RFR(XS): 8209736: runtime/RedefineTests/ModifyAnonymous.java fails with NullPointerException when running in CDS mode

[Jiangli Zhou]

Hi Calvin,


On 8/31/18 1:33 PM, Calvin Cheung wrote:
> Hi Jiangli,
>
> On 8/31/18, 1:10 PM, Jiangli Zhou wrote:
>> Hi Calvin,
>>
>> How about use a separate loop (before the main test loop in 
>> runTest()) to print out the class names in the allLoadedClasses array?
>  109     static void runTest() {
>  110         while (!done) {
>  111             Class[] allLoadedClasses = inst.getAllLoadedClasses();
>  112             int len = allLoadedClasses.length;
>  113             for (int idx = 0; idx < len; idx++) {
>
> Did you mean print out all the class names after line 111? There would 
> be too much output since there's a while loop enclosing it.
> Or did you mean something else?
Yes. If the failure does re-manifest again, we can compare the output 
with a normal run. That would give some useful information. How big is 
the allLoadedClasses?

Or, maybe we could print the classes if null is detected.
>> If null is discovered, throw a RuntimeException(). That helps to 
>> provide more debugging information and also will not silent the issue 
>> that causes the NPE if it does' resurface again.
> I don't think throwing a RuntimeException() gives anymore info than 
> the existing NPE.
> The idea of this change is that after a null clazz is encountered, let 
> the test continue to run. It may fail in a different way which may 
> give us more clues.
The NPE might be caused by a rare race condition, which might not affect 
the redefineClass process and the test could pass with the change. We 
should avoid such case.

Thanks,
Jiangli
>
> thanks,
> Calvin
>>
>> Thanks,
>>
>> Jiangli
>>
>>
>> On 8/31/18 11:33 AM, Calvin Cheung wrote:
>>> bug: https://bugs.openjdk.java.net/browse/JDK-8209736
>>>
>>> webrev: http://cr.openjdk.java.net/~ccheung/8209736/webrev.00/
>>>
>>> The test failure is no longer reproducible; it happened only once in 
>>> tier3 and once in tier6 testing.
>>> This simple change is just adding a null check on the variable clazz 
>>> and prints the array size and index if it is null.
>>>
>>> Testing: hs-tier{1,2,3} with default CDS archive in JDK.
>>>
>>> thanks,
>>> Calvin
>>