On Tue, 18 Nov 2025 14:35:16 GMT, Anton Artemov <[email protected]> wrote:
>> Hi, please consider the following changes: >> >> If suspension is allowed when a thread is re-entering an object monitor >> (OM), then a deadlock is possible: >> >> The waiting thread is made to be a successor and is unparked. Upon a >> suspension request, the thread will suspend itself whilst clearing the >> successor. The OM will be left unlocked (not grabbed by any thread), while >> the other threads are parked until a thread grabs the OM and the exits it. >> The suspended thread is on the entry-list and can be selected as a successor >> again. None of other threads can be woken up to grab the OM until the >> suspended thread has been resumed and successfully releases the OM. >> >> This can happen in two places where the successor could be suspended: >> 1: >> https://github.com/openjdk/jdk/blob/6322aaba63b235cb6c73d23a932210af318404ec/src/hotspot/share/runtime/objectMonitor.cpp#L1897 >> >> 2: >> https://github.com/openjdk/jdk/blob/6322aaba63b235cb6c73d23a932210af318404ec/src/hotspot/share/runtime/objectMonitor.cpp#L1149 >> >> The issues are addressed by not allowing suspension in case 1, and by >> handling the suspension request at a later stage, after the thread has >> grabbed the OM in `reenter_internal()` in case 2. In case of a suspension >> request, the thread exits the OM and enters it again once resumed. >> >> The JVMTI `waited` event posting (2nd one) is postponed until the suspended >> thread is resumed and has entered the OM again. The `enter` to the OM (in >> case `ExitOnSuspend` did exit) is done without posting any events. >> >> Tests are added for both scenarios. >> >> Tested in tiers 1 - 7. > > Anton Artemov has updated the pull request incrementally with one additional > commit since the last revision: > > 8366659: Added bool arg to notify_contended_enter Thank you for refactoring the test into several tests which share a common part. It is nice! May I ask you about more refactoring? I'll inline my comments with the refactoring suggestions. ------------- PR Comment: https://git.openjdk.org/jdk/pull/27040#issuecomment-3550803652
