xref: /openbsd-src/lib/libevent/event.c (revision 2b0358df1d88d06ef4139321dd05bd5e05d91eaf)
1 /*	$OpenBSD: event.c,v 1.19 2008/05/02 18:26:42 brad Exp $	*/
2 
3 /*
4  * Copyright (c) 2000-2004 Niels Provos <provos@citi.umich.edu>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. The name of the author may not be used to endorse or promote products
16  *    derived from this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 #ifdef HAVE_CONFIG_H
30 #include "config.h"
31 #endif
32 
33 #ifdef WIN32
34 #define WIN32_LEAN_AND_MEAN
35 #include <windows.h>
36 #undef WIN32_LEAN_AND_MEAN
37 #include "misc.h"
38 #endif
39 #include <sys/types.h>
40 #include <sys/tree.h>
41 #ifdef HAVE_SYS_TIME_H
42 #include <sys/time.h>
43 #else
44 #include <sys/_time.h>
45 #endif
46 #include <sys/queue.h>
47 #include <stdio.h>
48 #include <stdlib.h>
49 #ifndef WIN32
50 #include <unistd.h>
51 #endif
52 #include <errno.h>
53 #include <signal.h>
54 #include <string.h>
55 #include <assert.h>
56 #include <time.h>
57 
58 #include "event.h"
59 #include "event-internal.h"
60 #include "log.h"
61 
62 #ifdef HAVE_EVENT_PORTS
63 extern const struct eventop evportops;
64 #endif
65 #ifdef HAVE_SELECT
66 extern const struct eventop selectops;
67 #endif
68 #ifdef HAVE_POLL
69 extern const struct eventop pollops;
70 #endif
71 #ifdef HAVE_RTSIG
72 extern const struct eventop rtsigops;
73 #endif
74 #ifdef HAVE_EPOLL
75 extern const struct eventop epollops;
76 #endif
77 #ifdef HAVE_WORKING_KQUEUE
78 extern const struct eventop kqops;
79 #endif
80 #ifdef HAVE_DEVPOLL
81 extern const struct eventop devpollops;
82 #endif
83 #ifdef WIN32
84 extern const struct eventop win32ops;
85 #endif
86 
87 /* In order of preference */
88 const struct eventop *eventops[] = {
89 #ifdef HAVE_EVENT_PORTS
90 	&evportops,
91 #endif
92 #ifdef HAVE_WORKING_KQUEUE
93 	&kqops,
94 #endif
95 #ifdef HAVE_EPOLL
96 	&epollops,
97 #endif
98 #ifdef HAVE_DEVPOLL
99 	&devpollops,
100 #endif
101 #ifdef HAVE_RTSIG
102 	&rtsigops,
103 #endif
104 #ifdef HAVE_POLL
105 	&pollops,
106 #endif
107 #ifdef HAVE_SELECT
108 	&selectops,
109 #endif
110 #ifdef WIN32
111 	&win32ops,
112 #endif
113 	NULL
114 };
115 
116 /* Global state */
117 struct event_base *current_base = NULL;
118 extern struct event_base *evsignal_base;
119 static int use_monotonic;
120 
121 /* Handle signals - This is a deprecated interface */
122 int (*event_sigcb)(void);		/* Signal callback when gotsig is set */
123 volatile sig_atomic_t event_gotsig;	/* Set in signal handler */
124 
125 /* Prototypes */
126 static void	event_queue_insert(struct event_base *, struct event *, int);
127 static void	event_queue_remove(struct event_base *, struct event *, int);
128 static int	event_haveevents(struct event_base *);
129 
130 static void	event_process_active(struct event_base *);
131 
132 static int	timeout_next(struct event_base *, struct timeval **);
133 static void	timeout_process(struct event_base *);
134 static void	timeout_correct(struct event_base *, struct timeval *);
135 
136 static int
137 compare(struct event *a, struct event *b)
138 {
139 	if (timercmp(&a->ev_timeout, &b->ev_timeout, <))
140 		return (-1);
141 	else if (timercmp(&a->ev_timeout, &b->ev_timeout, >))
142 		return (1);
143 	if (a < b)
144 		return (-1);
145 	else if (a > b)
146 		return (1);
147 	return (0);
148 }
149 
150 static void
151 detect_monotonic(void)
152 {
153 #if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
154 	struct timespec	ts;
155 
156 	if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
157 		use_monotonic = 1;
158 #endif
159 }
160 
161 static int
