RFR: 8373468: Shenandoah: Mutator may block at _gc_waiters_lock after allocation failure even block parameter is false [v3]

[Xiaolong Peng]

On Thu, 11 Dec 2025 17:44:35 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Only load _requested_gc_cause once when figuring out pending requests
>
> src/hotspot/share/gc/shenandoah/shenandoahControlThread.hpp line 46:
> 
>> 44: 
>> 45:   ShenandoahSharedFlag               _gc_requested;
>> 46:   Atomic<GCCause::Cause>             _requested_gc_cause;
> 
> `_requested_gc_cause` should always be accessed when holding the `_control_lock`. Making this atomic should not be unnecessary.

Yes, the change to use Atomic for _requested_gc_cause is unnecessary, I have reverted it with a minor change for ShenandoahControlThread to always access  _requested_gc_cause with `_control_lock` held.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28758#discussion_r2611654969