uloop.c

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/*
 * uloop - event loop implementation
 *
 * Copyright (C) 2010-2016 Felix Fietkau <nbd@openwrt.org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <sys/time.h>
#include <sys/types.h>
 
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <poll.h>
#include <string.h>
#include <fcntl.h>
#include <stdbool.h>
#include <limits.h>
 
#include "uloop.h"
#include "utils.h"
 
#ifdef USE_KQUEUE
#include <sys/event.h>
#endif
#ifdef USE_EPOLL
#include <sys/epoll.h>
#include <sys/timerfd.h>
#endif
#include <sys/wait.h>
 
struct uloop_fd_event {
        struct uloop_fd *fd;
        unsigned int events;
};
 
struct uloop_fd_stack {
        struct uloop_fd_stack *next;
        struct uloop_fd *fd;
        unsigned int events;
};
 
static struct uloop_fd_stack *fd_stack = NULL;
 
#define ULOOP_MAX_EVENTS 10
 
static struct list_head timeouts = LIST_HEAD_INIT(timeouts);
static struct list_head processes = LIST_HEAD_INIT(processes);
static struct list_head signals = LIST_HEAD_INIT(signals);
 
static int poll_fd = -1;
bool uloop_cancelled = false;
bool uloop_handle_sigchld = true;
static int uloop_status = 0;
static bool do_sigchld = false;
 
static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
static int cur_fd, cur_nfds;
static int uloop_run_depth = 0;
 
uloop_fd_handler uloop_fd_set_cb = NULL;
 
int uloop_fd_add(struct uloop_fd *sock, unsigned int flags);
 
#ifdef USE_KQUEUE
#include "uloop-kqueue.c"
#endif
 
#ifdef USE_EPOLL
#include "uloop-epoll.c"
#endif
 
static void set_signo(uint64_t *signums, int signo)
{
        if (signo >= 1 && signo <= 64)
                *signums |= (1u << (signo - 1));
}
 
static bool get_signo(uint64_t signums, int signo)
{
        return (signo >= 1) && (signo <= 64) && (signums & (1u << (signo - 1)));
}
 
static void signal_consume(struct uloop_fd *fd, unsigned int events)
{
        struct uloop_signal *usig, *usig_next;
        uint64_t signums = 0;
        uint8_t buf[32];
        ssize_t nsigs;
 
        do {
                nsigs = read(fd->fd, buf, sizeof(buf));
 
                for (ssize_t i = 0; i < nsigs; i++)
                        set_signo(&signums, buf[i]);
        }
        while (nsigs > 0);
 
        list_for_each_entry_safe(usig, usig_next, &signals, list)
                if (get_signo(signums, usig->signo))
                        usig->cb(usig);
}
 
static int waker_pipe = -1;
static struct uloop_fd waker_fd = {
        .fd = -1,
        .cb = signal_consume,
};
 
static void waker_init_fd(int fd)
{
        fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
        fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
}
 
static int waker_init(void)
{
        int fds[2];
 
        if (waker_pipe >= 0)
                return 0;
 
        if (pipe(fds) < 0)
                return -1;
 
        waker_init_fd(fds[0]);
        waker_init_fd(fds[1]);
        waker_pipe = fds[1];
 
        waker_fd.fd = fds[0];
        waker_fd.cb = signal_consume;
        uloop_fd_add(&waker_fd, ULOOP_READ);
 
        return 0;
}
 
static void uloop_setup_signals(bool add);
 
int uloop_init(void)
{
        if (uloop_init_pollfd() < 0)
                return -1;
 
        if (waker_init() < 0) {
                uloop_done();
                return -1;
        }
 
        uloop_setup_signals(true);
 
        return 0;
}
 
static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
{
        struct uloop_fd_stack *cur;
 