162 gettime(struct timeval *tp)
163 {
164 #if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
165 	struct timespec	ts;
166 
167 	if (use_monotonic) {
168 		if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
169 			return (-1);
170 
171 		tp->tv_sec = ts.tv_sec;
172 		tp->tv_usec = ts.tv_nsec / 1000;
173 		return (0);
174 	}
175 #endif
176 
177 	return (gettimeofday(tp, NULL));
178 }
179 
180 RB_PROTOTYPE(event_tree, event, ev_timeout_node, compare);
181 
182 RB_GENERATE(event_tree, event, ev_timeout_node, compare);
183 
184 
185 struct event_base *
186 event_init(void)
187 {
188 	int i;
189 	struct event_base *base;
190 
191 	if ((base = calloc(1, sizeof(struct event_base))) == NULL)
192 		event_err(1, "%s: calloc");
193 
194 	event_sigcb = NULL;
195 	event_gotsig = 0;
196 
197 	detect_monotonic();
198 	gettime(&base->event_tv);
199 
200 	RB_INIT(&base->timetree);
201 	TAILQ_INIT(&base->eventqueue);
202 	TAILQ_INIT(&base->sig.signalqueue);
203 	base->sig.ev_signal_pair[0] = -1;
204 	base->sig.ev_signal_pair[1] = -1;
205 
206 	base->evbase = NULL;
207 	for (i = 0; eventops[i] && !base->evbase; i++) {
208 		base->evsel = eventops[i];
209 
210 		base->evbase = base->evsel->init(base);
211 	}
212 
213 	if (base->evbase == NULL)
214 		event_errx(1, "%s: no event mechanism available", __func__);
215 
216 	if (getenv("EVENT_SHOW_METHOD"))
217 		event_msgx("libevent using: %s\n",
218 			   base->evsel->name);
219 
220 	/* allocate a single active event queue */
221 	event_base_priority_init(base, 1);
222 
223 	current_base = base;
224 	return (base);
225 }
226 
227 void
228 event_base_free(struct event_base *base)
229 {
230 	int i;
231 
232 	if (base == NULL && current_base)
233 		base = current_base;
234         if (base == current_base)
235 		current_base = NULL;
236 
237 	assert(base);
238 	if (base->evsel->dealloc != NULL)
239 		base->evsel->dealloc(base, base->evbase);
240 	for (i=0; i < base->nactivequeues; ++i)
241 		assert(TAILQ_EMPTY(base->activequeues[i]));
242 
243 	assert(RB_EMPTY(&base->timetree));
244 
245 	for (i = 0; i < base->nactivequeues; ++i)
246 		free(base->activequeues[i]);
247 	free(base->activequeues);
248 
249 	assert(TAILQ_EMPTY(&base->eventqueue));
250 
251 	free(base);
252 }
253 
254 int
255 event_priority_init(int npriorities)
256 {
257   return event_base_priority_init(current_base, npriorities);
258 }
259 
260 int
261 event_base_priority_init(struct event_base *base, int npriorities)
262 {
263 	int i;
264 
265 	if (base->event_count_active)
266 		return (-1);
267 
268 	if (base->nactivequeues && npriorities != base->nactivequeues) {
269 		for (i = 0; i < base->nactivequeues; ++i) {
270 			free(base->activequeues[i]);
271 		}
272 		free(base->activequeues);
273 	}
274 
275 	/* Allocate our priority queues */
276 	base->nactivequeues = npriorities;
277 	base->activequeues = (struct event_list **)calloc(base->nactivequeues,
278 	    npriorities * sizeof(struct event_list *));
279 	if (base->activequeues == NULL)
280 		event_err(1, "%s: calloc", __func__);
281 
282 	for (i = 0; i < base->nactivequeues; ++i) {
283 		base->activequeues[i] = malloc(sizeof(struct event_list));
284 		if (base->activequeues[i] == NULL)
285 			event_err(1, "%s: malloc", __func__);
286 		TAILQ_INIT(base->activequeues[i]);
287 	}
288 
289 	return (0);
290 }
291 
292 int
293 event_haveevents(struct event_base *base)
294 {
295 	return (base->event_count > 0);
296 }
297 
298 /*
299  * Active events are stored in priority queues.  Lower priorities are always
300  * process before higher priorities.  Low priority events can starve high
301  * priority ones.
