From: emery@mitre-bedford.arpa (David Emery)
Subject: Re: Ada and Unix--Blocked Tasks
Date: 6 Aug 91 17:23:59 GMT [thread overview]
Message-ID: <EMERY.91Aug6102359@Dr_No.mitre.org> (raw)
In order for non-blocking I/O to work on Unix, several different
'actors' have to cooperate. First you need a Unix that supports
non-blocking I/O as a concept. Usually this works by having a system
call that `queues' the operation, and a signal that tells the
application when the I/O is done. Next you need a device driver that
also plays this game. Not all device drivers support non-blocking
I/O, even if the operating system provides the facility. Finally, you
need the Ada runtime to play along, by handling the signal correctly.
For this reason, it is almost impossible for a compiler vendor to
guarantee non-blocking I/O in all cases. In particular, the compiler
vendor cannot guarantee that the user`s devices and device drivers
'play along'. So take any vendor claims that they support
non-blocking I/O on Unix platforms (without specifying additional
requirements on the device drivers, etc.) with a grain of salt. It's
possible, and it will probably work on "reasonable systems with
reasonable devices", but it's not guaranteed, especially in the face
of third-party I/O devices.
dave
next reply other threads:[~1991-08-06 17:23 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
1991-08-06 17:23 David Emery [this message]
-- strict thread matches above, loose matches on Subject: below --
1991-08-16 15:43 Ada and Unix--Blocked Tasks bu.edu!inmet!offer
1991-08-14 15:24 torolab4.vnet.ibm.com!jrussell
1991-08-10 4:59 Robert I. Eachus
1991-08-07 1:35 Bob Kitzberger @midnight
1991-08-06 20:12 mcsun!corton!chorus!nocturne.chorus.fr!jloup
1991-08-06 18:48 Mike Murphy
1991-08-06 14:57 Drew Johnson
1991-08-06 14:32 Dan L. Pierson
1991-08-06 14:17 mcsun!corton!chorus!nocturne.chorus.fr!jloup
1991-08-06 12:32 Arthur Evans
1991-08-06 9:17 Jim Showalter
1991-08-06 4:05 Mike Feldman
1991-08-05 19:56 Howard E. Turner, Jr.
1991-08-05 19:04 EDWARD CRAGG
1991-08-05 16:06 David Emery
1991-08-05 15:25 Fred Stluka
1991-08-05 14:14 Paul Stachour
1991-08-05 5:08 cis.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!news.cs.indiana.e
1991-08-02 18:17 cis.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!cs.u
1991-08-02 13:28 Dennis Doubleday
1991-07-30 19:35 Dave Lewicki
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