        /*
         * Do not buffer events for level-triggered fds, they will keep firing.
         * Caller needs to take care of recursion issues.
         */
        if (!(fd->flags & ULOOP_EDGE_TRIGGER))
                return false;
 
        for (cur = fd_stack; cur; cur = cur->next) {
                if (cur->fd != fd)
                        continue;
 
                if (events < 0)
                        cur->fd = NULL;
                else
                        cur->events |= events | ULOOP_EVENT_BUFFERED;
 
                return true;
        }
 
        return false;
}
 
static void uloop_run_events(int64_t timeout)
{
        struct uloop_fd_event *cur;
        struct uloop_fd *fd;
 
        if (!cur_nfds) {
                cur_fd = 0;
                cur_nfds = uloop_fetch_events(timeout);
                if (cur_nfds < 0)
                        cur_nfds = 0;
        }
 
        while (cur_nfds > 0) {
                struct uloop_fd_stack stack_cur;
                unsigned int events;
 
                cur = &cur_fds[cur_fd++];
                cur_nfds--;
 
                fd = cur->fd;
                events = cur->events;
                if (!fd)
                        continue;
 
                if (!fd->cb)
                        continue;
 
                if (uloop_fd_stack_event(fd, cur->events))
                        continue;
 
                stack_cur.next = fd_stack;
                stack_cur.fd = fd;
                fd_stack = &stack_cur;
                do {
                        stack_cur.events = 0;
                        fd->cb(fd, events);
                        events = stack_cur.events & ULOOP_EVENT_MASK;
                } while (stack_cur.fd && events);
                fd_stack = stack_cur.next;
 
                return;
        }
}
 
int uloop_fd_add(struct uloop_fd *sock, unsigned int flags)
{
        unsigned int fl;
        int ret;
 
        if (!(flags & (ULOOP_READ | ULOOP_WRITE)))
                return uloop_fd_delete(sock);
 
        if (!sock->registered && !(flags & ULOOP_BLOCKING)) {
                fl = fcntl(sock->fd, F_GETFL, 0);
                fl |= O_NONBLOCK;
                fcntl(sock->fd, F_SETFL, fl);
        }
 
        ret = register_poll(sock, flags);
        if (ret < 0)
                goto out;
 
        if (uloop_fd_set_cb)
                uloop_fd_set_cb(sock, flags);
 
        sock->flags = flags;
        sock->registered = true;
        sock->eof = false;
        sock->error = false;
 
out:
        return ret;
}
 
int uloop_fd_delete(struct uloop_fd *fd)
{
        int ret;
        int i;
 
        for (i = 0; i < cur_nfds; i++) {
                if (cur_fds[cur_fd + i].fd != fd)
                        continue;
 
                cur_fds[cur_fd + i].fd = NULL;
        }
 
        if (!fd->registered)
                return 0;
 
        if (uloop_fd_set_cb)
                uloop_fd_set_cb(fd, 0);
 
        fd->registered = false;
        uloop_fd_stack_event(fd, -1);
        ret = __uloop_fd_delete(fd);
        fd->flags = 0;
 
        return ret;
}
 
static int64_t tv_diff(struct timeval *t1, struct timeval *t2)
{
        return
                (t1->tv_sec - t2->tv_sec) * 1000 +
                (t1->tv_usec - t2->tv_usec) / 1000;
}
 
int uloop_timeout_add(struct uloop_timeout *timeout)
{
        struct uloop_timeout *tmp;
        struct list_head *h = &timeouts;
 
        if (timeout->pending)
                return -1;
 
        list_for_each_entry(tmp, &timeouts, list) {
                if (tv_diff(&tmp->time, &timeout->time) > 0) {
                        h = &tmp->list;
                        break;
                }
        }
 
        list_add_tail(&timeout->list, h);
        timeout->pending = true;
 
        return 0;
}
 
static void uloop_gettime(struct timeval *tv)
{
        struct timespec ts;
 
        clock_gettime(CLOCK_MONOTONIC, &ts);
        tv->tv_sec = ts.tv_sec;
        tv->tv_usec = ts.tv_nsec / 1000;
}
 
int uloop_timeout_set(struct uloop_timeout *timeout, int msecs)
{
        struct timeval *time = &timeout->time;
 
        if (timeout->pending)
                uloop_timeout_cancel(timeout);
 
        uloop_gettime(time);
 
        time->tv_sec += msecs / 1000;
        time->tv_usec += (msecs % 1000) * 1000;
 
        if (time->tv_usec > 1000000) {
                time->tv_sec++;
                time->tv_usec -= 1000000;
        }
 
        return uloop_timeout_add(timeout);
}
 
int uloop_timeout_cancel(struct uloop_timeout *timeout)
{
        if (!timeout->pending)
                return -1;
 
