subr_taskqueue.c revision 208623 
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: head/sys/kern/subr_taskqueue.c 208623 2010-05-28 18:15:28Z zml $");
29
30#include <sys/param.h>
31#include <sys/systm.h>
32#include <sys/bus.h>
33#include <sys/interrupt.h>
34#include <sys/kernel.h>
35#include <sys/kthread.h>
36#include <sys/lock.h>
37#include <sys/malloc.h>
38#include <sys/mutex.h>
39#include <sys/proc.h>
40#include <sys/sched.h>
41#include <sys/taskqueue.h>
42#include <sys/unistd.h>
43#include <machine/stdarg.h>
44
45static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
46static void	*taskqueue_giant_ih;
47static void	*taskqueue_ih;
48
49struct taskqueue {
50	STAILQ_HEAD(, task)	tq_queue;
51	const char		*tq_name;
52	taskqueue_enqueue_fn	tq_enqueue;
53	void			*tq_context;
54	struct mtx		tq_mutex;
55	struct thread		**tq_threads;
56	int			tq_tcount;
57	int			tq_spin;
58	int			tq_flags;
59	int			tq_tasks_running;
60};
61
62#define	TQ_FLAGS_ACTIVE		(1 << 0)
63#define	TQ_FLAGS_BLOCKED	(1 << 1)
64#define	TQ_FLAGS_PENDING	(1 << 2)
65
66static __inline void
67TQ_LOCK(struct taskqueue *tq)
68{
69	if (tq->tq_spin)
70		mtx_lock_spin(&tq->tq_mutex);
71	else
72		mtx_lock(&tq->tq_mutex);
73}
74
75static __inline void
76TQ_UNLOCK(struct taskqueue *tq)
77{
78	if (tq->tq_spin)
79		mtx_unlock_spin(&tq->tq_mutex);
80	else
81		mtx_unlock(&tq->tq_mutex);
82}
83
84static __inline int
85TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
86    int t)
87{
88	if (tq->tq_spin)
89		return (msleep_spin(p, m, wm, t));
90	return (msleep(p, m, pri, wm, t));
91}
92
93static struct taskqueue *
94_taskqueue_create(const char *name, int mflags,
95		 taskqueue_enqueue_fn enqueue, void *context,
96		 int mtxflags, const char *mtxname)
97{
98	struct taskqueue *queue;
99
100	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
101	if (!queue)
102		return NULL;
103
104	STAILQ_INIT(&queue->tq_queue);
105	queue->tq_name = name;
106	queue->tq_enqueue = enqueue;
107	queue->tq_context = context;
108	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
109	queue->tq_flags |= TQ_FLAGS_ACTIVE;
110	mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
111
112	return queue;
113}
114
115struct taskqueue *
116taskqueue_create(const char *name, int mflags,
117		 taskqueue_enqueue_fn enqueue, void *context)
118{
119	return _taskqueue_create(name, mflags, enqueue, context,
120			MTX_DEF, "taskqueue");
121}
122
123/*
124 * Signal a taskqueue thread to terminate.
125 */
126static void
127taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
128{
129
130	while (tq->tq_tcount > 0) {
131		wakeup(tq);
132		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
133	}
134}
135
136void
137taskqueue_free(struct taskqueue *queue)
138{
139
140	TQ_LOCK(queue);
141	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
142	taskqueue_run(queue);
143	taskqueue_terminate(queue->tq_threads, queue);
144	mtx_destroy(&queue->tq_mutex);
145	free(queue->tq_threads, M_TASKQUEUE);
146	free(queue, M_TASKQUEUE);
147}
148
149int
150taskqueue_enqueue(struct taskqueue *queue, struct task *task)
151{
152	struct task *ins;
153	struct task *prev;
154
155	TQ_LOCK(queue);
156
157	/*
158	 * Count multiple enqueues.
159	 */
160	if (task->ta_pending) {
161		task->ta_pending++;
162		TQ_UNLOCK(queue);
163		return 0;
164	}
165
166	/*
167	 * Optimise the case when all tasks have the same priority.
168	 */
169	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
170	if (!prev || prev->ta_priority >= task->ta_priority) {
171		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
172	} else {
173		prev = NULL;
174		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
175		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
176			if (ins->ta_priority < task->ta_priority)
177				break;
178
179		if (prev)
180			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
181		else
182			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
183	}
184
185	task->ta_pending = 1;
186	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
187		queue->tq_enqueue(queue->tq_context);
188	else
189		queue->tq_flags |= TQ_FLAGS_PENDING;
190
191	TQ_UNLOCK(queue);
192
193	return 0;
194}
195
196void
197taskqueue_block(struct taskqueue *queue)
198{
199
200	TQ_LOCK(queue);
201	queue->tq_flags |= TQ_FLAGS_BLOCKED;
202	TQ_UNLOCK(queue);
203}
204
205void
206taskqueue_unblock(struct taskqueue *queue)
207{
208
209	TQ_LOCK(queue);
210	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
211	if (queue->tq_flags & TQ_FLAGS_PENDING) {
212		queue->tq_flags &= ~TQ_FLAGS_PENDING;
213		queue->tq_enqueue(queue->tq_context);
214	}
215	TQ_UNLOCK(queue);
216}
217
218void
219taskqueue_run(struct taskqueue *queue)
220{
221	struct task *task;
222	int owned, pending;
223
224	owned = mtx_owned(&queue->tq_mutex);
225	if (!owned)
226		TQ_LOCK(queue);
227	while (STAILQ_FIRST(&queue->tq_queue)) {
228		/*
229		 * Carefully remove the first task from the queue and
230		 * zero its pending count.
