RFR: 8320707: Virtual thread test updates

[Alan Bateman]

On Mon, 18 Dec 2023 20:37:29 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> I'm working on a test where I just added a CountDownLatch(1) and am wondering if I should do the same, but I'm not sure if there is something about these tests that is motivating the change.

CountDownLatch is great for many tests. It's not as powerful as a Phaser of course but good enough and usually easy to understand quickly what is going on. However, for tests that are testing thread state then you often want to have as few dependencies as possible. In the case of CountDownlatch, the await method may park. The countDown method may have to unpark waiters for for virtual threads it means potentially parking (to queue a task) when unparking, so temporary transitions that JVMTI has to be concerned with. The other thing is keeping tests simple/consistent, it can be hard to maintain tests where one test method coordinates with one approach, another test method does something different.

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PR Comment: https://git.openjdk.org/jdk/pull/17136#issuecomment-1862390382