uloop: use a waker for notifying sigchld and loop cancel events

Fix a race condition when do_sigchld, uloop_cancelled were set just
before epoll_wait(timeout=-1), resulting the loop stuck in the syscall
without noticing the events just happened

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/uloop-epoll.c b/uloop-epoll.c
index bb652fd3444aebc0a916cb411a915c482df02826..6014bea8cc51e93c236d8ddc1b3c0e83aa94384a 100644 (file)
--- a/uloop-epoll.c
+++ b/uloop-epoll.c
@@ -23,7 +23,7 @@
 #define EPOLLRDHUP 0x2000
 #endif
 
-int uloop_init(void)
+static int uloop_init_pollfd(void)
 {
        if (poll_fd >= 0)
                return 0;

diff --git a/uloop-kqueue.c b/uloop-kqueue.c
index 0cb1c14ff64ad65732ffac080ef639b222285b30..ba5595b838422f8f9ecb425236a216434d681e99 100644 (file)
--- a/uloop-kqueue.c
+++ b/uloop-kqueue.c
@@ -15,7 +15,7 @@
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
-int uloop_init(void)
+static int uloop_init_pollfd(void)
 {
        struct timespec timeout = { 0, 0 };
        struct kevent ev = {};

diff --git a/uloop.c b/uloop.c
index cd3de85e1435140c2807a75444848705f1f9b6ab..2612fbdbc8ee4e9a6bce75bca8bb52f74199e6a1 100644 (file)
--- a/uloop.c
+++ b/uloop.c
@@ -63,6 +63,8 @@ static bool do_sigchld = false;
 static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
 static int cur_fd, cur_nfds;
 
+int uloop_fd_add(struct uloop_fd *sock, unsigned int flags);
+
 #ifdef USE_KQUEUE
 #include "uloop-kqueue.c"
 #endif
@@ -71,6 +73,59 @@ static int cur_fd, cur_nfds;
 #include "uloop-epoll.c"
 #endif
 
+static void waker_consume(struct uloop_fd *fd, unsigned int events)
+{
+       char buf[4];
+
+       while (read(fd->fd, buf, 4) > 0)
+               ;
+}
+
+static int waker_pipe = -1;
+static struct uloop_fd waker_fd = {
+       .fd = -1,
+       .cb = waker_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_fd.fd = fds[0];
+       waker_fd.cb = waker_consume;
+       uloop_fd_add(&waker_fd, ULOOP_READ);
+
+       return 0;
+}
+
+int uloop_init(void)
+{
+       if (uloop_init_pollfd() < 0)
+               return -1;
+
+       if (waker_init() < 0) {
+               uloop_done();
+               return -1;
+       }
+
+       return 0;
+}
+
 static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
 {
        struct uloop_fd_stack *cur;
@@ -328,14 +383,21 @@ static void uloop_handle_processes(void)
 
 }
 
+static void uloop_signal_wake(void)
+{
+       write(waker_pipe, "w", 1);
+}
+
 static void uloop_handle_sigint(int signo)
 {
        uloop_cancelled = true;
+       uloop_signal_wake();
 }
 
 static void uloop_sigchld(int signo)
 {
        do_sigchld = true;
+       uloop_signal_wake();
 }
 
 static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
@@ -477,11 +539,17 @@ void uloop_run(void)
 
 void uloop_done(void)
 {
-       if (poll_fd < 0)
-               return;
+       if (poll_fd >= 0) {
+               close(poll_fd);
+               poll_fd = -1;
+       }
 
-       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();