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Diffstat (limited to 'contrib/libev/ev_epoll.c')
| -rw-r--r-- | contrib/libev/ev_epoll.c | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/contrib/libev/ev_epoll.c b/contrib/libev/ev_epoll.c new file mode 100644 index 0000000..58cfa68 --- /dev/null +++ b/contrib/libev/ev_epoll.c @@ -0,0 +1,298 @@ +/* + * libev epoll fd activity backend + * + * Copyright (c) 2007,2008,2009,2010,2011,2016,2017,2019 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. + * d) epoll doesn't work the same as select with many file descriptors + * (such as files). while not critical, no other advanced interface + * seems to share this (rather non-unixy) limitation. + * e) epoll claims to be embeddable, but in practise you never get + * a ready event for the epoll fd (broken: <=2.6.26, working: >=2.6.32). + * f) epoll_ctl returning EPERM means the fd is always ready. + * + * 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> + +#define EV_EMASK_EPERM 0x80 + +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 (ecb_expect_true (!epoll_ctl (backend_fd, oev && oldmask != nev ? EPOLL_CTL_MOD : EPOLL_CTL_ADD, fd, &ev))) + return; + + if (ecb_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 (ecb_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; + } + else if (ecb_expect_true (errno == EPERM)) + { + /* EPERM means the fd is always ready, but epoll is too snobbish */ + /* to handle it, unlike select or poll. */ + anfds [fd].emask = EV_EMASK_EPERM; + + /* add fd to epoll_eperms, if not already inside */ + if (!(oldmask & EV_EMASK_EPERM)) + { + array_needsize (int, epoll_eperms, epoll_epermmax, epoll_epermcnt + 1, array_needsize_noinit); + epoll_eperms [epoll_epermcnt++] = fd; + } + + return; + } + else + assert (("libev: I/O watcher with invalid fd found in epoll_ctl", errno != EBADF && errno != ELOOP && errno != EINVAL)); + + 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; + + if (ecb_expect_false (epoll_epermcnt)) + timeout = EV_TS_CONST (0.); + + /* 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, EV_TS_TO_MSEC (timeout)); + EV_ACQUIRE_CB; + + if (ecb_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. + * this only finds spurious notifications on egen updates + * other spurious notifications will be found by epoll_ctl, below + * we assume that fd is always in range, as we never shrink the anfds array + */ + if (ecb_expect_false ((uint32_t)anfds [fd].egen != (uint32_t)(ev->data.u64 >> 32))) + { + /* recreate kernel state */ + postfork |= 2; + continue; + } + + if (ecb_expect_false (got & ~want)) + { + anfds [fd].emask = want; + + /* + * we received an event but are not interested in it, try mod or del + * this often happens because we optimistically do not unregister fds + * when we are no longer interested in them, but also when we get spurious + * notifications for fds from another process. this is partially handled + * above with the gencounter check (== our fd is not the event fd), and + * partially here, when epoll_ctl returns an error (== a child has the fd + * but we closed it). + * note: for events such as POLLHUP, where we can't know whether it refers + * to EV_READ or EV_WRITE, we might issue redundant EPOLL_CTL_MOD calls. + */ + ev->events = (want & EV_READ ? EPOLLIN : 0) + | (want & EV_WRITE ? EPOLLOUT : 0); + + /* pre-2.6.9 kernels require a non-null pointer with EPOLL_CTL_DEL, */ + /* which is fortunately easy to do for us. */ + if (epoll_ctl (backend_fd, want ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, fd, ev)) + { + postfork |= 2; /* an error occurred, recreate kernel state */ + continue; + } + } + + fd_event (EV_A_ fd, got); + } + + /* if the receive array was full, increase its size */ + if (ecb_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); + } + + /* now synthesize events for all fds where epoll fails, while select works... */ + for (i = epoll_epermcnt; i--; ) + { + int fd = epoll_eperms [i]; + unsigned char events = anfds [fd].events & (EV_READ | EV_WRITE); + + if (anfds [fd].emask & EV_EMASK_EPERM && events) + fd_event (EV_A_ fd, events); + else + { + epoll_eperms [i] = epoll_eperms [--epoll_epermcnt]; + anfds [fd].emask = 0; + } + } +} + +static int +epoll_epoll_create (void) +{ + int fd; + +#if defined EPOLL_CLOEXEC && !defined __ANDROID__ + fd = epoll_create1 (EPOLL_CLOEXEC); + + if (fd < 0 && (errno == EINVAL || errno == ENOSYS)) +#endif + { + fd = epoll_create (256); + + if (fd >= 0) + fcntl (fd, F_SETFD, FD_CLOEXEC); + } + + return fd; +} + +inline_size +int +epoll_init (EV_P_ int flags) +{ + if ((backend_fd = epoll_epoll_create ()) < 0) + return 0; + + backend_mintime = EV_TS_CONST (1e-3); /* epoll does sometimes return early, this is just to avoid the worst */ + 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; +} + +inline_size +void +epoll_destroy (EV_P) +{ + ev_free (epoll_events); + array_free (epoll_eperm, EMPTY); +} + +ecb_cold +static void +epoll_fork (EV_P) +{ + close (backend_fd); + + while ((backend_fd = epoll_epoll_create ()) < 0) + ev_syserr ("(libev) epoll_create"); + + fd_rearm_all (EV_A); +} + |