1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
|
/*
* libev epoll fd activity backend
*
* Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 Marc Alexander Lehmann <libev@schmorp.de>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modifica-
* tion, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Alternatively, the contents of this file may be used under the terms of
* the GNU General Public License ("GPL") version 2 or any later version,
* in which case the provisions of the GPL are applicable instead of
* the above. If you wish to allow the use of your version of this file
* only under the terms of the GPL and not to allow others to use your
* version of this file under the BSD license, indicate your decision
* by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL. If you do not delete the
* provisions above, a recipient may use your version of this file under
* either the BSD or the GPL.
*/
/*
* general notes about epoll:
*
* a) epoll silently removes fds from the fd set. as nothing tells us
* that an fd has been removed otherwise, we have to continually
* "rearm" fds that we suspect *might* have changed (same
* problem with kqueue, but much less costly there).
* b) the fact that ADD != MOD creates a lot of extra syscalls due to a)
* and seems not to have any advantage.
* c) the inability to handle fork or file descriptors (think dup)
* limits the applicability over poll, so this is not a generic
* poll replacement.
* d) epoll doesn't work the same as select with many file descriptors
* (such as files). while not critical, no other advanced interface
* seems to share this (rather non-unixy) limitation.
* e) epoll claims to be embeddable, but in practise you never get
* a ready event for the epoll fd (broken: <=2.6.26, working: >=2.6.32).
* f) epoll_ctl returning EPERM means the fd is always ready.
*
* lots of "weird code" and complication handling in this file is due
* to these design problems with epoll, as we try very hard to avoid
* epoll_ctl syscalls for common usage patterns and handle the breakage
* ensuing from receiving events for closed and otherwise long gone
* file descriptors.
*/
#include <sys/epoll.h>
#define EV_EMASK_EPERM 0x80
static void
epoll_modify (EV_P_ int fd, int oev, int nev)
{
struct epoll_event ev;
unsigned char oldmask;
/*
* we handle EPOLL_CTL_DEL by ignoring it here
* on the assumption that the fd is gone anyways
* if that is wrong, we have to handle the spurious
* event in epoll_poll.
* if the fd is added again, we try to ADD it, and, if that
* fails, we assume it still has the same eventmask.
*/
if (!nev)
return;
oldmask = anfds [fd].emask;
anfds [fd].emask = nev;
/* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */
ev.data.u64 = (uint64_t)(uint32_t)fd
| ((uint64_t)(uint32_t)++anfds [fd].egen << 32);
ev.events = (nev & EV_READ ? EPOLLIN : 0)
| (nev & EV_WRITE ? EPOLLOUT : 0);
if (ecb_expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
return;
if (ecb_expect_true (errno == ENOENT))
{
/* if ENOENT then the fd went away, so try to do the right thing */
if (!nev)
goto dec_egen;
if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
return;
}
else if (ecb_expect_true (errno == EEXIST))
{
/* EEXIST means we ignored a previous DEL, but the fd is still active */
/* if the kernel mask is the same as the new mask, we assume it hasn't changed */
if (oldmask == nev)
goto dec_egen;
if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
return;
}
else if (ecb_expect_true (errno == EPERM))
{
/* EPERM means the fd is always ready, but epoll is too snobbish */
/* to handle it, unlike select or poll. */
anfds [fd].emask = EV_EMASK_EPERM;
/* add fd to epoll_eperms, if not already inside */
if (!(oldmask & EV_EMASK_EPERM))
{
array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, array_needsize_noinit);
epoll_eperms [epoll_epermcnt++] = fd;
}
return;
}
else
assert (("libev: I/O watcher with invalid fd found in epoll_ctl", errno != EBADF && errno != ELOOP && errno != EINVAL));
fd_kill (EV_A_ fd);
dec_egen:
/* we didn't successfully call epoll_ctl, so decrement the generation counter again */
--anfds [fd].egen;
}
static void
epoll_poll (EV_P_ ev_tstamp timeout)
{
int i;
int eventcnt;
if (ecb_expect_false (epoll_epermcnt))
timeout = EV_TS_CONST (0.);
/* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
/* the default libev max wait time, however. */
EV_RELEASE_CB;
eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, EV_TS_TO_MSEC (timeout));
EV_ACQUIRE_CB;
if (ecb_expect_false (eventcnt < 0))
{
if (errno != EINTR)
ev_syserr ("(libev) epoll_wait");
return;
}
for (i = 0; i < eventcnt; ++i)
{
struct epoll_event *ev = epoll_events + i;
int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
int want = anfds [fd].events;
int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
| (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
/*
* check for spurious notification.
* this only finds spurious notifications on egen updates
* other spurious notifications will be found by epoll_ctl, below
* we assume that fd is always in range, as we never shrink the anfds array
*/
if (ecb_expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
{
/* recreate kernel state */
postfork |= 2;
continue;
}
if (ecb_expect_false (got & ~want))
{
anfds [fd].emask = want;
/*
* we received an event but are not interested in it, try mod or del
* this often happens because we optimistically do not unregister fds
* when we are no longer interested in them, but also when we get spurious
* notifications for fds from another process. this is partially handled
* above with the gencounter check (== our fd is not the event fd), and
* partially here, when epoll_ctl returns an error (== a child has the fd
* but we closed it).
* note: for events such as POLLHUP, where we can't know whether it refers
* to EV_READ or EV_WRITE, we might issue redundant EPOLL_CTL_MOD calls.
*/
ev->events = (want & EV_READ ? EPOLLIN : 0)
| (want & EV_WRITE ? EPOLLOUT : 0);
/* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */
/* which is fortunately easy to do for us. */
if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
{
postfork |= 2; /* an error occurred, recreate kernel state */
continue;
}
}
fd_event (EV_A_ fd, got);
}
/* if the receive array was full, increase its size */
if (ecb_expect_false (eventcnt == epoll_eventmax))
{
ev_free (epoll_events);
epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1);
epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
}
/* now synthesize events for all fds where epoll fails, while select works... */
for (i = epoll_epermcnt; i--; )
{
int fd = epoll_eperms [i];
unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE);
if (anfds [fd].emask & EV_EMASK_EPERM && events)
fd_event (EV_A_ fd, events);
else
{
epoll_eperms [i] = epoll_eperms [--epoll_epermcnt];
anfds [fd].emask = 0;
}
}
}
static int
epoll_epoll_create (void)
{
int fd;
#if defined EPOLL_CLOEXEC && !defined __ANDROID__
fd = epoll_create1 (EPOLL_CLOEXEC);
if (fd < 0 && (errno == EINVAL || errno == ENOSYS))
#endif
{
fd = epoll_create (256);
if (fd >= 0)
fcntl (fd, F_SETFD, FD_CLOEXEC);
}
return fd;
}
inline_size
int
epoll_init (EV_P_ int flags)
{
if ((backend_fd = epoll_epoll_create ()) < 0)
return 0;
backend_mintime = EV_TS_CONST (1e-3); /* epoll does sometimes return early, this is just to avoid the worst */
backend_modify = epoll_modify;
backend_poll = epoll_poll;
epoll_eventmax = 64; /* initial number of events receivable per poll */
epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
return EVBACKEND_EPOLL;
}
inline_size
void
epoll_destroy (EV_P)
{
ev_free (epoll_events);
array_free (epoll_eperm, EMPTY);
}
ecb_cold
static void
epoll_fork (EV_P)
{
close (backend_fd);
while ((backend_fd = epoll_epoll_create ()) < 0)
ev_syserr ("(libev) epoll_create");
fd_rearm_all (EV_A);
}
|