subr_taskqueue.c revision 215021 
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 215021 2010-11-08 22:12:25Z jmallett $");
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_busy {
50	struct task	*tb_running;
51	TAILQ_ENTRY(taskqueue_busy) tb_link;
52};
53
54struct taskqueue {
55	STAILQ_HEAD(, task)	tq_queue;
56	const char		*tq_name;
57	taskqueue_enqueue_fn	tq_enqueue;
58	void			*tq_context;
59	TAILQ_HEAD(, taskqueue_busy) tq_active;
60	struct mtx		tq_mutex;
61	struct thread		**tq_threads;
62	int			tq_tcount;
63	int			tq_spin;
64	int			tq_flags;
65};
66
67#define	TQ_FLAGS_ACTIVE		(1 << 0)
68#define	TQ_FLAGS_BLOCKED	(1 << 1)
69#define	TQ_FLAGS_PENDING	(1 << 2)
70
71#define	TQ_LOCK(tq)							\
72	do {								\
73		if ((tq)->tq_spin)					\
74			mtx_lock_spin(&(tq)->tq_mutex);			\
75		else							\
76			mtx_lock(&(tq)->tq_mutex);			\
77	} while (0)
78
79#define	TQ_UNLOCK(tq)							\
80	do {								\
81		if ((tq)->tq_spin)					\
82			mtx_unlock_spin(&(tq)->tq_mutex);		\
83		else							\
84			mtx_unlock(&(tq)->tq_mutex);			\
85	} while (0)
86
87static __inline int
88TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
89    int t)
90{
91	if (tq->tq_spin)
92		return (msleep_spin(p, m, wm, t));
93	return (msleep(p, m, pri, wm, t));
94}
95
96static struct taskqueue *
97_taskqueue_create(const char *name, int mflags,
98		 taskqueue_enqueue_fn enqueue, void *context,
99		 int mtxflags, const char *mtxname)
100{
101	struct taskqueue *queue;
102
103	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
104	if (!queue)
105		return NULL;
106
107	STAILQ_INIT(&queue->tq_queue);
108	TAILQ_INIT(&queue->tq_active);
109	queue->tq_name = name;
110	queue->tq_enqueue = enqueue;
111	queue->tq_context = context;
112	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
113	queue->tq_flags |= TQ_FLAGS_ACTIVE;
114	mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
115
116	return queue;
117}
118
119struct taskqueue *
120taskqueue_create(const char *name, int mflags,
121		 taskqueue_enqueue_fn enqueue, void *context)
122{
123	return _taskqueue_create(name, mflags, enqueue, context,
124			MTX_DEF, "taskqueue");
125}
126
127/*
128 * Signal a taskqueue thread to terminate.
129 */
130static void
131taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
132{
133
134	while (tq->tq_tcount > 0) {
135		wakeup(tq);
136		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
137	}
138}
139
140void
141taskqueue_free(struct taskqueue *queue)
142{
143
144	TQ_LOCK(queue);
145	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
146	taskqueue_terminate(queue->tq_threads, queue);
147	KASSERT(TAILQ_EMPTY(&queue->tq_active), ("Tasks still running?"));
148	mtx_destroy(&queue->tq_mutex);
149	free(queue->tq_threads, M_TASKQUEUE);
150	free(queue, M_TASKQUEUE);
151}
152
153int
154taskqueue_enqueue(struct taskqueue *queue, struct task *task)
155{
156	struct task *ins;
157	struct task *prev;
158
159	TQ_LOCK(queue);
160
161	/*
162	 * Count multiple enqueues.
163	 */
164	if (task->ta_pending) {
165		task->ta_pending++;
166		TQ_UNLOCK(queue);
167		return 0;
168	}
169
170	/*
171	 * Optimise the case when all tasks have the same priority.