231		 */
232		task = STAILQ_FIRST(&queue->tq_queue);
233		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
234		pending = task->ta_pending;
235		task->ta_pending = 0;
236		queue->tq_tasks_running++;
237		TQ_UNLOCK(queue);
238
239		task->ta_func(task->ta_context, pending);
240
241		TQ_LOCK(queue);
242		queue->tq_tasks_running--;
243		wakeup(task);
244	}
245
246	/*
247	 * For compatibility, unlock on return if the queue was not locked
248	 * on entry, although this opens a race window.
249	 */
250	if (!owned)
251		TQ_UNLOCK(queue);
252}
253
254void
255taskqueue_drain(struct taskqueue *queue, struct task *task)
256{
257	if (queue->tq_spin) {		/* XXX */
258		mtx_lock_spin(&queue->tq_mutex);
259		while (task->ta_pending != 0 || queue->tq_tasks_running > 0)
260			msleep_spin(task, &queue->tq_mutex, "-", 0);
261		mtx_unlock_spin(&queue->tq_mutex);
262	} else {
263		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
264
265		mtx_lock(&queue->tq_mutex);
266		while (task->ta_pending != 0 || queue->tq_tasks_running > 0)
267			msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
268		mtx_unlock(&queue->tq_mutex);
269	}
270}
271
272static void
273taskqueue_swi_enqueue(void *context)
274{
275	swi_sched(taskqueue_ih, 0);
276}
277
278static void
279taskqueue_swi_run(void *dummy)
280{
281	taskqueue_run(taskqueue_swi);
282}
283
284static void
285taskqueue_swi_giant_enqueue(void *context)
286{
287	swi_sched(taskqueue_giant_ih, 0);
288}
289
290static void
291taskqueue_swi_giant_run(void *dummy)
292{
293	taskqueue_run(taskqueue_swi_giant);
294}
295
296int
297taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
298			const char *name, ...)
299{
300	va_list ap;
301	struct thread *td;
302	struct taskqueue *tq;
303	int i, error;
304	char ktname[MAXCOMLEN + 1];
305
306	if (count <= 0)
307		return (EINVAL);
308
309	tq = *tqp;
310
311	va_start(ap, name);
312	vsnprintf(ktname, sizeof(ktname), name, ap);
313	va_end(ap);
314
315	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
316	    M_NOWAIT | M_ZERO);
317	if (tq->tq_threads == NULL) {
318		printf("%s: no memory for %s threads\n", __func__, ktname);
319		return (ENOMEM);
320	}
321
322	for (i = 0; i < count; i++) {
323		if (count == 1)
324			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
325			    &tq->tq_threads[i], RFSTOPPED, 0, ktname);
326		else
327			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
328			    &tq->tq_threads[i], RFSTOPPED, 0,
329			    "%s_%d", ktname, i);
330		if (error) {
331			/* should be ok to continue, taskqueue_free will dtrt */
332			printf("%s: kthread_add(%s): error %d", __func__,
333			    ktname, error);
334			tq->tq_threads[i] = NULL;		/* paranoid */
335		} else
336			tq->tq_tcount++;
337	}
338	for (i = 0; i < count; i++) {
339		if (tq->tq_threads[i] == NULL)
340			continue;
341		td = tq->tq_threads[i];
342		thread_lock(td);
343		sched_prio(td, pri);
344		sched_add(td, SRQ_BORING);
345		thread_unlock(td);
346	}
347
348	return (0);
349}
350
351void
352taskqueue_thread_loop(void *arg)
353{
354	struct taskqueue **tqp, *tq;
355
356	tqp = arg;
357	tq = *tqp;
358	TQ_LOCK(tq);
359	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
360		taskqueue_run(tq);
361		/*
362		 * Because taskqueue_run() can drop tq_mutex, we need to
363		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
364		 * meantime, which means we missed a wakeup.
365		 */
366		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
367			break;
368		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
369	}
370
371	/* rendezvous with thread that asked us to terminate */
372	tq->tq_tcount--;
373	wakeup_one(tq->tq_threads);
374	TQ_UNLOCK(tq);
375	kthread_exit();
376}
377
378void
379taskqueue_thread_enqueue(void *context)
380{
381	struct taskqueue **tqp, *tq;
382
383	tqp = context;
384	tq = *tqp;
385
386	mtx_assert(&tq->tq_mutex, MA_OWNED);
387	wakeup_one(tq);
388}
389
390TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
391		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
392		     INTR_MPSAFE, &taskqueue_ih));
393
394TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
395		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
396		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
397
398TASKQUEUE_DEFINE_THREAD(thread);
399
400struct taskqueue *
401taskqueue_create_fast(const char *name, int mflags,
402		 taskqueue_enqueue_fn enqueue, void *context)
403{
404	return _taskqueue_create(name, mflags, enqueue, context,
405			MTX_SPIN, "fast_taskqueue");
406}
407
408/* NB: for backwards compatibility */
409int
410taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
411{
412	return taskqueue_enqueue(queue, task);
413}
414
415static void	*taskqueue_fast_ih;
416
417static void
418taskqueue_fast_enqueue(void *context)
419{
420	swi_sched(taskqueue_fast_ih, 0);
421}
422
423static void
424taskqueue_fast_run(void *dummy)
425{
426	taskqueue_run(taskqueue_fast);
427}
428
429TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
430	swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
431	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
432
433int
434taskqueue_member(struct taskqueue *queue, struct thread *td)
435{
436	int i, j, ret = 0;
437
438	TQ_LOCK(queue);
439	for (i = 0, j = 0; ; i++) {
440		if (queue->tq_threads[i] == NULL)
441			continue;
442		if (queue->tq_threads[i] == td) {
443			ret = 1;
444			break;
445		}
446		if (++j >= queue->tq_tcount)
447			break;
448	}
449	TQ_UNLOCK(queue);
450	return (ret);
451}
452