblock(struct taskqueue *queue)
416 {
417 
418 	TQ_LOCK(queue);
419 	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
420 	if (!STAILQ_EMPTY(&queue->tq_queue))
421 		queue->tq_enqueue(queue->tq_context);
422 	TQ_UNLOCK(queue);
423 }
424 
425 static void
426 taskqueue_run_locked(struct taskqueue *queue)
427 {
428 	struct taskqueue_busy tb;
429 	struct taskqueue_busy *tb_first;
430 	struct task *task;
431 	int pending;
432 
433 	KASSERT(queue != NULL, ("tq is NULL"));
434 	TQ_ASSERT_LOCKED(queue);
435 	tb.tb_running = NULL;
436 
437 	while (STAILQ_FIRST(&queue->tq_queue)) {
438 		TAILQ_INSERT_TAIL(&queue->tq_active, &tb, tb_link);
439 
440 		/*
441 		 * Carefully remove the first task from the queue and
442 		 * zero its pending count.
443 		 */
444 		task = STAILQ_FIRST(&queue->tq_queue);
445 		KASSERT(task != NULL, ("task is NULL"));
446 		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
447 		pending = task->ta_pending;
448 		task->ta_pending = 0;
449 		tb.tb_running = task;
450 		TQ_UNLOCK(queue);
451 
452 		KASSERT(task->ta_func != NULL, ("task->ta_func is NULL"));
453 		task->ta_func(task->ta_context, pending);
454 
455 		TQ_LOCK(queue);
456 		tb.tb_running = NULL;
457 		wakeup(task);
458 
459 		TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
460 		tb_first = TAILQ_FIRST(&queue->tq_active);
461 		if (tb_first != NULL &&
462 		    tb_first->tb_running == TB_DRAIN_WAITER)
463 			wakeup(tb_first);
464 	}
465 }
466 
467 void
468 taskqueue_run(struct taskqueue *queue)
469 {
470 
471 	TQ_LOCK(queue);
472 	taskqueue_run_locked(queue);
473 	TQ_UNLOCK(queue);
474 }
475 
476 static int
477 task_is_running(struct taskqueue *queue, struct task *task)
478 {
479 	struct taskqueue_busy *tb;
480 
481 	TQ_ASSERT_LOCKED(queue);
482 	TAILQ_FOREACH(tb, &queue->tq_active, tb_link) {
483 		if (tb->tb_running == task)
484 			return (1);
485 	}
486 	return (0);
487 }
488 
489 static int
490 taskqueue_cancel_locked(struct taskqueue *queue, struct task *task,
491     u_int *pendp)
492 {
493 
494 	if (task->ta_pending > 0)
495 		STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
496 	if (pendp != NULL)
497 		*pendp = task->ta_pending;
498 	task->ta_pending = 0;
499 	return (task_is_running(queue, task) ? EBUSY : 0);
500 }
501 
502 int
503 taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
504 {
505 	int error;
506 
507 	TQ_LOCK(queue);
508 	error = taskqueue_cancel_locked(queue, task, pendp);
509 	TQ_UNLOCK(queue);
510 
511 	return (error);
512 }
513 
514 int
515 taskqueue_cancel_timeout(struct taskqueue *queue,
516     struct timeout_task *timeout_task, u_int *pendp)
517 {
518 	u_int pending, pending1;
519 	int error;
520 
521 	TQ_LOCK(queue);
522 	pending = !!(callout_stop(&timeout_task->c) > 0);
523 	error = taskqueue_cancel_locked(queue, &timeout_task->t, &pending1);
524 	if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
525 		timeout_task->f &= ~DT_CALLOUT_ARMED;
526 		queue->tq_callouts--;
527 	}
528 	TQ_UNLOCK(queue);
529 
530 	if (pendp != NULL)
531 		*pendp = pending + pending1;
532 	return (error);
533 }
534 
535 void
536 taskqueue_drain(struct taskqueue *queue, struct task *task)
537 {
538 
539 	if (!queue->tq_spin)
540 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
541 
542 	TQ_LOCK(queue);
543 	while (task->ta_pending != 0 || task_is_running(queue, task))
