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From "Christopher Tubbs (JIRA)" <>
Subject [jira] [Updated] (ACCUMULO-853) Fields and parameters that are used as locks change to be final (where possible)
Date Tue, 18 Dec 2012 15:58:12 GMT


Christopher Tubbs updated ACCUMULO-853:

    Fix Version/s: 1.5.0
         Assignee: Eric Newton
> Fields and parameters that are used as locks change to be final (where possible)
> --------------------------------------------------------------------------------
>                 Key: ACCUMULO-853
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>            Reporter: Tim Halloran
>            Assignee: Eric Newton
>            Priority: Minor
>              Labels: patch
>             Fix For: 1.5.0
>         Attachments: accumulo.patch
> Examining locking in the code using SureLogic JSure I noticed many locks are not declared
final that could be.
> One reference why this may be "bad" is CERT:
> That said :-), this has two possible impacts of more immediate concern: memory model
and maintainability.
> 1) The memory model only guarantees publication of final fields that are not safely published
-- this is highly desired for fields used as lock objects because they may be the mechanism
for safe publication. Yes it might work, but as my buddy Brian Goetz says, Just because you
ran around with holding scissors all last week and didn't get hurt, is not a good rational
to keep doing it.
> 2) The CERT "rule" is about mutation -- the final flag helps to clarify that the reference
to the object used as a lock is not intended to be changed. Avoiding a change that breaks
a locking model.
> I also changed some lock objects from new String("foo") to new Object() (see patch),
could be reverted (but left final) if there is some reason for the use of the larger String
object. There was none I could see.
> I'm trying to verify a large portion of the lock usage statically and use a dynamic tool
(SureLogic Flashlight) to check other aspects, but this was a simple patch I could provide
right away as a small improvement.
> I have a patch, will attach (not a Jira expert yet)

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