I just took Simone's patch and applied it to the 3_0 branch. it did not
work. Here is the stacktrace. ...
Cause: java.lang.ClassCircularityError: java/lang/String
07:57:09,416 ERROR [STDERR] at
org.jboss.mx.capability.ReflectedMBeanDispatcher.invoke(ReflectedMBeanDispatcher.java:307)
07:57:09,417 ERROR [STDERR] at
org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:491)
07:57:09,417 ERROR [STDERR] at
com.candata.gateway.CCRAAbstract.invokeMethod(Unknown Source)
07:57:09,417 ERROR [STDERR] at
com.candata.gateway.CCRAAbstract.postMsg(Unknown Source)
07:57:09,417 ERROR [STDERR] at
com.candata.gateway.CCRAAbstract.recvMsg(Unknown Source)
07:57:09,418 ERROR [STDERR] at
com.candata.gateway.CCRAPoll.run(Unknown Source)
07:57:09,418 ERROR [STDERR] at java.lang.Thread.run(Thread.java:484)
On Fri, 2002-05-31 at 12:13, Bordet, Simone wrote:
> Hi,
>
> so I dug into the hotspot code for JDK 131, and I found the problem. I am too tired
>now to think for a solution, this is for you brave guys :)
>
> The problems arises from a 20 lines of code in
>src/share/vm/memory/systemDictionary.cpp (attached), method
>resolve_instance_class_or_null(...).
> The loading mechanism of the JVM is done in 2 steps:
>
> 1- look in a dictionary, if not found, put there a placeholder, then
> 2- load the class, calling loadClassInternal().
>
> Thread A comes in asking for class "cls1" with classloader cl1, the class has never
>been loaded, put a placeholder in the dictionary, and call loadClassInternal.
> Thread B comes in asking for class "cls1" with classloader cl1, there is already a
>placeholder, throw CCE.
>
> The key is to ask for the same class with the same classloader.
>
> I think this may happen with the UnifiedClassLoader scheme in several occasions, a
>simple example being:
>
> class Base {}
> class Derived1 extends Base {}
> class Derived2 extends Base {}
>
> If Base is loaded by classloader1, and we have 2 threads trying to load one Derived1
>and one Derived2 (and both need Base), we end up with 2 thread using the same
>classloader to load the same class, and the JVM code throws CCE.
>
> I wrote a simple testcase (attached), but it does not use JBoss classloaders,
>however should be trivial to code it against JBoss codebase. If someone can take care
>of it... thanks :P
>
> As I said I did not think enough to find a solution, but at least we all know where
>to start.
>
> Cheers
>
> Simon
>
> PS: it seems attachments are not allowed ?
>
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>
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