On Wed, 28 Jan 2026 09:35:00 GMT, Alan Bateman <[email protected]> wrote:
> JDK-8364343 upgraded the virtual thread transition management to be > independent of JVMTI. We can update java_lang_Thread::async_get_stack_trace > to use it and remove the suspend + retry code from Thread.getStackTrace. > > A summary of the changes: > > - java_lang_Thread::async_get_stack_trace is changed to use the new handshake > op so it can be called to get the stack trace of a started thread in any state > - Thread::getStackTrace is changed to use async_get_stack_trace for all cases > - The SUSPENDED substate in VirtualThread is removed > - JVM_CreateThreadSnapshot is changed to be usable when JVMTI is not compiled > in > - ThreadSnapshotFactory::get_thread_snapshot is changed to not upcall to > StackTraceElement to complete the init of the stack trace > > The changes mean that Thread::getStackTrace may be slower when sampling a > virtual thread in transition. This case should be rare, and it isn't really a > performance critical op anyway. I prototyped use a spin loop and an > increasing wait time in MountUnmountDisabler::disable_transition_for_one to > avoid the wait(10) but decided to leave it out for now. Future work may > examine this issue as there may be other cases (with JVMTI) that would > benefit from avoiding the wait. > > A future PR might propose to change Thread.getStackTrace to use > ThreadSnapshot and allow java_lang_Thread::async_get_stack_trace be removed. > This requires more extensive changes to ThreadSnapshotFactory to reduce > overhead when only the stack trace is required. > > Testing: tier1-5. The changes has been already been tested in the loom repo > for a few months. This pull request has now been integrated. Changeset: ac6e8d48 Author: Alan Bateman <[email protected]> URL: https://git.openjdk.org/jdk/commit/ac6e8d481a20b40e136263c0e0c075bd138677ab Stats: 669 lines in 21 files changed: 445 ins; 168 del; 56 mod 8376568: Change Thread::getStackTrace to use handshake op for all cases Reviewed-by: pchilanomate, sspitsyn ------------- PR: https://git.openjdk.org/jdk/pull/29461
