2-nd round RFR (XS) 6988950: JDWP exit error JVMTI_ERROR_WRONG_PHASE(112)

[serguei.spitsyn at oracle.com]

The updated webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/jdk/6988950-JDWP-wrong-phase.2/

The changes are:
   - added a comment recommended by Staffan
   - removed the ignore_wrong_phase() call from function classSignature()

The classSignature() function is called in 16 places.
Most of them do not tolerate the NULL in place of returned signature and 
will crash.
I'm not comfortable to fix all the occurrences now and suggest to return 
to this
issue after gaining experience with more failure cases that are still 
expected.
The failure with the classSignature() involved was observed only once in 
the nightly
and should be extremely rare reproducible.
I'll file a placeholder bug if necessary.

Thanks,
Serguei

On 10/28/14 6:11 PM, serguei.spitsyn at oracle.com wrote:
> Please, review the fix for:
>   https://bugs.openjdk.java.net/browse/JDK-6988950
>
>
> Open webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/jdk/6988950-JDWP-wrong-phase.1/ 
>
>
>
> Summary:
>
>    The failing scenario:
>      The debugger and the debuggee are well aware a VM shutdown has 
> been started in the target process.
>      The debugger at this point is not expected to send any commands 
> to the JDWP agent.
>      However, the JDI layer (debugger side) and the jdwp agent 
> (debuggee side)
>      are not in sync with the consumer layers.
>
>      One reason is because the test debugger does not invoke the JDI 
> method VirtualMachine.dispose().
>      Another reason is that the Debugger and the debuggee processes 
> are uneasy to sync in general.
>
>      As a result the following steps are possible:
>        - The test debugger sends a 'quit' command to the test debuggee
>        - The debuggee is normally exiting
>        - The jdwp backend reports (over the jdwp protocol) an 
> anonymous class unload event
>        - The JDI InternalEventHandler thread handles the 
> ClassUnloadEvent event
>        - The InternalEventHandler wants to uncache the matching 
> reference type.
>          If there is more than one class with the same host class 
> signature, it can't distinguish them,
>          and so, deletes all references and re-retrieves them again 
> (see tracing below):
>            MY_TRACE: JDI: 
> VirtualMachineImpl.retrieveClassesBySignature: 
> sig=Ljava/lang/invoke/LambdaForm$DMH;
>        - The jdwp backend debugLoop_run() gets the command from JDI 
> and calls the functions
>          classesForSignature() and classStatus() recursively.
>        - The classStatus() makes a call to the JVMTI GetClassStatus() 
> and gets the JVMTI_ERROR_WRONG_PHASE
>        - As a result the jdwp backend reports the JVMTI error to the 
> JDI, and so, the test fails
>
>      For details, see the analysis in bug report closed as a dup of 
> the bug 6988950:
>         https://bugs.openjdk.java.net/browse/JDK-8024865
>
>      Some similar cases can be found in the two bug reports (6988950 
> and 8024865) describing this issue.
>
>      The fix is to skip reporting the JVMTI_ERROR_WRONG_PHASE error as 
> it is normal at the VM shutdown.
>      The original jdwp backend implementation had a similar approach 
> for the raw monitor functions.
>      Threy use the ignore_vm_death() to workaround the 
> JVMTI_ERROR_WRONG_PHASE errors.
>      For reference, please, see the file: src/share/back/util.c
>
>
> Testing:
>   Run nsk.jdi.testlist, nsk.jdwp.testlist and JTREG com/sun/jdi tests
>
>
> Thanks,
> Serguei
>