tty layer and lbolt sleeps

[Mike Durian]

I'm trying to implement a serial protocol that is timing sensitive.
I'm noticing things like drains and reads and blocking until the
next kernel tick.  I believe this is due to the lbolt sleeps
in the tty.c code.

It looks like I can avoid these sleeps if isbackground() returns
false, however I can't figure out how to make this happen.  The
process is running in the foreground and my attempts to play
with the process group haven't helped.

Can anyone explain what is happening and nudge me towards a fix?

mike