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Comparing libev/ev_epoll.c (file contents):
Revision 1.31 by root, Sun Dec 9 03:51:18 2007 UTC vs.
Revision 1.77 by root, Mon Jul 1 20:47:38 2019 UTC

1/* 1/*
2 * libev epoll fd activity backend 2 * libev epoll fd activity backend
3 * 3 *
4 * Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de> 4 * Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 Marc Alexander Lehmann <libev@schmorp.de>
5 * All rights reserved. 5 * All rights reserved.
6 * 6 *
7 * Redistribution and use in source and binary forms, with or without 7 * Redistribution and use in source and binary forms, with or without modifica-
8 * modification, are permitted provided that the following conditions are 8 * tion, are permitted provided that the following conditions are met:
9 * met:
10 * 9 *
11 * * Redistributions of source code must retain the above copyright 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
12 * notice, this list of conditions and the following disclaimer. 14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
13 * 16 *
14 * * Redistributions in binary form must reproduce the above 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
15 * copyright notice, this list of conditions and the following 18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
16 * disclaimer in the documentation and/or other materials provided 19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
17 * with the distribution. 20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 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.
30 */ 38 */
31 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 * d) epoll doesn't work the same as select with many file descriptors
53 * (such as files). while not critical, no other advanced interface
54 * seems to share this (rather non-unixy) limitation.
55 * e) epoll claims to be embeddable, but in practise you never get
56 * a ready event for the epoll fd (broken: <=2.6.26, working: >=2.6.32).
57 * f) epoll_ctl returning EPERM means the fd is always ready.
58 *
59 * lots of "weird code" and complication handling in this file is due
60 * to these design problems with epoll, as we try very hard to avoid
61 * epoll_ctl syscalls for common usage patterns and handle the breakage
62 * ensuing from receiving events for closed and otherwise long gone
63 * file descriptors.
64 */
65
32#include <sys/epoll.h> 66#include <sys/epoll.h>
67
68#define EV_EMASK_EPERM 0x80
33 69
34static void 70static void
35epoll_modify (EV_P_ int fd, int oev, int nev) 71epoll_modify (EV_P_ int fd, int oev, int nev)
36{ 72{
37 int mode = nev ? oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD : EPOLL_CTL_DEL;
38
39 struct epoll_event ev; 73 struct epoll_event ev;
40 ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */ 74 unsigned char oldmask;
41 ev.events = 75
76 /*
77 * we handle EPOLL_CTL_DEL by ignoring it here
78 * on the assumption that the fd is gone anyways
79 * if that is wrong, we have to handle the spurious
80 * event in epoll_poll.
81 * if the fd is added again, we try to ADD it, and, if that
82 * fails, we assume it still has the same eventmask.
83 */
84 if (!nev)
85 return;
86
87 oldmask = anfds [fd].emask;
88 anfds [fd].emask = nev;
89
90 /* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */
91 ev.data.u64 = (uint64_t)(uint32_t)fd
92 | ((uint64_t)(uint32_t)++anfds [fd].egen << 32);
42 (nev & EV_READ ? EPOLLIN : 0) 93 ev.events = (nev & EV_READ ? EPOLLIN : 0)
43 | (nev & EV_WRITE ? EPOLLOUT : 0); 94 | (nev & EV_WRITE ? EPOLLOUT : 0);
44 95
45 if (expect_false (epoll_ctl (backend_fd, mode, fd, &ev))) 96 if (ecb_expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
97 return;
98
99 if (ecb_expect_true (errno == ENOENT))
100 {
46 if (errno != ENOENT /* on ENOENT the fd went away, so try to do the right thing */ 101 /* if ENOENT then the fd went away, so try to do the right thing */
102 if (!nev)
103 goto dec_egen;
104
47 || (nev && epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))) 105 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
106 return;
107 }
108 else if (ecb_expect_true (errno == EEXIST))
109 {
110 /* EEXIST means we ignored a previous DEL, but the fd is still active */
111 /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
112 if (oldmask == nev)
113 goto dec_egen;
114
115 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
116 return;
117 }
118 else if (ecb_expect_true (errno == EPERM))
119 {
120 /* EPERM means the fd is always ready, but epoll is too snobbish */
121 /* to handle it, unlike select or poll. */
122 anfds [fd].emask = EV_EMASK_EPERM;
123
124 /* add fd to epoll_eperms, if not already inside */
125 if (!(oldmask & EV_EMASK_EPERM))
126 {
127 array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, array_needsize_noinit);
128 epoll_eperms [epoll_epermcnt++] = fd;
129 }
130
131 return;
132 }
133 else
134 assert (("libev: I/O watcher with invalid fd found in epoll_ctl", errno != EBADF && errno != ELOOP && errno != EINVAL));
135
48 fd_kill (EV_A_ fd); 136 fd_kill (EV_A_ fd);
137
138dec_egen:
139 /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
140 --anfds [fd].egen;
49} 141}
50 142
51static void 143static void
52epoll_poll (EV_P_ ev_tstamp timeout) 144epoll_poll (EV_P_ ev_tstamp timeout)
53{ 145{
54 int i; 146 int i;
147 int eventcnt;
148
149 if (ecb_expect_false (epoll_epermcnt))
150 timeout = 0.;
151
152 /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
153 /* the default libev max wait time, however. */
154 EV_RELEASE_CB;
55 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.)); 155 eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, timeout * 1e3);
156 EV_ACQUIRE_CB;
56 157
57 if (expect_false (eventcnt < 0)) 158 if (ecb_expect_false (eventcnt < 0))
58 { 159 {
59 if (errno != EINTR) 160 if (errno != EINTR)
60 syserr ("(libev) epoll_wait"); 161 ev_syserr ("(libev) epoll_wait");
61 162
62 return; 163 return;
63 } 164 }
64 165
65 for (i = 0; i < eventcnt; ++i) 166 for (i = 0; i < eventcnt; ++i)
66 fd_event ( 167 {
67 EV_A_ 168 struct epoll_event *ev = epoll_events + i;
68 epoll_events [i].data.u64, 169
170 int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
171 int want = anfds [fd].events;
69 (epoll_events [i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) 172 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
70 | (epoll_events [i].events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0) 173 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
71 ); 174
175 /*
176 * check for spurious notification.
