RFR: 8309688: Data race on java.io.ClassCache$CacheRef.strongReferent

[Alan Bateman]

On Thu, 8 Jun 2023 22:06:56 GMT, Man Cao <manc at openjdk.org> wrote:

> Could anyone review this small fix for a data race in java.io.ClassCache$CacheRef? This fix makes the code safer by making the code data-race-free.

If I read the existing code correctly, ClassCache::get can't return null. If there are two threads racing then it's okay for both to read a non-null strong ref, one read non-null and the other null, or both read null (if someone else cleared it). It just means there may be fallback to the soft ref or if that gets cleared then the remove/re-compute the ClassValue. Maybe more eyes are needed but it could be that this TSAN is reporting a false positive here.

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PR Comment: https://git.openjdk.org/jdk/pull/14386#issuecomment-1584614945