subr_taskqueue.c revision 213739 
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 213739 2010-10-12 18:36:03Z mdf $");
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 task		*tq_running;
55	struct mtx		tq_mutex;
56	struct thread		**tq_threads;
57	int			tq_tcount;
58	int			tq_spin;
59	int			tq_flags;
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_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, struct task **tpp)
219{
220	struct task *task;
221	int pending;
222
223	mtx_assert(&queue->tq_mutex, MA_OWNED);
224	while (STAILQ_FIRST(&queue->tq_queue)) {
225		/*
226		 * Carefully remove the first task from the queue and
227		 * zero its pending count.
228		 */
229		task = STAILQ_FIRST(&queue->tq_queue);
230		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
231		pending = task->ta_pending;
232		task->ta_pending = 0;
233		task->ta_running = tpp;
234		*tpp = task;
235		TQ_UNLOCK(queue);
236
237		task->ta_func(task->ta_context, pending);
238
239		TQ_LOCK(queue);
240		*tpp = NULL;
241		wakeup(task);
242	}
243}
244
245void
246taskqueue_drain(struct taskqueue *queue, struct task *task)
247{
248
249	if (!queue->tq_spin)
250		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
251
252	TQ_LOCK(queue);
253	while (task->ta_pending != 0 ||
254	    (task->ta_running != NULL && task == *task->ta_running)) {
255		TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
256	}
257	TQ_UNLOCK(queue);
258}
259
260static void
261taskqueue_swi_enqueue(void *context)
262{
263	swi_sched(taskqueue_ih, 0);
264}
265
266static void
267taskqueue_swi_run(void *dummy)
268{
269	TQ_LOCK(taskqueue_swi);
270	taskqueue_run(taskqueue_swi, &taskqueue_swi->tq_running);
271	TQ_UNLOCK(taskqueue_swi);
272}
273
274static void
275taskqueue_swi_giant_enqueue(void *context)
276{
277	swi_sched(taskqueue_giant_ih, 0);
278}
279
280static void
281taskqueue_swi_giant_run(void *dummy)
282{
283	TQ_LOCK(taskqueue_swi_giant);
284	taskqueue_run(taskqueue_swi_giant, &taskqueue_swi_giant->tq_running);
285	TQ_UNLOCK(taskqueue_swi_giant);
286}
287
288int
289taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
290			const char *name, ...)
291{
292	va_list ap;
293	struct thread *td;
294	struct taskqueue *tq;
295	int i, error;
296	char ktname[MAXCOMLEN + 1];
297
298	if (count <= 0)
299		return (EINVAL);
300
301	tq = *tqp;
302
303	va_start(ap, name);
304	vsnprintf(ktname, sizeof(ktname), name, ap);
305	va_end(ap);
306
307	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
308	    M_NOWAIT | M_ZERO);
309	if (tq->tq_threads == NULL) {
310		printf("%s: no memory for %s threads\n", __func__, ktname);
311		return (ENOMEM);
312	}
313
314	for (i = 0; i < count; i++) {
315		if (count == 1)
316			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
317			    &tq->tq_threads[i], RFSTOPPED, 0, "%s", ktname);
318		else
319			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
320			    &tq->tq_threads[i], RFSTOPPED, 0,
321			    "%s_%d", ktname, i);
322		if (error) {
323			/* should be ok to continue, taskqueue_free will dtrt */
324			printf("%s: kthread_add(%s): error %d", __func__,
325			    ktname, error);
326			tq->tq_threads[i] = NULL;		/* paranoid */
327		} else
328			tq->tq_tcount++;
329	}
330	for (i = 0; i < count; i++) {
331		if (tq->tq_threads[i] == NULL)
332			continue;
333		td = tq->tq_threads[i];
334		thread_lock(td);
335		sched_prio(td, pri);
336		sched_add(td, SRQ_BORING);
337		thread_unlock(td);
338	}
339
340	return (0);
341}
342
343void
344taskqueue_thread_loop(void *arg)
345{
346	struct taskqueue **tqp, *tq;
347	struct task *running;
348
349	/*
350	 * The kernel stack space is globaly addressable, and it would
351	 * be an error to ask whether a task is running after the
352	 * taskqueue has been released.  So it is safe to have the
353	 * task point back to an address in the taskqueue's stack to
354	 * determine if the task is running.
