When a tty driver uses an input "silo" (ring buffer?) that is
emptied into the tty layer by a lower level (soft) interrupt,
how should input flow control be handled?  The current input
handler does not try to block input when the silo becomes
nearly full, so when there is a sufficiently heavy interrupt
load on the macine, the silo overflows just because the soft
interrupt has not yet had a chance to copy the input to the
tty layer, where input flow control is handled.

Is there a general mechanism for dealing with this problem?

Gordon