RFR (S) 8209889: RedefineStress tests crash

[dean.long at oracle.com]

On 10/4/18 11:28 AM, coleen.phillimore at oracle.com wrote:
>
>
> On 10/4/18 2:00 PM, dean.long at oracle.com wrote:
>> So having a raw CompileTask* is like having a raw Method*.  I'm 
>> tempted to suggest a new CompiledTaskHandle, but it would only be 
>> used in one place, so how about changing CompileTaskWrapper so we 
>> could do something like this instead:
>>
>>     CompileTaskWrapper ctw(queue->get());
>>     CompileTask* task = ctw.task();
>
> I started down this path but since CompileTaskWrapper cannot 
> completely encapsulate CompileTask to make it safe, the code I have I 
> think is just as good.  Also, adding NULL checks seems like it would 
> allow some new behavoir that is now an invariant (ie CompileTask is 
> never NULL).
>

OK.  Reviewed.

dl

> Thanks,
> Coleen
>>
>> CompileTaskWrapper would need to be able to handle a NULL task 
>> gracefully.
>>
>> dl
>>
>> On 10/4/18 4:45 AM, coleen.phillimore at oracle.com wrote:
>>> Summary: Create CompileTaskWrapper before potential safepoint
>>>
>>> open webrev at http://cr.openjdk.java.net/~coleenp/8209889.01/webrev
>>> bug link https://bugs.openjdk.java.net/browse/JDK-8209889
>>>
>>> MetadataOnStackMark needs to find the CompileTask in the current 
>>> thread, or else the Method isn't marked as being alive, so if it's 
>>> old/obsolete, it is freed.  There are checks to disable adding old 
>>> methods to the compile queue but if the method is redefined after 
>>> this point, there may be a preexisting bug that we compile an old 
>>> method.  This change just fixes the crash.
>>>
>>> Can some compiler person (Martin?) look at where I moved 
>>> possibly_add_compiler_threads and let me know if that looks okay? 
>>> There's a comment in the change that says why you need to create the 
>>> CompileTaskWrapper before that call.  I couldn't find a place to put 
>>> a NoSafepointVerifier.
>>>
>>> Tested with the test that failed, which doesn't reproduce the bug 
>>> except rarely, and test/hotspot/jtreg/compiler tests. tier1 an 2 in 
>>> progress.
>>>
>>> Thanks,
>>> Coleen
>>
>