[CRIU] [PATCH v2] tty: Restore controlling terminal once per session

[Cyrill Gorcunov]

On Mon, Nov 09, 2015 at 08:10:53PM +0300, Cyrill Gorcunov wrote:
> On Mon, Nov 09, 2015 at 08:04:29PM +0300, Pavel Emelyanov wrote:
> > 
> > Hm... What if I open /dev/ptmx and then two (or more) /dev/pts/X ? Would
> > the same problem arise?
> 
> I think yes.

You know, for pts we've a workaround already :)

tty_find_restoring_task
	...
	if (info->tie->sid) {
		if (!tty_is_master(info)) {
			if (tty_has_active_pair(info))

here, if we get fd which has opened pts, we simply ignore it,
because we're restoring controlling terminal via fake slave
(see below)

				return 0;
			else
				goto shell_job;
		}

static int tty_restore_ctl_terminal(struct file_desc *d, int fd)
	...
	if (is_pty(info->driver)) {
		...
		fake = pty_alloc_fake_slave(info);
		...
	}

IOW, for pty devices we have multiple instance of fd properly
handled, but this doesn't apply to VT devices and probably
any other in future.

	Cyrill