/* $NetBSD: epoll.c,v 1.1.1.3 2021/04/07 02:43:14 christos Exp $ */ /* * Copyright 2000-2007 Niels Provos * Copyright 2007-2012 Niels Provos, Nick Mathewson * * Redistribution and use in source and binary forms, with or without * modification, 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. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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. */ #include "event2/event-config.h" #include __RCSID("$NetBSD: epoll.c,v 1.1.1.3 2021/04/07 02:43:14 christos Exp $"); #include "evconfig-private.h" #ifdef EVENT__HAVE_EPOLL #include #include #include #ifdef EVENT__HAVE_SYS_TIME_H #include #endif #include #include #include #include #include #include #include #include #include #ifdef EVENT__HAVE_FCNTL_H #include #endif #ifdef EVENT__HAVE_SYS_TIMERFD_H #include #endif #include "event-internal.h" #include "evsignal-internal.h" #include "event2/thread.h" #include "evthread-internal.h" #include "log-internal.h" #include "evmap-internal.h" #include "changelist-internal.h" #include "time-internal.h" /* Since Linux 2.6.17, epoll is able to report about peer half-closed connection using special EPOLLRDHUP flag on a read event. */ #if !defined(EPOLLRDHUP) #define EPOLLRDHUP 0 #define EARLY_CLOSE_IF_HAVE_RDHUP 0 #else #define EARLY_CLOSE_IF_HAVE_RDHUP EV_FEATURE_EARLY_CLOSE #endif #include "epolltable-internal.h" #if defined(EVENT__HAVE_SYS_TIMERFD_H) && \ defined(EVENT__HAVE_TIMERFD_CREATE) && \ defined(HAVE_POSIX_MONOTONIC) && defined(TFD_NONBLOCK) && \ defined(TFD_CLOEXEC) /* Note that we only use timerfd if TFD_NONBLOCK and TFD_CLOEXEC are available and working. This means that we can't support it on 2.6.25 (where timerfd was introduced) or 2.6.26, since 2.6.27 introduced those flags. */ #define USING_TIMERFD #endif struct epollop { struct epoll_event *events; int nevents; int epfd; #ifdef USING_TIMERFD int timerfd; #endif }; static void *epoll_init(struct event_base *); static int epoll_dispatch(struct event_base *, struct timeval *); static void epoll_dealloc(struct event_base *); static const struct eventop epollops_changelist = { "epoll (with changelist)", epoll_init, event_changelist_add_, event_changelist_del_, epoll_dispatch, epoll_dealloc, 1, /* need reinit */ EV_FEATURE_ET|EV_FEATURE_O1| EARLY_CLOSE_IF_HAVE_RDHUP, EVENT_CHANGELIST_FDINFO_SIZE }; static int epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd, short old, short events, void *p); static int epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd, short old, short events, void *p); const struct eventop epollops = { "epoll", epoll_init, epoll_nochangelist_add, epoll_nochangelist_del, epoll_dispatch, epoll_dealloc, 1, /* need reinit */ EV_FEATURE_ET|EV_FEATURE_O1|EV_FEATURE_EARLY_CLOSE, 0 }; #define INITIAL_NEVENT 32 #define MAX_NEVENT 4096 /* On Linux kernels at least up to 2.6.24.4, epoll can't handle timeout * values bigger than (LONG_MAX - 999ULL)/HZ. HZ in the wild can be * as big as 1000, and LONG_MAX can be as small as (1<<31)-1, so the * largest number of msec we can support here is 2147482. Let's * round that down by 47 seconds. */ #define MAX_EPOLL_TIMEOUT_MSEC (35*60*1000) static void * epoll_init(struct event_base *base) { int epfd = -1; struct epollop *epollop; #ifdef EVENT__HAVE_EPOLL_CREATE1 /* First, try the shiny new epoll_create1 interface, if we have it. */ epfd = epoll_create1(EPOLL_CLOEXEC); #endif if (epfd == -1) { /* Initialize the kernel queue using the old interface. (The size field is ignored since 2.6.8.) */ if ((epfd = epoll_create(32000)) == -1) { if (errno != ENOSYS) event_warn("epoll_create"); return (NULL); } evutil_make_socket_closeonexec(epfd); } if (!