getty: explain when setsid() fails. no code changes

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

1 files changed, 10 insertions, 0 deletions

diff --git a/loginutils/getty.c b/loginutils/getty.c
index 0f060ae6c..4b1b73bef 100644
--- a/loginutils/getty.c
+++ b/loginutils/getty.c
@@ -556,6 +556,16 @@ int getty_main(int argc UNUSED_PARAM, char **argv)
                         //      pid, getppid(),
                         //      getsid(0), getpgid(0));
                         bb_perror_msg_and_die("setsid");
+                        /*
+                         * When we can end up here?
+                         * Example: setsid() fails when run alone in interactive shell:
+                         *  # getty 115200 /dev/tty2
+                         * because shell's child (getty) is put in a new process group.
+                         * But doesn't fail if shell is not interactive
+                         * (and therefore doesn't create process groups for pipes),
+                         * or if getty is not the first process in the process group:
+                         *  # true | getty 115200 /dev/tty2
+                         */
                 }
                 /* Looks like we are already a session leader.
                  * In this case (setsid failed) we may still have ctty,