RFR: 8320318: ObjectMonitor Responsible thread [v2]

[Fredrik Bredberg]

On Fri, 13 Sep 2024 15:36:58 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update one, after the review
>
> src/hotspot/share/runtime/objectMonitor.cpp line 920:
> 
>> 918:   // To that end, the exit() operation must have at least STST|LDST
>> 919:   // "release" barrier semantics.  Specifically, there must be at least a
>> 920:   // STST|LDST barrier in exit() before the ST of null into _owner that drops
> 
> This sentence: Is the membar before or after the ST that drops the lock?

It's the release barrier before the store that drops the lock. I'ts described [here](https://github.com/openjdk/jdk/blob/d2c6db2b9673ab8381bc7c86ada90da552350cb8/src/hotspot/share/runtime/objectMonitor.cpp#L1104).

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PR Review Comment: https://git.openjdk.org/jdk/pull/19454#discussion_r1763250484