544 		TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
545 	TQ_UNLOCK(queue);
546 }
547 
548 void
549 taskqueue_drain_all(struct taskqueue *queue)
550 {
551 
552 	if (!queue->tq_spin)
553 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
554 
555 	TQ_LOCK(queue);
556 	taskqueue_drain_tq_queue(queue);
557 	taskqueue_drain_tq_active(queue);
558 	TQ_UNLOCK(queue);
559 }
560 
561 void
562 taskqueue_drain_timeout(struct taskqueue *queue,
563     struct timeout_task *timeout_task)
564 {
565 
566 	callout_drain(&timeout_task->c);
567 	taskqueue_drain(queue, &timeout_task->t);
568 }
569 
570 static void
571 taskqueue_swi_enqueue(void *context)
572 {
573 	swi_sched(taskqueue_ih, 0);
574 }
575 
576 static void
577 taskqueue_swi_run(void *dummy)
578 {
579 	taskqueue_run(taskqueue_swi);
580 }
581 
582 static void
583 taskqueue_swi_giant_enqueue(void *context)
584 {
585 	swi_sched(taskqueue_giant_ih, 0);
586 }
587 
588 static void
589 taskqueue_swi_giant_run(void *dummy)
590 {
591 	taskqueue_run(taskqueue_swi_giant);
592 }
593 
594 #ifndef FSTACK
595 static int
596 _taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
597     cpuset_t *mask, const char *name, va_list ap)
598 {
599 	char ktname[MAXCOMLEN + 1];
600 	struct thread *td;
601 	struct taskqueue *tq;
602 	int i, error;
603 
604 	if (count <= 0)
605 		return (EINVAL);
606 
607 	vsnprintf(ktname, sizeof(ktname), name, ap);
608 	tq = *tqp;
609 
610 	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
611 	    M_NOWAIT | M_ZERO);
612 	if (tq->tq_threads == NULL) {
613 		printf("%s: no memory for %s threads\n", __func__, ktname);
614 		return (ENOMEM);
615 	}
616 
617 	for (i = 0; i < count; i++) {
618 		if (count == 1)
619 			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
620 			    &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
621 		else
622 			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
623 			    &tq->tq_threads[i], RFSTOPPED, 0,
624 			    "%s_%d", ktname, i);
625 		if (error) {
626 			/* should be ok to continue, taskqueue_free will dtrt */
627 			printf("%s: kthread_add(%s): error %d", __func__,
628 			    ktname, error);
629 			tq->tq_threads[i] = NULL;		/* paranoid */
630 		} else
631 			tq->tq_tcount++;
632 	}
633 	for (i = 0; i < count; i++) {
634 		if (tq->tq_threads[i] == NULL)
635 			continue;
636 		td = tq->tq_threads[i];
637 		if (mask) {
638 			error = cpuset_setthread(td->td_tid, mask);
639 			/*
640 			 * Failing to pin is rarely an actual fatal error;
641 			 * it'll just affect performance.
642 			 */
643 			if (error)
644 				printf("%s: curthread=%llu: can't pin; "
645 				    "error=%d\n",
646 				    __func__,
647 				    (unsigned long long) td->td_tid,
648 				    error);
649 		}
650 		thread_lock(td);
651 		sched_prio(td, pri);
652 		sched_add(td, SRQ_BORING);
653 		thread_unlock(td);
654 	}
655 
656 	return (0);
657 }
658 #endif
659 
660 int
661 taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
662     const char *name, ...)
663 {
664 #ifndef FSTACK
665 	va_list ap;
666 	int error;
667 
668 	va_start(ap, name);
669 	error = _taskqueue_start_threads(tqp, count, pri, NULL, name, ap);
670 	va_end(ap);
671 	return (error);
672 #else
673     return (0);
674 #endif
675 }
676 
677 int
678 taskqueue_start_threads_cpuset(struct taskqueue **tqp, int count, int pri,
679     cpuset_t *mask, const char *name, ...)
