Just reposting the message
http://lists.squeakfoundation.org/pipermail/squeak-dev/2017-September/195308.html
below so that it gets a proper subject line.


Note: SharedQueue and SharedQueue2 are both in the image.
SharedQueue2 was included into Squeak version 3.9 by MarcusDenker
(10-07-2005) for further testing.

Lex Spoon notes one year later that no problems have come to light. We
should start migrating to this. All it requires is replacing
SharedQueue by SharedQueue2.

Then two years later (12-17-2008)  Keith_Hodges  proposes a migration script

"fix begin"
Installer mantis bug: 1375 fix: 'M1375-SharedQueue2Enable.1.cs'.
WorldState initialize.
EventSensor initialize.
"fix end"

We need somebody to have a look at this script
'M1375-SharedQueue2Enable.1.cs' if it is still good to do the task.

BTW Pharo does not have two implementations of SharedQueue.

HH.


SharedQueue
I provide synchronized communication of arbitrary objects between
Processes. An object is sent by sending the message nextPut: and
received by sending the message next. If no object has been sent when
a next message is sent, the Process requesting the object will be
suspended until one is sent.

SharedQueue2
An implementation of a shared queue based on class Monitor.  Clients
may may place items on the queue using nextPut: or remove them using
methods like next or nextOrNil.  Items are removed in first-in
first-out (FIFO) order.  It is safe for multiple threads to access the
same shared queue, which is why this is a "shared" queue.

[monitor] is used to synchronize access from multiple threads.

[items] is an ordered collection holding the items that are in the
queue.  New items are added  at the end, and old items are removed
from the beginning.

All methods must hold the monitor while they run.







Levente Uzonyi
<leves at caesar.elte.hu>	Wed, Sep 20, 2017 at 6:44 PM
Reply-To: The general-purpose Squeak developers list
<squeak-dev at lists.squeakfoundation.org>
To: The general-purpose Squeak developers list
<squeak-dev at lists.squeakfoundation.org>
On Wed, 20 Sep 2017, H. Hirzel wrote:


    On 9/20/17, Levente Uzonyi <leves at caesar.elte.hu> wrote:

        These methods were there to make it possible to migrate from SharedQueue
        to SharedQueue2 in a live system.


    Could you please give some more background information about this migration?


http://bugs.squeak.org/view.php?id=1375


        That migration has not happened yet,


    Is there a reason not to do it after 5 years?


The mantis issue above has a few potential reasons.
Another one may be that now there are other potential shared queue
implementations to replace SharedQueue.