[jdk20] RFR: 8296955: Kitchensink.java failed with "double free or corruption (!prev): <addr>"

[Coleen Phillimore]

On Fri, 9 Dec 2022 12:27:42 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> Thanks to Kim for the diagnosis of this problem.  G1 cleans up nmethods in parallel threads during a safepoint and may post or queue unload events to be posted.  The event posting creates jmethodIDs.  The jmethodID code assumes that it's thread safe in a safepoint, which it is not.
> I removed this optimization, which isn't much of an optimization (did run some sanity performance tests) and is unsafe in the modern code.
> Tested with tier1-7, where tier5 found the original bug.

The JmethodIdCreation_lock used to be a safepoint checking lock, and have higher rank.  It's now a no-safepoint lock and has a relatively low ranking so this change is safer from rank checking than when it was first written.

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PR: https://git.openjdk.org/jdk20/pull/10