RE: Dangling mutexes

Version of i5/OS? There appear to be some PTFs with that terminology....

V5R2 - SI23357
V5R3 - SI24074

hth,
Eric

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Peter Connell
Sent: Monday, March 10, 2008 2:55 AM
To: RPG400-L@xxxxxxxxxxxx
Subject: Dangling mutexes


These animals appear to be like bats that you don't know you got.

We've had some technical zealots mosey about our system and they've come
up with these dangling mutexes, which they claim may be impacting our i5
performance.
Well, we certainly have never been anywhere near these things using RPG
or CL and only know they exist cos they're mentioned as an option on the
SysReq menu.
Nevertheless, we've been told that we should not have them.

Does anyone else have them?

The zealots have furnished a library called MUTEXTOOL which flags mutex
activity by job within the system.
It would appear that some of our high level operations drop into lower
level APIs that create these mutexes, for example jobs that spawn Qshell
by submitting QP0ZSPWP and maybe sockets that pass descriptors, but
there are a host of system things that seem to create these mutexes
without us knowing.
By and large the lower level code, which we have no control over, seems
to create mutexes with gay abandon, so normally, I don't think this
matters much at all.

The problem, or perceived problem, arises when these things are not
cleaned up, leaving dangling mutexes, so I'm told.
There is also some suggestion of memory leakages here.
Is it possible for something to dangle even after a job completes?

Well, as an RPGer, I certainly don't know how we've created all this
dangling.
Is it possible for mutexes to dangle if a job has an exception and
terminates in a default manner without a thorough cleanup?
Perhaps, ending subsystems or jobs immediately could be the cause.
I know there are some cases were programmers have used RCLACTGRP
*eligible in production code directly contrary to my advice.

One example, that appears to create lots of these dangling mutexes is a
little monitor routine I threw together once as a Qshell script.
It loops by running an OS400 command via the system cmd, redirecting the
output, sleeps for 30 seconds and then runs it again, all day everyday.
While I soon realized that this spawned a new process with each
iteration, it's been running for years without any noticeable effect
other than recycling the 6 digit job number more quickly. Of course, I
could spend more time on a more complex process but if it works and does
not appear to break anything then, hey, why bother.

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