RFR (S) 8209889: RedefineStress tests crash

[coleen.phillimore at oracle.com]

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).

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
>