2005-05-23 Paul Jakma <paul@dishone.st>

2005-05-23 Paul Jakma <paul@dishone.st>

	* workqueue.h: Add a WQ_QUEUE_BLOCKED item_status return code,
	  to allow a queue function to indicate the queue is not
	  ready/blocked - rather than any problem with the item at hand.
	  Add a notion of being able to 'plug' and 'unplug' a queue.
	  Add helpers to plug/unplug a queue.
	  Add a completion callback, to be called when a queue is emptied.
	* workqueue.c: (work_queue_new) remove useless list_free.
	  (work_queue_schedule) new internal helper function to schedule
	  queue, if appropriate.
	  (work_queue_add) use work_queue_schedule
	  (show_work_queues) Print 'P' if queue is plugged.
	  (work_queue_plug) new API function, plug a queue - ie prevent it
	  from 'drained' / processed / scheduled.
	  (work_queue_unplug) unplug a queue, allowing it to be drained
	  / scheduled / processed again.
	  (work_queue_run) Add support for WQ_QUEUE_BLOCKED.
	  Add comment for RETRY_NOW case.
	  Make hysteris more aggresive in ramping up granularity, improves
	  performance significantly.
	  Add support for calling completion callback when queue is emptied,
	  possibly useful for knowing when to unplug a queue.