getty: add O_NONBLOCK to open which is used to drop ctty

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/loginutils/getty.c b/loginutils/getty.c
index 230846008..3496f0284 100644
--- a/loginutils/getty.c
+++ b/loginutils/getty.c
@@ -556,10 +556,12 @@ int getty_main(int argc UNUSED_PARAM, char **argv)
                  * In this case (setsid failed) we may still have ctty,
                  * and it may be different from tty we need to control!
                  * If we still have ctty, on Linux ioctl(TIOCSCTTY)
-                 * (which we are going to call a bit later) always fails.
-                 * Try to drop ctty now to prevent that.
+                 * (which we are going to use a bit later) always fails -
+                 * even if we try to take ctty which is already ours!
+                 * Try to drop old ctty now to prevent that.
+                 * Use O_NONBLOCK: old ctty may be a serial line.
                  */
-                fd = open("/dev/tty", O_RDWR);
+                fd = open("/dev/tty", O_RDWR | O_NONBLOCK);
                 if (fd >= 0) {
                         ioctl(fd, TIOCNOTTY);
                         close(fd);