302  */
303 
304 static void
305 event_process_active(struct event_base *base)
306 {
307 	struct event *ev;
308 	struct event_list *activeq = NULL;
309 	int i;
310 	short ncalls;
311 
312 	if (!base->event_count_active)
313 		return;
314 
315 	for (i = 0; i < base->nactivequeues; ++i) {
316 		if (TAILQ_FIRST(base->activequeues[i]) != NULL) {
317 			activeq = base->activequeues[i];
318 			break;
319 		}
320 	}
321 
322 	assert(activeq != NULL);
323 
324 	for (ev = TAILQ_FIRST(activeq); ev; ev = TAILQ_FIRST(activeq)) {
325 		event_queue_remove(base, ev, EVLIST_ACTIVE);
326 
327 		/* Allows deletes to work */
328 		ncalls = ev->ev_ncalls;
329 		ev->ev_pncalls = &ncalls;
330 		while (ncalls) {
331 			ncalls--;
332 			ev->ev_ncalls = ncalls;
333 			(*ev->ev_callback)((int)ev->ev_fd, ev->ev_res, ev->ev_arg);
334 			if (event_gotsig)
335 				return;
336 		}
337 	}
338 }
339 
340 /*
341  * Wait continously for events.  We exit only if no events are left.
342  */
343 
344 int
345 event_dispatch(void)
346 {
347 	return (event_loop(0));
348 }
349 
350 int
351 event_base_dispatch(struct event_base *event_base)
352 {
353   return (event_base_loop(event_base, 0));
354 }
355 
356 static void
357 event_loopexit_cb(int fd, short what, void *arg)
358 {
359 	struct event_base *base = arg;
360 	base->event_gotterm = 1;
361 }
362 
363 /* not thread safe */
364 int
365 event_loopexit(struct timeval *tv)
366 {
367 	return (event_once(-1, EV_TIMEOUT, event_loopexit_cb,
368 		    current_base, tv));
369 }
370 
371 int
372 event_base_loopexit(struct event_base *event_base, struct timeval *tv)
373 {
374 	return (event_base_once(event_base, -1, EV_TIMEOUT, event_loopexit_cb,
375 		    event_base, tv));
376 }
377 
378 /* not thread safe */
379 
380 int
381 event_loop(int flags)
382 {
383 	return event_base_loop(current_base, flags);
384 }
385 
386 int
387 event_base_loop(struct event_base *base, int flags)
388 {
389 	const struct eventop *evsel = base->evsel;
390 	void *evbase = base->evbase;
391 	struct timeval tv;
392 	struct timeval *tv_p;
393 	int res, done;
394 
395 #ifndef WIN32
396 	if(!TAILQ_EMPTY(&base->sig.signalqueue))
397 		evsignal_base = base;
398 #endif
399 	done = 0;
400 	while (!done) {
401 		/* Calculate the initial events that we are waiting for */
402 		if (evsel->recalc(base, evbase, 0) == -1)
403 			return (-1);
404 
405 		/* Terminate the loop if we have been asked to */
406 		if (base->event_gotterm) {
407 			base->event_gotterm = 0;
408 			break;
409 		}
410 
411 		/* You cannot use this interface for multi-threaded apps */
412 		while (event_gotsig) {
413 			event_gotsig = 0;
414 			if (event_sigcb) {
415 				res = (*event_sigcb)();
416 				if (res == -1) {
417 					errno = EINTR;
418 					return (-1);
419 				}
420 			}
421 		}
422 
423 		timeout_correct(base, &tv);
424 
425 		tv_p = &tv;
426 		if (!base->event_count_active && !(flags & EVLOOP_NONBLOCK)) {
427 			timeout_next(base, &tv_p);
428 		} else {
429 			/*
430 			 * if we have active events, we just poll new events
431 			 * without waiting.
