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

[Barbara Morris <bmorris@xxxxxxxxxx>]

Steve Richter wrote:
> ...
> Hans Boldt wrote:
> >Of course, then the task is to identify all uses of items in the
> >global structures and add mutexes around all of them. Again, time
> >consuming for development, as well as slowing down the resulting
> >program.
> 
> ok.  a threadsafe(*yes *no) hspec handles the run time isssue right?
> 

But it's not as simple as putting a mutex around each access to a global
structure.  The global static structures are interrelated, so each RPG
procedure would pretty much be a critical section.

That's the basis of RPG's existing (since V4R4 I think)
THREAD(*SERIALIZE) support that controls access to the procedures in a
module so that only one thread is in a module at any one time.  This
protects the static storage in the module, making the module thread-safe
assuming it isn't doing anything thread-unsafe.  If the procedures are
quick-running, the application *may* even get some multi-thread
benefits.  (But the THREAD(*SERIALIZE) support was added specifically so
that RPG programs could run safety in an already threaded environment;
it wasn't added to enable multi-threaded RPG apps.)