select.c revision 1.2 
1/*	$NetBSD: select.c,v 1.2 2013/04/11 16:56:41 christos Exp $	*/
2/*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
3
4/*
5 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
6 * Copyright 2007-2012 Niels Provos and Nick Mathewson
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30#include "event2/event-config.h"
31#include <sys/cdefs.h>
32__RCSID("$NetBSD: select.c,v 1.2 2013/04/11 16:56:41 christos Exp $");
33
34#include <sys/types.h>
35#ifdef _EVENT_HAVE_SYS_TIME_H
36#include <sys/time.h>
37#endif
38#ifdef _EVENT_HAVE_SYS_SELECT_H
39#include <sys/select.h>
40#endif
41#include <sys/queue.h>
42#include <signal.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include <string.h>
46#include <unistd.h>
47#include <errno.h>
48
49#include "event-internal.h"
50#include "evsignal-internal.h"
51#include "event2/thread.h"
52#include "evthread-internal.h"
53#include "log-internal.h"
54#include "evmap-internal.h"
55
56#ifndef _EVENT_HAVE_FD_MASK
57/* This type is mandatory, but Android doesn't define it. */
58typedef unsigned long fd_mask;
59#endif
60
61#ifndef NFDBITS
62#define NFDBITS (sizeof(fd_mask)*8)
63#endif
64
65/* Divide positive x by y, rounding up. */
66#define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))
67
68/* How many bytes to allocate for N fds? */
69#define SELECT_ALLOC_SIZE(n) \
70	(DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
71
72struct selectop {
73	int event_fds;		/* Highest fd in fd set */
74	int event_fdsz;
75	int resize_out_sets;
76	fd_set *event_readset_in;
77	fd_set *event_writeset_in;
78	fd_set *event_readset_out;
79	fd_set *event_writeset_out;
80};
81
82static void *select_init(struct event_base *);
83static int select_add(struct event_base *, int, short old, short events, void*);
84static int select_del(struct event_base *, int, short old, short events, void*);
85static int select_dispatch(struct event_base *, struct timeval *);
86static void select_dealloc(struct event_base *);
87
88const struct eventop selectops = {
89	"select",
90	select_init,
91	select_add,
92	select_del,
93	select_dispatch,
94	select_dealloc,
95	0, /* doesn't need reinit. */
96	EV_FEATURE_FDS,
97	0,
98};
99
100static int select_resize(struct selectop *sop, int fdsz);
101static void select_free_selectop(struct selectop *sop);
102
103static void *
104select_init(struct event_base *base)
105{
106	struct selectop *sop;
107
108	if (!(sop = mm_calloc(1, sizeof(struct selectop))))
109		return (NULL);
110
111	if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
112		select_free_selectop(sop);
113		return (NULL);
114	}
115
116	evsig_init(base);
117
118	return (sop);
119}
120
121#ifdef CHECK_INVARIANTS
122static void
123check_selectop(struct selectop *sop)
124{
125	/* nothing to be done here */
126}
127#else
128#define check_selectop(sop) do { (void) sop; } while (/*CONSTCOND*/0)
129#endif
130
131static int
132select_dispatch(struct event_base *base, struct timeval *tv)
133{
134	int res=0, i, j, nfds;
135	struct selectop *sop = base->evbase;
136
137	check_selectop(sop);
138	if (sop->resize_out_sets) {
139		fd_set *readset_out=NULL, *writeset_out=NULL;
140		size_t sz = sop->event_fdsz;
141		if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
142			return (-1);
143		sop->event_readset_out = readset_out;
144		if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
145			/* We don't free readset_out here, since it was
146			 * already successfully reallocated. The next time
147			 * we call select_dispatch, the realloc will be a
148			 * no-op. */
149			return (-1);
150		}
151		sop->event_writeset_out = writeset_out;
152		sop->resize_out_sets = 0;
153	}
154
155	memcpy(sop->event_readset_out, sop->event_readset_in,
156	       sop->event_fdsz);
157	memcpy(sop->event_writeset_out, sop->event_writeset_in,
158	       sop->event_fdsz);
159
160	nfds = sop->event_fds+1;
161
162	EVBASE_RELEASE_LOCK(base, th_base_lock);
163
164	res = select(nfds, sop->event_readset_out,
165	    sop->event_writeset_out, NULL, tv);
166
167	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
168
169	check_selectop(sop);
170
171	if (res == -1) {
172		if (errno != EINTR) {
173			event_warn("select");
174			return (-1);
175		}
176
177		return (0);
178	}
179
180	event_debug(("%s: select reports %d", __func__, res));
181
182	check_selectop(sop);
183	i = random() % nfds;
184	for (j = 0; j < nfds; ++j) {
185		if (++i >= nfds)
186			i = 0;
187		res = 0;
188		if (FD_ISSET(i, sop->event_readset_out))
189			res |= EV_READ;
190		if (FD_ISSET(i, sop->event_writeset_out))
191			res |= EV_WRITE;
192
193		if (res == 0)
194			continue;
195
196		evmap_io_active(base, i, res);
197	}
198	check_selectop(sop);
199
200	return (0);
201}
202
203static int
204select_resize(struct selectop *sop, int fdsz)
205{
206	fd_set *readset_in = NULL;
207	fd_set *writeset_in = NULL;
208
209	if (sop->event_readset_in)
210		check_selectop(sop);
211
212	if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
213		goto error;
214	sop->event_readset_in = readset_in;
215	if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
216		/* Note that this will leave event_readset_in expanded.
