RFR: 8214068: ZGC crashes with vmTestbase/nsk/jdi/ReferenceType/instances/instances004/TestDescription.java

[Erik Österlund]

Hi Per,

Looks good.

Thanks,
/Erik

On 2018-11-21 10:11, Per Liden wrote:
> This patch adds a missing load barrier to the JVMTI heap walker. In 
> VM_HeapWalkOperation::collect_simple_roots() the SimpleRootsClosure 
> closure should not do raw loads of oops. Instead it should be loading 
> them using NativeAccess<AS_NO_KEEPALIVE>::oop_load().
>
> This problem only affects ZGC, since it's (so far) the only collector 
> that scans JNIHandles concurrently.
>
> The problem was easily reproducible when running 
> vmTestbase/nsk/jdi/ReferenceType/instances/instances004/TestDescription.java. 
> However, for some reason this isn't reproducing in our CI pipeline, 
> likely because of luck with timing. For example, this is harder to 
> reproduce in a scenario where your using a smaller heap and hence have 
> GC cycles happen more frequently.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8214068
> Webrev: http://cr.openjdk.java.net/~pliden/8214068/webrev.0
>
> /Per