(epollop = mm_calloc(1, sizeof(struct epollop)))) { close(epfd); return (NULL); } epollop->epfd = epfd; /* Initialize fields */ epollop->events = mm_calloc(INITIAL_NEVENT, sizeof(struct epoll_event)); if (epollop->events == NULL) { mm_free(epollop); close(epfd); return (NULL); } epollop->nevents = INITIAL_NEVENT; if ((base->flags & EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST) != 0 || ((base->flags & EVENT_BASE_FLAG_IGNORE_ENV) == 0 && evutil_getenv_("EVENT_EPOLL_USE_CHANGELIST") != NULL)) { base->evsel = &epollops_changelist; } #ifdef USING_TIMERFD /* The epoll interface ordinarily gives us one-millisecond precision, so on Linux it makes perfect sense to use the CLOCK_MONOTONIC_COARSE timer. But when the user has set the new PRECISE_TIMER flag for an event_base, we can try to use timerfd to give them finer granularity. */ if ((base->flags & EVENT_BASE_FLAG_PRECISE_TIMER) && base->monotonic_timer.monotonic_clock == CLOCK_MONOTONIC) { int fd; fd = epollop->timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC); if (epollop->timerfd >= 0) { struct epoll_event epev; memset(&epev, 0, sizeof(epev)); epev.data.fd = epollop->timerfd; epev.events = EPOLLIN; if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, fd, &epev) < 0) { event_warn("epoll_ctl(timerfd)"); close(fd); epollop->timerfd = -1; } } else { if (errno != EINVAL && errno != ENOSYS) { /* These errors probably mean that we were * compiled with timerfd/TFD_* support, but * we're running on a kernel that lacks those. */ event_warn("timerfd_create"); } epollop->timerfd = -1; } } else { epollop->timerfd = -1; } #endif evsig_init_(base); return (epollop); } static const char * change_to_string(int change) { change &= (EV_CHANGE_ADD|EV_CHANGE_DEL); if (change == EV_CHANGE_ADD) { return "add"; } else if (change == EV_CHANGE_DEL) { return "del"; } else if (change == 0) { return "none"; } else { return "???"; } } static const char * epoll_op_to_string(int op) { return op == EPOLL_CTL_ADD?"ADD": op == EPOLL_CTL_DEL?"DEL": op == EPOLL_CTL_MOD?"MOD": "???"; } #define PRINT_CHANGES(op, events, ch, status) \ "Epoll %s(%d) on fd %d " status ". " \ "Old events were %d; " \ "read change was %d (%s); " \ "write change was %d (%s); " \ "close change was %d (%s)", \ epoll_op_to_string(op), \ events, \ ch->fd, \ ch->old_events, \ ch->read_change, \ change_to_string(ch->read_change), \ ch->write_change, \ change_to_string(ch->write_change), \ ch->close_change, \ change_to_string(ch->close_change) static int epoll_apply_one_change(struct event_base *base, struct epollop *epollop, const struct event_change *ch) { struct epoll_event epev; int op, events = 0; int idx; idx = EPOLL_OP_TABLE_INDEX(ch); op = epoll_op_table[idx].op; events = epoll_op_table[idx].events; if (!events) { EVUTIL_ASSERT(op == 0); return 0; } if ((ch->read_change|ch->write_change|ch->close_change) & EV_CHANGE_ET) events |= EPOLLET; memset(&epev, 0, sizeof(epev)); epev.data.fd = ch->fd; epev.events = events; if (epoll_ctl(epollop->epfd, op, ch->fd, &epev) == 0) { event_debug((PRINT_CHANGES(op, epev.events, ch, "okay"))); return 0; } switch (op) { case EPOLL_CTL_MOD: if (errno == ENOENT) { /* If a MOD operation fails with ENOENT, the * fd was probably closed and re-opened. We * should retry the operation as an ADD. */ if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, ch->fd, &epev) == -1) { event_warn("Epoll MOD(%d) on %d retried as ADD; that failed too", (int)epev.events, ch->fd); return -1; } else { event_debug(("Epoll MOD(%d) on %d retried as ADD; succeeded.", (int)epev.events, ch->fd)); return 0; } } break; case EPOLL_CTL_ADD: if (errno == EEXIST) { /* If an ADD operation fails with EEXIST, * either the operation was redundant (as with a * precautionary add), or we ran into a fun * kernel bug where using dup*() to duplicate the * same file into the same fd gives you the same epitem * rather than a fresh one. For the second case, * we must retry with MOD. */ if (epoll_ctl(epollop->epfd, EPOLL_CTL_MOD, ch->fd, &epev) == -1) { event_warn("Epoll ADD(%d) on %d retried as MOD; that failed too", (int)epev.events, ch->fd); return -1; } else { event_debug(("Epoll ADD(%d) on %d retried as MOD; succeeded.", (int)epev.events, ch->fd)); return 0; } } break; case EPOLL_CTL_DEL: if (errno == ENOENT || errno == EBADF || errno == EPERM) { /* If a delete fails with one of these errors, * that's fine too: we closed the fd before we * got around to calling epoll_dispatch. */ event_debug(("Epoll DEL(%d) on fd %d gave %s: DEL was unnecessary.", (int)epev.events, ch->fd, strerror(errno))); return 0; } break; default: break; } event_warn(PRINT_CHANGES(op, epev.events, ch, "failed")); return -1; } static