Date:	Thu, 4 Jul 1996 11:07:07 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To:	Stavel Jan <STAVEL AT dame DOT fee DOT vutbr DOT cz>
Cc:	djgpp AT delorie DOT com
Subject:	Re: Small question
In-Reply-To:	<1EBA8C15144@dame.fee.vutbr.cz>
Message-Id:	<Pine.SUN.3.91.960704110027.23994I-100000@is>
Mime-Version:	1.0

On Thu, 4 Jul 1996, Stavel Jan wrote:

>    I'm writting some handle of interrupt (timer). I use memory acces.
>  Must I think about non re-entry of famous Dos ( mainly disk 
>  acces) during using memory ( exceeded RAM ) which will be virtually 
> paging on disk.

An interrupt handler which runs on a system with virtual memory must lock 
all the memory it touches (code and data) so they will be *never* paged 
out.  Otherwise, on systems with low amounts of installed RAM, the 
handler might be paged out, and when the interrupt hits, the machine will 
certainly crash.  There are library functions in DJGPP to lock parts of 
memory that ensures they will never be paged out.

You might look at the examples of interrupt handlers in DJGPP by fetching 
the following file via ftp:

  ftp://ftp.delorie.com/pub/djgpp/contrib/sample-interrupt-handlers-v2.zip

>    Does dpmi use its routines for virtually paging memory on disk
>  or uses classical dos write ones ?

You didn't expect the DPMI server to include substitutes for the DOS 
file-handling code, did you?  Of course it used DOS, otherwise that would 
be a full-blown operating system, not a DPMI server.

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