RFR: 8369238: Allow virtual thread preemption on some common class initialization paths [v10]

[Patricio Chilano Mateo]

On Wed, 29 Oct 2025 06:02:57 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add const to references
>
> src/hotspot/share/runtime/javaCalls.cpp line 61:
> 
>> 59:   assert(!thread->owns_locks(), "must release all locks when leaving VM");
>> 60:   guarantee(thread->can_call_java(), "cannot make java calls from the native compiler");
>> 61:   assert(!thread->preempting(), "");
> 
> I'm not sure why this is checked here, and there is no error message to tell me. If we did get here with `preempting` set what would that mean?

This is a safety check since a thread marked as preempted should not be making upcalls to Java. It should be bailing out from methods and returning to the VM entry point. I found we could get here from the exception path (from your other comment below) when there was no `NoPreemptMark` there.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27802#discussion_r2475389912