Virtual threads created more platform threads

[Peter Eastham]

I hope to not create noise with my own comments, and I will concur with you
that JEP 491 should mean this is resolved in Java 24, which Jianbin Chen
should try out before and then alongside Robert's recommendation for
creating a very simple reproduction.

As Java 21 is still the current LTS, it isn't completely unreasonable to
forward concerns to the mailing list. My understanding in this particular
case is that JEP 491 is not going to be back ported to Java 21 as it has a
dependency from a change in Java 23. (Potentially more, I can't remember
the conversation completely, I only skimmed that email chain)


Thanks,
- Peter

P.S. As I do a similar job, I'd like to call out that Vendors letting the
occasional support question slip into here is a fine price to pay for the
amount of questions they handle instead.



On Tue, Jul 1, 2025, 9:17 PM Chen Liang <liangchenblue at gmail.com> wrote:

> Hello, I don't think this would happen for JDK 24 - JEP 491 removed the
> code that calls Blocker in Object.wait, which is exactly the goal of that
> JEP.
>
> Note that virtual threads are still pinned when call stack goes into
> native, as native execution may pass address to stack variables that will
> be lost in context switches. In these cases, the traditional managed block
> happens again.
>
> P.S. I personally think it is somewhat not responsible for JDK vendors to
> ask users to upstream a question for an older JDK release that might no
> longer apply on the latest release to a development-oriented mailing list.
>
> On Tue, Jul 1, 2025 at 9:47 PM Jianbin Chen <jianbin at apache.org> wrote:
>
>>
>> Hi Loom-dev Community,
>>
>> I have a question about platform thread creation triggered by calling
>> future.get() within virtual threads, and I would like to ask the community
>> for assistance. The detailed information can be found in this issue:
>> https://github.com/adoptium/adoptium-support/issues/1319. I hope to
>> receive some help from the community regarding this matter. Thank you.
>> Additionally, I'd like to know if this situation will still occur in JDK
>> 24 and above?
>>
>> Best Regards.
>> Jianbin Chen, github-id: funky-eyes
>>
>>
>> Best Regards.
>> Jianbin Chen, github-id: funky-eyes
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/loom-dev/attachments/20250701/fb6c5218/attachment-0001.htm>