Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!mailrus!tut.cis.ohio-state.edu!ucbvax!mtxinu!taniwha!paul
From: paul@taniwha.UUCP (Paul Campbell)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Having Fun? [Re: Standard File and Desk Accessories]
Keywords: Globals, Party, Enough!
Message-ID: <377@taniwha.UUCP>
Date: 9 Jun 89 21:54:42 GMT
References: <4972@umd5.umd.edu> <2026@husc6.harvard.edu> <22694@santra.UUCP>
Reply-To: paul@taniwha.UUCP (Paul Campbell)
Organization: Taniwha Systems Design, Oakland
Lines: 41

In article <22694@santra.UUCP> jmunkki@santra.UUCP (Juri Munkki) writes:
>To install the VBL task, you call this routine and to control what it does
>you just change its variables. (Remember that this is "multitasking" so that
>you have to use some sort of locking to prevent the vbl task from seeing
>changes that aren't complete.)

This brings up one of my chief beefs about the MacOS, if you are doing
something like this involving:

	VBL's
	DDP socket listeners
	IO completion routines
	Deferred Tasks
	Device interrupt handlers

in short anything asynchronous - there are no primitives short of
'or.w #$0700, sr' that you can use to do synchronization between application
code and asynchronous code. I don't think that 'normal' applications should 
ever have to turn interrupts off, instead I think that the correct solution
is to have a trap that defers the delivery of 'Deferred Tasks' untill 
the trap is called again to turn them on again.  Since all the other above 
asynchronous operations can Q deferred tasks this is a lowest common
denominator, and since the queueing of deferred tasks is relatively
cheap it is also a relatively inexpensive solution. APPLE ARE YOU LISTENING?

This brings up another issue I've never really pursued, I use the deferred
task manager to process incoming DDP packets. (My DDP listener Q's a 
deffered task). IM V really only mentions DTs being delivered on the
return from level 1 and 2 interrupts, it doesn't mention Appletalk ...
however it does work - my question is: Does it work because Appletalk
calls out queued deferred tasks on return from interrupts (to IPL 0)
or do my tasks get called out after the next clock tick? I suspect
the latter ....


	Paul
-- 
Paul Campbell
Taniwha Systems Design			UUCP:		..!mtxinu!taniwha!paul 
Oakland CA				AppleLink:	D3213
Achtung! Ve are from ze Interface Police! Ve vant to look und feel!