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From "Sahoo (JIRA)" <j...@apache.org>
Subject [jira] Updated: (FELIX-2791) NPE in getStartLevel
Date Wed, 19 Jan 2011 16:56:43 GMT

     [ https://issues.apache.org/jira/browse/FELIX-2791?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Sahoo updated FELIX-2791:

    Comment: was deleted

(was: Even better would be to synchronize start() and stop() methods in FileInstall instead
of always paying the cost of making the field volatile.)

> NPE in getStartLevel
> --------------------
>                 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
>            Priority: Blocker
>             Fix For: fileinstall-3.1.6
> 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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