subr_taskqueue.c revision 188548 
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 188548 2009-02-13 01:16:51Z thompsa $");
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;
48static STAILQ_HEAD(taskqueue_list, taskqueue) taskqueue_queues;
49static struct mtx taskqueue_queues_mutex;
50
51struct taskqueue {
52	STAILQ_ENTRY(taskqueue)	tq_link;
53	STAILQ_HEAD(, task)	tq_queue;
54	const char		*tq_name;
55	taskqueue_enqueue_fn	tq_enqueue;
56	void			*tq_context;
57	struct task		*tq_running;
58	struct mtx		tq_mutex;
59	struct thread		**tq_threads;
60	int			tq_tcount;
61	int			tq_spin;
62	int			tq_flags;
63};
64
65#define	TQ_FLAGS_ACTIVE		(1 << 0)
66#define	TQ_FLAGS_BLOCKED	(1 << 1)
67#define	TQ_FLAGS_PENDING	(1 << 2)
68
69static __inline void
70TQ_LOCK(struct taskqueue *tq)
71{
72	if (tq->tq_spin)
73		mtx_lock_spin(&tq->tq_mutex);
74	else
75		mtx_lock(&tq->tq_mutex);
76}
77
78static __inline void
79TQ_UNLOCK(struct taskqueue *tq)
80{
81	if (tq->tq_spin)
82		mtx_unlock_spin(&tq->tq_mutex);
83	else
84		mtx_unlock(&tq->tq_mutex);
85}
86
87static void	init_taskqueue_list(void *data);
88
89static __inline int
90TQ_SLEEP(struct taskqueue *tq, void *p, struct mtx *m, int pri, const char *wm,
91    int t)
92{
93	if (tq->tq_spin)
94		return (msleep_spin(p, m, wm, t));
95	return (msleep(p, m, pri, wm, t));
96}
97
98static void
99init_taskqueue_list(void *data __unused)
100{
101
102	mtx_init(&taskqueue_queues_mutex, "taskqueue list", NULL, MTX_DEF);
103	STAILQ_INIT(&taskqueue_queues);
104}
105SYSINIT(taskqueue_list, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_taskqueue_list,
106    NULL);
107
108static struct taskqueue *
109_taskqueue_create(const char *name, int mflags,
110		 taskqueue_enqueue_fn enqueue, void *context,
111		 int mtxflags, const char *mtxname)
112{
113	struct taskqueue *queue;
114
115	queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
116	if (!queue)
117		return NULL;
118
119	STAILQ_INIT(&queue->tq_queue);
120	queue->tq_name = name;
121	queue->tq_enqueue = enqueue;
122	queue->tq_context = context;
123	queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
124	queue->tq_flags |= TQ_FLAGS_ACTIVE;
125	mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);
126
127	mtx_lock(&taskqueue_queues_mutex);
128	STAILQ_INSERT_TAIL(&taskqueue_queues, queue, tq_link);
129	mtx_unlock(&taskqueue_queues_mutex);
130
131	return queue;
132}
133
134struct taskqueue *
135taskqueue_create(const char *name, int mflags,
136		 taskqueue_enqueue_fn enqueue, void *context)
137{
138	return _taskqueue_create(name, mflags, enqueue, context,
139			MTX_DEF, "taskqueue");
140}
141
142/*
143 * Signal a taskqueue thread to terminate.
144 */
145static void
146taskqueue_terminate(struct thread **pp, struct taskqueue *tq)
147{
148
149	while (tq->tq_tcount > 0) {
150		wakeup(tq);
151		TQ_SLEEP(tq, pp, &tq->tq_mutex, PWAIT, "taskqueue_destroy", 0);
152	}
153}
154
155void
156taskqueue_free(struct taskqueue *queue)
157{
158
159	mtx_lock(&taskqueue_queues_mutex);
160	STAILQ_REMOVE(&taskqueue_queues, queue, taskqueue, tq_link);
161	mtx_unlock(&taskqueue_queues_mutex);
162
163	TQ_LOCK(queue);
164	queue->tq_flags &= ~TQ_FLAGS_ACTIVE;
165	taskqueue_run(queue);
166	taskqueue_terminate(queue->tq_threads, queue);
167	mtx_destroy(&queue->tq_mutex);
168	free(queue->tq_threads, M_TASKQUEUE);
169	free(queue, M_TASKQUEUE);
170}
171
172/*
173 * Returns with the taskqueue locked.
