xref: /freebsd/sys/kern/subr_taskqueue.c (revision 5477372324b92240a96310ef2d45fa44ce8d0a93)
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 #define	DT_DRAIN_IN_PROGRESS	(1 << 1)
85 
86 #define	TQ_LOCK(tq)							\
87 	do {								\
88 		if ((tq)->tq_spin)					\
89 			mtx_lock_spin(&(tq)->tq_mutex);			\
90 		else							\
91 			mtx_lock(&(tq)->tq_mutex);			\
92 	} while (0)
93 #define	TQ_ASSERT_LOCKED(tq)	mtx_assert(&(tq)->tq_mutex, MA_OWNED)
94 
95 #define	TQ_UNLOCK(tq)							\
96 	do {								\
97 		if ((tq)->tq_spin)					\
98 			mtx_unlock_spin(&(tq)->tq_mutex);		\
99 		else							\
100 			mtx_unlock(&(tq)->tq_mutex);			\
101 	} while (0)
102 #define	TQ_ASSERT_UNLOCKED(tq)	mtx_assert(&(tq)->tq_mutex, MA_NOTOWNED)
103 
104 void
105 _timeout_task_init(struct taskqueue *queue, struct timeout_task *timeout_task,
106     int priority, task_fn_t func, void *context)
107 {
108 
109 	TASK_INIT(&timeout_task->t, priority, func, context);
110 	callout_init_mtx(&timeout_task->c, &queue->tq_mutex,
111 	    CALLOUT_RETURNUNLOCKED);
112 	timeout_task->q = queue;
113 	timeout_task->f = 0;
114 }
115 
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 
125 static struct taskqueue *
126 _taskqueue_create(const char *name, int mflags,
127 		 taskqueue_enqueue_fn enqueue, void *context,
128 		 int mtxflags, const char *mtxname __unused)
129 {
130 	struct taskqueue *queue;
131 	char *tq_name;
132 
133 	tq_name = malloc(TASKQUEUE_NAMELEN, M_TASKQUEUE, mflags | M_ZERO);
134 	if (tq_name == NULL)
135 		return (NULL);
136 
137 	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
138 	if (queue == NULL) {
139 		free(tq_name, M_TASKQUEUE);
140 		return (NULL);
141 	}
142 
143 	snprintf(tq_name, TASKQUEUE_NAMELEN, "%s", (name) ? name : "taskqueue");
144 
145 	STAILQ_INIT(&queue->tq_queue);
146 	TAILQ_INIT(&queue->tq_active);
147 	queue->tq_enqueue = enqueue;
148 	queue->tq_context = context;
149 	queue->tq_name = tq_name;
150 	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
151 	queue->tq_flags |= TQ_FLAGS_ACTIVE;
152 	if (enqueue == taskqueue_fast_enqueue ||
153 	    enqueue == taskqueue_swi_enqueue ||
154 	    enqueue == taskqueue_swi_giant_enqueue ||
155 	    enqueue == taskqueue_thread_enqueue)
156 		queue->tq_flags |= TQ_FLAGS_UNLOCKED_ENQUEUE;
157 	mtx_init(&queue->tq_mutex, tq_name, NULL, mtxflags);
158 
159 	return (queue);
160 }
161 
162 struct taskqueue *
163 taskqueue_create(const char *name, int mflags,
164 		 taskqueue_enqueue_fn enqueue, void *context)
165 {
166 
167 	return _taskqueue_create(name, mflags, enqueue, context,
168 			MTX_DEF, name);
169 }
170 
171 void
172 taskqueue_set_callback(struct taskqueue *queue,
173     enum taskqueue_callback_type cb_type, taskqueue_callback_fn callback,
174     void *context)
175 {
176 
177 	KASSERT(((cb_type >= TASKQUEUE_CALLBACK_TYPE_MIN) &&
178 	    (cb_type <= TASKQUEUE_CALLBACK_TYPE_MAX)),
179 	    ("Callback type %d not valid, must be %d-%d", cb_type,
180 	    TASKQUEUE_CALLBACK_TYPE_MIN, TASKQUEUE_CALLBACK_TYPE_MAX));
181 	KASSERT((queue->tq_callbacks[cb_type] == NULL),
182 	    ("Re-initialization of taskqueue callback?"));
183 
184 	queue->tq_callbacks[cb_type] = callback;
185 	queue->tq_cb_contexts[cb_type] = context;
186 }
187 
188 /*
189  * Signal a taskqueue thread to terminate.
