subr_taskqueue.c revision 207439 
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 207439 2010-04-30 16:29:05Z 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};
60
61#define	TQ_FLAGS_ACTIVE		(1 << 0)
62#define	TQ_FLAGS_BLOCKED	(1 << 1)
63#define	TQ_FLAGS_PENDING	(1 << 2)
64
65static __inline void
66TQ_LOCK(struct taskqueue *tq)
67{
68	if (tq->tq_spin)
69		mtx_lock_spin(&tq->tq_mutex);
70	else
71		mtx_lock(&tq->tq_mutex);
72}
73
74static __inline void
75TQ_UNLOCK(struct taskqueue *tq)
76{
77	if (tq->tq_spin)
78		mtx_unlock_spin(&tq->tq_mutex);
79	else
80		mtx_unlock(&tq->tq_mutex);
81}
82
83static __inline int
84TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
85    int t)
86{
87	if (tq->tq_spin)
88		return (msleep_spin(p, m, wm, t));
89	return (msleep(p, m, pri, wm, t));
90}
91
92static struct taskqueue *
93_taskqueue_create(const char *name, int mflags,
94		 taskqueue_enqueue_fn enqueue, void *context,
95		 int mtxflags, const char *mtxname)
96{
97	struct taskqueue *queue;
98
99	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
100	if (!queue)
101		return NULL;
102
103	STAILQ_INIT(&queue->tq_queue);
104	queue->tq_name = name;
105	queue->tq_enqueue = enqueue;
106	queue->tq_context = context;
107	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
108	queue->tq_flags |= TQ_FLAGS_ACTIVE;
109	mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
110
111	return queue;
112}
113
114struct taskqueue *
115taskqueue_create(const char *name, int mflags,
116		 taskqueue_enqueue_fn enqueue, void *context)
117{
118	return _taskqueue_create(name, mflags, enqueue, context,
119			MTX_DEF, "taskqueue");
120}
121
122/*
123 * Signal a taskqueue thread to terminate.
124 */
125static void
126taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
127{
128
129	while (tq->tq_tcount > 0) {
130		wakeup(tq);
131		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
132	}
133}
134
135void
136taskqueue_free(struct taskqueue *queue)
137{
138
139	TQ_LOCK(queue);
140	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
141	taskqueue_run(queue);
142	taskqueue_terminate(queue->tq_threads, queue);
143	mtx_destroy(&queue->tq_mutex);
144	free(queue->tq_threads, M_TASKQUEUE);
145	free(queue, M_TASKQUEUE);
146}
147
148int
149taskqueue_enqueue(struct taskqueue *queue, struct task *task)
150{
151	struct task *ins;
152	struct task *prev;
153
154	TQ_LOCK(queue);
155
156	/*
157	 * Count multiple enqueues.
158	 */
159	if (task->ta_pending) {
160		task->ta_pending++;
161		TQ_UNLOCK(queue);
162		return 0;
163	}
164
165	/*
166	 * Optimise the case when all tasks have the same priority.
167	 */
168	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
169	if (!prev || prev->ta_priority >= task->ta_priority) {
170		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
171	} else {
172		prev = NULL;
173		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
174		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
175			if (ins->ta_priority < task->ta_priority)
176				break;
177
178		if (prev)
179			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
180		else
181			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
182	}
183
184	task->ta_pending = 1;
185	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
186		queue->tq_enqueue(queue->tq_context);
187	else
188		queue->tq_flags |= TQ_FLAGS_PENDING;
189
190	TQ_UNLOCK(queue);
191
192	return 0;
193}
194
195void
196taskqueue_block(struct taskqueue *queue)
197{
198
199	TQ_LOCK(queue);
200	queue->tq_flags |= TQ_FLAGS_BLOCKED;
201	TQ_UNLOCK(queue);
202}
203
204void
205taskqueue_unblock(struct taskqueue *queue)
206{
207
208	TQ_LOCK(queue);
209	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
210	if (queue->tq_flags & TQ_FLAGS_PENDING) {
211		queue->tq_flags &= ~TQ_FLAGS_PENDING;
212		queue->tq_enqueue(queue->tq_context);
213	}
214	TQ_UNLOCK(queue);
215}
216
217void
218taskqueue_run(struct taskqueue *queue)
219{
220	struct task *task;
221	int owned, pending;
222
223	owned = mtx_owned(&queue->tq_mutex);
224	if (!owned)
225		TQ_LOCK(queue);
226	while (STAILQ_FIRST(&queue->tq_queue)) {
227		/*
228		 * Carefully remove the first task from the queue and
229		 * zero its pending count.
230		 */
231		task = STAILQ_FIRST(&queue->tq_queue);
232		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
233		pending = task->ta_pending;
234		task->ta_pending = 0;
235		task->ta_flags |= TA_FLAGS_RUNNING;
236		TQ_UNLOCK(queue);
237
238		task->ta_func(task->ta_context, pending);
239
240		TQ_LOCK(queue);
241		task->ta_flags &= ~TA_FLAGS_RUNNING;
242		wakeup(task);
243	}
244
245	/*
246	 * For compatibility, unlock on return if the queue was not locked
247	 * on entry, although this opens a race window.
