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 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: |
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10 | * |
9 | * |
11 | * * Redistributions of source code must retain the above copyright |
10 | * 1. Redistributions of source code must retain the above copyright notice, |
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11 | * this list of conditions and the following disclaimer. |
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12 | * |
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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 |
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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 | * |
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19 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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20 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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21 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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22 | * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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23 | * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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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. |
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27 | * |
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28 | * Alternatively, the contents of this file may be used under the terms of |
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29 | * the GNU General Public License ("GPL") version 2 or any later version, |
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30 | * in which case the provisions of the GPL are applicable instead of |
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31 | * the above. If you wish to allow the use of your version of this file |
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32 | * only under the terms of the GPL and not to allow others to use your |
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33 | * version of this file under the BSD license, indicate your decision |
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34 | * by deleting the provisions above and replace them with the notice |
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35 | * and other provisions required by the GPL. If you do not delete the |
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36 | * provisions above, a recipient may use your version of this file under |
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37 | * either the BSD or the GPL. |
30 | */ |
38 | */ |
31 | |
39 | |
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40 | /* |
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41 | * general notes about epoll: |
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42 | * |
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43 | * a) epoll silently removes fds from the fd set. as nothing tells us |
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44 | * that an fd has been removed otherwise, we have to continually |
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45 | * "rearm" fds that we suspect *might* have changed (same |
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46 | * problem with kqueue, but much less costly there). |
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47 | * b) the fact that ADD != MOD creates a lot of extra syscalls due to a) |
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48 | * and seems not to have any advantage. |
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49 | * c) the inability to handle fork or file descriptors (think dup) |
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50 | * limits the applicability over poll, so this is not a generic |
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51 | * poll replacement. |
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52 | * d) epoll doesn't work the same as select with many file descriptors |
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53 | * (such as files). while not critical, no other advanced interface |
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54 | * seems to share this (rather non-unixy) limitation. |
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55 | * e) epoll claims to be embeddable, but in practise you never get |
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56 | * a ready event for the epoll fd (broken: <=2.6.26, working: >=2.6.32). |
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57 | * f) epoll_ctl returning EPERM means the fd is always ready. |
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58 | * |
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59 | * lots of "weird code" and complication handling in this file is due |
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60 | * to these design problems with epoll, as we try very hard to avoid |
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61 | * epoll_ctl syscalls for common usage patterns and handle the breakage |
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62 | * ensuing from receiving events for closed and otherwise long gone |
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63 | * file descriptors. |
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64 | */ |
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65 | |
32 | #include <sys/epoll.h> |
66 | #include <sys/epoll.h> |
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67 | |
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68 | #define EV_EMASK_EPERM 0x80 |
33 | |
69 | |
34 | static void |
70 | static void |
35 | epoll_modify (EV_P_ int fd, int oev, int nev) |
71 | epoll_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; |
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38 | |
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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 | |
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76 | /* |
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77 | * we handle EPOLL_CTL_DEL by ignoring it here |
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78 | * on the assumption that the fd is gone anyways |
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79 | * if that is wrong, we have to handle the spurious |
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80 | * event in epoll_poll. |
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81 | * if the fd is added again, we try to ADD it, and, if that |
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82 | * fails, we assume it still has the same eventmask. |
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83 | */ |
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84 | if (!nev) |