190  */
191 static void
192 taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
193 {
194 
195 	while (tq->tq_tcount > 0 || tq->tq_callouts > 0) {
196 		wakeup(tq);
197 		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
198 	}
199 }
200 
201 void
202 taskqueue_free(struct taskqueue *queue)
203 {
204 
205 	TQ_LOCK(queue);
206 	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
207 	taskqueue_terminate(queue->tq_threads, queue);
208 	KASSERT(TAILQ_EMPTY(&queue->tq_active), ("Tasks still running?"));
209 	KASSERT(queue->tq_callouts == 0, ("Armed timeout tasks"));
210 	mtx_destroy(&queue->tq_mutex);
211 	free(queue->tq_threads, M_TASKQUEUE);
212 	free(queue->tq_name, M_TASKQUEUE);
213 	free(queue, M_TASKQUEUE);
214 }
215 
216 static int
217 taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
218 {
219 	struct task *ins;
220 	struct task *prev;
221 
222 	KASSERT(task->ta_func != NULL, ("enqueueing task with NULL func"));
223 	/*
224 	 * Count multiple enqueues.
225 	 */
226 	if (task->ta_pending) {
227 		if (task->ta_pending < USHRT_MAX)
228 			task->ta_pending++;
229 		TQ_UNLOCK(queue);
230 		return (0);
231 	}
232 
233 	/*
234 	 * Optimise the case when all tasks have the same priority.
235 	 */
236 	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
237 	if (!prev || prev->ta_priority >= task->ta_priority) {
238 		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
239 	} else {
240 		prev = NULL;
241 		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
242 		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
243 			if (ins->ta_priority < task->ta_priority)
244 				break;
245 
246 		if (prev)
247 			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
248 		else
249 			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
250 	}
251 
252 	task->ta_pending = 1;
253 	if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) != 0)
254 		TQ_UNLOCK(queue);
255 	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
256 		queue->tq_enqueue(queue->tq_context);
257 	if ((queue->tq_flags & TQ_FLAGS_UNLOCKED_ENQUEUE) == 0)
258 		TQ_UNLOCK(queue);
259 
260 	/* Return with lock released. */
261 	return (0);
262 }
263 
264 int
265 taskqueue_enqueue(struct taskqueue *queue, struct task *task)
266 {
267 	int res;
268 
269 	TQ_LOCK(queue);
270 	res = taskqueue_enqueue_locked(queue, task);
271 	/* The lock is released inside. */
272 
273 	return (res);
274 }
275 
276 static void
277 taskqueue_timeout_func(void *arg)
278 {
279 	struct taskqueue *queue;
280 	struct timeout_task *timeout_task;
281 
282 	timeout_task = arg;
283 	queue = timeout_task->q;
284 	KASSERT((timeout_task->f & DT_CALLOUT_ARMED) != 0, ("Stray timeout"));
285 	timeout_task->f &= ~DT_CALLOUT_ARMED;
286 	queue->tq_callouts--;
287 	taskqueue_enqueue_locked(timeout_task->q, &timeout_task->t);
288 	/* The lock is released inside. */
289 }
290 
291 int
292 taskqueue_enqueue_timeout(struct taskqueue *queue,
293     struct timeout_task *timeout_task, int ticks)
294 {
295 	int res;
296 
297 	TQ_LOCK(queue);
298 	KASSERT(timeout_task->q == NULL || timeout_task->q == queue,
299 	    ("Migrated queue"));
300 	KASSERT(!queue->tq_spin, ("Timeout for spin-queue"));
301 	timeout_task->q = queue;
302 	res = timeout_task->t.ta_pending;
303 	if (timeout_task->f & DT_DRAIN_IN_PROGRESS) {
304 		/* Do nothing */
305 		TQ_UNLOCK(queue);
306 		res = -1;
307 	} else if (ticks == 0) {
308 		taskqueue_enqueue_locked(queue, &timeout_task->t);
309 		/* The lock is released inside. */
310 	} else {
311 		if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
312 			res++;
313 		} else {
314 			queue->tq_callouts++;
315 			timeout_task->f |= DT_CALLOUT_ARMED;
316 			if (ticks < 0)
317 				ticks = -ticks; /* Ignore overflow. */
318 		}
319 		if (ticks > 0) {
320 			callout_reset(&timeout_task->c, ticks,
321 			    taskqueue_timeout_func, timeout_task);
322 		}
323 		TQ_UNLOCK(queue);
324 	}
325 	return (res);
326 }
327 
328 static void
329 taskqueue_task_nop_fn(void *context, int pending)
330 {
331 }
332 
333 /*
334  * Block until all currently queued tasks in this taskqueue
335  * have begun execution.  Tasks queued during execution of
336  * this function are ignored.
