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Comparing libev/ev_epoll.c (file contents):
Revision 1.33 by root, Tue Dec 25 07:05:45 2007 UTC vs.
Revision 1.43 by root, Fri Nov 7 15:07:50 2008 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 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 *
… …
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 * 52 *
53 * lots of "weird code" and complication handling in this file is due 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 54 * to these design problems with epoll, as we try very hard to avoid
55 * epoll_ctl syscalls for common usage patterns. 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.
56 */ 58 */
57 59
58#include <sys/epoll.h> 60#include <sys/epoll.h>
59 61
60static void 62static void
61epoll_modify (EV_P_ int fd, int oev, int nev) 63epoll_modify (EV_P_ int fd, int oev, int nev)
62{ 64{
63 struct epoll_event ev; 65 struct epoll_event ev;
66 unsigned char oldmask;
64 67
65 /* 68 /*
66 * we handle EPOLL_CTL_DEL by ignoring it here 69 * we handle EPOLL_CTL_DEL by ignoring it here
67 * on the assumption that the fd is gone anyways 70 * on the assumption that the fd is gone anyways
68 * if that is wrong, we have to handle the spurious 71 * if that is wrong, we have to handle the spurious
69 * event in epoll_poll. 72 * event in epoll_poll.
73 * if the fd is added again, we try to ADD it, and, if that
74 * fails, we assume it still has the same eventmask.
70 */ 75 */
71 if (!nev) 76 if (!nev)
72 return; 77 return;
73 78
74 ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */ 79 oldmask = anfds [fd].emask;
80 anfds [fd].emask = nev;
81
82 /* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */
83 ev.data.u64 = (uint64_t)(uint32_t)fd
84 | ((uint64_t)(uint32_t)++anfds [fd].egen << 32);
75 ev.events = (nev & EV_READ ? EPOLLIN : 0) 85 ev.events = (nev & EV_READ ? EPOLLIN : 0)
76 | (nev & EV_WRITE ? EPOLLOUT : 0); 86 | (nev & EV_WRITE ? EPOLLOUT : 0);
77 87
78 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) 88 if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev)))
79 return; 89 return;
80 90
81 if (expect_true (errno == ENOENT)) 91 if (expect_true (errno == ENOENT))
82 { 92 {
83 /* on ENOENT the fd went away, so try to do the right thing */ 93 /* if ENOENT then the fd went away, so try to do the right thing */
84 if (!nev) 94 if (!nev)
85 return; 95 goto dec_egen;
86 96
87 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev)) 97 if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev))
88 return; 98 return;
89 } 99 }
90 else if (expect_true (errno == EEXIST)) 100 else if (expect_true (errno == EEXIST))
91 { 101 {
92 /* on EEXIST we ignored a previous DEL */ 102 /* EEXIST means we ignored a previous DEL, but the fd is still active */
103 /* if the kernel mask is the same as the new mask, we assume it hasn't changed */
104 if (oldmask == nev)
105 goto dec_egen;
106
93 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev)) 107 if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev))
94 return; 108 return;
95 } 109 }
96 110
97 fd_kill (EV_A_ fd); 111 fd_kill (EV_A_ fd);
112
113dec_egen:
114 /* we didn't successfully call epoll_ctl, so decrement the generation counter again */
115 --anfds [fd].egen;
98} 116}
99 117
100static void 118static void
101epoll_poll (EV_P_ ev_tstamp timeout) 119epoll_poll (EV_P_ ev_tstamp timeout)
102{ 120{
… …
104 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.)); 122 int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.));
105 123
106 if (expect_false (eventcnt < 0)) 124 if (expect_false (eventcnt < 0))
107 { 125 {
108 if (errno != EINTR) 126 if (errno != EINTR)
109 syserr ("(libev) epoll_wait"); 127 ev_syserr ("(libev) epoll_wait");
110 128
111 return; 129 return;
112 } 130 }
113 131
114 for (i = 0; i < eventcnt; ++i) 132 for (i = 0; i < eventcnt; ++i)
115 { 133 {
116 struct epoll_event *ev = epoll_events + i; 134 struct epoll_event *ev = epoll_events + i;
117 135
118 int fd = ev->data.u64; 136 int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */
137 int want = anfds [fd].events;
119 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) 138 int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
120 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0); 139 | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0);
121 int want = anfds [fd].events; 140
141 /* check for spurious notification */
142 if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32)))
143 {
144 /* recreate kernel state */
145 postfork = 1;
146 continue;
147 }
122 148
123 if (expect_false (got & ~want)) 149 if (expect_false (got & ~want))
124 { 150 {
151 anfds [fd].emask = want;
152
125 /* we received an event but are not interested in it, try mod or del */ 153 /* we received an event but are not interested in it, try mod or del */
154 /* I don't think we ever need MOD, but let's handle it anyways */
126 ev->events = (want & EV_READ ? EPOLLIN : 0) 155 ev->events = (want & EV_READ ? EPOLLIN : 0)
127 | (want & EV_WRITE ? EPOLLOUT : 0); 156 | (want & EV_WRITE ? EPOLLOUT : 0);
128 157
129 epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev); 158 if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev))
159 {
160 postfork = 1; /* an error occured, recreate kernel state */
161 continue;
162 }
130 } 163 }
131 164
132 fd_event (EV_A_ fd, got); 165 fd_event (EV_A_ fd, got);
133 } 166 }
134 167
… …
153 186
154 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */ 187 backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */
155 backend_modify = epoll_modify; 188 backend_modify = epoll_modify;
156 backend_poll = epoll_poll; 189 backend_poll = epoll_poll;
157 190
158 epoll_eventmax = 64; /* intiial number of events receivable per poll */ 191 epoll_eventmax = 64; /* initial number of events receivable per poll */
159 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); 192 epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax);
160 193
161 return EVBACKEND_EPOLL; 194 return EVBACKEND_EPOLL;
162} 195}
163 196
… …
171epoll_fork (EV_P) 204epoll_fork (EV_P)
172{ 205{
173 close (backend_fd); 206 close (backend_fd);
174 207
175 while ((backend_fd = epoll_create (256)) < 0) 208 while ((backend_fd = epoll_create (256)) < 0)
176 syserr ("(libev) epoll_create"); 209 ev_syserr ("(libev) epoll_create");
177 210
178 fcntl (backend_fd, F_SETFD, FD_CLOEXEC); 211 fcntl (backend_fd, F_SETFD, FD_CLOEXEC);
179 212
180 fd_rearm_all (EV_A); 213 fd_rearm_all (EV_A);
181} 214}

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