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Comparing libev/ev_epoll.c (file contents):
Revision 1.2 by root, Tue Oct 30 23:54:38 2007 UTC vs.
Revision 1.38 by root, Wed Oct 29 06:32:48 2008 UTC

1/*
2 * libev epoll fd activity backend
3 *
4 * Copyright (c) 2007,2008 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 and handle the breakage
56 * ensuing from receiving events for closed and otherwise long gone
57 * file descriptors.
58 */
59
1#include <sys/epoll.h> 60#include <sys/epoll.h>
2 61
3static int epoll_fd = -1;
4
5static void 62static void
6epoll_modify (int fd, int oev, int nev) 63epoll_modify (EV_P_ int fd, int oev, int nev)
7{ 64{
8 int mode = nev ? oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD : EPOLL_CTL_DEL;
9
10 struct epoll_event ev; 65 struct epoll_event ev;
11 ev.data.fd = fd; 66 unsigned char oldmask;
12 ev.events = 67
68 /*
69 * we handle EPOLL_CTL_DEL by ignoring it here
70 * on the assumption that the fd is gone anyways
71 * if that is wrong, we have to handle the spurious
72 * event in epoll_poll.
73 * the fd is later added, we try to ADD it, and, if that
74 * fails, we assume it still has the same eventmask.
75 */
76 if (!nev)
77 return;
78
79 oldmask = anfds [fd].emask;
80 anfds [fd].emask = nev;
81
82 /* store the generation counter in the upper 32 bits */
83 ev.data.u64 = fd | ((uint64_t)++anfds [fd].egen << 32);
13 (nev & EV_READ ? EPOLLIN : 0) 84 ev.events = (nev & EV_READ ? EPOLLIN : 0)
14 | (nev & EV_WRITE ? EPOLLOUT : 0); 85 | (nev & EV_WRITE ? EPOLLOUT : 0);
15 86
16 fprintf (stderr, "reify %d,%d,%d m%d (r=%d)\n", fd, oev, nev, mode,//D 87 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
17 epoll_ctl (epoll_fd, mode, fd, &ev) 88 return;
18 );//D
19}
20 89
21void epoll_postfork_child (void) 90 if (expect_true (errno == ENOENT))
22{ 91 {
23 int fd; 92 /* if ENOENT then the fd went away, so try to do the right thing */
93 if (!nev)
94 goto dec_egen;
24 95
25 epoll_fd = epoll_create (256); 96 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
97 return;
98 }
99 else if (expect_true (errno == EEXIST))
100 {
101 /* EEXIST means we ignored a previous DEL, but the fd is still active */
102 /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
103 if (oldmask == nev)
104 goto dec_egen;
26 105
27 /* re-register interest in fds */ 106 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
28 for (fd = 0; fd < anfdmax; ++fd) 107 return;
29 if (anfds [fd].wev) 108 }
30 epoll_modify (fd, EV_NONE, anfds [fd].wev);
31}
32 109
33static struct epoll_event *events; 110 fd_kill (EV_A_ fd);
34static int eventmax;
35 111
112dec_egen:
113 /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
114 --anfds [fd].egen;
115}
116
117static void
36static void epoll_poll (ev_tstamp timeout) 118epoll_poll (EV_P_ ev_tstamp timeout)
37{ 119{
38 int eventcnt = epoll_wait (epoll_fd, events, eventmax, ceil (timeout * 1000.));
39 int i; 120 int i;
121 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
40 122
41 if (eventcnt < 0) 123 if (expect_false (eventcnt < 0))
124 {
125 if (errno != EINTR)
126 ev_syserr ("(libev) epoll_wait");
127
42 return; 128 return;
129 }
43 130
44 for (i = 0; i < eventcnt; ++i) 131 for (i = 0; i < eventcnt; ++i)
45 fd_event ( 132 {
46 events [i].data.fd, 133 struct epoll_event *ev = epoll_events + i;
134
135 int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
136 int want = anfds [fd].events;
47 (events [i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) 137 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
48 | (events [i].events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0) 138 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
49 ); 139
140 /* check for spurious notification */
141 if (expect_false (anfds [fd].egen != (unsigned char)(ev->data.u64 >> 32)))
142 {
143 /* recreate kernel state */
144 postfork = 1;
145 continue;
146 }
147
148 if (expect_false (got & ~want))
149 {
150 anfds [fd].emask = want;
151
152 /* we received an event but are not interested in it, try mod or del */
153 /* I don't think we ever need MOD, but let's handle it anyways */
154 ev->events = (want & EV_READ ? EPOLLIN : 0)
155 | (want & EV_WRITE ? EPOLLOUT : 0);
156
157 if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
158 {
159 postfork = 1; /* an error occured, recreate kernel state */
160 continue;
161 }
162 }
163
164 fd_event (EV_A_ fd, got);
165 }
50 166
51 /* if the receive array was full, increase its size */ 167 /* if the receive array was full, increase its size */
52 if (eventcnt == eventmax) 168 if (expect_false (eventcnt == epoll_eventmax))
53 { 169 {
54 free (events); 170 ev_free (epoll_events);
55 eventmax += eventmax >> 1; 171 epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
56 events = malloc (sizeof (struct epoll_event) * eventmax); 172 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
57 } 173 }
58} 174}
59 175
176int inline_size
60int epoll_init (int flags) 177epoll_init (EV_P_ int flags)
61{ 178{
62 epoll_fd = epoll_create (256); 179 backend_fd = epoll_create (256);
63 180
64 if (epoll_fd < 0) 181 if (backend_fd < 0)
65 return 0; 182 return 0;
66 183
67 ev_method = EVMETHOD_EPOLL; 184 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
68 method_fudge = 1e-3; /* needed to compensate for epoll returning early */ 185
186 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
69 method_modify = epoll_modify; 187 backend_modify = epoll_modify;
70 method_poll = epoll_poll; 188 backend_poll = epoll_poll;
71 189
72 eventmax = 64; /* intiial number of events receivable per poll */ 190 epoll_eventmax = 64; /* initial number of events receivable per poll */
73 events = malloc (sizeof (struct epoll_event) * eventmax); 191 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
74 192
75 return 1; 193 return EVBACKEND_EPOLL;
76} 194}
195
196void inline_size
197epoll_destroy (EV_P)
198{
199 ev_free (epoll_events);
200}
201
202void inline_size
203epoll_fork (EV_P)
204{
205 close (backend_fd);
206
207 while ((backend_fd = epoll_create (256)) < 0)
208 ev_syserr ("(libev) epoll_create");
209
210 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
211
212 fd_rearm_all (EV_A);
213}
214

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