Fix interaction of VMInit and ThreadStart events.

Real world agents require that one is able to create, and run, new
threads while the VMInit event is still being executed. Further, these
require that ThreadStart events can occur concurrently with the VMInit
event. This CL enables this behavior and adds a test for the
interaction of these two events.

Test: ./test.py --host -j50
Bug: 62821960
Bug: 34415266

Change-Id: I305f1ce3f1df9bf5a7e33027e0724f5fbac5c0f1

1 files changed, 12 insertions, 12 deletions

diff --git a/openjdkjvmti/ti_thread.cc b/openjdkjvmti/ti_thread.cc
index 6fa73f8a8c..b0a1a8556a 100644
--- a/openjdkjvmti/ti_thread.cc
+++ b/openjdkjvmti/ti_thread.cc
@@ -57,13 +57,14 @@ namespace openjdkjvmti {
 
 art::ArtField* ThreadUtil::context_class_loader_ = nullptr;
 
-struct ThreadCallback : public art::ThreadLifecycleCallback, public art::RuntimePhaseCallback {
+struct ThreadCallback : public art::ThreadLifecycleCallback {
   jthread GetThreadObject(art::Thread* self) REQUIRES_SHARED(art::Locks::mutator_lock_) {
     if (self->GetPeer() == nullptr) {
       return nullptr;
     }
     return self->GetJniEnv()->AddLocalReference<jthread>(self->GetPeer());
   }
+
   template <ArtJvmtiEvent kEvent>
   void Post(art::Thread* self) REQUIRES_SHARED(art::Locks::mutator_lock_) {
     DCHECK_EQ(self, art::Thread::Current());
@@ -96,15 +97,6 @@ struct ThreadCallback : public art::ThreadLifecycleCallback, public art::Runtime
     Post<ArtJvmtiEvent::kThreadEnd>(self);
   }
 
-  void NextRuntimePhase(RuntimePhase phase) OVERRIDE REQUIRES_SHARED(art::Locks::mutator_lock_) {
-    if (phase == RuntimePhase::kInit) {
-      // We moved to VMInit. Report the main thread as started (it was attached early, and must
-      // not be reported until Init.
-      started = true;
-      Post<ArtJvmtiEvent::kThreadStart>(art::Thread::Current());
-    }
-  }
-
   EventHandler* event_handler = nullptr;
   bool started = false;
 };
@@ -121,10 +113,19 @@ void ThreadUtil::Register(EventHandler* handler) {
                                     art::ThreadState::kWaitingForDebuggerToAttach);
   art::ScopedSuspendAll ssa("Add thread callback");
   runtime->GetRuntimeCallbacks()->AddThreadLifecycleCallback(&gThreadCallback);
-  runtime->GetRuntimeCallbacks()->AddRuntimePhaseCallback(&gThreadCallback);
+}
+
+void ThreadUtil::VMInitEventSent() {
+  // We should have already started.
+  DCHECK(gThreadCallback.started);
+  // We moved to VMInit. Report the main thread as started (it was attached early, and must not be
+  // reported until Init.
+  gThreadCallback.Post<ArtJvmtiEvent::kThreadStart>(art::Thread::Current());
 }
 
 void ThreadUtil::CacheData() {
+  // We must have started since it is now safe to cache our data;
+  gThreadCallback.started = true;
   art::ScopedObjectAccess soa(art::Thread::Current());
   art::ObjPtr<art::mirror::Class> thread_class =
       soa.Decode<art::mirror::Class>(art::WellKnownClasses::java_lang_Thread);
@@ -140,7 +141,6 @@ void ThreadUtil::Unregister() {
   art::ScopedSuspendAll ssa("Remove thread callback");
   art::Runtime* runtime = art::Runtime::Current();
   runtime->GetRuntimeCallbacks()->RemoveThreadLifecycleCallback(&gThreadCallback);
-  runtime->GetRuntimeCallbacks()->RemoveRuntimePhaseCallback(&gThreadCallback);
 }
 
 jvmtiError ThreadUtil::GetCurrentThread(jvmtiEnv* env ATTRIBUTE_UNUSED, jthread* thread_ptr) {