248	 */
249	if (!owned)
250		TQ_UNLOCK(queue);
251}
252
253void
254taskqueue_drain(struct taskqueue *queue, struct task *task)
255{
256	if (queue->tq_spin) {		/* XXX */
257		mtx_lock_spin(&queue->tq_mutex);
258		while (task->ta_pending != 0 ||
259		    (task->ta_flags & TA_FLAGS_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 ||
267		    (task->ta_flags & TA_FLAGS_RUNNING) != 0)
268			msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
269		mtx_unlock(&queue->tq_mutex);
270	}
271}
272
273static void
274taskqueue_swi_enqueue(void *context)
275{
276	swi_sched(taskqueue_ih, 0);
277}
278
279static void
280taskqueue_swi_run(void *dummy)
281{
282	taskqueue_run(taskqueue_swi);
283}
284
285static void
286taskqueue_swi_giant_enqueue(void *context)
287{
288	swi_sched(taskqueue_giant_ih, 0);
289}
290
291static void
292taskqueue_swi_giant_run(void *dummy)
293{
294	taskqueue_run(taskqueue_swi_giant);
295}
296
297int
298taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
299			const char *name, ...)
300{
301	va_list ap;
302	struct thread *td;
303	struct taskqueue *tq;
304	int i, error;
305	char ktname[MAXCOMLEN + 1];
306
307	if (count <= 0)
308		return (EINVAL);
309
310	tq = *tqp;
311
312	va_start(ap, name);
313	vsnprintf(ktname, sizeof(ktname), name, ap);
314	va_end(ap);
315
316	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
317	    M_NOWAIT | M_ZERO);
318	if (tq->tq_threads == NULL) {
319		printf("%s: no memory for %s threads\n", __func__, ktname);
320		return (ENOMEM);
321	}
322
323	for (i = 0; i < count; i++) {
324		if (count == 1)
325			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
326			    &tq->tq_threads[i], RFSTOPPED, 0, ktname);
327		else
328			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
329			    &tq->tq_threads[i], RFSTOPPED, 0,
330			    "%s_%d", ktname, i);
331		if (error) {
332			/* should be ok to continue, taskqueue_free will dtrt */
333			printf("%s: kthread_add(%s): error %d", __func__,
334			    ktname, error);
335			tq->tq_threads[i] = NULL;		/* paranoid */
336		} else
337			tq->tq_tcount++;
338	}
339	for (i = 0; i < count; i++) {
340		if (tq->tq_threads[i] == NULL)
341			continue;
342		td = tq->tq_threads[i];
343		thread_lock(td);
344		sched_prio(td, pri);
345		sched_add(td, SRQ_BORING);
346		thread_unlock(td);
347	}
348
349	return (0);
350}
351
352void
353taskqueue_thread_loop(void *arg)
354{
355	struct taskqueue **tqp, *tq;
356
357	tqp = arg;
358	tq = *tqp;
359	TQ_LOCK(tq);
360	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
361		taskqueue_run(tq);
362		/*
363		 * Because taskqueue_run() can drop tq_mutex, we need to
364		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
365		 * meantime, which means we missed a wakeup.
366		 */
367		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
368			break;
369		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
370	}
371
372	/* rendezvous with thread that asked us to terminate */
373	tq->tq_tcount--;
374	wakeup_one(tq->tq_threads);
375	TQ_UNLOCK(tq);
376	kthread_exit();
377}
378
379void
380taskqueue_thread_enqueue(void *context)
381{
382	struct taskqueue **tqp, *tq;
383
384	tqp = context;
385	tq = *tqp;
386
387	mtx_assert(&tq->tq_mutex, MA_OWNED);
388	wakeup_one(tq);
389}
390
391TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
392		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
393		     INTR_MPSAFE, &taskqueue_ih));
394
395TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
396		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
397		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
398
399TASKQUEUE_DEFINE_THREAD(thread);
400
401struct taskqueue *
402taskqueue_create_fast(const char *name, int mflags,
403		 taskqueue_enqueue_fn enqueue, void *context)
404{
405	return _taskqueue_create(name, mflags, enqueue, context,
406			MTX_SPIN, "fast_taskqueue");
407}
408
409/* NB: for backwards compatibility */
410int
411taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
412{
413	return taskqueue_enqueue(queue, task);
414}
415
416static void	*taskqueue_fast_ih;
417
418static void
419taskqueue_fast_enqueue(void *context)
420{
421	swi_sched(taskqueue_fast_ih, 0);
422}
423
424static void
425taskqueue_fast_run(void *dummy)
426{
427	taskqueue_run(taskqueue_fast);
428}
429
430TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
431	swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
432	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
433
434int
435taskqueue_member(struct taskqueue *queue, struct thread *td)
436{
437	int i, j, ret = 0;
438
439	TQ_LOCK(queue);
440	for (i = 0, j = 0; ; i++) {
441		if (queue->tq_threads[i] == NULL)
442			continue;
443		if (queue->tq_threads[i] == td) {
444			ret = 1;
445			break;
446		}
447		if (++j >= queue->tq_tcount)
448			break;
449	}
450	TQ_UNLOCK(queue);
451	return (ret);
452}
453