RFR: 8254874: ZGC: JNIHandleBlock verification failure in stack watermark processing

[Stefan Karlsson]

On Sat, 17 Oct 2020 08:38:10 GMT, Per Liden <pliden at openjdk.org> wrote:

>> The cm03t001 test creates a local JNI handle in the prepare function. It later uses that handle from a callback
>> function, from another thread. When the callback runs, ZGC applies a load barrier to that handle and self-heals it in
>> the other threads stack. Later when that thread verifies its stack, during the start of its stack processing, it finds
>> that the oop is unexpectedly not "bad".  It's invalid to send a local JNI handle over to another thread:
>> https://docs.oracle.com/en/java/javase/15/docs/specs/jni/design.html#global-and-local-references
>> So, my proposed fix is to convert the local handle to a global handle.
>> 
>> I've tested this with the reproducer in the bug report.
>
> Marked as reviewed by pliden (Reviewer).

Thanks for reviewing!

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PR: https://git.openjdk.java.net/jdk/pull/701