invariant, causing timer events not to be posted
when due.
Specifically, isc_heap_delete() moved the last element of the heap to
the vacated position and then attempted to restore the heap invariant
by calling sink_down(). This works when the last element has a lower
priority than the one being deleted, and this is often the case
because the last element tends to have a low priority. However, it is
not guaranteed to be the lowest. When deleting an item of a lower
priority than the last item, restoring the invariant requires a call
to float_up(), not sink_down().
isc_heap_delete_now calls either float_up() or sink_down() as needed,
and INSISTs have been added to verify that the heap invariant indeed
holds after the calls.
Andreas Gustafsson
4c94069644