Your fix works too I suspect better than mine & since you've a better idea of what
you are doing with tty layer than I do we'll stick with
your fix.

Ok. 

Do you want me to switch off the low latency stuff in the
driver?

Lets leave it for now - it can get sorted properly when everything is
stable - no rush.

I also need to investigate the tty_kref_put & tty_kref_get
& when it was added to the kernel so I can fix stuff for our
internal driver

About 2.6.27/28 and while it closes some small race conditions on exit
its not essential so probably not worth worrying about for older kernels