355	 */
356	running = NULL;
357
358	tqp = arg;
359	tq = *tqp;
360	TQ_LOCK(tq);
361	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
362		taskqueue_run(tq, &running);
363		/*
364		 * Because taskqueue_run() can drop tq_mutex, we need to
365		 * check if the TQ_FLAGS_ACTIVE flag wasn't removed in the
366		 * meantime, which means we missed a wakeup.
367		 */
368		if ((tq->tq_flags & TQ_FLAGS_ACTIVE) == 0)
369			break;
370		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
371	}
372	taskqueue_run(tq, &running);
373
374	/* rendezvous with thread that asked us to terminate */
375	tq->tq_tcount--;
376	wakeup_one(tq->tq_threads);
377	TQ_UNLOCK(tq);
378	kthread_exit();
379}
380
381void
382taskqueue_thread_enqueue(void *context)
383{
384	struct taskqueue **tqp, *tq;
385
386	tqp = context;
387	tq = *tqp;
388
389	mtx_assert(&tq->tq_mutex, MA_OWNED);
390	wakeup_one(tq);
391}
392
393TASKQUEUE_DEFINE(swi, taskqueue_swi_enqueue, NULL,
394		 swi_add(NULL, "task queue", taskqueue_swi_run, NULL, SWI_TQ,
395		     INTR_MPSAFE, &taskqueue_ih));
396
397TASKQUEUE_DEFINE(swi_giant, taskqueue_swi_giant_enqueue, NULL,
398		 swi_add(NULL, "Giant taskq", taskqueue_swi_giant_run,
399		     NULL, SWI_TQ_GIANT, 0, &taskqueue_giant_ih));
400
401TASKQUEUE_DEFINE_THREAD(thread);
402
403struct taskqueue *
404taskqueue_create_fast(const char *name, int mflags,
405		 taskqueue_enqueue_fn enqueue, void *context)
406{
407	return _taskqueue_create(name, mflags, enqueue, context,
408			MTX_SPIN, "fast_taskqueue");
409}
410
411/* NB: for backwards compatibility */
412int
413taskqueue_enqueue_fast(struct taskqueue *queue, struct task *task)
414{
415	return taskqueue_enqueue(queue, task);
416}
417
418static void	*taskqueue_fast_ih;
419
420static void
421taskqueue_fast_enqueue(void *context)
422{
423	swi_sched(taskqueue_fast_ih, 0);
424}
425
426static void
427taskqueue_fast_run(void *dummy)
428{
429	TQ_LOCK(taskqueue_fast);
430	taskqueue_run(taskqueue_fast, &taskqueue_fast->tq_running);
431	TQ_UNLOCK(taskqueue_fast);
432}
433
434TASKQUEUE_FAST_DEFINE(fast, taskqueue_fast_enqueue, NULL,
435	swi_add(NULL, "Fast task queue", taskqueue_fast_run, NULL,
436	SWI_TQ_FAST, INTR_MPSAFE, &taskqueue_fast_ih));
437
438int
439taskqueue_member(struct taskqueue *queue, struct thread *td)
440{
441	int i, j, ret = 0;
442
443	TQ_LOCK(queue);
444	for (i = 0, j = 0; ; i++) {
445		if (queue->tq_threads[i] == NULL)
446			continue;
447		if (queue->tq_threads[i] == td) {
448			ret = 1;
449			break;
450		}
451		if (++j >= queue->tq_tcount)
452			break;
453	}
454	TQ_UNLOCK(queue);
455	return (ret);
456}
457