RFR: 8359827: Test runtime/Thread/ThreadCountLimit.java should run exclusively [v6]

[David Holmes]

On Tue, 22 Jul 2025 12:18:26 GMT, SendaoYan <syan at openjdk.org> wrote:

>> Hi all,
>> 
>> The test runtime/Thread/ThreadCountLimit.java was observed fails when run with other tests. The test start subprocess with [shell prefix command](https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/runtime/Thread/ThreadCountLimit.java#L82) `ulimit -u 4096` which intend to limite the usage of thread number. But this will cause test fails when this test run with other tests. I create a demo to demonstrate that.
>> 
>> I start a java process which will create 5k threads, and then I can not start new java process with prefix `ulimit -u 4096` on the same machine.
>> 
>> <img width="1573" height="182" alt="image" src="https://github.com/user-attachments/assets/8dd53ade-cad7-4a2f-b5d9-d4b2d200b728" />
>> 
>> 
>> [ManyThreads.java.txt](https://github.com/user-attachments/files/21324354/ManyThreads.java.txt)
>> 
>> So it's necessary to make this test run sperately to make this test success.
>> Change has been verified locally, test-fix only, risk is low.
>
> SendaoYan has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Revert "Use 'docker run --pids-limit 4096' to instead the original 'ulimit -u 4096'"
>    
>    This reverts commit f993419b20b5dd2273a4f6c3c54e79fb8f955383.
>  - Revert "Remove extra whitespaces"
>    
>    This reverts commit 374c297b52b03e8b471465010f99b1b6bc3174f0.

Testing - please ignore.

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PR Comment: https://git.openjdk.org/jdk/pull/26401#issuecomment-3105189258