        list_del(&timeout->list);
        timeout->pending = false;
 
        return 0;
}
 
int uloop_timeout_remaining(struct uloop_timeout *timeout)
{
        int64_t td;
        struct timeval now;
 
        if (!timeout->pending)
                return -1;
 
        uloop_gettime(&now);
 
        td = tv_diff(&timeout->time, &now);
 
        if (td > INT_MAX)
                return INT_MAX;
        else if (td < INT_MIN)
                return INT_MIN;
        else
                return (int)td;
}
 
int64_t uloop_timeout_remaining64(struct uloop_timeout *timeout)
{
        struct timeval now;
 
        if (!timeout->pending)
                return -1;
 
        uloop_gettime(&now);
 
        return tv_diff(&timeout->time, &now);
}
 
int uloop_process_add(struct uloop_process *p)
{
        struct uloop_process *tmp;
        struct list_head *h = &processes;
 
        if (p->pending)
                return -1;
 
        list_for_each_entry(tmp, &processes, list) {
                if (tmp->pid > p->pid) {
                        h = &tmp->list;
                        break;
                }
        }
 
        list_add_tail(&p->list, h);
        p->pending = true;
 
        return 0;
}
 
int uloop_process_delete(struct uloop_process *p)
{
        if (!p->pending)
                return -1;
 
        list_del(&p->list);
        p->pending = false;
 
        return 0;
}
 
static void uloop_handle_processes(void)
{
        struct uloop_process *p, *tmp;
        pid_t pid;
        int ret;
 
        do_sigchld = false;
 
        while (1) {
                pid = waitpid(-1, &ret, WNOHANG);
                if (pid < 0 && errno == EINTR)
                        continue;
 
                if (pid <= 0)
                        return;
 
                list_for_each_entry_safe(p, tmp, &processes, list) {
                        if (p->pid < pid)
                                continue;
 
                        if (p->pid > pid)
                                break;
 
                        uloop_process_delete(p);
                        p->cb(p, ret);
                }
        }
 
}
 
int uloop_interval_set(struct uloop_interval *timer, unsigned int msecs)
{
        return timer_register(timer, msecs);
}
 
int uloop_interval_cancel(struct uloop_interval *timer)
{
        return timer_remove(timer);
}
 
int64_t uloop_interval_remaining(struct uloop_interval *timer)
{
        return timer_next(timer);
}
 
static void uloop_signal_wake(int signo)
{
        uint8_t sigbyte = signo;
 
        if (signo == SIGCHLD)
                do_sigchld = true;
 
        do {
                if (write(waker_pipe, &sigbyte, 1) < 0) {
                        if (errno == EINTR)
                                continue;
                }
                break;
        } while (1);
}
 
static void uloop_handle_sigint(int signo)
{
        uloop_status = signo;
        uloop_cancelled = true;
        uloop_signal_wake(signo);
}
 
static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
{
        struct sigaction s;
        struct sigaction *act;
 
        act = NULL;
        sigaction(signum, NULL, &s);
 
        if (add) {
                if (s.sa_handler == SIG_DFL) { /* Do not override existing custom signal handlers */
                        memcpy(old, &s, sizeof(struct sigaction));
                        s.sa_handler = handler;
                        s.sa_flags = 0;
                        act = &s;
                }
        }
        else if (s.sa_handler == handler) { /* Do not restore if someone modified our handler */
                        act = old;
        }
 
        if (act != NULL)
                sigaction(signum, act, NULL);
}
 
static void uloop_ignore_signal(int signum, bool ignore)
{
        struct sigaction s;
        void *new_handler = NULL;
 
        sigaction(signum, NULL, &s);
 
        if (ignore) {
                if (s.sa_handler == SIG_DFL) /* Ignore only if there isn't any custom handler */
                        new_handler = SIG_IGN;
        } else {
                if (s.sa_handler == SIG_IGN) /* Restore only if noone modified our SIG_IGN */
                        new_handler = SIG_DFL;
        }
 
        if (new_handler) {
                s.sa_handler = new_handler;
                s.sa_flags = 0;
                sigaction(signum, &s, NULL);
        }
}
 
