uloop: try to use signalfd for signal handling if available

Signed-off-by: Felix Fietkau <nbd@nbd.name>

uloop-epoll.c

@@ -16,6 +16,8 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <sys/signalfd.h>
+
 /**
  * FIXME: uClibc < 0.9.30.3 does not define EPOLLRDHUP for Linux >= 2.6.17
  */
@@ -23,8 +25,63 @@
 #define EPOLLRDHUP 0x2000
 #endif
 
+static void
+uloop_signal_fd_cb(struct uloop_fd *fd, unsigned int events)
+{
+	struct signalfd_siginfo fdsi;
+	int ret;
+
+retry:
+	ret = read(fd->fd, &fdsi, sizeof(fdsi));
+	if (ret < 0 && errno == EINTR)
+		goto retry;
+
+	if (ret != sizeof(fdsi))
+		return;
+
+	uloop_handle_signal(fdsi.ssi_signo);
+}
+
+static bool
+uloop_setup_signalfd(bool add)
+{
+	static struct uloop_fd sfd = {
+		.cb = uloop_signal_fd_cb
+	};
+	static sigset_t prev_mask;
+	sigset_t mask;
+
+	if (signal_fd < 0)
+		return false;
+
+	sigemptyset(&mask);
+
+	if (!add) {
+		uloop_fd_delete(&sfd);
+		sigprocmask(SIG_BLOCK, &prev_mask, NULL);
+	} else {
+		sigaddset(&mask, SIGQUIT);
+		sigaddset(&mask, SIGINT);
+		sigaddset(&mask, SIGTERM);
+		sigaddset(&mask, SIGCHLD);
+		sigprocmask(SIG_BLOCK, &mask, &prev_mask);
+
+		sfd.fd = signal_fd;
+		uloop_fd_add(&sfd, ULOOP_READ | ULOOP_EDGE_TRIGGER);
+	}
+
+	if (signalfd(signal_fd, &mask, SFD_NONBLOCK | SFD_CLOEXEC) < 0) {
+		sigprocmask(SIG_BLOCK, &prev_mask, NULL);
+		return false;
+	}
+
+	return true;
+}
+
 int uloop_init(void)
 {
+	sigset_t mask;
+
 	if (poll_fd >= 0)
 		return 0;
 
@@ -33,6 +90,10 @@ int uloop_init(void)
 		return -1;
 
 	fcntl(poll_fd, F_SETFD, fcntl(poll_fd, F_GETFD) | FD_CLOEXEC);
+
+	sigemptyset(&mask);
+	signal_fd = signalfd(-1, &mask, SFD_NONBLOCK | SFD_CLOEXEC);
+
 	return 0;
 }
 

uloop-kqueue.c

@@ -15,6 +15,13 @@
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
+
+static bool
+uloop_setup_signalfd(bool add)
+{
+	return false;
+}
+
 int uloop_init(void)
 {
 	struct timespec timeout = { 0, 0 };

uloop.c

@@ -56,6 +56,7 @@ static struct uloop_fd_stack *fd_stack = NULL;
 static struct list_head timeouts = LIST_HEAD_INIT(timeouts);
 static struct list_head processes = LIST_HEAD_INIT(processes);
 
+static int signal_fd = -1;
 static int poll_fd = -1;
 bool uloop_cancelled = false;
 static bool do_sigchld = false;
@@ -63,6 +64,8 @@ static bool do_sigchld = false;
 static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
 static int cur_fd, cur_nfds;
 
+static void uloop_handle_signal(int signo);
+
 #ifdef USE_KQUEUE
 #include "uloop-kqueue.c"
 #endif
@@ -325,15 +328,18 @@ static void uloop_handle_processes(void)
 
 }
 
-static void uloop_handle_sigint(int signo)
+static void uloop_handle_signal(int signo)
 {
+	switch (signo) {
+	case SIGINT:
+	case SIGQUIT:
+	case SIGTERM:
 		uloop_cancelled = true;
-}
-
-static void uloop_sigchld(int signo)
-{
+		break;
+	case SIGCHLD:
 		do_sigchld = true;
 	}
+}
 
 static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
 {
@@ -385,9 +391,13 @@ 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);
-	uloop_install_handler(SIGCHLD, uloop_sigchld, &old_sigchld, add);
+	if (uloop_setup_signalfd(add))
+		return;
+
+	uloop_install_handler(SIGINT, uloop_handle_signal, &old_sigint, add);
+	uloop_install_handler(SIGTERM, uloop_handle_signal, &old_sigterm, add);
+	uloop_install_handler(SIGQUIT, uloop_handle_signal, &old_sigterm, add);
+	uloop_install_handler(SIGCHLD, uloop_handle_signal, &old_sigchld, add);
 
 	uloop_ignore_signal(SIGPIPE, add);
 }
@@ -474,6 +484,11 @@ void uloop_run(void)
 
 void uloop_done(void)
 {
+	if (signal_fd >= 0) {
+		close(signal_fd);
+		signal_fd = -1;
+	}
+
 	if (poll_fd < 0)
 		return;