432 			 */
433 			timerclear(&tv);
434 		}
435 
436 		/* If we have no events, we just exit */
437 		if (!event_haveevents(base)) {
438 			event_debug(("%s: no events registered.", __func__));
439 			return (1);
440 		}
441 
442 		res = evsel->dispatch(base, evbase, tv_p);
443 
444 		if (res == -1)
445 			return (-1);
446 
447 		timeout_process(base);
448 
449 		if (base->event_count_active) {
450 			event_process_active(base);
451 			if (!base->event_count_active && (flags & EVLOOP_ONCE))
452 				done = 1;
453 		} else if (flags & EVLOOP_NONBLOCK)
454 			done = 1;
455 	}
456 
457 	event_debug(("%s: asked to terminate loop.", __func__));
458 	return (0);
459 }
460 
461 /* Sets up an event for processing once */
462 
463 struct event_once {
464 	struct event ev;
465 
466 	void (*cb)(int, short, void *);
467 	void *arg;
468 };
469 
470 /* One-time callback, it deletes itself */
471 
472 static void
473 event_once_cb(int fd, short events, void *arg)
474 {
475 	struct event_once *eonce = arg;
476 
477 	(*eonce->cb)(fd, events, eonce->arg);
478 	free(eonce);
479 }
480 
481 /* not threadsafe, event scheduled once. */
482 int
483 event_once(int fd, short events,
484     void (*callback)(int, short, void *), void *arg, struct timeval *tv)
485 {
486 	return event_base_once(current_base, fd, events, callback, arg, tv);
487 }
488 
489 /* Schedules an event once */
490 int
491 event_base_once(struct event_base *base, int fd, short events,
492     void (*callback)(int, short, void *), void *arg, struct timeval *tv)
493 {
494 	struct event_once *eonce;
495 	struct timeval etv;
496 	int res;
497 
498 	/* We cannot support signals that just fire once */
499 	if (events & EV_SIGNAL)
500 		return (-1);
501 
502 	if ((eonce = calloc(1, sizeof(struct event_once))) == NULL)
503 		return (-1);
504 
505 	eonce->cb = callback;
506 	eonce->arg = arg;
507 
508 	if (events == EV_TIMEOUT) {
509 		if (tv == NULL) {
510 			timerclear(&etv);
511 			tv = &etv;
512 		}
513 
514 		evtimer_set(&eonce->ev, event_once_cb, eonce);
515 	} else if (events & (EV_READ|EV_WRITE)) {
516 		events &= EV_READ|EV_WRITE;
517 
518 		event_set(&eonce->ev, fd, events, event_once_cb, eonce);
519 	} else {
520 		/* Bad event combination */
521 		free(eonce);
522 		return (-1);
523 	}
524 
525 	res = event_base_set(base, &eonce->ev);
526 	if (res == 0)
527 		res = event_add(&eonce->ev, tv);
528 	if (res != 0) {
529 		free(eonce);
530 		return (res);
531 	}
532 
533 	return (0);
534 }
535 
536 void
537 event_set(struct event *ev, int fd, short events,
538 	  void (*callback)(int, short, void *), void *arg)
539 {
540 	/* Take the current base - caller needs to set the real base later */
541 	ev->ev_base = current_base;
542 
543 	ev->ev_callback = callback;
544 	ev->ev_arg = arg;
545 	ev->ev_fd = fd;
546 	ev->ev_events = events;
547 	ev->ev_res = 0;
548 	ev->ev_flags = EVLIST_INIT;
549 	ev->ev_ncalls = 0;
550 	ev->ev_pncalls = NULL;
551 
552 	/* by default, we put new events into the middle priority */
553 	if(current_base)
554 		ev->ev_pri = current_base->nactivequeues/2;
555 }
556 
557 int
558 event_base_set(struct event_base *base, struct event *ev)
559 {
560 	/* Only innocent events may be assigned to a different base */
561 	if (ev->ev_flags != EVLIST_INIT)
562 		return (-1);
563 
564 	ev->ev_base = base;
565 	ev->ev_pri = base->nactivequeues/2;
566 
567 	return (0);
568 }
569 
570 /*
571  * Set's the priority of an event - if an event is already scheduled
572  * changing the priority is going to fail.