337  */
338 static void
339 taskqueue_drain_tq_queue(struct taskqueue *queue)
340 {
341 	struct task t_barrier;
342 
343 	if (STAILQ_EMPTY(&queue->tq_queue))
344 		return;
345 
346 	/*
347 	 * Enqueue our barrier after all current tasks, but with
348 	 * the highest priority so that newly queued tasks cannot
349 	 * pass it.  Because of the high priority, we can not use
350 	 * taskqueue_enqueue_locked directly (which drops the lock
351 	 * anyway) so just insert it at tail while we have the
352 	 * queue lock.
353 	 */
354 	TASK_INIT(&t_barrier, USHRT_MAX, taskqueue_task_nop_fn, &t_barrier);
355 	STAILQ_INSERT_TAIL(&queue->tq_queue, &t_barrier, ta_link);
356 	t_barrier.ta_pending = 1;
357 
358 	/*
359 	 * Once the barrier has executed, all previously queued tasks
360 	 * have completed or are currently executing.
361 	 */
362 	while (t_barrier.ta_pending != 0)
363 		TQ_SLEEP(queue, &t_barrier, &queue->tq_mutex, PWAIT, "-", 0);
364 }
365 
366 /*
367  * Block until all currently executing tasks for this taskqueue
368  * complete.  Tasks that begin execution during the execution
369  * of this function are ignored.
370  */
371 static void
372 taskqueue_drain_tq_active(struct taskqueue *queue)
373 {
374 	struct taskqueue_busy tb_marker, *tb_first;
375 
376 	if (TAILQ_EMPTY(&queue->tq_active))
377 		return;
378 
379 	/* Block taskq_terminate().*/
380 	queue->tq_callouts++;
381 
382 	/*
383 	 * Wait for all currently executing taskqueue threads
384 	 * to go idle.
385 	 */
386 	tb_marker.tb_running = TB_DRAIN_WAITER;
387 	TAILQ_INSERT_TAIL(&queue->tq_active, &tb_marker, tb_link);
388 	while (TAILQ_FIRST(&queue->tq_active) != &tb_marker)
389 		TQ_SLEEP(queue, &tb_marker, &queue->tq_mutex, PWAIT, "-", 0);
390 	TAILQ_REMOVE(&queue->tq_active, &tb_marker, tb_link);
391 
392 	/*
393 	 * Wakeup any other drain waiter that happened to queue up
394 	 * without any intervening active thread.
395 	 */
396 	tb_first = TAILQ_FIRST(&queue->tq_active);
397 	if (tb_first != NULL && tb_first->tb_running == TB_DRAIN_WAITER)
398 		wakeup(tb_first);
399 
400 	/* Release taskqueue_terminate(). */
401 	queue->tq_callouts--;
402 	if ((queue->tq_flags & TQ_FLAGS_ACTIVE) == 0)
403 		wakeup_one(queue->tq_threads);
404 }
405 
406 void
407 taskqueue_block(struct taskqueue *queue)
408 {
409 
410 	TQ_LOCK(queue);
411 	queue->tq_flags |= TQ_FLAGS_BLOCKED;
412 	TQ_UNLOCK(queue);
413 }
414 
415 void
416 taskqueue_unblock(struct taskqueue *queue)
417 {
418 
419 	TQ_LOCK(queue);
420 	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
421 	if (!STAILQ_EMPTY(&queue->tq_queue))
422 		queue->tq_enqueue(queue->tq_context);
423 	TQ_UNLOCK(queue);
424 }
425 
426 static void
427 taskqueue_run_locked(struct taskqueue *queue)
428 {
429 	struct taskqueue_busy tb;
430 	struct taskqueue_busy *tb_first;
431 	struct task *task;
432 	int pending;
433 
434 	KASSERT(queue != NULL, ("tq is NULL"));
435 	TQ_ASSERT_LOCKED(queue);
436 	tb.tb_running = NULL;
437 
438 	while (STAILQ_FIRST(&queue->tq_queue)) {
439 		TAILQ_INSERT_TAIL(&queue->tq_active, &tb, tb_link);
440 
441 		/*
442 		 * Carefully remove the first task from the queue and
443 		 * zero its pending count.
