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Mail Archives: djgpp/1997/03/21/08:40:44

Message-Id: <199703211327.OAA21219@math.amu.edu.pl>
Comments: Authenticated sender is <grendel AT hoth DOT amu DOT edu DOT pl>
From: "Mark Habersack" <grendel AT hoth DOT amu DOT edu DOT pl>
Organization: PPP (Pesticide Powered Pumpkins)
To: "Anthony Q. Bachler" <cwhizard AT NOSPAM DOT sockets DOT net>
Date: Fri, 21 Mar 1997 14:27:14 +0100
MIME-Version: 1.0
Subject: Re: DJGPP gurus: interrupts wrappers are reentrant ?
Reply-to: grendel AT hoth DOT amu DOT edu DOT pl
CC: djgpp AT delorie DOT com
In-reply-to: <01bc34b3$b02471a0$LocalHost@anthonyb>

Once upon a time (on 20 Mar 97 at 14:55) Anthony Q. Bachler said:

> Try clearing the interupt enable bit of the MSW as one of the first steps in
> the ISR.  This will cause the hardware to store any interupts that occur and
> execute them when you reenable them.  To disable them use the CLI assembly
> instruction.  To reenable them use the STI instruction.  A word of caution,
> STI should be immediately followed by an IRET to prevent the problem you are
> experienceing.  The problem you are having is that the stack is being
> corrupted.  When you perform an STI, the processor should hold off executing
> any pending interupts until after the next command.  I know for a fact that
> it works this way on the 8086-80686.  On a different processor, it may work
> differently.  The above details are for the intel CPU's, but the method is
> the same for most others.
This won't work under many DPMI servers (as well as under many, perhaps all, 
multitasking environments - WinNT, Linux/DOSEMU, OS/2, OpenDOS MultiTasker) - 
they virtualize the interrupts and STI & CLI instructions are emulated by the 
underlying software. They have effect only on the current application/VM. 
Several days ago I've posted to this newsgroup a short proggy which makes the 
interrupts reentrant. Subject: line of the thread had an ISR string in it - 
browse mail archives on http://www.delorie.com/djgpp/ and you should be able 
to find the message. If not then e-mail me privately and I'll send you the 
code.

---------- Visit http://ananke.amu.edu.pl/~grendel ------------
You're just a waste of time, you're just a babbling face, you're
just three sick holes that run like sores, you're fucking waste
you're like a slug on the floor, oh you're usless and ugly and
useless and ugly, and shiver and shake when I think of how you
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