errors at a lower ipl. clist starvation problems can cause hundreds of
tty buffer overflows per second and logging them all amplified the
problems. This problem was less serious in 1.1.5.
Avoid a race in the check for starting a new block of output. com_events
was sometimes messed up and siopoll() looped endlessly. This bug was
introduced in 2.0.
Clean up previous 2 commits. Rename sio_registerdev() to sioregisterdev()
to match the (bad) surrounding naming conventions. There should be a
generic_registerdev().