172	 */
173	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
174	if (!prev || prev->ta_priority >= task->ta_priority) {
175		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
176	} else {
177		prev = NULL;
178		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
179		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
180			if (ins->ta_priority < task->ta_priority)
181				break;
182
183		if (prev)
184			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
185		else
186			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
187	}
188
189	task->ta_pending = 1;
190	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
191		queue->tq_enqueue(queue->tq_context);
192	else
193		queue->tq_flags |= TQ_FLAGS_PENDING;
194
195	TQ_UNLOCK(queue);
196
197	return 0;
198}
199
200void
201taskqueue_block(struct taskqueue *queue)
202{
203
204	TQ_LOCK(queue);
205	queue->tq_flags |= TQ_FLAGS_BLOCKED;
206	TQ_UNLOCK(queue);
207}
208
209void
210taskqueue_unblock(struct taskqueue *queue)
211{
212
213	TQ_LOCK(queue);
214	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
215	if (queue->tq_flags & TQ_FLAGS_PENDING) {
216		queue->tq_flags &= ~TQ_FLAGS_PENDING;
217		queue->tq_enqueue(queue->tq_context);
218	}
219	TQ_UNLOCK(queue);
220}
221
222static void
223taskqueue_run_locked(struct taskqueue *queue)
224{
225	struct taskqueue_busy tb;
226	struct task *task;
227	int pending;
228
229	mtx_assert(&queue->tq_mutex, MA_OWNED);
230	tb.tb_running = NULL;
231	TAILQ_INSERT_TAIL(&queue->tq_active, &tb, tb_link);
232
233	while (STAILQ_FIRST(&queue->tq_queue)) {
234		/*
235		 * Carefully remove the first task from the queue and
236		 * zero its pending count.
237		 */
238		task = STAILQ_FIRST(&queue->tq_queue);
239		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
240		pending = task->ta_pending;
241		task->ta_pending = 0;
242		tb.tb_running = task;
243		TQ_UNLOCK(queue);
244
245		task->ta_func(task->ta_context, pending);
246
247		TQ_LOCK(queue);
248		tb.tb_running = NULL;
249		wakeup(task);
250	}
251	TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
252}
253
254void
255taskqueue_run(struct taskqueue *queue)
256{
257
258	TQ_LOCK(queue);
259	taskqueue_run_locked(queue);
260	TQ_UNLOCK(queue);
261}
262
263static int
264task_is_running(struct taskqueue *queue, struct task *task)
265{
266	struct taskqueue_busy *tb;
267
268	mtx_assert(&queue->tq_mutex, MA_OWNED);
269	TAILQ_FOREACH(tb, &queue->tq_active, tb_link) {
270		if (tb->tb_running == task)
271			return (1);
272	}
273	return (0);
274}
275
276int
277taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
278{
279	u_int pending;
280	int error;
281
282	TQ_LOCK(queue);
283	if ((pending = task->ta_pending) > 0)
284		STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
285	task->ta_pending = 0;
286	error = task_is_running(queue, task) ? EBUSY : 0;
287	TQ_UNLOCK(queue);
288
289	if (pendp != NULL)
290		*pendp = pending;
291	return (error);
292}
293
294void
295taskqueue_drain(struct taskqueue *queue, struct task *task)
296{
297
298	if (!queue->tq_spin)
299		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
300
301	TQ_LOCK(queue);
302	while (task->ta_pending != 0 || task_is_running(queue, task))
303		TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
304	TQ_UNLOCK(queue);
305}
306
307static void
308taskqueue_swi_enqueue(void *context)
309{
310	swi_sched(taskqueue_ih, 0);
311}
312
313static void
314taskqueue_swi_run(void *dummy)
315{
316	taskqueue_run(taskqueue_swi);
317}
318
319static void
320taskqueue_swi_giant_enqueue(void *context)
321{
322	swi_sched(taskqueue_giant_ih, 0);
323}
324
325static void
326taskqueue_swi_giant_run(void *dummy)
327{
328	taskqueue_run(taskqueue_swi_giant);
329}
330
331int
332taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
333			const char *name, ...)
