From: James Edward Gray II <james@...>
Date: 2006-05-04T22:40:19+09:00
Subject: Re: concurrency question

On May 4, 2006, at 7:34 AM, Robert Klemme wrote:

> 2006/5/3, Eric Hodel <drbrain@segment7.net>:
>> On May 3, 2006, at 12:58 PM, Trish Ball wrote:
>>
>> > I am new to concurrency issues, and am working with DRb (also  
>> new to
>> > this).  My DRb class assigns a value to an instance variable  
>> that will
>> > be accessed by my client.  Is there a possibility with a  
>> concurrency
>> > issue if the client tries the access that variable when it is being
>> > assigned.
>>
>> No.
>>
>> > @list = LabelList.new(@label_list)
>> >
>> > Will I need a mutex around this?
>>
>> It will see either the old value or the new value.  Nothing will
>> break otherwise.
>
> IMHO this cannot be answered correctly with the information we have so
> far.

The example had one client reading the value and one server setting  
it.  Under those circumstances, I think Eric's answer is right on.

> You are right with regard to assignment semantics (i.e.
> assignment is atomic in current Ruby runtime)

I'm fairly certain assignment is not an atomic action in Ruby.   
There's a pretty good example of this on page 142 of the PickAxe (2nd  
Edition).

James Edward Gray II