RFR (M) 8067662: "java.lang.NullPointerException: Method name is null" from StackTraceElement.<init>

[serguei.spitsyn at oracle.com]

Coleen,

Thank you for review and great idea to use the method name cp index!
However, this approach is going stop working if we get rid of the CP 
merge in the future.

Thanks,
Serguei

On 3/13/15 10:40 AM, Coleen Phillimore wrote:
>
> Serguei,
>
> This looks good.  This works a lot harder to find the original method 
> than the code used to.
>
> Thanks,
> Coleen
>
> On 3/13/15, 1:27 AM, serguei.spitsyn at oracle.com wrote:
>> Please, review the jdk 9 fix for:
>>   https://bugs.openjdk.java.net/browse/JDK-8067662
>>
>>
>> Open hotspot webrev:
>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/hotspot/8067662-JVMTI-trace.1/ 
>>
>>
>> Open webrev for unit test update:
>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2015/jdk/8067662-JVMTI-trace-test.1/ 
>>
>>
>>
>> Summary:
>>   An NPE is trown in a thread dumping via JMX when doing CPU 
>> profiling in NetBeans Profiler and VisualVM.
>>   The issue is that the methods and related klass versions are not 
>> kept alive if a class redefinition
>>   takes place between catching a Throwable and taking a thread dump.
>>   It can result in loosing an obsolete method, and so, the 
>> reconstruction of method name becomes impossible.
>>   In such a case, the null reference is returned instead of a valid 
>> method name.
>>
>>   The solution is to use current klass version and method orig_idnum 
>> instead of ordinary method idnum
>>   to find required method pointer. In the worst case when the related 
>> klass version is gone
>>   (was not included to or was removed from the previous_versions 
>> linked list), a saved method name
>>   CP index of the latest klass version can be used to restore the 
>> method name.
>>   The footprint extra overhead for this approach is u2 per stack frame.
>>
>>   The plan is also to backport the fix to 8u60.
>>
>> Testing:
>>   In progress: nsk redefine classes tests, JTREG java/lang/instrument
>>
>>
>> Thanks,
>> Serguei
>