573  */
574 
575 int
576 event_priority_set(struct event *ev, int pri)
577 {
578 	if (ev->ev_flags & EVLIST_ACTIVE)
579 		return (-1);
580 	if (pri < 0 || pri >= ev->ev_base->nactivequeues)
581 		return (-1);
582 
583 	ev->ev_pri = pri;
584 
585 	return (0);
586 }
587 
588 /*
589  * Checks if a specific event is pending or scheduled.
590  */
591 
592 int
593 event_pending(struct event *ev, short event, struct timeval *tv)
594 {
595 	struct timeval	now, res;
596 	int flags = 0;
597 
598 	if (ev->ev_flags & EVLIST_INSERTED)
599 		flags |= (ev->ev_events & (EV_READ|EV_WRITE));
600 	if (ev->ev_flags & EVLIST_ACTIVE)
601 		flags |= ev->ev_res;
602 	if (ev->ev_flags & EVLIST_TIMEOUT)
603 		flags |= EV_TIMEOUT;
604 	if (ev->ev_flags & EVLIST_SIGNAL)
605 		flags |= EV_SIGNAL;
606 
607 	event &= (EV_TIMEOUT|EV_READ|EV_WRITE|EV_SIGNAL);
608 
609 	/* See if there is a timeout that we should report */
610 	if (tv != NULL && (flags & event & EV_TIMEOUT)) {
611 		gettime(&now);
612 		timersub(&ev->ev_timeout, &now, &res);
613 		/* correctly remap to real time */
614 		gettimeofday(&now, NULL);
615 		timeradd(&now, &res, tv);
616 	}
617 
618 	return (flags & event);
619 }
620 
621 int
622 event_add(struct event *ev, struct timeval *tv)
623 {
624 	struct event_base *base = ev->ev_base;
625 	const struct eventop *evsel = base->evsel;
626 	void *evbase = base->evbase;
627 
628 	event_debug((
629 		 "event_add: event: %p, %s%s%scall %p",
630 		 ev,
631 		 ev->ev_events & EV_READ ? "EV_READ " : " ",
632 		 ev->ev_events & EV_WRITE ? "EV_WRITE " : " ",
633 		 tv ? "EV_TIMEOUT " : " ",
634 		 ev->ev_callback));
635 
636 	assert(!(ev->ev_flags & ~EVLIST_ALL));
637 
638 	if (tv != NULL) {
639 		struct timeval now;
640 
641 		if (ev->ev_flags & EVLIST_TIMEOUT)
642 			event_queue_remove(base, ev, EVLIST_TIMEOUT);
643 
644 		/* Check if it is active due to a timeout.  Rescheduling
645 		 * this timeout before the callback can be executed
646 		 * removes it from the active list. */
647 		if ((ev->ev_flags & EVLIST_ACTIVE) &&
648 		    (ev->ev_res & EV_TIMEOUT)) {
649 			/* See if we are just active executing this
650 			 * event in a loop
651 			 */
652 			if (ev->ev_ncalls && ev->ev_pncalls) {
653 				/* Abort loop */
654 				*ev->ev_pncalls = 0;
655 			}
656 
657 			event_queue_remove(base, ev, EVLIST_ACTIVE);
658 		}
659 
660 		gettime(&now);
661 		timeradd(&now, tv, &ev->ev_timeout);
662 
663 		event_debug((
664 			 "event_add: timeout in %d seconds, call %p",
665 			 tv->tv_sec, ev->ev_callback));
666 
667 		event_queue_insert(base, ev, EVLIST_TIMEOUT);
668 	}
669 
670 	if ((ev->ev_events & (EV_READ|EV_WRITE)) &&
671 	    !(ev->ev_flags & (EVLIST_INSERTED|EVLIST_ACTIVE))) {
672 		event_queue_insert(base, ev, EVLIST_INSERTED);
673 
674 		return (evsel->add(evbase, ev));
675 	} else if ((ev->ev_events & EV_SIGNAL) &&
676 	    !(ev->ev_flags & EVLIST_SIGNAL)) {
677 		event_queue_insert(base, ev, EVLIST_SIGNAL);
678 
679 		return (evsel->add(evbase, ev));
680 	}
681 
682 	return (0);
683 }
684 
