From:	"Colin W. Glenn" <cwg01 AT gnofn DOT org>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: DJGPP gurus: interrupts wrappers are reentrant ?
Date:	Fri, 21 Mar 1997 21:34:53 -0600
Organization:	Greater New Orleans Free-Net
Lines:	22
Message-ID:	<Pine.GSO.3.95.970321213302.23040I-100000@sparkie.gnofn.org>
References:	<332BADAD DOT 63C7A87E AT lmn DOT pub DOT ro> <01bc34b3$b02471a0$LocalHost AT anthonyb>
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Pardon me for sticking my two cents in here, but wasn't the prior state of
the interrupt flag pushed on the stack with the rest?  And doesn't a IRET
pop the flags and restore that state?

On 20 Mar 1997, Anthony Q. Bachler wrote:
> 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.

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