334{
335	va_list ap;
336	struct thread *td;
337	struct taskqueue *tq;
338	int i, error;
339	char ktname[MAXCOMLEN + 1];
340
341	if (count <= 0)
342		return (EINVAL);
343
344	tq = *tqp;
345
346	va_start(ap, name);
347	vsnprintf(ktname, sizeof(ktname), name, ap);
348	va_end(ap);
349
350	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
351	    M_NOWAIT | M_ZERO);
352	if (tq->tq_threads == NULL) {
353		printf("%s: no memory for %s threads\n", __func__, ktname);
354		return (ENOMEM);
355	}
356
357	for (i = 0; i < count; i++) {
358		if (count == 1)
359			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
360			    &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
361		else
362			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
363			    &tq->tq_threads[i], RFSTOPPED, 0,
364			    "%s_%d", ktname, i);
365		if (error) {
366			/* should be ok to continue, taskqueue_free will dtrt */
367			printf("%s: kthread_add(%s): error %d", __func__,
368			    ktname, error);
369			tq->tq_threads[i] = NULL;		/* paranoid */
370		} else
371			tq->tq_tcount++;
372	}
373	for (i = 0; i < count; i++) {
374		if (tq->tq_threads[i] == NULL)
375			continue;
376		td = tq->tq_threads[i];
377		thread_lock(td);
378		sched_prio(td, pri);
379		sched_add(td, SRQ_BORING);
380		thread_unlock(td);
381	}
382
383	return (0);
384}
385
386void
387taskqueue_thread_loop(void *arg)
388{
389	struct taskqueue **tqp, *tq;
390
391	tqp = arg;
392	tq = *tqp;
393	TQ_LOCK(tq);
394	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
395		taskqueue_run_locked(tq);
396		/*
397		 * Because taskqueue_run() can drop tq_mutex, we need to
398		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
399		 * meantime, which means we missed a wakeup.
400		 */
401		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
402			break;
403		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
404	}
405	taskqueue_run_locked(tq);
406
407	/* rendezvous with thread that asked us to terminate */
408	tq->tq_tcount--;
409	wakeup_one(tq->tq_threads);
410	TQ_UNLOCK(tq);
411	kthread_exit();
412}
413
414void
415taskqueue_thread_enqueue(void *context)
416{
417	struct taskqueue **tqp, *tq;
418
419	tqp = context;
420	tq = *tqp;
421
422	mtx_assert(&tq->tq_mutex, MA_OWNED);
423	wakeup_one(tq);
424}
425
426TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
427		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
428		     INTR_MPSAFE, &taskqueue_ih));
429
430TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
431		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
432		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
433
434TASKQUEUE_DEFINE_THREAD(thread);
435
436struct taskqueue *
437taskqueue_create_fast(const char *name, int mflags,
438		 taskqueue_enqueue_fn enqueue, void *context)
439{
440	return _taskqueue_create(name, mflags, enqueue, context,
441			MTX_SPIN, "fast_taskqueue");
442}
443
444/* NB: for backwards compatibility */
445int
446taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
447{
448	return taskqueue_enqueue(queue, task);
449}
450
451static void	*taskqueue_fast_ih;
452
453static void
454taskqueue_fast_enqueue(void *context)
455{
456	swi_sched(taskqueue_fast_ih, 0);
457}
458
459static void
460taskqueue_fast_run(void *dummy)
461{
462	taskqueue_run(taskqueue_fast);
463}
464
465TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
466	swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
467	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
468
469int
470taskqueue_member(struct taskqueue *queue, struct thread *td)
471{
472	int i, j, ret = 0;
473
474	TQ_LOCK(queue);
475	for (i = 0, j = 0; ; i++) {
476		if (queue->tq_threads[i] == NULL)
477			continue;
478		if (queue->tq_threads[i] == td) {
479			ret = 1;
480			break;
481		}
482		if (++j >= queue->tq_tcount)
483			break;
484	}
485	TQ_UNLOCK(queue);
486	return (ret);
487}
488