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https://issues.apache.org/jira/browse/CONFIGURATION-407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12831176#action_12831176
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Sebb commented on CONFIGURATION-407:
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If the same INIConfiguration instance is shared between threads, and one
updates the shared config, then in the absence of synchronization, the other
threads won't necessarily see the updated values. This is because the JVM is
allowed to cache values in both the writer and reader threads.
In order to ensure that cached values are correctly published, some form on
synch. is needed.
For example, the reader has to synch. on the same object as the writer.
Or one can use volatile.
Or, for example the configuration can be created in one thread, which then
starts other threads that read it. Thread.start() acts as the lock in this case.
But if the writer thread subsequently changes the shared state, additional
synch. will be needed to guarantee safe publication to the existing threads.
By the way, the test case does not appear to test changes to the global
INIConfiguration.
> HierarchicalINIConfiguration can throw an exception if the global section is
> accessed concurrently
> --------------------------------------------------------------------------------------------------
>
> Key: CONFIGURATION-407
> URL: https://issues.apache.org/jira/browse/CONFIGURATION-407
> Project: Commons Configuration
> Issue Type: Bug
> Affects Versions: 1.6
> Reporter: Oliver Heger
> Assignee: Oliver Heger
> Fix For: 1.7
>
>
> If the global section of a hierarchical INI configuration is requested, a new
> ViewNode is created which becomes the root node of a new configuration for
> the global section. Nodes representing properties of the global section are
> added to this ViewNode. This operation temporarily changes the parent node of
> these nodes which may cause problems if the method is called by multiple
> threads concurrently. Because access to a section is a read-only operation,
> this should be thread-safe.
> The probability that this error happens is pretty low IMO. Therefore it
> should be hard to create a unit test.
> The issue can be fixed by synchronizing the add operation to the ViewNode.
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