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85 | return; |
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86 | |
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87 | oldmask = anfds [fd].emask; |
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88 | anfds [fd].emask = nev; |
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89 | |
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90 | /* store the generation counter in the upper 32 bits, the fd in the lower 32 bits */ |
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91 | ev.data.u64 = (uint64_t)(uint32_t)fd |
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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 (epoll_ctl (epoll_fd, mode, fd, &ev)) |
96 | if (expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) |
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97 | return; |
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98 | |
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99 | if (expect_true (errno == ENOENT)) |
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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 */ |
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102 | if (!nev) |
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103 | goto dec_egen; |
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104 | |
47 | || (nev && epoll_ctl (epoll_fd, EPOLL_CTL_ADD, fd, &ev))) |
105 | if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev)) |
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106 | return; |
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107 | } |
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108 | else if (expect_true (errno == EEXIST)) |
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109 | { |
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110 | /* EEXIST means we ignored a previous DEL, but the fd is still active */ |
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111 | /* if the kernel mask is the same as the new mask, we assume it hasn't changed */ |
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112 | if (oldmask == nev) |
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113 | goto dec_egen; |
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114 | |
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115 | if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev)) |
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116 | return; |
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117 | } |
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118 | else if (expect_true (errno == EPERM)) |
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119 | { |
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120 | /* EPERM means the fd is always ready, but epoll is too snobbish */ |
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121 | /* to handle it, unlike select or poll. */ |
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122 | anfds [fd].emask = EV_EMASK_EPERM; |
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123 | |
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124 | /* add fd to epoll_eperms, if not already inside */ |
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125 | if (!(oldmask & EV_EMASK_EPERM)) |
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126 | { |
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127 | array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, EMPTY2); |
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128 | epoll_eperms [epoll_epermcnt++] = fd; |
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129 | } |
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130 | |
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131 | return; |
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132 | } |
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133 | |
48 | fd_kill (EV_A_ fd); |
134 | fd_kill (EV_A_ fd); |
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135 | |
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136 | dec_egen: |
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137 | /* we didn't successfully call epoll_ctl, so decrement the generation counter again */ |
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138 | --anfds [fd].egen; |
49 | } |
139 | } |
50 | |
140 | |
51 | static void |
141 | static void |
52 | epoll_poll (EV_P_ ev_tstamp timeout) |
142 | epoll_poll (EV_P_ ev_tstamp timeout) |
53 | { |
143 | { |
54 | int i; |
144 | int i; |
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145 | int eventcnt; |
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146 | |
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147 | if (expect_false (epoll_epermcnt)) |
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148 | timeout = 0.; |
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149 | |
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150 | /* epoll wait times cannot be larger than (LONG_MAX - 999UL) / HZ msecs, which is below */ |
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151 | /* the default libev max wait time, however. */ |
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152 | EV_RELEASE_CB; |
55 | int eventcnt = epoll_wait (epoll_fd, epoll_events, epoll_eventmax, ceil (timeout * 1000.)); |
153 | eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, timeout * 1e3); |
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154 | EV_ACQUIRE_CB; |
56 | |
155 | |
57 | if (eventcnt < 0) |
156 | if (expect_false (eventcnt < 0)) |
58 | { |
157 | { |
59 | if (errno != EINTR) |
158 | if (errno != EINTR) |
60 | syserr ("(libev) epoll_wait"); |
159 | ev_syserr ("(libev) epoll_wait"); |
61 | |
160 | |
62 | return; |
161 | return; |
63 | } |
162 | } |
64 | |
163 | |
65 | for (i = 0; i < eventcnt; ++i) |
164 | for (i = 0; i < eventcnt; ++i) |
66 | fd_event ( |
165 | { |
67 | EV_A_ |
166 | struct epoll_event *ev = epoll_events + i; |
68 | epoll_events [i].data.u64, |
167 | |
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168 | int fd = (uint32_t)ev->data.u64; /* mask out the lower 32 bits */ |
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169 | int want = anfds [fd].events; |
69 | (epoll_events [i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) |
170 | int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) |
70 | | (epoll_events [i].events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0) |
171 | | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0); |
71 | ); |
172 | |
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173 | /* check for spurious notification */ |
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174 | /* we assume that fd is always in range, as we never shrink the anfds array */ |
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175 | if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32))) |
