Finalizer calls Reference.get() from the Finalizer to acquire the finalizee. Concurrent reference processing GCs like Shenandoah and ZGC would return NULL for unreachable referents, and thus would not call finalize() on them.
ZGC works around this by fixing the referent before enqueuing, so that the barrier would take the fast-path, but Shenandoah cannot do this. It is ok to bypass the barrier altogether in this place, because the FinalReference is inactive and marking and reference-discovery treat inactive FinalReferences like strong references. Testing: - [x] hotspot_gc_shenandoah - [x] tier1 +UseShenandoahGC +ShenandoahVerify - [x] tier2 +UseShenandoahGC +ShenandoahVerify - [ ] tier1 - [ ] tier2 ------------- Commit messages: - 8256106: Bypass intrinsic/barrier when calling Reference.get() from Finalizer Changes: https://git.openjdk.java.net/jdk/pull/1140/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1140&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8256106 Stats: 8 lines in 2 files changed: 7 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/1140.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/1140/head:pull/1140 PR: https://git.openjdk.java.net/jdk/pull/1140
