Re: threading in rpg. was RPG and Web.. (was Using OO conceptsinRPG)

Steve: It is possible to do threading in RPG, I have done it (however it is
easier to do in C).  There are a few "gotchas".

1) Never set on LR in a thread.  This will take down the entire job.
2) Service programs are shared amongst threads and only one thread can
access a function at a time.
3) File pointers are shared amongst threads.

I found this PDF to be helpful (it is 2mg):
http://www.damontech.com/OS400PthreadAPIs.pdf

I hope this helps,
Schadd Gray
Damon Technologies, Inc.
www.damontech.com

----- Original Message ----- 
From: "Hans Boldt" <boldt@xxxxxxxxxx>
To: <rpg400-l@xxxxxxxxxxxx>
Sent: Wednesday, May 21, 2003 7:09 AM
Subject: Re: threading in rpg. was RPG and Web.. (was Using OO
conceptsinRPG)


> Steve Richter wrote:
> > As of V5R2, with IO direct into a data struct, procs dont have to use
any
> > global variables.  And if files are opened and accessed using some sort
of a
> > handle, then file I/O could be thread safe.
> >
> > Interestingly, a lot of the changes that would make an rpg proc
threadsafe,
> > like no global mapping of fields thru a data struct, file opens that are
> > local to a proc and passed with a handle from proc to proc, would make
the
> > code more modular and less error prone.
>
> Steve: I think you're still missing something here. If the only
> issue were user defined variables, there would be no problem with
> threading. At least there wouldn't be a problem for the compiler -
> all the synchronization issues would fall squarely on the back of
> the RPG programmer. No, the problem is with the compiler-generated
> internal data structures. Things like file control blocks and
> feedback areas, and also data structures involved with the RPG
> exception model.
>
> If you really think you have to do a threaded application, and you
> want part of it RPG, go right ahead. The way to do it now would be
> to write some of your code in C, which calls RPG procedures in
> modules compiled with THREAD(*SERIALIZE). If you can understand all
> the issues involved with threading, you can certainly handle a bit
> of C programming. ;-)
>
> Cheers! Hans
>
>
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