685 int
686 event_del(struct event *ev)
687 {
688 	struct event_base *base;
689 	const struct eventop *evsel;
690 	void *evbase;
691 
692 	event_debug(("event_del: %p, callback %p",
693 		 ev, ev->ev_callback));
694 
695 	/* An event without a base has not been added */
696 	if (ev->ev_base == NULL)
697 		return (-1);
698 
699 	base = ev->ev_base;
700 	evsel = base->evsel;
701 	evbase = base->evbase;
702 
703 	assert(!(ev->ev_flags & ~EVLIST_ALL));
704 
705 	/* See if we are just active executing this event in a loop */
706 	if (ev->ev_ncalls && ev->ev_pncalls) {
707 		/* Abort loop */
708 		*ev->ev_pncalls = 0;
709 	}
710 
711 	if (ev->ev_flags & EVLIST_TIMEOUT)
712 		event_queue_remove(base, ev, EVLIST_TIMEOUT);
713 
714 	if (ev->ev_flags & EVLIST_ACTIVE)
715 		event_queue_remove(base, ev, EVLIST_ACTIVE);
716 
717 	if (ev->ev_flags & EVLIST_INSERTED) {
718 		event_queue_remove(base, ev, EVLIST_INSERTED);
719 		return (evsel->del(evbase, ev));
720 	} else if (ev->ev_flags & EVLIST_SIGNAL) {
721 		event_queue_remove(base, ev, EVLIST_SIGNAL);
722 		return (evsel->del(evbase, ev));
723 	}
724 
725 	return (0);
726 }
727 
728 void
729 event_active(struct event *ev, int res, short ncalls)
730 {
731 	/* We get different kinds of events, add them together */
732 	if (ev->ev_flags & EVLIST_ACTIVE) {
733 		ev->ev_res |= res;
734 		return;
735 	}
736 
737 	ev->ev_res = res;
738 	ev->ev_ncalls = ncalls;
739 	ev->ev_pncalls = NULL;
740 	event_queue_insert(ev->ev_base, ev, EVLIST_ACTIVE);
741 }
742 
743 static int
744 timeout_next(struct event_base *base, struct timeval **tv_p)
745 {
746 	struct timeval now;
747 	struct event *ev;
748 	struct timeval *tv = *tv_p;
749 
750 	if ((ev = RB_MIN(event_tree, &base->timetree)) == NULL) {
751 		/* if no time-based events are active wait for I/O */
752 		*tv_p = NULL;
753 		return (0);
754 	}
755 
756 	if (gettime(&now) == -1)
757 		return (-1);
758 
759 	if (timercmp(&ev->ev_timeout, &now, <=)) {
760 		timerclear(tv);
761 		return (0);
762 	}
763 
764 	timersub(&ev->ev_timeout, &now, tv);
765 
766 	assert(tv->tv_sec >= 0);
767 	assert(tv->tv_usec >= 0);
768 
769 	event_debug(("timeout_next: in %d seconds", tv->tv_sec));
770 	return (0);
771 }
772 
773 /*
774  * Determines if the time is running backwards by comparing the current
775  * time against the last time we checked.  Not needed when using clock
776  * monotonic.
777  */
778 
779 static void
780 timeout_correct(struct event_base *base, struct timeval *tv)
781 {
782 	struct event *ev;
783 	struct timeval off;
784 
785 	if (use_monotonic)
786 		return;
787 
788 	/* Check if time is running backwards */
789 	gettime(tv);
790 	if (timercmp(tv, &base->event_tv, >=)) {
791 		base->event_tv = *tv;
792 		return;
793 	}
794 
795 	event_debug(("%s: time is running backwards, corrected",
796 		    __func__));
797 	timersub(&base->event_tv, tv, &off);
798 
799 	/*
800 	 * We can modify the key element of the node without destroying
801 	 * the key, beause we apply it to all in the right order.
