On Fri, 17 Nov 2023 05:37:46 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
>> The handshakes support for virtual threads is needed to simplify the JVMTI >> implementation for virtual threads. There is a significant duplication in >> the JVMTI code to differentiate code intended to support platform, virtual >> threads or both. The handshakes are unified, so it is enough to define just >> one handshake for both platform and virtual thread. >> At the low level, the JVMTI code supporting platform and virtual threads >> still can be different. >> This implementation is based on the `JvmtiVTMSTransitionDisabler` class. >> >> The internal API includes two new classes: >> - `JvmtiHandshake` and `JvmtiUnifiedHandshakeClosure` >> >> The `JvmtiUnifiedHandshakeClosure` defines two different callback >> functions: `do_thread()` and `do_vthread()`. >> >> The first JVMTI functions are picked first to be converted to use the >> `JvmtiHandshake`: >> - `GetStackTrace`, `GetFrameCount`, `GetFrameLocation`, `NotifyFramePop` >> >> To get the test results clean, the update also fixes the test issue: >> [8318631](https://bugs.openjdk.org/browse/JDK-8318631): >> GetStackTraceSuspendedStressTest.java failed with "check_jvmti_status: JVMTI >> function returned error: JVMTI_ERROR_THREAD_NOT_ALIVE (15)" >> >> Testing: >> - the mach5 tiers 1-6 are all passed > > Serguei Spitsyn has updated the pull request incrementally with one > additional commit since the last revision: > > review: add jdk_internal_vm_Continuation::done(cont) check to > JvmtiEnvBase::is_vthread_alive src/hotspot/share/prims/jvmtiEnvBase.cpp line 1989: > 1987: } else { > 1988: Handshake::execute(hs_cl, tlh, target_jt); // delegate to > Handshake implementation > 1989: } Every implementation of JvmtiUnitedHandshakeClosure has to check if the target thread is virtual and call do_vthread manually. I'd suggest to handle this by proxy class, something like Suggestion: class Adapter : public HandshakeClosure { JvmtiUnitedHandshakeClosure* _hs_cl; Handle _target_h; public: Adapter(JvmtiUnitedHandshakeClosure* hs_cl, Handle target_h) : HandshakeClosure(hs_cl->name()), _hs_cl(hs_cl), _target_h(target_h) {} virtual void do_thread(Thread* thread) { if (java_lang_VirtualThread::is_instance(_target_h())) { // virtual thread _hs_cl->do_vthread(_target_h); } else { _hs_cl->do_thread(target); } } } adapter(hs_cl, target_h); if (self) { // target thread is current adapter.do_thread(target_jt); // execute handshake closure callback on current thread directly } else { Handshake::execute(&adapter, tlh, target_jt); // delegate to Handshake implementation } ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16460#discussion_r1398042638
