/* * libev epoll fd activity backend * * Copyright (c) 2007 Marc Alexander Lehmann <libev@schmorp.de> * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * 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 COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, 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 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * 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. * * 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. */ #include <sys/epoll.h> static void epoll_modify (EV_P_ int fd, int oev, int nev) { struct epoll_event ev; /* * 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 (!nev) return; ev.data.u64 = fd; /* use u64 to fully initialise the struct, for nicer strace etc. */ ev.events = (nev & EV_READ ? EPOLLIN : 0) | (nev & EV_WRITE ? EPOLLOUT : 0); if (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) return; if (expect_true (errno == ENOENT)) { /* on ENOENT the fd went away, so try to do the right thing */ if (!nev) return; if (!epoll_ctl (backend_fd, EPOLL_CTL_ADD, fd, &ev)) return; } else if (expect_true (errno == EEXIST)) { /* on EEXIST we ignored a previous DEL */ if (!epoll_ctl (backend_fd, EPOLL_CTL_MOD, fd, &ev)) return; } fd_kill (EV_A_ fd); } static void epoll_poll (EV_P_ ev_tstamp timeout) { int i; int eventcnt = epoll_wait (backend_fd, epoll_events, epoll_eventmax, (int)ceil (timeout * 1000.)); if (expect_false (eventcnt < 0)) { if (errno != EINTR) syserr ("(libev) epoll_wait"); return; } for (i = 0; i < eventcnt; ++i) { struct epoll_event *ev = epoll_events + i; int fd = ev->data.u64; int got = (ev->events & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0) | (ev->events & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0); int want = anfds [fd].events; if (expect_false (got & ~want)) { /* we received an event but are not interested in it, try mod or del */ ev->events = (want & EV_READ ? EPOLLIN : 0) | (want & EV_WRITE ? EPOLLOUT : 0); epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev); } fd_event (EV_A_ fd, got); } /* if the receive array was full, increase its size */ if (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); } } int inline_size epoll_init (EV_P_ int flags) { backend_fd = epoll_create (256); if (backend_fd < 0) return 0; fcntl (backend_fd, F_SETFD, FD_CLOEXEC); backend_fudge = 0.; /* kernel sources seem to indicate this to be zero */ backend_modify = epoll_modify; backend_poll = epoll_poll; epoll_eventmax = 64; /* intiial number of events receivable per poll */ epoll_events = (struct epoll_event *)ev_malloc (sizeof (struct epoll_event) * epoll_eventmax); return EVBACKEND_EPOLL; } void inline_size epoll_destroy (EV_P) { ev_free (epoll_events); } void inline_size epoll_fork (EV_P) { close (backend_fd); while ((backend_fd = epoll_create (256)) < 0) syserr ("(libev) epoll_create"); fcntl (backend_fd, F_SETFD, FD_CLOEXEC); fd_rearm_all (EV_A); }