Copyright (C) 1999-2001, 2004, 2016 Internet Systems Consortium, Inc. ("ISC")

This Source Code Form is subject to the terms of the Mozilla Public

License, v. 2.0. If a copy of the MPL was not distributed with this

file, You can obtain one at http://mozilla.org/MPL/2.0/.

$Id: tasks,v 1.7 2004/03/05 05:04:47 marka Exp $

Changes I made last week to the task code simplified the task shutdown

and termination model. Here's how things now work:

When a task is shutdown:

Any "on shutdown" events for the task are posted

The "shutting down" attribute of the task is set

Any attempts to add shutdown events with isc_task_onshutdown()

will fail, since the task is already shutting down

Task shutdown can be initiated explicity, via a call to isc_task_shutdown(),

or implicitly, when the following conditions occur:

The "shutting down" attribute of the task is not set

The task has no references

The task has an empty event queue

Task termination occurs when:

The "shutting down" attribute of the task is set

The task has no references

The task has an empty event queue

Notes from the task/event discussion led by Bob Halley on 13 March 2000:

A task is an event queue.

(task) --V

(event)-->(event)-->(event)

(runnable queue)--V

(task)-->(task)-->(task)

Normally only one task manager in an application.

Task becomes runnable if it has a non-empty event queue.

One or more worker threads run tasks.

Event routines should be relatively short.

Only one runnable queue that all workers share.

Events for a task are always posted serially. Multiple worker threads

will not be working on multiple events for one task at the same time.

isc_event_send, posting an event, can't fail. It just adds an event

to the task queue.

Event action (callback) rules:

* no locks held on your behald when entering a callback.

* not allowed to block, except when aquiring a lock.

* not allowed to hold a lock when exiting the callback.

TIMERS?

OMAPI -- need taskmgr to omapi_lib_init

-- one task per client connection