RFR (XS) 8059924: com/sun/management/DiagnosticCommandMBean/DcmdMBeanPermissionsTest.java: assert(Universe::verify_in_progress() || !SafepointSynchronize::is_at_safepoint()) failed: invariant

[Aleksey Shipilev]

Anyone?

Thanks,
-Aleksey.

On 10/09/2014 04:43 PM, Aleksey Shipilev wrote:
> Keith, Lois, thanks for review!
> 
> I think I need another Runtime Reviewer?
> 
> Definitely need a sponsor. Here is the changeset:
>  http://cr.openjdk.java.net/~shade/8059924/8059924.changeset
> 
> Thanks,
> -Aleksey.
> 
> On 10/09/2014 03:39 PM, Lois Foltan wrote:
>> Aleksey, this looks good.
>> Lois
>>
>> On 10/9/2014 3:21 AM, Aleksey Shipilev wrote:
>>> Hi,
>>>
>>> There is a regression introduced by:
>>>   https://bugs.openjdk.java.net/browse/JDK-8059595
>>>
>>> The regression is tracked here:
>>>   https://bugs.openjdk.java.net/browse/JDK-8059924
>>>
>>> ...and here is a fix:
>>>   http://cr.openjdk.java.net/~shade/8059924/webrev.00/
>>>
>>> Testing: JPRT, jdk/test/com/sun/management
>>>
>>> The comment there should be self-explanatory. The failure requires a
>>> precise sequence of events to happen: we should be at safepoint, and
>>> call klass->external_name() on a previously untouched class. Before
>>> JDK-8059595, Verifier always did klass->external_name() for all verified
>>> classes, causing a performance trouble.
>>>
>>> This might explain why the failure happens on com/sun/management tests
>>> that do VM operations (GC_HeapInspection in reported failure case). This
>>> reproduces perfectly with DcmdMBeanPermissionsTest, and the test is
>>> fixed with the VM change above.
>>>
>>> The alternative would be to backout the JDK-8059595 change completely,
>>> but this gets us back to weird piggybacking on klass->external_name()
>>> during the verification. Other alternatives: returning 0 from hashcode
>>> during safepoint is obviously unsafe; returning zero-hashcode string
>>> from klass->external_name() is potentially unsafe if someone is using
>>> the name as the map key downstream.
>>>
>>> -Aleksey.
>>
>