Re: 3.4+ tty lockdep trace

[Alan Cox <alan@linux.intel.com>]

> Applying Ming's patch over Alan's 2 patches from yesterday, I'm still
> seeing two lockdep warnings. Full trace attached.

In that code path we've just succesfully done

	tty_lock_pair(tty, o_tty)

(no warning issued)

We've then called into tty_ldisc_release which has done

	tty_unlock_pair(tty, o_tty);

and then

	tty_lock_pair(tty, o_tty);

which can't error unless our locking hosed

and at that point we then then do a recursive

	tty_ldisc_release(o_tty, NULL)

which embarrassingly already has a comment above it I put there saying


        /* This will need doing differently if we need to lock */


Let me go rewrite that particular routine to make sense with the
locking in place.