/* * libev epoll fd activity backend * * Copyright (c) 2007,2008,2009 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. * * 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> 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 (expect_true (!epoll_ctl (backend_fd, oev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) return; if (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 (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; } 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; /* 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, (int)ceil (timeout * 1000.)); EV_ACQUIRE_CB; if (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 */ if (expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32))) { /* recreate kernel state */ postfork = 1; continue; } if (expect_false (got & ~want)) { anfds [fd].emask = want; /* we received an event but are not interested in it, try mod or del */ /* I don't think we ever need MOD, but let's handle it anyways */ ev->events = (want & EV_READ ? EPOLLIN : 0) | (want & EV_WRITE ? EPOLLOUT : 0); if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev)) { postfork = 1; /* an error occured, recreate kernel state */ continue; } } 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) { #ifdef EPOLL_CLOEXEC backend_fd = epoll_create1 (EPOLL_CLOEXEC); if (backend_fd <= 0) #endif 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; /* initial 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) ev_syserr ("(libev) epoll_create"); fcntl (backend_fd, F_SETFD, FD_CLOEXEC); fd_rearm_all (EV_A); }