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

[serguei.spitsyn at oracle.com]

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
>>>
>>>
>>>
>