RFR (M) 8155951: VM crash in nsk/jvmti/RedefineClasses/StressRedefine: assert failed: Corrupted constant pool

[Coleen Phillimore]

Thanks, again, Serguei!
Coleen

On 5/16/16 1:33 PM, serguei.spitsyn at oracle.com wrote:
> Coleen,
>
> It looks good.
> Good catch by David H.
>
> Thanks,
> Serguei
>
> On 5/16/16 09:28, Coleen Phillimore wrote:
>>
>> David, Thank you for looking at this change.
>>
>> On 5/15/16 9:51 PM, David Holmes wrote:
>>> Hi Coleen,
>>>
>>> On 13/05/2016 4:14 AM, Coleen Phillimore wrote:
>>>> 8151066: assert(0 <= i && i < length()) failed: index out of bounds
>>>> Summary: lock classes for redefinition because constant pool merging
>>>> isn't thread safe, use method constant pool because constant pool
>>>> merging doesn't make equivalent cpCaches because of invokedynamic
>>>>
>>>> I had to make these changes together.   See bugs for more details.
>>>>
>>>> open webrev at http://cr.openjdk.java.net/~coleenp/8155951/webrev
>>>> bug link https://bugs.openjdk.java.net/browse/JDK-8155951
>>>> bug link https://bugs.openjdk.java.net/browse/JDK-8151066
>>>
>>> In general the locking approach seems okay - as long as all mutating 
>>> actions on the constantpool are being guarded with this locking.
>>>
>>> But I'm concerned that you are using a bit in _misc_flags for this 
>>> mutable state. It isn't clear to me when the other bits in 
>>> _misc_flags might be set but I'm assuming only during initial class 
>>> parsing, or some other single-threaded use? Putting a mutable bit 
>>> into such a flag set is fragile and can only be done once.
>>
>> I was uneasy about this too.  Most of the _misc_flags are set during 
>> initialization but there are a couple that are set while the vm is 
>> running.   I moved _is_being_redefined to a bool sized gap just about 
>> the _misc_flags, which makes me more confident of the state of this 
>> field when doing locking.
>>
>> Retesting this small change with StressRedefine in a loop.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8155951.02/webrev
>>
>> Thanks,
>> Coleen
>>
>>>
>>> Thanks,
>>> David
>>>
>>>
>>>> Tested with rbt nightly test and 24 hours with StressRedefine test.
>>>>
>>>> Thanks,
>>>> Coleen
>>>>
>>>>
>>>>
>>
>