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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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This file is part of systemd.
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Copyright 2011 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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#include <sys/epoll.h>
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#include <sys/timerfd.h>
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#include "dbus-loop.h"
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#include "dbus-common.h"
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/* Minimal implementation of the dbus loop which integrates all dbus
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* events into a single epoll fd which we can triviall integrate with
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* other loops. Note that this is not used in the main systemd daemon
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* since we run a more elaborate mainloop there. */
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typedef struct EpollData {
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static dbus_bool_t add_watch(DBusWatch *watch, void *data) {
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struct epoll_event ev;
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e = new0(EpollData, 1);
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e->fd = dbus_watch_get_unix_fd(watch);
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e->is_timeout = false;
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ev.events = bus_flags_to_events(watch);
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if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0) {
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if (errno != EEXIST) {
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/* Hmm, bloody D-Bus creates multiple watches on the
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* same fd. epoll() does not like that. As a dirty
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* hack we simply dup() the fd and hence get a second
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* one we can safely add to the epoll(). */
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if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0) {
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close_nointr_nofail(e->fd);
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e->fd_is_dupped = true;
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dbus_watch_set_data(watch, e, NULL);
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static void remove_watch(DBusWatch *watch, void *data) {
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e = dbus_watch_get_data(watch);
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assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_DEL, e->fd, NULL) >= 0);
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close_nointr_nofail(e->fd);
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static void toggle_watch(DBusWatch *watch, void *data) {
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struct epoll_event ev;
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e = dbus_watch_get_data(watch);
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ev.events = bus_flags_to_events(watch);
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assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_MOD, e->fd, &ev) == 0);
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static int timeout_arm(EpollData *e) {
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struct itimerspec its;
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assert(e->is_timeout);
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if (dbus_timeout_get_enabled(e->object)) {
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timespec_store(&its.it_value, dbus_timeout_get_interval(e->object) * USEC_PER_MSEC);
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its.it_interval = its.it_value;
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if (timerfd_settime(e->fd, 0, &its, NULL) < 0)
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static dbus_bool_t add_timeout(DBusTimeout *timeout, void *data) {
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struct epoll_event ev;
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e = new0(EpollData, 1);
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e->fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC);
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e->is_timeout = true;
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if (timeout_arm(e) < 0)
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if (epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_ADD, e->fd, &ev) < 0)
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dbus_timeout_set_data(timeout, e, NULL);
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close_nointr_nofail(e->fd);
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static void remove_timeout(DBusTimeout *timeout, void *data) {
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e = dbus_timeout_get_data(timeout);
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assert_se(epoll_ctl(PTR_TO_INT(data), EPOLL_CTL_DEL, e->fd, NULL) >= 0);
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close_nointr_nofail(e->fd);
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static void toggle_timeout(DBusTimeout *timeout, void *data) {
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e = dbus_timeout_get_data(timeout);
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log_error("Failed to rearm timer: %s", strerror(-r));
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int bus_loop_open(DBusConnection *c) {
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fd = epoll_create1(EPOLL_CLOEXEC);
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if (!dbus_connection_set_watch_functions(c, add_watch, remove_watch, toggle_watch, INT_TO_PTR(fd), NULL) ||
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!dbus_connection_set_timeout_functions(c, add_timeout, remove_timeout, toggle_timeout, INT_TO_PTR(fd), NULL)) {
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close_nointr_nofail(fd);
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int bus_loop_dispatch(int fd) {
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struct epoll_event event;
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n = epoll_wait(fd, &event, 1, 0);
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return errno == EAGAIN || errno == EINTR ? 0 : -errno;
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assert_se(d = event.data.ptr);
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DBusTimeout *t = d->object;
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if (dbus_timeout_get_enabled(t))
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dbus_timeout_handle(t);
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DBusWatch *w = d->object;
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if (dbus_watch_get_enabled(w))
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dbus_watch_handle(w, bus_events_to_flags(event.events));