444 		 */
445 		task = STAILQ_FIRST(&queue->tq_queue);
446 		KASSERT(task != NULL, ("task is NULL"));
447 		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
448 		pending = task->ta_pending;
449 		task->ta_pending = 0;
450 		tb.tb_running = task;
451 		TQ_UNLOCK(queue);
452 
453 		KASSERT(task->ta_func != NULL, ("task->ta_func is NULL"));
454 		task->ta_func(task->ta_context, pending);
455 
456 		TQ_LOCK(queue);
457 		tb.tb_running = NULL;
458 		wakeup(task);
459 
460 		TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
461 		tb_first = TAILQ_FIRST(&queue->tq_active);
462 		if (tb_first != NULL &&
463 		    tb_first->tb_running == TB_DRAIN_WAITER)
464 			wakeup(tb_first);
465 	}
466 }
467 
468 void
469 taskqueue_run(struct taskqueue *queue)
470 {
471 
472 	TQ_LOCK(queue);
473 	taskqueue_run_locked(queue);
474 	TQ_UNLOCK(queue);
475 }
476 
477 static int
478 task_is_running(struct taskqueue *queue, struct task *task)
479 {
480 	struct taskqueue_busy *tb;
481 
482 	TQ_ASSERT_LOCKED(queue);
483 	TAILQ_FOREACH(tb, &queue->tq_active, tb_link) {
484 		if (tb->tb_running == task)
485 			return (1);
486 	}
487 	return (0);
488 }
489 
490 /*
491  * Only use this function in single threaded contexts. It returns
492  * non-zero if the given task is either pending or running. Else the
493  * task is idle and can be queued again or freed.
494  */
495 int
496 taskqueue_poll_is_busy(struct taskqueue *queue, struct task *task)
497 {
498 	int retval;
499 
500 	TQ_LOCK(queue);
501 	retval = task->ta_pending > 0 || task_is_running(queue, task);
502 	TQ_UNLOCK(queue);
503 
504 	return (retval);
505 }
506 
507 static int
508 taskqueue_cancel_locked(struct taskqueue *queue, struct task *task,
509     u_int *pendp)
510 {
511 
512 	if (task->ta_pending > 0)
513 		STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
514 	if (pendp != NULL)
515 		*pendp = task->ta_pending;
516 	task->ta_pending = 0;
517 	return (task_is_running(queue, task) ? EBUSY : 0);
518 }
519 
520 int
521 taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
522 {
523 	int error;
524 
525 	TQ_LOCK(queue);
526 	error = taskqueue_cancel_locked(queue, task, pendp);
527 	TQ_UNLOCK(queue);
528 
529 	return (error);
530 }
531 
532 int
533 taskqueue_cancel_timeout(struct taskqueue *queue,
534     struct timeout_task *timeout_task, u_int *pendp)
535 {
536 	u_int pending, pending1;
537 	int error;
538 
539 	TQ_LOCK(queue);
540 	pending = !!(callout_stop(&timeout_task->c) > 0);
541 	error = taskqueue_cancel_locked(queue, &timeout_task->t, &pending1);
542 	if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) {
543 		timeout_task->f &= ~DT_CALLOUT_ARMED;
544 		queue->tq_callouts--;
545 	}
546 	TQ_UNLOCK(queue);
547 
548 	if (pendp != NULL)
549 		*pendp = pending + pending1;
550 	return (error);
551 }
552 
553 void
554 taskqueue_drain(struct taskqueue *queue, struct task *task)
555 {
556 
557 	if (!queue->tq_spin)
558 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
559 
560 	TQ_LOCK(queue);
561 	while (task->ta_pending != 0 || task_is_running(queue, task))
562 		TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
563 	TQ_UNLOCK(queue);
564 }
565 
566 void
567 taskqueue_drain_all(struct taskqueue *queue)
568 {
569 
570 	if (!queue->tq_spin)
571 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
