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From std-unix-request@uunet.uu.net Thu Aug 30 14:18:37 1990
Received: from cs.utexas.edu by uunet.uu.net (5.61/1.14) with SMTP
id AA03070; Thu, 30 Aug 90 14:18:37 -0400
Posted-Date: 30 Aug 90 12:31:01 GMT
Received: by cs.utexas.edu (5.64/1.76)
From: tct!chip@cs.utexas.edu (Chip Salzenberg)
Newsgroups: comp.std.unix
Subject: Re: Standards Update, IEEE 1003.4: Real-time Extensions
Message-Id: <477@usenix.ORG>
References: <448@usenix.ORG> <467@usenix.ORG> <470@usenix.ORG>
Sender: std-unix@usenix.ORG
Organization: Teltronics/TCT, Sarasota, FL
X-Submissions: std-unix@uunet.uu.net
Date: 30 Aug 90 12:31:01 GMT
Reply-To: std-unix@uunet.uu.net
To: std-unix@uunet.uu.net
From: chip@tct.uucp (Chip Salzenberg)
According to sp@mysteron.osf.org (Simon Patience):
>Some realtime embedded systems do not have a file system but do want
>semaphores. So this allows them to have them without having to bring
>in the baggage a file system would entail.
I was under the impression that POSIX was designing a portable Unix
interface. Without a filesystem, you don't have Unix, do you?
Besides, a given embedded system's library could easily emulate a
baby-simple filesystem.
>Secondly, as far as threads, which are supposed to be light weight,
>are concerned it allows semaphores to be implmented in user space
>rather than forcing them into the kernel for the file system.
The desire for user-space support indicates to me that there should be
some provision for non-filesystem (anonymous) IPCs that can be created
and used without kernel intervention. This need does not reduce the
desirability of putting global IPCs in the filesystem.
>A good reason for *not* having IPC handles in the file system is to allow
>network IPC to use the same interfaces.
Filesystem entities can be used to trigger network activity by the
kernel (or its stand-in), even if they do not reside on shared
filesystems.
--
Chip Salzenberg at Teltronics/TCT <chip@tct.uucp>, <uunet!pdn!tct!chip>
Volume-Number: Volume 21, Number 74