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176 | { |
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177 | /* recreate kernel state */ |
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178 | postfork = 1; |
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179 | continue; |
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180 | } |
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181 | |
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182 | if (expect_false (got & ~want)) |
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183 | { |
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184 | anfds [fd].emask = want; |
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185 | |
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186 | /* we received an event but are not interested in it, try mod or del */ |
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187 | /* I don't think we ever need MOD, but let's handle it anyways */ |
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188 | ev->events = (want & EV_READ ? EPOLLIN : 0) |
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189 | | (want & EV_WRITE ? EPOLLOUT : 0); |
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190 | |
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191 | /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */ |
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192 | /* which is fortunately easy to do for us. */ |
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193 | if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev)) |
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194 | { |
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195 | postfork = 1; /* an error occurred, recreate kernel state */ |
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196 | continue; |
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197 | } |
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198 | } |
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199 | |
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200 | fd_event (EV_A_ fd, got); |
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201 | } |
72 | |
202 | |
73 | /* if the receive array was full, increase its size */ |
203 | /* if the receive array was full, increase its size */ |
74 | if (expect_false (eventcnt == epoll_eventmax)) |
204 | if (expect_false (eventcnt == epoll_eventmax)) |
75 | { |
205 | { |
76 | ev_free (epoll_events); |
206 | ev_free (epoll_events); |
77 | epoll_eventmax = array_roundsize (epoll_events, epoll_eventmax << 1); |
207 | epoll_eventmax = array_nextsize (sizeof (struct epoll_event), epoll_eventmax, epoll_eventmax + 1); |
78 | epoll_events = ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); |
208 | epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); |
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209 | } |
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210 | |
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211 | /* now synthesize events for all fds where epoll fails, while select works... */ |
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212 | for (i = epoll_epermcnt; i--; ) |
79 | } |
213 | { |
80 | } |
214 | int fd = epoll_eperms [i]; |
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215 | unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE); |
81 | |
216 | |
82 | static int |
217 | if (anfds [fd].emask & EV_EMASK_EPERM && events) |
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218 | fd_event (EV_A_ fd, events); |
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219 | else |
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220 | epoll_eperms [i] = epoll_eperms [--epoll_epermcnt]; |
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221 | } |
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222 | } |
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223 | |
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224 | int inline_size |
83 | epoll_init (EV_P_ int flags) |
225 | epoll_init (EV_P_ int flags) |
84 | { |
226 | { |
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227 | #ifdef EPOLL_CLOEXEC |
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228 | backend_fd = epoll_create1 (EPOLL_CLOEXEC); |
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229 | |
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230 | if (backend_fd <= 0) |
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231 | #endif |
85 | epoll_fd = epoll_create (256); |
232 | backend_fd = epoll_create (256); |
86 | |
233 | |
87 | if (epoll_fd < 0) |
234 | if (backend_fd < 0) |
88 | return 0; |
235 | return 0; |
89 | |
236 | |
90 | fcntl (epoll_fd, F_SETFD, FD_CLOEXEC); |
237 | fcntl (backend_fd, F_SETFD, FD_CLOEXEC); |
91 | |
238 | |
92 | method_fudge = 1e-3; /* needed to compensate for epoll returning early */ |
239 | backend_fudge = 1./1024.; /* epoll does sometimes return early, this is just to avoid the worst */ |
93 | method_modify = epoll_modify; |
240 | backend_modify = epoll_modify; |
94 | method_poll = epoll_poll; |
241 | backend_poll = epoll_poll; |
95 | |
242 | |
96 | epoll_eventmax = 64; /* intiial number of events receivable per poll */ |
243 | epoll_eventmax = 64; /* initial number of events receivable per poll */ |
97 | epoll_events = ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); |
244 | epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); |
98 | |
245 | |
99 | return EVMETHOD_EPOLL; |
246 | return EVBACKEND_EPOLL; |
100 | } |
247 | } |
101 | |
248 | |
102 | static void |
249 | void inline_size |
103 | epoll_destroy (EV_P) |
250 | epoll_destroy (EV_P) |
104 | { |
251 | { |
105 | close (epoll_fd); |
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106 | |
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107 | ev_free (epoll_events); |
252 | ev_free (epoll_events); |
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253 | array_free (epoll_eperm, EMPTY); |
108 | } |
254 | } |
109 | |
255 | |
110 | static void |
256 | void inline_size |
111 | epoll_fork (EV_P) |
257 | epoll_fork (EV_P) |
112 | { |
258 | { |
113 | for (;;) |
259 | close (backend_fd); |
114 | { |
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115 | epoll_fd = epoll_create (256); |
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116 | |
260 | |
117 | if (epoll_fd >= 0) |
261 | while ((backend_fd = epoll_create (256)) < 0) |
118 | break; |
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119 | |
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120 | syserr ("(libev) epoll_create"); |
262 | ev_syserr ("(libev) epoll_create"); |
121 | } |
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122 | |
263 | |
123 | fcntl (epoll_fd, F_SETFD, FD_CLOEXEC); |
264 | fcntl (backend_fd, F_SETFD, FD_CLOEXEC); |
124 | |
265 | |
125 | fd_rearm_all (EV_A); |
266 | fd_rearm_all (EV_A); |
126 | } |
267 | } |
127 | |
268 | |