177 * this only finds spurious notifications on egen updates
178 * other spurious notifications will be found by epoll_ctl, below
179 * we assume that fd is always in range, as we never shrink the anfds array
180 */
181 if (ecb_expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
182 {
183 /* recreate kernel state */
184 postfork |= 2;
185 continue;
186 }
187
188 if (ecb_expect_false (got & ~want))
189 {
190 anfds [fd].emask = want;
191
192 /*
193 * we received an event but are not interested in it, try mod or del
194 * this often happens because we optimistically do not unregister fds
195 * when we are no longer interested in them, but also when we get spurious
196 * notifications for fds from another process. this is partially handled
197 * above with the gencounter check (== our fd is not the event fd), and
198 * partially here, when epoll_ctl returns an error (== a child has the fd
199 * but we closed it).
200 */
201 ev->events = (want & EV_READ ? EPOLLIN : 0)
202 | (want & EV_WRITE ? EPOLLOUT : 0);
203
204 /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */
205 /* which is fortunately easy to do for us. */
206 if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
207 {
208 postfork |= 2; /* an error occurred, recreate kernel state */
209 continue;
210 }
211 }
212
213 fd_event (EV_A_ fd, got);
214 }
72 215
73 /* if the receive array was full, increase its size */ 216 /* if the receive array was full, increase its size */
74 if (expect_false (eventcnt == epoll_eventmax)) 217 if (ecb_expect_false (eventcnt == epoll_eventmax))
75 { 218 {
76 ev_free (epoll_events); 219 ev_free (epoll_events);
77 epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1); 220 epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
78 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); 221 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
79 } 222 }
80}
81 223
224 /* now synthesize events for all fds where epoll fails, while select works... */
225 for (i = epoll_epermcnt; i--; )
226 {
227 int fd = epoll_eperms [i];
228 unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE);
229
230 if (anfds [fd].emask & EV_EMASK_EPERM && events)
231 fd_event (EV_A_ fd, events);
232 else
233 {
234 epoll_eperms [i] = epoll_eperms [--epoll_epermcnt];
235 anfds [fd].emask = 0;
236 }
237 }
238}
239
240static int
241epoll_epoll_create (void)
242{
243 int fd;
244
245#if defined EPOLL_CLOEXEC && !defined __ANDROID__
246 fd = epoll_create1 (EPOLL_CLOEXEC);
247
248 if (fd < 0 && (errno == EINVAL || errno == ENOSYS))
249#endif
250 {
251 fd = epoll_create (256);
252
253 if (fd >= 0)
254 fcntl (fd, F_SETFD, FD_CLOEXEC);
255 }
256
257 return fd;
258}
259
82int inline_size 260inline_size
261int
83epoll_init (EV_P_ int flags) 262epoll_init (EV_P_ int flags)
84{ 263{
85 backend_fd = epoll_create (256); 264 if ((backend_fd = epoll_epoll_create ()) < 0)
86
87 if (backend_fd < 0)
88 return 0; 265 return 0;
89 266
90 fcntl (backend_fd, F_SETFD, FD_CLOEXEC); 267 backend_mintime = 1e-3; /* epoll does sometimes return early, this is just to avoid the worst */
91
92 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
93 backend_modify = epoll_modify; 268 backend_modify = epoll_modify;
94 backend_poll = epoll_poll; 269 backend_poll = epoll_poll;
95 270
96 epoll_eventmax = 64; /* intiial number of events receivable per poll */ 271 epoll_eventmax = 64; /* initial number of events receivable per poll */
97 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); 272 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
98 273
99 return EVBACKEND_EPOLL; 274 return EVBACKEND_EPOLL;
100} 275}
101 276
102void inline_size 277inline_size
278void
103epoll_destroy (EV_P) 279epoll_destroy (EV_P)
104{ 280{
105 ev_free (epoll_events); 281 ev_free (epoll_events);
282 array_free (epoll_eperm, EMPTY);
106} 283}
107 284
108void inline_size 285inline_size
286void
109epoll_fork (EV_P) 287epoll_fork (EV_P)
110{ 288{
111 close (backend_fd); 289 close (backend_fd);
112 290
113 while ((backend_fd = epoll_create (256)) < 0) 291 while ((backend_fd = epoll_epoll_create ()) < 0)
114 syserr ("(libev) epoll_create"); 292 ev_syserr ("(libev) epoll_create");
115
116 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
117 293
118 fd_rearm_all (EV_A); 294 fd_rearm_all (EV_A);
119} 295}
120 296

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