[jira] Commented: (FELIX-2791) NPE in getStartLevel due to race condition

["Sahoo (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FELIX-2791?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12984069#action_12984069 ] 

Sahoo commented on FELIX-2791:
------------------------------

The exception is about startLevel being null. Where is configAdmin coming into picture?

> NPE in getStartLevel due to race condition
> ------------------------------------------
>
>                 Key: FELIX-2791
>                 URL: https://issues.apache.org/jira/browse/FELIX-2791
>             Project: Felix
>          Issue Type: Bug
>          Components: File Install
>    Affects Versions: fileinstall-3.1.4
>            Reporter: Sahoo
>            Assignee: Sahoo
>            Priority: Blocker
>             Fix For: fileinstall-3.1.6
>
>         Attachments: patch.txt
>
>
> We are using FileInstall 3.1.4 and one of our user is seeing the following exception repeated in the directory watcher main loop continuously:
> java.lang.NullPointerException
>         at org.apache.felix.fileinstall.internal.FileInstall.getStartLevel(FileInstall.java:283)
>         at org.apache.felix.fileinstall.internal.FileInstall.getStartLevel(FileInstall.java:276)
>         at org.apache.felix.fileinstall.internal.DirectoryWatcher.run(DirectoryWatcher.java:237)
> In main loop, we have serious trouble: java.lang.NullPointerException
> NPE comes from FileInstall.java:283, which looks like this:
>             return (StartLevel) startLevel.waitForService(timeout);
> It looks like a concurrency bug to me in FileInstall. The only explanation that I have so far is that in the target environment, code is getting reordered and hence directory watcher thread is spwaned before startLevel is initialzed.. Since startLevel is not declared volatile, nor is it accessed from a synchronized block, DirectoryWatcher thread continues to see the stale value.
> So, I suggest we change startLevel to a volatile field. Any comments?

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