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Comparing libev/ev_epoll.c (file contents):
Revision 1.1 by root, Tue Oct 30 20:59:31 2007 UTC vs.
Revision 1.77 by root, Mon Jul 1 20:47:38 2019 UTC

1/*
2 * libev epoll fd activity backend
3 *
4 * Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 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 * 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
1#include <sys/epoll.h> 66#include <sys/epoll.h>
2 67
3static int epoll_fd = -1; 68#define EV_EMASK_EPERM 0x80
4 69
5static void 70static void
6epoll_reify_fd (int fd) 71epoll_modify (EV_P_ int fd, int oev, int nev)
7{ 72{
8 ANFD *anfd = anfds + fd;
9 struct ev_io *w;
10
11 int wev = 0;
12
13 for (w = anfd->head; w; w = w->next)
14 wev |= w->events;
15
16 if (anfd->wev != wev)
17 {
18 int mode = wev ? anfd->wev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD : EPOLL_CTL_DEL;
19 struct epoll_event ev; 73 struct epoll_event ev;
20 ev.events = wev; 74 unsigned char oldmask;
21 ev.data.fd = fd; 75
22 fprintf (stderr, "reify %d,%d,%d m%d (r=%d)\n", fd, anfd->wev, wev, mode,//D 76 /*
23 epoll_ctl (epoll_fd, mode, fd, &ev) 77 * we handle EPOLL_CTL_DEL by ignoring it here
24 );//D 78 * on the assumption that the fd is gone anyways
25 anfd->wev = wev; 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);
93 ev.events = (nev & EV_READ ? EPOLLIN : 0)
94 | (nev & EV_WRITE ? EPOLLOUT : 0);
95
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))
26 } 100 {
27} 101 /* if ENOENT then the fd went away, so try to do the right thing */
102 if (!nev)
103 goto dec_egen;
28 104
29void epoll_postfork_child (void) 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
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;
141}
142
143static void
144epoll_poll (EV_P_ ev_tstamp timeout)
30{ 145{
31 int i; 146 int i;
147 int eventcnt;
32 148
33 epoll_fd = epoll_create (256); 149 if (ecb_expect_false (epoll_epermcnt))
150 timeout = 0.;
34 151
35 for (i = 0; i < anfdmax; ++i) 152 /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
36 epoll_reify_fd (i); 153 /* the default libev max wait time, however. */
37} 154 EV_RELEASE_CB;
38
39static void epoll_reify (void)
40{
41 int i;
42 for (i = 0; i < fdchangecnt; ++i)
43 epoll_reify_fd (fdchanges [i]);
44}
45
46static struct epoll_event *events;
47static int eventmax;
48
49static void epoll_poll (ev_tstamp timeout)
50{
51 int eventcnt = epoll_wait (epoll_fd, events, eventmax, ceil (timeout * 1000.)); 155 eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, timeout * 1e3);
52 int i; 156 EV_ACQUIRE_CB;
53 157
54 if (eventcnt < 0) 158 if (ecb_expect_false (eventcnt < 0))
159 {
160 if (errno != EINTR)
161 ev_syserr ("(libev) epoll_wait");
162
55 return; 163 return;
164 }
56 165
57 for (i = 0; i < eventcnt; ++i) 166 for (i = 0; i < eventcnt; ++i)
58 fd_event ( 167 {
59 events [i].data.fd, 168 struct epoll_event *ev = epoll_events + i;
169
170 int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
171 int want = anfds [fd].events;
60 (events [i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP | EPOLLPRI) ? EV_WRITE : 0) 172 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
61 | (events [i].events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0) 173 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
62 ); 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 }
63 215
64 /* if the receive array was full, increase its size */ 216 /* if the receive array was full, increase its size */
65 if (eventcnt == eventmax) 217 if (ecb_expect_false (eventcnt == epoll_eventmax))
66 { 218 {
67 free (events); 219 ev_free (epoll_events);
68 eventmax += eventmax >> 1; 220 epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
69 events = malloc (sizeof (struct epoll_event) * eventmax); 221 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
222 }
223
224 /* now synthesize events for all fds where epoll fails, while select works... */
225 for (i = epoll_epermcnt; i--; )
70 } 226 {
71} 227 int fd = epoll_eperms [i];
228 unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE);
72 229
73int epoll_init (int flags) 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)
74{ 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 {
75 epoll_fd = epoll_create (256); 251 fd = epoll_create (256);
76 252
77 if (epoll_fd < 0) 253 if (fd >= 0)
254 fcntl (fd, F_SETFD, FD_CLOEXEC);
255 }
256
257 return fd;
258}
259
260inline_size
261int
262epoll_init (EV_P_ int flags)
263{
264 if ((backend_fd = epoll_epoll_create ()) < 0)
78 return 0; 265 return 0;
79 266
80 ev_method = EVMETHOD_EPOLL; 267 backend_mintime = 1e-3; /* epoll does sometimes return early, this is just to avoid the worst */
81 method_fudge = 1e-3; /* needed to compensate fro epoll returning early */ 268 backend_modify = epoll_modify;
82 method_reify = epoll_reify;
83 method_poll = epoll_poll; 269 backend_poll = epoll_poll;
84 270
85 eventmax = 64; /* intiial number of events receivable per poll */ 271 epoll_eventmax = 64; /* initial number of events receivable per poll */
86 events = malloc (sizeof (struct epoll_event) * eventmax); 272 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
87 273
88 return 1; 274 return EVBACKEND_EPOLL;
89} 275}
276
277inline_size
278void
279epoll_destroy (EV_P)
280{
281 ev_free (epoll_events);
282 array_free (epoll_eperm, EMPTY);
283}
284
285inline_size
286void
287epoll_fork (EV_P)
288{
289 close (backend_fd);
290
291 while ((backend_fd = epoll_epoll_create ()) < 0)
292 ev_syserr ("(libev) epoll_create");
293
294 fd_rearm_all (EV_A);
295}
296

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