static void uloop_setup_signals(bool add)
{
        static struct sigaction old_sigint, old_sigchld, old_sigterm;
 
        uloop_install_handler(SIGINT, uloop_handle_sigint, &old_sigint, add);
        uloop_install_handler(SIGTERM, uloop_handle_sigint, &old_sigterm, add);
 
        if (uloop_handle_sigchld)
                uloop_install_handler(SIGCHLD, uloop_signal_wake, &old_sigchld, add);
 
        uloop_ignore_signal(SIGPIPE, add);
}
 
int uloop_signal_add(struct uloop_signal *s)
{
        struct list_head *h = &signals;
        struct uloop_signal *tmp;
        struct sigaction sa;
 
        if (s->pending)
                return -1;
 
        list_for_each_entry(tmp, &signals, list) {
                if (tmp->signo > s->signo) {
                        h = &tmp->list;
                        break;
                }
        }
 
        list_add_tail(&s->list, h);
        s->pending = true;
 
        sigaction(s->signo, NULL, &s->orig);
 
        if (s->orig.sa_handler != uloop_signal_wake) {
                sa.sa_handler = uloop_signal_wake;
                sa.sa_flags = 0;
                sigemptyset(&sa.sa_mask);
                sigaction(s->signo, &sa, NULL);
        }
 
        return 0;
}
 
int uloop_signal_delete(struct uloop_signal *s)
{
        if (!s->pending)
                return -1;
 
        list_del(&s->list);
        s->pending = false;
 
        if (s->orig.sa_handler != uloop_signal_wake)
                sigaction(s->signo, &s->orig, NULL);
 
        return 0;
}
 
int uloop_get_next_timeout(void)
{
        struct uloop_timeout *timeout;
        struct timeval tv;
        int64_t diff;
 
        if (list_empty(&timeouts))
                return -1;
 
        uloop_gettime(&tv);
 
        timeout = list_first_entry(&timeouts, struct uloop_timeout, list);
        diff = tv_diff(&timeout->time, &tv);
        if (diff < 0)
                return 0;
        if (diff > INT_MAX)
                return INT_MAX;
 
        return diff;
}
 
static void uloop_process_timeouts(void)
{
        struct uloop_timeout *t;
        struct timeval tv;
 
        if (list_empty(&timeouts))
                return;
 
        uloop_gettime(&tv);
        while (!list_empty(&timeouts)) {
                t = list_first_entry(&timeouts, struct uloop_timeout, list);
 
                if (tv_diff(&t->time, &tv) > 0)
                        break;
 
                uloop_timeout_cancel(t);
                if (t->cb)
                        t->cb(t);
        }
}
 
static void uloop_clear_timeouts(void)
{
        struct uloop_timeout *t, *tmp;
 
        list_for_each_entry_safe(t, tmp, &timeouts, list)
                uloop_timeout_cancel(t);
}
 
static void uloop_clear_processes(void)
{
        struct uloop_process *p, *tmp;
 
        list_for_each_entry_safe(p, tmp, &processes, list)
                uloop_process_delete(p);
}
 
bool uloop_cancelling(void)
{
        return uloop_run_depth > 0 && uloop_cancelled;
}
 
int uloop_run_timeout(int timeout)
{
        int next_time = 0;
 
        uloop_run_depth++;
 
        uloop_status = 0;
        uloop_cancelled = false;
        do {
                uloop_process_timeouts();
 
                if (do_sigchld)
                        uloop_handle_processes();
 
                if (uloop_cancelled)
                        break;
 
                next_time = uloop_get_next_timeout();
                if (timeout >= 0 && (next_time < 0 || timeout < next_time))
                                next_time = timeout;
                uloop_run_events(next_time);
        } while (!uloop_cancelled && timeout < 0);
 
        --uloop_run_depth;
 
        return uloop_status;
}
 
void uloop_done(void)
{
        uloop_setup_signals(false);
 
        if (poll_fd >= 0) {
                close(poll_fd);
                poll_fd = -1;
        }
 
        if (waker_pipe >= 0) {
                uloop_fd_delete(&waker_fd);
                close(waker_pipe);
                close(waker_fd.fd);
                waker_pipe = -1;
        }
 
        uloop_clear_timeouts();
        uloop_clear_processes();
}