Alan Cox wrote:

quoted

 - Then, are we certain that there's no case where the tty layer will
call us with some lock held or in an atomic context ? To be honest,
I've totally lost track of the locking rules in tty land lately so it
might well be ok, but something to verify.

Some of the less well behaved line disciplines do this and always have
done.

I had a backtrace in my kernel log recently which looked like that,
while doing PPP over Bluetooth RFCOMM.  Resulted in AppArmor
complaining that it's hook was being called in irq context.

-- Jamie