Calling unexport does not quiet down poll(2)

I’m contentedly using poll(2) to handle interrupts - typical test catches all the edges
in an ASCII character at 9600 baud, but…
in practice I’d like to turn off interrupt handling while servicing an interrupt because
the interrupts will be delivered by a schmitt trigger at 60 Hz and there’s no point in
just ignoring them; it seems better to temporarily free kernel load. However,
if I call unexport(gpio-pin) then poll(2) starts reporting interrupts very quickly forever without
any interrupts actually taking place.
The only way I can quiet it down is to write a (high) value to the gpio pin so poll()
will not trigger on rising edge anymore. I’m wondering why unexport() alone doesn’t work.