Cancel respawn getty on serial tty

[Laurent Bercot]

> Sample tty_idle.c source:
> 
> #include <unistd.h>
> 
> int main( int argc, char* argv )
> {
>   close(0);
>   close(1);
>   close(2);
>   while (1) pause();
> }

 Hey Harald,
 Depending on your configuration, this will not work. Because you are
doing more than you need - and in this case this might be harmful.
 Closing 0, 1 and 2 will normally remove all references to the terminal
you are being executed in. Since your tty_idle program is the only user
of ttyS0 at the time it is executed, closing those fds - and thus
removing all references to ttyS0 - will make some kernels deconfigure
the serial port, and you will have gained nothing.
 Don't close anything, just pause(), and you will keep the serial line
open.

-- 
 Laurent