RFR: 8349094: GenShen: Race between control and regulator threads may violate assertions [v18]

[Y. Srinivas Ramakrishna]

On Fri, 28 Feb 2025 17:17:17 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> There are several changes to the operation of Shenandoah's control threads here.
>> * The reason for cancellation is now recorded in `ShenandoahHeap::_cancelled_gc` as a `GCCause`, instead of various member variables in the control thread.
>>   *  The cancellation handling is driven entirely by the cancellation cause
>>   * The graceful shutdown, alloc failure, humongous alloc failure and preemption requested flags are all removed
>>   * The shutdown sequence is simpler
>> * The generational control thread uses a lock to coordinate updates to the requested cause and generation
>>   * APIs have been simplified to avoid converting between the generation `type` and the actual generation instance
>>   * The old heuristic, rather than the control thread itself, is now responsible for resuming old generation cycles
>>   *  The control thread doesn't loop on its own (unless the pacer is enabled).
>> 
>> ## Testing
>> * jtreg hotspot_gc_shenandoah
>> * dacapo, extremem, diluvian, specjbb2015, specjvm2018, heapothesys
>
> William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 37 commits:
> 
>  - Merge remote-tracking branch 'jdk/master' into fix-control-regulator-threads
>  - Don't check for shutdown in control thread loop condition
>    
>    It may cause the thread to exit before it is requested to stop
>  - Add assertions about old gen state when resuming old cycles
>  - Remove duplicated field pointer for old generation
>  - Improve names and comments
>  - Merge tag 'jdk-25+11' into fix-control-regulator-threads
>    
>    Added tag jdk-25+11 for changeset 0131c1bf
>  - Address review feedback (better comments, better names)
>  - Merge remote-tracking branch 'jdk/master' into fix-control-regulator-threads
>  - Old gen bootstrap cycle must make it to init mark
>  - Merge remote-tracking branch 'jdk/master' into fix-control-regulator-threads
>  - ... and 27 more: https://git.openjdk.org/jdk/compare/e98df71d...37e445d6

🚢

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Marked as reviewed by ysr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23475#pullrequestreview-2655535655