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Comparing libev/ev_epoll.c (file contents):
Revision 1.34 by root, Fri May 23 16:37:38 2008 UTC vs.
Revision 1.50 by root, Tue Mar 23 23:45:12 2010 UTC

1/* 1/*
2 * libev epoll fd activity backend 2 * libev epoll fd activity backend
3 * 3 *
4 * Copyright (c) 2007,2008 Marc Alexander Lehmann <libev@schmorp.de> 4 * Copyright (c) 2007,2008,2009,2010 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 modifica- 7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met: 8 * tion, are permitted provided that the following conditions are met:
9 * 9 *
… …
47 * b) the fact that ADD != MOD creates a lot of extra syscalls due to a) 47 * b) the fact that ADD != MOD creates a lot of extra syscalls due to a)
48 * and seems not to have any advantage. 48 * and seems not to have any advantage.
49 * c) the inability to handle fork or file descriptors (think dup) 49 * c) the inability to handle fork or file descriptors (think dup)
50 * limits the applicability over poll, so this is not a generic 50 * limits the applicability over poll, so this is not a generic
51 * poll replacement. 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.
52 * 57 *
53 * lots of "weird code" and complication handling in this file is due 58 * 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 59 * to these design problems with epoll, as we try very hard to avoid
55 * epoll_ctl syscalls for common usage patterns. 60 * epoll_ctl syscalls for common usage patterns and handle the breakage
61 * ensuing from receiving events for closed and otherwise long gone
62 * file descriptors.
56 */ 63 */
57 64
58#include <sys/epoll.h> 65#include <sys/epoll.h>
59 66
60static void 67static void
61epoll_modify (EV_P_ int fd, int oev, int nev) 68epoll_modify (EV_P_ int fd, int oev, int nev)
62{ 69{
63 struct epoll_event ev; 70 struct epoll_event ev;
71 unsigned char oldmask;
64 72
65 /* 73 /*
66 * we handle EPOLL_CTL_DEL by ignoring it here 74 * we handle EPOLL_CTL_DEL by ignoring it here
67 * on the assumption that the fd is gone anyways 75 * on the assumption that the fd is gone anyways
68 * if that is wrong, we have to handle the spurious 76 * if that is wrong, we have to handle the spurious
69 * event in epoll_poll. 77 * event in epoll_poll.
78 * if the fd is added again, we try to ADD it, and, if that
79 * fails, we assume it still has the same eventmask.
70 */ 80 */
71 if (!nev) 81 if (!nev)
72 return; 82 return;
73 83
74 ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */ 84 oldmask = anfds [fd].emask;
85 anfds [fd].emask = nev;
86
87 /* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */
88 ev.data.u64 = (uint64_t)(uint32_t)fd
89 | ((uint64_t)(uint32_t)++anfds [fd].egen << 32);
75 ev.events = (nev & EV_READ ? EPOLLIN : 0) 90 ev.events = (nev & EV_READ ? EPOLLIN : 0)
76 | (nev & EV_WRITE ? EPOLLOUT : 0); 91 | (nev & EV_WRITE ? EPOLLOUT : 0);
77 92
78 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) 93 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
79 return; 94 return;
80 95
81 if (expect_true (errno == ENOENT)) 96 if (expect_true (errno == ENOENT))
82 { 97 {
83 /* on ENOENT the fd went away, so try to do the right thing */ 98 /* if ENOENT then the fd went away, so try to do the right thing */
84 if (!nev) 99 if (!nev)
85 return; 100 goto dec_egen;
86 101
87 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev)) 102 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
88 return; 103 return;
89 } 104 }
90 else if (expect_true (errno == EEXIST)) 105 else if (expect_true (errno == EEXIST))
91 { 106 {
92 /* on EEXIST we ignored a previous DEL */ 107 /* EEXIST means we ignored a previous DEL, but the fd is still active */
108 /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
109 if (oldmask == nev)
110 goto dec_egen;
111
93 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev)) 112 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
94 return; 113 return;
95 } 114 }
96 115
97 fd_kill (EV_A_ fd); 116 fd_kill (EV_A_ fd);
117
118dec_egen:
119 /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