802 	 */
803 	RB_FOREACH(ev, event_tree, &base->timetree)
804 		timersub(&ev->ev_timeout, &off, &ev->ev_timeout);
805 }
806 
807 void
808 timeout_process(struct event_base *base)
809 {
810 	struct timeval now;
811 	struct event *ev, *next;
812 
813 	gettime(&now);
814 
815 	for (ev = RB_MIN(event_tree, &base->timetree); ev; ev = next) {
816 		if (timercmp(&ev->ev_timeout, &now, >))
817 			break;
818 		next = RB_NEXT(event_tree, &base->timetree, ev);
819 
820 		event_queue_remove(base, ev, EVLIST_TIMEOUT);
821 
822 		/* delete this event from the I/O queues */
823 		event_del(ev);
824 
825 		event_debug(("timeout_process: call %p",
826 			 ev->ev_callback));
827 		event_active(ev, EV_TIMEOUT, 1);
828 	}
829 }
830 
831 void
832 event_queue_remove(struct event_base *base, struct event *ev, int queue)
833 {
834 	int docount = 1;
835 
836 	if (!(ev->ev_flags & queue))
837 		event_errx(1, "%s: %p(fd %d) not on queue %x", __func__,
838 			   ev, ev->ev_fd, queue);
839 
840 	if (ev->ev_flags & EVLIST_INTERNAL)
841 		docount = 0;
842 
843 	if (docount)
844 		base->event_count--;
845 
846 	ev->ev_flags &= ~queue;
847 	switch (queue) {
848 	case EVLIST_ACTIVE:
849 		if (docount)
850 			base->event_count_active--;
851 		TAILQ_REMOVE(base->activequeues[ev->ev_pri],
852 		    ev, ev_active_next);
853 		break;
854 	case EVLIST_SIGNAL:
855 		TAILQ_REMOVE(&base->sig.signalqueue, ev, ev_signal_next);
856 		break;
857 	case EVLIST_TIMEOUT:
858 		RB_REMOVE(event_tree, &base->timetree, ev);
859 		break;
860 	case EVLIST_INSERTED:
861 		TAILQ_REMOVE(&base->eventqueue, ev, ev_next);
862 		break;
863 	default:
864 		event_errx(1, "%s: unknown queue %x", __func__, queue);
865 	}
866 }
867 
868 void
869 event_queue_insert(struct event_base *base, struct event *ev, int queue)
870 {
871 	int docount = 1;
872 
873 	if (ev->ev_flags & queue) {
874 		/* Double insertion is possible for active events */
875 		if (queue & EVLIST_ACTIVE)
876 			return;
877 
878 		event_errx(1, "%s: %p(fd %d) already on queue %x", __func__,
879 			   ev, ev->ev_fd, queue);
880 	}
881 
882 	if (ev->ev_flags & EVLIST_INTERNAL)
883 		docount = 0;
884 
885 	if (docount)
886 		base->event_count++;
887 
888 	ev->ev_flags |= queue;
889 	switch (queue) {
890 	case EVLIST_ACTIVE:
891 		if (docount)
892 			base->event_count_active++;
893 		TAILQ_INSERT_TAIL(base->activequeues[ev->ev_pri],
894 		    ev,ev_active_next);
895 		break;
896 	case EVLIST_SIGNAL:
897 		TAILQ_INSERT_TAIL(&base->sig.signalqueue, ev, ev_signal_next);
898 		break;
899 	case EVLIST_TIMEOUT: {
900 		struct event *tmp = RB_INSERT(event_tree, &base->timetree, ev);
901 		assert(tmp == NULL);
902 		break;
903 	}
904 	case EVLIST_INSERTED:
905 		TAILQ_INSERT_TAIL(&base->eventqueue, ev, ev_next);
906 		break;
907 	default:
908 		event_errx(1, "%s: unknown queue %x", __func__, queue);
909 	}
910 }
911 
912 /* Functions for debugging */
913 
914 const char *
915 event_get_version(void)
916 {
917 	return (LIBEVENT_VERSION);
918 }
919 
920 /*
921  * No thread-safe interface needed - the information should be the same
922  * for all threads.
923  */
924 
925 const char *
926 event_get_method(void)
927 {
928 	return (current_base->evsel->name);
929 }
930