RFR: 8373120: Virtual thread stuck in BLOCKED state [v3]

[Alan Bateman]

On Tue, 20 Jan 2026 20:46:04 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Please review the following patch. This fixes a bug in how we handle state changes for the timed `Object.wait` case in `afterYield`, which can leave a virtual thread stuck in the `BLOCKED` state. It can be triggered by two consecutive calls to timed `Object.wait`, if the first call receives a notification and the second call relies on the timeout task to wake up the thread. I added the full sequence of events that leads to the vthread getting stuck in JBS.
>> 
>> The fix is to check for `notified` and attempt to change the state to `BLOCKED` inside the synchronized block. This guarantees that we don't change the state of an already new timed `Object.wait` call.
>> 
>> The PR includes a new test which reproduces the issue when run several times in mach5. It's a hybrid of my original repro test and another one created by @AlanBateman.
>> 
>> Thanks,
>> Patricio
>
> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Randomly choose platform or virtual notifier

Marked as reviewed by alanb (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/29255#pullrequestreview-3686247862