RFR: 8369227: Virtual thread stuck in PARKED state

[Patricio Chilano Mateo]

On Wed, 31 Dec 2025 08:08:49 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> A regression since we changed the VirtualThread implementation to use use FJP delayed task handling (JDK-8351927) in JDK 25.
> 
> If a virtual thread does a timed-park, followed immediately by an untimed-park, while racing with both an async unpark and the execution of cancelled timeout-task, then it is possible for the virtual thread to get stuck in the parked state. More specifically, it is possible for stars to align to create the scenario where parkTimeoutExpired makes available the parking permit but it doesn't continue the thread because it has moved on to an untimed-park.  A small oversight that crept in when the timeout support was migrated to use the new delay scheduler.
> 
> Testing: tier1-5. New stress tests added, and existing stress test TimedWaitALot updated.

Looks good to me.

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Marked as reviewed by pchilanomate (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/29011#pullrequestreview-3631767826