174 */
175struct taskqueue *
176taskqueue_find(const char *name)
177{
178	struct taskqueue *queue;
179
180	mtx_lock(&taskqueue_queues_mutex);
181	STAILQ_FOREACH(queue, &taskqueue_queues, tq_link) {
182		if (strcmp(queue->tq_name, name) == 0) {
183			TQ_LOCK(queue);
184			mtx_unlock(&taskqueue_queues_mutex);
185			return queue;
186		}
187	}
188	mtx_unlock(&taskqueue_queues_mutex);
189	return NULL;
190}
191
192int
193taskqueue_enqueue(struct taskqueue *queue, struct task *task)
194{
195	struct task *ins;
196	struct task *prev;
197
198	TQ_LOCK(queue);
199
200	/*
201	 * Count multiple enqueues.
202	 */
203	if (task->ta_pending) {
204		task->ta_pending++;
205		TQ_UNLOCK(queue);
206		return 0;
207	}
208
209	/*
210	 * Optimise the case when all tasks have the same priority.
211	 */
212	prev = STAILQ_LAST(&queue->tq_queue, task, ta_link);
213	if (!prev || prev->ta_priority >= task->ta_priority) {
214		STAILQ_INSERT_TAIL(&queue->tq_queue, task, ta_link);
215	} else {
216		prev = NULL;
217		for (ins = STAILQ_FIRST(&queue->tq_queue); ins;
218		     prev = ins, ins = STAILQ_NEXT(ins, ta_link))
219			if (ins->ta_priority < task->ta_priority)
220				break;
221
222		if (prev)
223			STAILQ_INSERT_AFTER(&queue->tq_queue, prev, task, ta_link);
224		else
225			STAILQ_INSERT_HEAD(&queue->tq_queue, task, ta_link);
226	}
227
228	task->ta_pending = 1;
229	if ((queue->tq_flags & TQ_FLAGS_BLOCKED) == 0)
230		queue->tq_enqueue(queue->tq_context);
231	else
232		queue->tq_flags |= TQ_FLAGS_PENDING;
233
234	TQ_UNLOCK(queue);
235
236	return 0;
237}
238
239void
240taskqueue_block(struct taskqueue *queue)
241{
242
243	TQ_LOCK(queue);
244	queue->tq_flags |= TQ_FLAGS_BLOCKED;
245	TQ_UNLOCK(queue);
246}
247
248void
249taskqueue_unblock(struct taskqueue *queue)
250{
251
252	TQ_LOCK(queue);
253	queue->tq_flags &= ~TQ_FLAGS_BLOCKED;
254	if (queue->tq_flags & TQ_FLAGS_PENDING) {
255		queue->tq_flags &= ~TQ_FLAGS_PENDING;
256		queue->tq_enqueue(queue->tq_context);
257	}
258	TQ_UNLOCK(queue);
259}
260
261void
262taskqueue_run(struct taskqueue *queue)
263{
264	struct task *task;
265	int owned, pending;
266
267	owned = mtx_owned(&queue->tq_mutex);
268	if (!owned)
269		TQ_LOCK(queue);
270	while (STAILQ_FIRST(&queue->tq_queue)) {
271		/*
272		 * Carefully remove the first task from the queue and
273		 * zero its pending count.
