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

Per Liden per.liden at oracle.com
Wed Nov 21 09:11:23 UTC 2018

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 
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


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