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From "Clement Escoffier (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (FELIX-3500) InstanceManager concurrency issue: "A methodID cannot be associated with a method from the POJO class"
Date Mon, 07 May 2012 12:56:50 GMT

     [ https://issues.apache.org/jira/browse/FELIX-3500?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Clement Escoffier reassigned FELIX-3500:
----------------------------------------

    Assignee: Clement Escoffier
    
> InstanceManager concurrency issue: "A methodID cannot be associated with a method from
the POJO class"
> ------------------------------------------------------------------------------------------------------
>
>                 Key: FELIX-3500
>                 URL: https://issues.apache.org/jira/browse/FELIX-3500
>             Project: Felix
>          Issue Type: Bug
>          Components: iPOJO
>    Affects Versions: ipojo-core-1.8.2
>            Reporter: Francois Valdy
>            Assignee: Clement Escoffier
>
> InstanceManager.getMethodByID(String) claims to be thread-safe (or not to require synchronization)
but is not.
> It results in random messages "A methodID cannot be associated with a method from the
POJO class" (which were downgraded from ERROR to INFO), but has unknown side effect bugs (as
it returns null for valid methods when that happens).
> If 2 threads call this method with the same parameter:
> - both won't find it in the cache (m_methods.get(methodId) == null)
> - one will register it: !m_methods.containsValue(mets[i]) is true
> - second thread will NOT register it (because the first one did, hence the value is in
the map), and will return null <-- bug
> Other issues may occur from the fact that an HashMap (unsafe) is used without synchronization,
for instance a well-known infinite loop.
> I think one fix (to keep the same method semantics) under J2SE 1.3 would be to:
> - use Hashtable instead of HashMap (safe as the value is never null)
> - replace the code within the loop by:
>                 if (m_methods.containsValue(mets[i]))
>                 {
>                     method = (Method) m_methods.get(methodId);
>                     if (method != null)
>                     {
>                         return method;
>                     }
>                 }
>                 else if (MethodMetadata.computeMethodId(mets[i]).equals(methodId))
>                 {
>                     // Store the new methodId
>                     m_methods.put(methodId, mets[i]);
>                     return mets[i];
>                 }
> However I'm not sure about the purpose of the containsValue check purpose (which is also
very expensive as it traverses the entire map).
> Thanks.

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