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From: Terry Lambert <terry@lambert.org>
Message-Id: <199702052141.OAA15633@phaeton.artisoft.com>
Subject: Re: sigwait and threads?
To: lada@ws2301.gud.siemens.co.at (Hr.Ladavac)
Date: Wed, 5 Feb 1997 14:41:56 -0700 (MST)
Cc: ljo@Mcs.Net, hackers@FreeBSD.ORG
In-Reply-To: <199702051749.AA254324944@ws2301.gud.siemens.co.at> from "Hr.Ladavac" at Feb 5, 97 06:49:04 pm
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> Another difference that DCE requires and Draft 8 has thrown out is 
> pthread_detach().

Ouch.  This sucks bad.


I have four threading models available, each with a different level
of concurrency.  I'll use the Microsoft names for them, and draw a
better picture than Microsoft has ever drawn for them.  Microsoft
can pay me to use my picture, if they want it.  8-).

Key:

[1]   Caller 1

(a)   Context a

,----.
|A   | Thread A
`----'


         Call Flow                  Concurrency model
-----------------------------    -----------------------------

1.	Single threaded
	o	One object for all caller instances
	o	Object is not multithreaded
	o	Object is not thread reentrant
	o	Threads are not context reentrant
	o	Calls are serialized, not concurrent
          ____________
[1] \    |            |              [1]-->
     v   |   ,----.   |
[2]->O-->|---|A(a)|-->|-->                 [2]-->
     ^   |   `----'   |
[3] /    |____________|                          [3]-->


2.	Apartment threaded
	o	One object for all caller instances
	o	One thread per caller instance
	o	Object is multithreaded
	o	Object is not thread reentrant
	o	Threads are not context reentrant
	o	Calls are serialized, but appear concurrent
          ____________
         |            |
         |   ,----.   |
[1]->O-->|---|A(a)|-->|-->           [1]-->
         |   `----'   |
         |   ,----.   |
[2]->O-->|---|B(b)|-->|-->           [2]-->
         |   `----'   |
         |   ,----.   |
[3]->O-->|---|C(c)|-->|-->           [3]-->
         |   `----'   |
         |____________|

3.	Rental Threaded
	o	One object for all caller instances
	o	Threads are not instanced per caller instance
	o	Object is multithreaded
	o	Object is thread reentrant
	o	Threads are not context reentrant
	o	Calls are thread concurrent; for N callers of M
		threads, where N > M, serialization is N div M
          ____________
         |            |
         |   ,----.   |
[1]->O-->|---|A(a)|-->|-->           [1]-->
         |   `----'   |
         |   ,----.   |
[2]->O-->|---|B(b)|-->|-->           [2]-->
         |   `----'   |
         |   ,----.   |
[3]->O-->|---|A(c)|-->|-->                 [3]-->
         |   `----'   |
         |____________|

4.	Free Threaded
	o	One object for all caller instances
	o	Threads are not instanced per caller instance
	o	Object is multithreaded
	o	Object is thread reentrant
	o	Threads are context reentrant
	o	Calls are context concurrent to the ability of a
		thread to process multiple blocking operations
		by making the call and reentring on another context
          ____________
         |            |
         |   ,----.   |
[1]->O-->|---|A(a)|-->|-->           [1]-->
         |   `----'   |
         |   ,----.   |
[2]->O-->|---|B(b)|-->|-->           [2]-->
         |   `----'   |
         |   ,----.   |
[3]->O-->|---|A(c)|-->|-->           [3]-->
         |   `----'   |
         |____________|

Without thread attach/detach notification, I can't implement my
callable objects as being Rental or Free threaded.


					Regards,
					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.