217		 * That's okay; we wouldn't want to free it, since that would
218		 * change the semantics of select_resize from "expand the
219		 * readset_in and writeset_in, or return -1" to "expand the
220		 * *set_in members, or trash them and return -1."
221		 */
222		goto error;
223	}
224	sop->event_writeset_in = writeset_in;
225	sop->resize_out_sets = 1;
226
227	memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
228	    fdsz - sop->event_fdsz);
229	memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
230	    fdsz - sop->event_fdsz);
231
232	sop->event_fdsz = fdsz;
233	check_selectop(sop);
234
235	return (0);
236
237 error:
238	event_warn("malloc");
239	return (-1);
240}
241
242
243static int
244select_add(struct event_base *base, int fd, short old, short events, void *p)
245{
246	struct selectop *sop = base->evbase;
247	(void) p;
248
249	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
250	check_selectop(sop);
251	/*
252	 * Keep track of the highest fd, so that we can calculate the size
253	 * of the fd_sets for select(2)
254	 */
255	if (sop->event_fds < fd) {
256		int fdsz = sop->event_fdsz;
257
258		if (fdsz < (int)sizeof(fd_mask))
259			fdsz = (int)sizeof(fd_mask);
260
261		/* In theory we should worry about overflow here.  In
262		 * reality, though, the highest fd on a unixy system will
263		 * not overflow here. XXXX */
264		while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
265			fdsz *= 2;
266
267		if (fdsz != sop->event_fdsz) {
268			if (select_resize(sop, fdsz)) {
269				check_selectop(sop);
270				return (-1);
271			}
272		}
273
274		sop->event_fds = fd;
275	}
276
277	if (events & EV_READ)
278		FD_SET(fd, sop->event_readset_in);
279	if (events & EV_WRITE)
280		FD_SET(fd, sop->event_writeset_in);
281	check_selectop(sop);
282
283	return (0);
284}
285
286/*
287 * Nothing to be done here.
288 */
289
290static int
291select_del(struct event_base *base, int fd, short old, short events, void *p)
292{
293	struct selectop *sop = base->evbase;
294	(void)p;
295
296	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
297	check_selectop(sop);
298
299	if (sop->event_fds < fd) {
300		check_selectop(sop);
301		return (0);
302	}
303
304	if (events & EV_READ)
305		FD_CLR(fd, sop->event_readset_in);
306
307	if (events & EV_WRITE)
308		FD_CLR(fd, sop->event_writeset_in);
309
310	check_selectop(sop);
311	return (0);
312}
313
314static void
315select_free_selectop(struct selectop *sop)
316{
317	if (sop->event_readset_in)
318		mm_free(sop->event_readset_in);
319	if (sop->event_writeset_in)
320		mm_free(sop->event_writeset_in);
321	if (sop->event_readset_out)
322		mm_free(sop->event_readset_out);
323	if (sop->event_writeset_out)
324		mm_free(sop->event_writeset_out);
325
326	memset(sop, 0, sizeof(struct selectop));
327	mm_free(sop);
328}
329
330static void
331select_dealloc(struct event_base *base)
332{
333	evsig_dealloc(base);
334
335	select_free_selectop(base->evbase);
336}
337