Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!b.gp.cs.cmu.edu!Ralf.Brown@B.GP.CS.CMU.EDU
From: Ralf.Brown@B.GP.CS.CMU.EDU
Newsgroups: comp.os.msdos.programmer
Subject: Re: INT 21 AX=5D06 Swap DOS data space call
Message-ID: <26b6e460@ralf>
Date: 1 Aug 90 14:17:04 GMT
Sender: ralf@b.gp.cs.cmu.edu
Organization: Carnegie Mellon University School of Computer Science
Lines: 17
In-Reply-To: <jbf6cm79f@tmsoft.uucp>

In article <jbf6cm79f@tmsoft.uucp>, mshiels@tmsoft.uucp (Michael A. Shiels) wrote:
}Does DOS do it's own semaphoring with INT 2A AX=80xx/AX=81xx to ensure you
}don't swap in the middle of a drive read/write?

Not really.  DOS protects a few sections of code that absolutely
positively cannot be reentered.  Much of the SHARE.EXE code consists of
such critical sections--wouldn't want to interrupt the search whether a
file is currently open with an open of that file, would we?  However,
DOS itself does not check the semaphores at all.  That is left up to
whatever software is doing the reentering (that software also has to
maintain the semaphores itself).

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