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<== Date ==> <== Thread ==>

Subject: DEC Threads
From: [email protected] (Jeff Hill)
To: "EPICS-tech-talk" <[email protected]>
Date: Wed, 1 Dec 1999 10:37:37 -0700
All,

It would vastly simplify EPICS if we didn't have
to worry about two execution models: multi-threaded and 
single-threaded. It occurs to me that possibly all commonly 
used operating systems support multiple threads of execution 
in one process at this time.

Do any of you know of a successful, commonly used, operating 
system that does not support multiple threads of execution 
in one process?

For instance, is anyone still using SUNOS4 at this point? 

I suspect that SGI UNIX and HPUX both support multiple
threads of execution in one process. Can anyone confirm this.

I have been looking briefly at DEC threads and this appears 
to be a real threading package: if a thread makes a 
blocking VMS system call it will _not_ prevent other threads 
from running. Are there any VMS guru's out there that can
confirm or deny this conclusion? Perhaps there are versions 
of VMS in use that don't allow use of DEC threads? The book I 
have on DEC threads is from 1991. 

Another issue:
Even if we discover that all OS support a multi-threaded model
we are not out of the woods. Many client side tools are coded 
following a single threaded model so we would need to preserver 
backwards compatibility, and therefore be careful to run 
asynchronous callbacks only from the primary thread of control?

Jeff
______________________________________________
Jeffrey O. Hill         E-mail [email protected]
LANL MS H820            Voice  505 665 1831
Los Alamos NM 87545 USA FAX    505 665 5107


Replies:
Re: DEC Threads J. Frederick Bartlett ([email protected])

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