xref: /freebsd/contrib/libevent/poll.c (revision dd41de95a84d979615a2ef11df6850622bf6184e)
1 /*	$OpenBSD: poll.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
2 
3 /*
4  * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
5  * Copyright 2007-2012 Niels Provos and Nick Mathewson
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 #include "event2/event-config.h"
30 #include "evconfig-private.h"
31 
32 #ifdef EVENT__HAVE_POLL
33 
34 #include <sys/types.h>
35 #ifdef EVENT__HAVE_SYS_TIME_H
36 #include <sys/time.h>
37 #endif
38 #include <sys/queue.h>
39 #include <poll.h>
40 #include <signal.h>
41 #include <limits.h>
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include <string.h>
45 #include <unistd.h>
46 #include <errno.h>
47 
48 #include "event-internal.h"
49 #include "evsignal-internal.h"
50 #include "log-internal.h"
51 #include "evmap-internal.h"
52 #include "event2/thread.h"
53 #include "evthread-internal.h"
54 #include "time-internal.h"
55 
56 struct pollidx {
57 	int idxplus1;
58 };
59 
60 struct pollop {
61 	int event_count;		/* Highest number alloc */
62 	int nfds;			/* Highest number used */
63 	int realloc_copy;		/* True iff we must realloc
64 					 * event_set_copy */
65 	struct pollfd *event_set;
66 	struct pollfd *event_set_copy;
67 };
68 
69 static void *poll_init(struct event_base *);
70 static int poll_add(struct event_base *, int, short old, short events, void *idx);
71 static int poll_del(struct event_base *, int, short old, short events, void *idx);
72 static int poll_dispatch(struct event_base *, struct timeval *);
73 static void poll_dealloc(struct event_base *);
74 
75 const struct eventop pollops = {
76 	"poll",
77 	poll_init,
78 	poll_add,
79 	poll_del,
80 	poll_dispatch,
81 	poll_dealloc,
82 	0, /* doesn't need_reinit */
83 	EV_FEATURE_FDS,
84 	sizeof(struct pollidx),
85 };
86 
87 static void *
88 poll_init(struct event_base *base)
89 {
90 	struct pollop *pollop;
91 
92 	if (!(pollop = mm_calloc(1, sizeof(struct pollop))))
93 		return (NULL);
94 
95 	evsig_init_(base);
96 
97 	evutil_weakrand_seed_(&base->weakrand_seed, 0);
98 
99 	return (pollop);
100 }
101 
102 #ifdef CHECK_INVARIANTS
103 static void
104 poll_check_ok(struct pollop *pop)
105 {
106 	int i, idx;
107 	struct event *ev;
108 
109 	for (i = 0; i < pop->fd_count; ++i) {
110 		idx = pop->idxplus1_by_fd[i]-1;
111 		if (idx < 0)
112 			continue;
113 		EVUTIL_ASSERT(pop->event_set[idx].fd == i);
114 	}
115 	for (i = 0; i < pop->nfds; ++i) {
116 		struct pollfd *pfd = &pop->event_set[i];
117 		EVUTIL_ASSERT(pop->idxplus1_by_fd[pfd->fd] == i+1);
118 	}
119 }
120 #else
121 #define poll_check_ok(pop)
122 #endif
123 
124 static int
125 poll_dispatch(struct event_base *base, struct timeval *tv)
126 {
127 	int res, i, j, nfds;
128 	long msec = -1;
129 	struct pollop *pop = base->evbase;
130 	struct pollfd *event_set;
131 
132 	poll_check_ok(pop);
133 
134 	nfds = pop->nfds;
135 
136 #ifndef EVENT__DISABLE_THREAD_SUPPORT
137 	if (base->th_base_lock) {
138 		/* If we're using this backend in a multithreaded setting,
139 		 * then we need to work on a copy of event_set, so that we can
140 		 * let other threads modify the main event_set while we're
141 		 * polling. If we're not multithreaded, then we'll skip the
142 		 * copy step here to save memory and time. */
143 		if (pop->realloc_copy) {
144 			struct pollfd *tmp = mm_realloc(pop->event_set_copy,
145 			    pop->event_count * sizeof(struct pollfd));
146 			if (tmp == NULL) {
147 				event_warn("realloc");
148 				return -1;
149 			}
150 			pop->event_set_copy = tmp;
151 			pop->realloc_copy = 0;
152 		}
153 		memcpy(pop->event_set_copy, pop->event_set,
154 		    sizeof(struct pollfd)*nfds);
155 		event_set = pop->event_set_copy;
156 	} else {
157 		event_set = pop->event_set;
158 	}
159 #else
160 	event_set = pop->event_set;
161 #endif
162 
163 	if (tv != NULL) {
164 		msec = evutil_tv_to_msec_(tv);
165 		if (msec < 0 || msec > INT_MAX)
166 			msec = INT_MAX;
167 	}
168 
169 	EVBASE_RELEASE_LOCK(base, th_base_lock);
170 
171 	res = poll(event_set, nfds, msec);
