/*
* poll works by consuming the bitmask in pn_revents. If there are
* events available, poll returns immediately. If not, it issues a
* poll to userspace, selrecords itself and returns with no available
* events. When the file server returns, it executes puffs_parkdone_poll(),
* where available events are added to the bitmask. selnotify() is
* then also executed by that function causing us to enter here again
* and hopefully find the missing bits (unless someone got them first,
* in which case it starts all over again).
*/