RFR: 8280844: Epoch shift synchronization point for Compiler threads is inadequate [v2]

[Doug Simon]

On Mon, 16 May 2022 11:37:43 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> Greetings,
>> 
>> [JDK-8233111](https://bugs.openjdk.java.net/browse/JDK-8233111) attempted to address artefact tagging for Compiler threads, letting threads run _thread_in_native to avoid the transition. Unfortunately, that attempt proved inadequate.
>> 
>> The epoch race is avoided only by performing the transition to _thread_in_vm.
>> 
>> Testing: jdk_jfr
>> 
>> Thanks
>> Markus
>
> Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision:
> 
>   delegate assertion

src/hotspot/share/compiler/compilerEvent.cpp line 119:

> 117: }
> 118: 
> 119: // As part of event commit, a Method* is tagged as a function of an epoch.

This transition is not necessary for JVMCI compiler threads: https://github.com/openjdk/jdk/pull/12787

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PR: https://git.openjdk.org/jdk/pull/8724