[PATCH] ash: setsid and TIOCSCTTY when enabling job control.

[Denys Vlasenko]

On Tuesday 13 March 2012 00:56, Avery Pennarun wrote:
> Both calls will fail if we are already a process group leader, or the
> process group leader is not us, or we already have a controlling terminal.
> So basically these calls are harmless in the worst case, and get rid of the
> annoying "can't access tty; job control turned off" problem in the best
> case.  In other words, CTRL-C and CTRL-Z will work.
> 
> This makes busybox sh job control usable with "init=/bin/sh" on the Linux
> kernel command line.

I don't think so. In this case, stdio is redirected to /dev/console.
In Linux, /dev/console can't be a controlling terminal.

> ---
>  shell/ash.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/shell/ash.c b/shell/ash.c
> index 5671a52..5259dd2 100644
> --- a/shell/ash.c
> +++ b/shell/ash.c
> @@ -3727,6 +3727,8 @@ setjobctl(int on)
>  		if (fd < 0)
>  			goto out;
>  		/* fd is a tty at this point */
> +		setsid();

Creating new session for every interactive shell?
I have a feeling this is breaking a lot of things.

> +		ioctl(fd, TIOCSCTTY, 0);

This *might* be ok....

>  		close_on_exec_on(fd);
>  		do { /* while we are in the background */
>  			pgrp = tcgetpgrp(fd);

-- 
vda