RFR: 8373944: ObjectMonitor::ExitOnSuspend can call java_lang_VirtualThread::set_onWaitingList() while in safepoint

[Fredrik Bredberg]

On Thu, 19 Feb 2026 16:36:01 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

> Please review the following patch. `ExitOnSuspend::operator()` may run while a safepoint is in progress, which can lead to crashes because releasing the monitor involves touching oops if the successor is a virtual thread. The proposed fix is to process pending operations before releasing the monitor.
> I added a new test that reliably reproduces the issue with the extra `assert_not_at_safepoint()` added in this patch, and verified the issue is now fixed.
> 
> Thanks,
> Patricio

There is almost always more than meets the eye when it comes to ExitOnSuspend. So it's nice to see a small code change to sort out this current problem, and a very well written test. Thank you!

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Marked as reviewed by fbredberg (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/29822#pullrequestreview-3841600409