120 --anfds [fd].egen;
98} 121}
99 122
100static void 123static void
101epoll_poll (EV_P_ ev_tstamp timeout) 124epoll_poll (EV_P_ ev_tstamp timeout)
102{ 125{
103 int i; 126 int i;
127 int eventcnt;
128
129 /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */
130 /* the default libev max wait time, however. */
131 EV_RELEASE_CB;
104 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.)); 132 eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
133 EV_ACQUIRE_CB;
105 134
106 if (expect_false (eventcnt < 0)) 135 if (expect_false (eventcnt < 0))
107 { 136 {
108 if (errno != EINTR) 137 if (errno != EINTR)
109 syserr ("(libev) epoll_wait"); 138 ev_syserr ("(libev) epoll_wait");
110 139
111 return; 140 return;
112 } 141 }
113 142
114 for (i = 0; i < eventcnt; ++i) 143 for (i = 0; i < eventcnt; ++i)
115 { 144 {
116 struct epoll_event *ev = epoll_events + i; 145 struct epoll_event *ev = epoll_events + i;
117 146
118 int fd = ev->data.u64; 147 int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
148 int want = anfds [fd].events;
119 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) 149 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
120 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0); 150 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
121 int want = anfds [fd].events; 151
152 /* check for spurious notification */
153 if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
154 {
155 /* recreate kernel state */
156 postfork = 1;
157 continue;
158 }
122 159
123 if (expect_false (got & ~want)) 160 if (expect_false (got & ~want))
124 { 161 {
162 anfds [fd].emask = want;
163
125 /* we received an event but are not interested in it, try mod or del */ 164 /* we received an event but are not interested in it, try mod or del */
165 /* I don't think we ever need MOD, but let's handle it anyways */
126 ev->events = (want & EV_READ ? EPOLLIN : 0) 166 ev->events = (want & EV_READ ? EPOLLIN : 0)
127 | (want & EV_WRITE ? EPOLLOUT : 0); 167 | (want & EV_WRITE ? EPOLLOUT : 0);
128 168
169 /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */
170 /* which is fortunately easy to do for us. */
129 epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev); 171 if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
172 {
173 postfork = 1; /* an error occured, recreate kernel state */
174 continue;
175 }
130 } 176 }
131 177
132 fd_event (EV_A_ fd, got); 178 fd_event (EV_A_ fd, got);
133 } 179 }
134 180
… …
142} 188}
143 189
144int inline_size 190int inline_size
145epoll_init (EV_P_ int flags) 191epoll_init (EV_P_ int flags)
146{ 192{
193#ifdef EPOLL_CLOEXEC
194 backend_fd = epoll_create1 (EPOLL_CLOEXEC);
195
196 if (backend_fd <= 0)
197#endif
147 backend_fd = epoll_create (256); 198 backend_fd = epoll_create (256);
148 199
149 if (backend_fd < 0) 200 if (backend_fd < 0)
150 return 0; 201 return 0;
151 202
152 fcntl (backend_fd, F_SETFD, FD_CLOEXEC); 203 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
153 204
154 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */ 205 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
155 backend_modify = epoll_modify; 206 backend_modify = epoll_modify;
156 backend_poll = epoll_poll; 207 backend_poll = epoll_poll;
157 208
158 epoll_eventmax = 64; /* intiial number of events receivable per poll */ 209 epoll_eventmax = 64; /* initial number of events receivable per poll */
159 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); 210 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
160 211
161 return EVBACKEND_EPOLL; 212 return EVBACKEND_EPOLL;
162} 213}
163 214
… …
171epoll_fork (EV_P) 222epoll_fork (EV_P)
172{ 223{
173 close (backend_fd); 224 close (backend_fd);
174 225
175 while ((backend_fd = epoll_create (256)) < 0) 226 while ((backend_fd = epoll_create (256)) < 0)
176 syserr ("(libev) epoll_create"); 227 ev_syserr ("(libev) epoll_create");
177 228
178 fcntl (backend_fd, F_SETFD, FD_CLOEXEC); 229 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
179 230
180 fd_rearm_all (EV_A); 231 fd_rearm_all (EV_A);
181} 232}

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