Newsgroups:	comp.os.msdos.djgpp
From:	starx AT pacbell DOT net (StarWeaver)
Subject:	Re: What I have to lock?
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 991019171800 DOT 14637D-100000 AT is>
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Date:	Mon, 08 Nov 1999 07:39:09 GMT
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Earlier, djgpp AT delorie DOT com wrote:
>
>On Tue, 19 Oct 1999, Paolo Gava wrote:
>
>> I wrote a multi-thread application (under windows98 and djgpp V2.02) in
>> which, with a timer, every 10ms I do a context switch and wake up an other
>> thread (if there is one).
>
>Are you doing this from a hardware interrupt handler that hooks the 
>timer tick?  If so, you are in for a bumpy ride: the DPMI spec explicitly
>forbids to switch stacks in a hardware interrupt handler.
>
>Does your program work?  I'd expect it to crash.
>
>> My question is: do I have to lock stack and all the code that the thread
>> call? (This means lock everything) or I can do something better?
>
>You must lock everything.  At least under CWSDPMI, your program will 
>crash immediately unless you lock everything.  I believe it will also 
>crash in Windows, although maybe not so fast.
>
>But again, I think this approach to multi-tasking is almost impossible in 
>the DPMI environment.
>
>An alternative is to use the setitimer library function and make the 
>handler for the signal SIGALRM be your scheduler.  This has some 
>disadvantages, but at least you will be playing by the DPMI rules, not 
>against them.
>
>> If I have to lock everything, I have to consider the possibility to disable
>> virtual memory to make sure my program doesn't page, how bad is it?
>
>You cannot disable virtual memory under Windows.

Sure you can. Right click 'My Computer' -> Properties (or control panel -> 
system), -> performance tab -> virtual memory -> let me specify ... -> 
disable.

Not that you would want to. _Bad_ things will happen to your performance. I 
belive i accidentally ended up with it set this way once, and the effect was 
somewhat simmalar as the diffrence between running Quake right now on this p2 
voodoo 3, and playing it on an eight meg pure dos 486 without 
smartdrive--times 500.

Hope that clears some things up...
-StarWeaver Blue

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