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/cvs/libev/ev_epoll.c
Revision: 1.33
Committed: Tue Dec 25 07:05:45 2007 UTC (16 years, 7 months ago) by root
Content type: text/plain
Branch: MAIN
CVS Tags: rel-2_01, rel-3_31, rel-3_33, rel-3_4, rel-3_3, rel-3_2, rel-3_1, rel-3_0
Changes since 1.32: +30 -22 lines
Log Message:
*** empty log message ***

File Contents

# Content
1 /*
2 * libev epoll fd activity backend
3 *
4 * Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
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 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26 * OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Alternatively, the contents of this file may be used under the terms of
29 * the GNU General Public License ("GPL") version 2 or any later version,
30 * in which case the provisions of the GPL are applicable instead of
31 * the above. If you wish to allow the use of your version of this file
32 * only under the terms of the GPL and not to allow others to use your
33 * version of this file under the BSD license, indicate your decision
34 * by deleting the provisions above and replace them with the notice
35 * and other provisions required by the GPL. If you do not delete the
36 * provisions above, a recipient may use your version of this file under
37 * either the BSD or the GPL.
38 */
39
40 /*
41 * general notes about epoll:
42 *
43 * a) epoll silently removes fds from the fd set. as nothing tells us
44 * that an fd has been removed otherwise, we have to continually
45 * "rearm" fds that we suspect *might* have changed (same
46 * problem with kqueue, but much less costly there).
47 * b) the fact that ADD != MOD creates a lot of extra syscalls due to a)
48 * and seems not to have any advantage.
49 * c) the inability to handle fork or file descriptors (think dup)
50 * limits the applicability over poll, so this is not a generic
51 * poll replacement.
52 *
53 * lots of "weird code" and complication handling in this file is due
54 * to these design problems with epoll, as we try very hard to avoid
55 * epoll_ctl syscalls for common usage patterns.
56 */
57
58 #include <sys/epoll.h>
59
60 static void
61 epoll_modify (EV_P_ int fd, int oev, int nev)
62 {
63 struct epoll_event ev;
64
65 /*
66 * we handle EPOLL_CTL_DEL by ignoring it here
67 * on the assumption that the fd is gone anyways
68 * if that is wrong, we have to handle the spurious
69 * event in epoll_poll.
70 */
71 if (!nev)
72 return;
73
74 ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */
75 ev.events = (nev & EV_READ ? EPOLLIN : 0)
76 | (nev & EV_WRITE ? EPOLLOUT : 0);
77
78 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
79 return;
80
81 if (expect_true (errno == ENOENT))
82 {
83 /* on ENOENT the fd went away, so try to do the right thing */
84 if (!nev)
85 return;
86
87 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
88 return;
89 }
90 else if (expect_true (errno == EEXIST))
91 {
92 /* on EEXIST we ignored a previous DEL */
93 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
94 return;
95 }
96
97 fd_kill (EV_A_ fd);
98 }
99
100 static void
101 epoll_poll (EV_P_ ev_tstamp timeout)
102 {
103 int i;
104 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
105
106 if (expect_false (eventcnt < 0))
107 {
108 if (errno != EINTR)
109 syserr ("(libev) epoll_wait");
110
111 return;
112 }
113
114 for (i = 0; i < eventcnt; ++i)
115 {
116 struct epoll_event *ev = epoll_events + i;
117
118 int fd = ev->data.u64;
119 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
120 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
121 int want = anfds [fd].events;
122
123 if (expect_false (got & ~want))
124 {
125 /* we received an event but are not interested in it, try mod or del */
126 ev->events = (want & EV_READ ? EPOLLIN : 0)
127 | (want & EV_WRITE ? EPOLLOUT : 0);
128
129 epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev);
130 }
131
132 fd_event (EV_A_ fd, got);
133 }
134
135 /* if the receive array was full, increase its size */
136 if (expect_false (eventcnt == epoll_eventmax))
137 {
138 ev_free (epoll_events);
139 epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
140 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
141 }
142 }
143
144 int inline_size
145 epoll_init (EV_P_ int flags)
146 {
147 backend_fd = epoll_create (256);
148
149 if (backend_fd < 0)
150 return 0;
151
152 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
153
154 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
155 backend_modify = epoll_modify;
156 backend_poll = epoll_poll;
157
158 epoll_eventmax = 64; /* intiial number of events receivable per poll */
159 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
160
161 return EVBACKEND_EPOLL;
162 }
163
164 void inline_size
165 epoll_destroy (EV_P)
166 {
167 ev_free (epoll_events);
168 }
169
170 void inline_size
171 epoll_fork (EV_P)
172 {
173 close (backend_fd);
174
175 while ((backend_fd = epoll_create (256)) < 0)
176 syserr ("(libev) epoll_create");
177
178 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
179
180 fd_rearm_all (EV_A);
181 }
182