680 {
681 #ifndef FSTACK
682 	va_list ap;
683 	int error;
684 
685 	va_start(ap, name);
686 	error = _taskqueue_start_threads(tqp, count, pri, mask, name, ap);
687 	va_end(ap);
688 	return (error);
689 #else
690     return (0);
691 #endif
692 }
693 
694 static inline void
695 taskqueue_run_callback(struct taskqueue *tq,
696     enum taskqueue_callback_type cb_type)
697 {
698 	taskqueue_callback_fn tq_callback;
699 
700 	TQ_ASSERT_UNLOCKED(tq);
701 	tq_callback = tq->tq_callbacks[cb_type];
702 	if (tq_callback != NULL)
703 		tq_callback(tq->tq_cb_contexts[cb_type]);
704 }
705 
706 void
707 taskqueue_thread_loop(void *arg)
708 {
709 	struct taskqueue **tqp, *tq;
710 
711 	tqp = arg;
712 	tq = *tqp;
713 	taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_INIT);
714 	TQ_LOCK(tq);
715 	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
716 		/* XXX ? */
717 		taskqueue_run_locked(tq);
718 		/*
719 		 * Because taskqueue_run() can drop tq_mutex, we need to
720 		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
721 		 * meantime, which means we missed a wakeup.
722 		 */
723 		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
724 			break;
725 		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
726 	}
727 	taskqueue_run_locked(tq);
728 	/*
729 	 * This thread is on its way out, so just drop the lock temporarily
730 	 * in order to call the shutdown callback.  This allows the callback
731 	 * to look at the taskqueue, even just before it dies.
732 	 */
733 	TQ_UNLOCK(tq);
734 	taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_SHUTDOWN);
735 	TQ_LOCK(tq);
736 
737 	/* rendezvous with thread that asked us to terminate */
738 	tq->tq_tcount--;
739 	wakeup_one(tq->tq_threads);
740 	TQ_UNLOCK(tq);
741 	kthread_exit();
742 }
743 
744 void
745 taskqueue_thread_enqueue(void *context)
746 {
747 	struct taskqueue **tqp, *tq;
748 
749 	tqp = context;
750 	tq = *tqp;
751 	wakeup_one(tq);
752 }
753 
754 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
755 		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
756 		     INTR_MPSAFE, &taskqueue_ih));
757 
758 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
759 		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
760 		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
761 
762 TASKQUEUE_DEFINE_THREAD(thread);
763 
764 struct taskqueue *
765 taskqueue_create_fast(const char *name, int mflags,
766 		 taskqueue_enqueue_fn enqueue, void *context)
767 {
768 	return _taskqueue_create(name, mflags, enqueue, context,
769 			MTX_SPIN, "fast_taskqueue");
770 }
771 
772 static void	*taskqueue_fast_ih;
773 
774 static void
775 taskqueue_fast_enqueue(void *context)
776 {
777 	swi_sched(taskqueue_fast_ih, 0);
778 }
779 
780 static void
781 taskqueue_fast_run(void *dummy)
782 {
783 	taskqueue_run(taskqueue_fast);
784 }
785 
786 TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
787 	swi_add(NULL, "fast taskq", taskqueue_fast_run, NULL,
788 	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
789 
790 int
791 taskqueue_member(struct taskqueue *queue, struct thread *td)
792 {
793 	int i, j, ret = 0;
794 
795 	for (i = 0, j = 0; ; i++) {
796 		if (queue->tq_threads[i] == NULL)
797 			continue;
798 		if (queue->tq_threads[i] == td) {
799 			ret = 1;
800 			break;
801 		}
802 		if (++j >= queue->tq_tcount)
803 			break;
804 	}
805 	return (ret);
806 }
807