int epoll_apply_changes(struct event_base *base) { struct event_changelist *changelist = &base->changelist; struct epollop *epollop = base->evbase; struct event_change *ch; int r = 0; int i; for (i = 0; i < changelist->n_changes; ++i) { ch = &changelist->changes[i]; if (epoll_apply_one_change(base, epollop, ch) < 0) r = -1; } return (r); } static int epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd, short old, short events, void *p) { struct event_change ch; ch.fd = fd; ch.old_events = old; ch.read_change = ch.write_change = ch.close_change = 0; if (events & EV_WRITE) ch.write_change = EV_CHANGE_ADD | (events & EV_ET); if (events & EV_READ) ch.read_change = EV_CHANGE_ADD | (events & EV_ET); if (events & EV_CLOSED) ch.close_change = EV_CHANGE_ADD | (events & EV_ET); return epoll_apply_one_change(base, base->evbase, &ch); } static int epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd, short old, short events, void *p) { struct event_change ch; ch.fd = fd; ch.old_events = old; ch.read_change = ch.write_change = ch.close_change = 0; if (events & EV_WRITE) ch.write_change = EV_CHANGE_DEL | (events & EV_ET); if (events & EV_READ) ch.read_change = EV_CHANGE_DEL | (events & EV_ET); if (events & EV_CLOSED) ch.close_change = EV_CHANGE_DEL | (events & EV_ET); return epoll_apply_one_change(base, base->evbase, &ch); } static int epoll_dispatch(struct event_base *base, struct timeval *tv) { struct epollop *epollop = base->evbase; struct epoll_event *events = epollop->events; int i, res; long timeout = -1; #ifdef USING_TIMERFD if (epollop->timerfd >= 0) { struct itimerspec is; is.it_interval.tv_sec = 0; is.it_interval.tv_nsec = 0; if (tv == NULL) { /* No timeout; disarm the timer. */ is.it_value.tv_sec = 0; is.it_value.tv_nsec = 0; } else { if (tv->tv_sec == 0 && tv->tv_usec == 0) { /* we need to exit immediately; timerfd can't * do that. */ timeout = 0; } is.it_value.tv_sec = tv->tv_sec; is.it_value.tv_nsec = tv->tv_usec * 1000; } /* TODO: we could avoid unnecessary syscalls here by only calling timerfd_settime when the top timeout changes, or when we're called with a different timeval. */ if (timerfd_settime(epollop->timerfd, 0, &is, NULL) < 0) { event_warn("timerfd_settime"); } } else #endif if (tv != NULL) { timeout = evutil_tv_to_msec_(tv); if (timeout < 0 || timeout > MAX_EPOLL_TIMEOUT_MSEC) { /* Linux kernels can wait forever if the timeout is * too big; see comment on MAX_EPOLL_TIMEOUT_MSEC. */ timeout = MAX_EPOLL_TIMEOUT_MSEC; } } epoll_apply_changes(base); event_changelist_remove_all_(&base->changelist, base); EVBASE_RELEASE_LOCK(base, th_base_lock); res = epoll_wait(epollop->epfd, events, epollop->nevents, timeout); EVBASE_ACQUIRE_LOCK(base, th_base_lock); if (res == -1) { if (errno != EINTR) { event_warn("epoll_wait"); return (-1); } return (0); } event_debug(("%s: epoll_wait reports %d", __func__, res)); EVUTIL_ASSERT(res <= epollop->nevents); for (i = 0; i < res; i++) { int what = events[i].events; short ev = 0; #ifdef USING_TIMERFD if (events[i].data.fd == epollop->timerfd) continue; #endif if (what & EPOLLERR) { ev = EV_READ | EV_WRITE; } else if ((what & EPOLLHUP) && !(what & EPOLLRDHUP)) { ev = EV_READ | EV_WRITE; } else { if (what & EPOLLIN) ev |= EV_READ; if (what & EPOLLOUT) ev |= EV_WRITE; if (what & EPOLLRDHUP) ev |= EV_CLOSED; } if (!ev) continue; evmap_io_active_(base, events[i].data.fd, ev | EV_ET); } if (res == epollop->nevents && epollop->nevents < MAX_NEVENT) { /* We used all of the event space this time. We should be ready for more events next time. */ int new_nevents = epollop->nevents * 2; struct epoll_event *new_events; new_events = mm_realloc(epollop->events, new_nevents * sizeof(struct epoll_event)); if (new_events) { epollop->events = new_events; epollop->nevents = new_nevents; } } return (0); } static void epoll_dealloc(struct event_base *base) { struct epollop *epollop = base->evbase; evsig_dealloc_(base); if (epollop->events) mm_free(epollop->events); if (epollop->epfd >= 0) close(epollop->epfd); #ifdef USING_TIMERFD if (epollop->timerfd >= 0) close(epollop->timerfd); #endif memset(epollop, 0, sizeof(struct epollop)); mm_free(epollop); } #endif /* EVENT__HAVE_EPOLL */