A set of busy-poll functions.
See Scheduler.add_busy_poller for the user-level interface.
create ()
creates a new empty set.
add t f
adds function f
to the set t
. f
will run every time poll
is called.
f
runs with the same execution context that was in effect when add
was called.
When poll
is called and f
returns `Stop_polling
, the result of add
becomes
determined and f
is removed from the set. Also, if f
raises, it is removed from
the set and the exception is sent to the monitor in effect when add
was called,
poll t
runs every function in the set t
.