subr_taskqueue.c revision 154205 
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 154205 2006-01-11 00:37:13Z scottl $");
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/taskqueue.h>
41#include <sys/unistd.h>
42
43static MALLOC_DEFINE(M_TASKQUEUE, "taskqueue", "Task Queues");
44static void	*taskqueue_giant_ih;
45static void	*taskqueue_ih;
46static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
47static struct mtx taskqueue_queues_mutex;
48
49struct taskqueue {
50	STAILQ_ENTRY(taskqueue)	tq_link;
51	STAILQ_HEAD(, task)	tq_queue;
52	const char		*tq_name;
53	taskqueue_enqueue_fn	tq_enqueue;
54	void			*tq_context;
55	struct task		*tq_running;
56	struct mtx		tq_mutex;
57	struct proc		**tq_pproc;
58	int			tq_spin;
59};
60
61static __inline void
62TQ_LOCK(struct taskqueue *tq)
63{
64	if (tq->tq_spin)
65		mtx_lock_spin(&tq->tq_mutex);
66	else
67		mtx_lock(&tq->tq_mutex);
68}
69
70static __inline void
71TQ_UNLOCK(struct taskqueue *tq)
72{
73	if (tq->tq_spin)
74		mtx_unlock_spin(&tq->tq_mutex);
75	else
76		mtx_unlock(&tq->tq_mutex);
77}
78
79static void	init_taskqueue_list(void *data);
80
81static __inline int
82TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
83    int t)
84{
85	if (tq->tq_spin)
86		return (msleep_spin(p, m, wm, t));
87	return (msleep(p, m, pri, wm, t));
88}
89
90static void
91init_taskqueue_list(void *data __unused)
92{
93
94	mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
95	STAILQ_INIT(&taskqueue_queues);
96}
97SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
98    NULL);
99
100static struct taskqueue *
101_taskqueue_create(const char *name, int mflags,
102		 taskqueue_enqueue_fn enqueue, void *context,
103		 struct proc **pp,
104		 int mtxflags, const char *mtxname)
105{
106	struct taskqueue *queue;
107
108	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
109	if (!queue)
110		return 0;
111
112	STAILQ_INIT(&queue->tq_queue);
113	queue->tq_name = name;
114	queue->tq_enqueue = enqueue;
115	queue->tq_context = context;
116	queue->tq_pproc = pp;
117	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
118	mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
119
120	mtx_lock(&taskqueue_queues_mutex);
121	STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
122	mtx_unlock(&taskqueue_queues_mutex);
123
124	return queue;
125}
126
127struct taskqueue *
128taskqueue_create(const char *name, int mflags,
129		 taskqueue_enqueue_fn enqueue, void *context,
130		 struct proc **pp)
131{
132	return _taskqueue_create(name, mflags, enqueue, context, pp,
133			MTX_DEF, "taskqueue");
134}
135
136/*
137 * Signal a taskqueue thread to terminate.
138 */
139static void
140taskqueue_terminate(struct proc **pp, struct taskqueue *tq)
141{
142	struct proc *p;
143
144	p = *pp;
145	*pp = NULL;
146	if (p) {
147		wakeup_one(tq);
148		TQ_SLEEP(tq, p, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
149	}
150}
151
152void
153taskqueue_free(struct taskqueue *queue)
154{
155
156	mtx_lock(&taskqueue_queues_mutex);
157	STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
158	mtx_unlock(&taskqueue_queues_mutex);
159
160	TQ_LOCK(queue);
161	taskqueue_run(queue);
162	taskqueue_terminate(queue->tq_pproc, queue);
163	mtx_destroy(&queue->tq_mutex);
164	free(queue, M_TASKQUEUE);
165}
166
167/*
168 * Returns with the taskqueue locked.
169 */
170struct taskqueue *
171taskqueue_find(const char *name)
172{
173	struct taskqueue *queue;
174
175	mtx_lock(&taskqueue_queues_mutex);
176	STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
177		if (strcmp(queue->tq_name, name) == 0) {
178			TQ_LOCK(queue);
179			mtx_unlock(&taskqueue_queues_mutex);
180			return queue;
181		}
182	}
183	mtx_unlock(&taskqueue_queues_mutex);
184	return NULL;
185}
186
187int
188taskqueue_enqueue(struct taskqueue *queue, struct task *task)
189{
190	struct task *ins;
191	struct task *prev;
192
193	TQ_LOCK(queue);
194
195	/*
196	 * Count multiple enqueues.
197	 */
198	if (task->ta_pending) {
199		task->ta_pending++;
200		TQ_UNLOCK(queue);
201		return 0;
202	}
203
204	/*
205	 * Optimise the case when all tasks have the same priority.