172 
173 	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
174 
175 	if (res == -1) {
176 		if (errno != EINTR) {
177 			event_warn("poll");
178 			return (-1);
179 		}
180 
181 		return (0);
182 	}
183 
184 	event_debug(("%s: poll reports %d", __func__, res));
185 
186 	if (res == 0 || nfds == 0)
187 		return (0);
188 
189 	i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
190 	for (j = 0; j < nfds; j++) {
191 		int what;
192 		if (++i == nfds)
193 			i = 0;
194 		what = event_set[i].revents;
195 		if (!what)
196 			continue;
197 
198 		res = 0;
199 
200 		/* If the file gets closed notify */
201 		if (what & (POLLHUP|POLLERR|POLLNVAL))
202 			what |= POLLIN|POLLOUT;
203 		if (what & POLLIN)
204 			res |= EV_READ;
205 		if (what & POLLOUT)
206 			res |= EV_WRITE;
207 		if (res == 0)
208 			continue;
209 
210 		evmap_io_active_(base, event_set[i].fd, res);
211 	}
212 
213 	return (0);
214 }
215 
216 static int
217 poll_add(struct event_base *base, int fd, short old, short events, void *idx_)
218 {
219 	struct pollop *pop = base->evbase;
220 	struct pollfd *pfd = NULL;
221 	struct pollidx *idx = idx_;
222 	int i;
223 
224 	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
225 	if (!(events & (EV_READ|EV_WRITE)))
226 		return (0);
227 
228 	poll_check_ok(pop);
229 	if (pop->nfds + 1 >= pop->event_count) {
230 		struct pollfd *tmp_event_set;
231 		int tmp_event_count;
232 
233 		if (pop->event_count < 32)
234 			tmp_event_count = 32;
235 		else
236 			tmp_event_count = pop->event_count * 2;
237 
238 		/* We need more file descriptors */
239 		tmp_event_set = mm_realloc(pop->event_set,
240 				 tmp_event_count * sizeof(struct pollfd));
241 		if (tmp_event_set == NULL) {
242 			event_warn("realloc");
243 			return (-1);
244 		}
245 		pop->event_set = tmp_event_set;
246 
247 		pop->event_count = tmp_event_count;
248 		pop->realloc_copy = 1;
249 	}
250 
251 	i = idx->idxplus1 - 1;
252 
253 	if (i >= 0) {
254 		pfd = &pop->event_set[i];
255 	} else {
256 		i = pop->nfds++;
257 		pfd = &pop->event_set[i];
258 		pfd->events = 0;
259 		pfd->fd = fd;
260 		idx->idxplus1 = i + 1;
261 	}
262 
263 	pfd->revents = 0;
264 	if (events & EV_WRITE)
265 		pfd->events |= POLLOUT;
266 	if (events & EV_READ)
267 		pfd->events |= POLLIN;
268 	poll_check_ok(pop);
269 
270 	return (0);
271 }
272 
273 /*
274  * Nothing to be done here.
275  */
276 
277 static int
278 poll_del(struct event_base *base, int fd, short old, short events, void *idx_)
279 {
280 	struct pollop *pop = base->evbase;
281 	struct pollfd *pfd = NULL;
282 	struct pollidx *idx = idx_;
283 	int i;
284 
285 	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
286 	if (!(events & (EV_READ|EV_WRITE)))
287 		return (0);
288 
289 	poll_check_ok(pop);
290 	i = idx->idxplus1 - 1;
291 	if (i < 0)
292 		return (-1);
293 
294 	/* Do we still want to read or write? */
295 	pfd = &pop->event_set[i];
296 	if (events & EV_READ)
297 		pfd->events &= ~POLLIN;
298 	if (events & EV_WRITE)
299 		pfd->events &= ~POLLOUT;
300 	poll_check_ok(pop);
301 	if (pfd->events)
302 		/* Another event cares about that fd. */
303 		return (0);
304 
305 	/* Okay, so we aren't interested in that fd anymore. */
306 	idx->idxplus1 = 0;
307 
308 	--pop->nfds;
309 	if (i != pop->nfds) {
310 		/*
311 		 * Shift the last pollfd down into the now-unoccupied
312 		 * position.
313 		 */
314 		memcpy(&pop->event_set[i], &pop->event_set[pop->nfds],
315 		       sizeof(struct pollfd));
316 		idx = evmap_io_get_fdinfo_(&base->io, pop->event_set[i].fd);
317 		EVUTIL_ASSERT(idx);
318 		EVUTIL_ASSERT(idx->idxplus1 == pop->nfds + 1);
319 		idx->idxplus1 = i + 1;
320 	}
321 
322 	poll_check_ok(pop);
323 	return (0);
324 }
325 
326 static void
327 poll_dealloc(struct event_base *base)
328 {
329 	struct pollop *pop = base->evbase;
330 
331 	evsig_dealloc_(base);
332 	if (pop->event_set)
333 		mm_free(pop->event_set);
334 	if (pop->event_set_copy)
335 		mm_free(pop->event_set_copy);
336 
337 	memset(pop, 0, sizeof(struct pollop));
338 	mm_free(pop);
339 }
340 
341 #endif /* EVENT__HAVE_POLL */
342