572 
573 	TQ_LOCK(queue);
574 	taskqueue_drain_tq_queue(queue);
575 	taskqueue_drain_tq_active(queue);
576 	TQ_UNLOCK(queue);
577 }
578 
579 void
580 taskqueue_drain_timeout(struct taskqueue *queue,
581     struct timeout_task *timeout_task)
582 {
583 
584 	/*
585 	 * Set flag to prevent timer from re-starting during drain:
586 	 */
587 	TQ_LOCK(queue);
588 	KASSERT((timeout_task->f & DT_DRAIN_IN_PROGRESS) == 0,
589 	    ("Drain already in progress"));
590 	timeout_task->f |= DT_DRAIN_IN_PROGRESS;
591 	TQ_UNLOCK(queue);
592 
593 	callout_drain(&timeout_task->c);
594 	taskqueue_drain(queue, &timeout_task->t);
595 
596 	/*
597 	 * Clear flag to allow timer to re-start:
598 	 */
599 	TQ_LOCK(queue);
600 	timeout_task->f &= ~DT_DRAIN_IN_PROGRESS;
601 	TQ_UNLOCK(queue);
602 }
603 
604 static void
605 taskqueue_swi_enqueue(void *context)
606 {
607 	swi_sched(taskqueue_ih, 0);
608 }
609 
610 static void
611 taskqueue_swi_run(void *dummy)
612 {
613 	taskqueue_run(taskqueue_swi);
614 }
615 
616 static void
617 taskqueue_swi_giant_enqueue(void *context)
618 {
619 	swi_sched(taskqueue_giant_ih, 0);
620 }
621 
622 static void
623 taskqueue_swi_giant_run(void *dummy)
624 {
625 	taskqueue_run(taskqueue_swi_giant);
626 }
627 
628 static int
629 _taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
630     cpuset_t *mask, const char *name, va_list ap)
631 {
632 	char ktname[MAXCOMLEN + 1];
633 	struct thread *td;
634 	struct taskqueue *tq;
635 	int i, error;
636 
637 	if (count <= 0)
638 		return (EINVAL);
639 
640 	vsnprintf(ktname, sizeof(ktname), name, ap);
641 	tq = *tqp;
642 
643 	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
644 	    M_NOWAIT | M_ZERO);
645 	if (tq->tq_threads == NULL) {
646 		printf("%s: no memory for %s threads\n", __func__, ktname);
647 		return (ENOMEM);
648 	}
649 
650 	for (i = 0; i < count; i++) {
651 		if (count == 1)
652 			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
653 			    &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
654 		else
655 			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
656 			    &tq->tq_threads[i], RFSTOPPED, 0,
657 			    "%s_%d", ktname, i);
658 		if (error) {
659 			/* should be ok to continue, taskqueue_free will dtrt */
660 			printf("%s: kthread_add(%s): error %d", __func__,
661 			    ktname, error);
662 			tq->tq_threads[i] = NULL;		/* paranoid */
663 		} else
664 			tq->tq_tcount++;
665 	}
666 	if (tq->tq_tcount == 0) {
667 		free(tq->tq_threads, M_TASKQUEUE);
668 		tq->tq_threads = NULL;
669 		return (ENOMEM);
670 	}
671 	for (i = 0; i < count; i++) {
672 		if (tq->tq_threads[i] == NULL)
673 			continue;
674 		td = tq->tq_threads[i];
675 		if (mask) {
676 			error = cpuset_setthread(td->td_tid, mask);
677 			/*
678 			 * Failing to pin is rarely an actual fatal error;
679 			 * it'll just affect performance.
680 			 */
681 			if (error)
682 				printf("%s: curthread=%llu: can't pin; "
683 				    "error=%d\n",
684 				    __func__,
685 				    (unsigned long long) td->td_tid,
686 				    error);
687 		}
688 		thread_lock(td);
689 		sched_prio(td, pri);
690 		sched_add(td, SRQ_BORING);
691 		thread_unlock(td);
692 	}
693 
694 	return (0);
695 }
696 
697 int
698 taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
699     const char *name, ...)