206	 */
207	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
208	if (!prev || prev->ta_priority >= task->ta_priority) {
209		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
210	} else {
211		prev = 0;
212		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
213		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
214			if (ins->ta_priority < task->ta_priority)
215				break;
216
217		if (prev)
218			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
219		else
220			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
221	}
222
223	task->ta_pending = 1;
224	queue->tq_enqueue(queue->tq_context);
225
226	TQ_UNLOCK(queue);
227
228	return 0;
229}
230
231void
232taskqueue_run(struct taskqueue *queue)
233{
234	struct task *task;
235	int owned, pending;
236
237	owned = mtx_owned(&queue->tq_mutex);
238	if (!owned)
239		TQ_LOCK(queue);
240	while (STAILQ_FIRST(&queue->tq_queue)) {
241		/*
242		 * Carefully remove the first task from the queue and
243		 * zero its pending count.
244		 */
245		task = STAILQ_FIRST(&queue->tq_queue);
246		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
247		pending = task->ta_pending;
248		task->ta_pending = 0;
249		queue->tq_running = task;
250		TQ_UNLOCK(queue);
251
252		task->ta_func(task->ta_context, pending);
253
254		TQ_LOCK(queue);
255		queue->tq_running = NULL;
256		wakeup(task);
257	}
258
259	/*
260	 * For compatibility, unlock on return if the queue was not locked
261	 * on entry, although this opens a race window.
262	 */
263	if (!owned)
264		TQ_UNLOCK(queue);
265}
266
267void
268taskqueue_drain(struct taskqueue *queue, struct task *task)
269{
270	if (queue->tq_spin) {		/* XXX */
271		mtx_lock_spin(&queue->tq_mutex);
272		while (task->ta_pending != 0 || task == queue->tq_running)
273			msleep_spin(task, &queue->tq_mutex, "-", 0);
274		mtx_unlock_spin(&queue->tq_mutex);
275	} else {
276		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
277
278		mtx_lock(&queue->tq_mutex);
279		while (task->ta_pending != 0 || task == queue->tq_running)
280			msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
281		mtx_unlock(&queue->tq_mutex);
282	}
283}
284
285static void
286taskqueue_swi_enqueue(void *context)
287{
288	swi_sched(taskqueue_ih, 0);
289}
290
291static void
292taskqueue_swi_run(void *dummy)
293{
294	taskqueue_run(taskqueue_swi);
295}
296
297static void
298taskqueue_swi_giant_enqueue(void *context)
299{
300	swi_sched(taskqueue_giant_ih, 0);
301}
302
303static void
304taskqueue_swi_giant_run(void *dummy)
305{
306	taskqueue_run(taskqueue_swi_giant);
307}
308
309void
310taskqueue_thread_loop(void *arg)
311{
312	struct taskqueue **tqp, *tq;
313
314	tqp = arg;
315	tq = *tqp;
316	TQ_LOCK(tq);
317	do {
318		taskqueue_run(tq);
319		TQ_SLEEP(tq, tq, &tq->tq_mutex, curthread->td_priority, "-", 0);
320	} while (*tq->tq_pproc != NULL);
321
322	/* rendezvous with thread that asked us to terminate */
323	wakeup_one(tq);
324	TQ_UNLOCK(tq);
325	kthread_exit(0);
326}
327
328void
329taskqueue_thread_enqueue(void *context)
330{
331	struct taskqueue **tqp, *tq;
332
333	tqp = context;
334	tq = *tqp;
335
336	mtx_assert(&tq->tq_mutex, MA_OWNED);
337	wakeup_one(tq);
338}
339
340TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, 0,
341		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
342		     INTR_MPSAFE, &taskqueue_ih));
343
344TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, 0,
345		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
346		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
347
348TASKQUEUE_DEFINE_THREAD(thread);
349
350struct taskqueue *
351taskqueue_create_fast(const char *name, int mflags,
352		 taskqueue_enqueue_fn enqueue, void *context,
353		 struct proc **pp)
354{
355	return _taskqueue_create(name, mflags, enqueue, context, pp,
356			MTX_SPIN, "fast_taskqueue");
357}
358
359/* NB: for backwards compatibility */
360int
361taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
362{
363	return taskqueue_enqueue(queue, task);
364}
365
366static void	*taskqueue_fast_ih;
367
368static void
369taskqueue_fast_enqueue(void *context)
370{
371	swi_sched(taskqueue_fast_ih, 0);
372}
373
374static void
375taskqueue_fast_run(void *dummy)
376{
377	taskqueue_run(taskqueue_fast);
378}
379
380TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, 0,
381	swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
382	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
383