274		 */
275		task = STAILQ_FIRST(&queue->tq_queue);
276		STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
277		pending = task->ta_pending;
278		task->ta_pending = 0;
279		queue->tq_running = task;
280		TQ_UNLOCK(queue);
281
282		task->ta_func(task->ta_context, pending);
283
284		TQ_LOCK(queue);
285		queue->tq_running = NULL;
286		wakeup(task);
287	}
288
289	/*
290	 * For compatibility, unlock on return if the queue was not locked
291	 * on entry, although this opens a race window.
292	 */
293	if (!owned)
294		TQ_UNLOCK(queue);
295}
296
297void
298taskqueue_drain(struct taskqueue *queue, struct task *task)
299{
300	if (queue->tq_spin) {		/* XXX */
301		mtx_lock_spin(&queue->tq_mutex);
302		while (task->ta_pending != 0 || task == queue->tq_running)
303			msleep_spin(task, &queue->tq_mutex, "-", 0);
304		mtx_unlock_spin(&queue->tq_mutex);
305	} else {
306		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
307
308		mtx_lock(&queue->tq_mutex);
309		while (task->ta_pending != 0 || task == queue->tq_running)
310			msleep(task, &queue->tq_mutex, PWAIT, "-", 0);
311		mtx_unlock(&queue->tq_mutex);
312	}
313}
314
315static void
316taskqueue_swi_enqueue(void *context)
317{
318	swi_sched(taskqueue_ih, 0);
319}
320
321static void
322taskqueue_swi_run(void *dummy)
323{
324	taskqueue_run(taskqueue_swi);
325}
326
327static void
328taskqueue_swi_giant_enqueue(void *context)
329{
330	swi_sched(taskqueue_giant_ih, 0);
331}
332
333static void
334taskqueue_swi_giant_run(void *dummy)
335{
336	taskqueue_run(taskqueue_swi_giant);
337}
338
339int
340taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
341			const char *name, ...)
342{
343	va_list ap;
344	struct thread *td;
345	struct taskqueue *tq;
346	int i, error;
347	char ktname[MAXCOMLEN];
348
349	if (count <= 0)
350		return (EINVAL);
351
352	tq = *tqp;
353
354	va_start(ap, name);
355	vsnprintf(ktname, MAXCOMLEN, name, ap);
356	va_end(ap);
357
358	tq->tq_threads = malloc(sizeof(struct thread *) * count, M_TASKQUEUE,
359	    M_NOWAIT | M_ZERO);
360	if (tq->tq_threads == NULL) {
361		printf("%s: no memory for %s threads\n", __func__, ktname);
362		return (ENOMEM);
363	}
364
365	for (i = 0; i < count; i++) {
366		if (count == 1)
367			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
368			    &tq->tq_threads[i], RFSTOPPED, 0, ktname);
369		else
370			error = kthread_add(taskqueue_thread_loop, tqp, NULL,
371			    &tq->tq_threads[i], RFSTOPPED, 0,
372			    "%s_%d", ktname, i);
373		if (error) {
374			/* should be ok to continue, taskqueue_free will dtrt */
375			printf("%s: kthread_add(%s): error %d", __func__,
376			    ktname, error);
377			tq->tq_threads[i] = NULL;		/* paranoid */
378		} else
379			tq->tq_tcount++;
380	}
381	for (i = 0; i < count; i++) {
382		if (tq->tq_threads[i] == NULL)
383			continue;
384		td = tq->tq_threads[i];
385		thread_lock(td);
386		sched_prio(td, pri);
387		sched_add(td, SRQ_BORING);
388		thread_unlock(td);
389	}
390
391	return (0);
392}
393
394void
395taskqueue_thread_loop(void *arg)
396{
397	struct taskqueue **tqp, *tq;
398
399	tqp = arg;
400	tq = *tqp;
401	TQ_LOCK(tq);
402	while ((tq->tq_flags & TQ_FLAGS_ACTIVE) != 0) {
403		taskqueue_run(tq);
404		TQ_SLEEP(tq, tq, &tq->tq_mutex, 0, "-", 0);
405	};
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