700 {
701 	va_list ap;
702 	int error;
703 
704 	va_start(ap, name);
705 	error = _taskqueue_start_threads(tqp, count, pri, NULL, name, ap);
706 	va_end(ap);
707 	return (error);
708 }
709 
710 int
711 taskqueue_start_threads_cpuset(struct taskqueue **tqp, int count, int pri,
712     cpuset_t *mask, const char *name, ...)
713 {
714 	va_list ap;
715 	int error;
716 
717 	va_start(ap, name);
718 	error = _taskqueue_start_threads(tqp, count, pri, mask, name, ap);
719 	va_end(ap);
720 	return (error);
721 }
722 
723 static inline void
724 taskqueue_run_callback(struct taskqueue *tq,
725     enum taskqueue_callback_type cb_type)
726 {
727 	taskqueue_callback_fn tq_callback;
728 
729 	TQ_ASSERT_UNLOCKED(tq);
730 	tq_callback = tq->tq_callbacks[cb_type];
731 	if (tq_callback != NULL)
732 		tq_callback(tq->tq_cb_contexts[cb_type]);
733 }
734 
735 void
736 taskqueue_thread_loop(void *arg)
737 {
738 	struct taskqueue **tqp, *tq;
739 
740 	tqp = arg;
741 	tq = *tqp;
742 	taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_INIT);
743 	TQ_LOCK(tq);
744 	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
745 		/* XXX ? */
746 		taskqueue_run_locked(tq);
747 		/*
748 		 * Because taskqueue_run() can drop tq_mutex, we need to
749 		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
750 		 * meantime, which means we missed a wakeup.
751 		 */
752 		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
753 			break;
754 		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
755 	}
756 	taskqueue_run_locked(tq);
757 	/*
758 	 * This thread is on its way out, so just drop the lock temporarily
759 	 * in order to call the shutdown callback.  This allows the callback
760 	 * to look at the taskqueue, even just before it dies.
761 	 */
762 	TQ_UNLOCK(tq);
763 	taskqueue_run_callback(tq, TASKQUEUE_CALLBACK_TYPE_SHUTDOWN);
764 	TQ_LOCK(tq);
765 
766 	/* rendezvous with thread that asked us to terminate */
767 	tq->tq_tcount--;
768 	wakeup_one(tq->tq_threads);
769 	TQ_UNLOCK(tq);
770 	kthread_exit();
771 }
772 
773 void
774 taskqueue_thread_enqueue(void *context)
775 {
776 	struct taskqueue **tqp, *tq;
777 
778 	tqp = context;
779 	tq = *tqp;
780 	wakeup_one(tq);
781 }
782 
783 TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
784 		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
785 		     INTR_MPSAFE, &taskqueue_ih));
786 
787 TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
788 		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
789 		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
790 
791 TASKQUEUE_DEFINE_THREAD(thread);
792 
793 struct taskqueue *
794 taskqueue_create_fast(const char *name, int mflags,
795 		 taskqueue_enqueue_fn enqueue, void *context)
796 {
797 	return _taskqueue_create(name, mflags, enqueue, context,
798 			MTX_SPIN, "fast_taskqueue");
799 }
800 
801 static void	*taskqueue_fast_ih;
802 
803 static void
804 taskqueue_fast_enqueue(void *context)
805 {
806 	swi_sched(taskqueue_fast_ih, 0);
807 }
808 
809 static void
810 taskqueue_fast_run(void *dummy)
811 {
812 	taskqueue_run(taskqueue_fast);
813 }
814 
815 TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
816 	swi_add(NULL, "fast taskq", taskqueue_fast_run, NULL,
817 	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
818 
819 int
820 taskqueue_member(struct taskqueue *queue, struct thread *td)
821 {
822 	int i, j, ret = 0;
823 
824 	for (i = 0, j = 0; ; i++) {
825 		if (queue->tq_threads[i] == NULL)
826 			continue;
827 		if (queue->tq_threads[i] == td) {
828 			ret = 1;
829 			break;
830 		}
831 		if (++j >= queue->tq_tcount)
832 			break;
833 	}
834 	return (ret);
835 }
836