8264279: Shenandoah: Missing handshake after JDK-8263427

Reviewed-by: shade

Author: zhengyu123

src/hotspot/share/gc/shenandoah/shenandoahConcurrentGC.cpp

@@ -807,6 +807,12 @@ void ShenandoahConcurrentGC::op_weak_roots() {
     ShenandoahConcurrentWeakRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_weak_roots_work);
     heap->workers()->run_task(&task);
   }
+
+  // Perform handshake to flush out dead oops
+  {
+    ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
+    heap->rendezvous_threads();
+  }
 }
 
 void ShenandoahConcurrentGC::op_class_unloading() {

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -1551,6 +1551,17 @@ class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionCl
   bool is_thread_safe() { return true; }
 };
 
+class ShenandoahRendezvousClosure : public HandshakeClosure {
+public:
+  inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
+  inline void do_thread(Thread* thread) {}
+};
+
+void ShenandoahHeap::rendezvous_threads() {
+  ShenandoahRendezvousClosure cl;
+  Handshake::execute(&cl);
+}
+
 void ShenandoahHeap::recycle_trash() {
   free_set()->recycle_trash();
 }

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -126,6 +126,7 @@ class ShenandoahHeap : public CollectedHeap {
   friend class ShenandoahConcurrentGC;
   friend class ShenandoahDegenGC;
   friend class ShenandoahFullGC;
+  friend class ShenandoahUnload;
 
 // ---------- Locks that guard important data structures in Heap
 //
@@ -371,8 +372,8 @@ class ShenandoahHeap : public CollectedHeap {
   void update_heap_region_states(bool concurrent);
   void rebuild_free_set(bool concurrent);
 
+  void rendezvous_threads();
   void recycle_trash();
-
 public:
   void notify_gc_progress()    { _progress_last_gc.set();   }
   void notify_gc_no_progress() { _progress_last_gc.unset(); }

src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp

@@ -82,6 +82,7 @@ class outputStream;
   f(conc_weak_roots,                                "Concurrent Weak Roots")           \
   f(conc_weak_roots_work,                           "  Roots")                         \
   SHENANDOAH_PAR_PHASE_DO(conc_weak_roots_work_,    "    CWR: ", f)                    \
+  f(conc_weak_roots_rendezvous,                     "  Rendezvous")                    \
   f(conc_cleanup_early,                             "Concurrent Cleanup")              \
   f(conc_class_unload,                              "Concurrent Class Unloading")      \
   f(conc_class_unload_unlink,                       "  Unlink Stale")                  \

src/hotspot/share/gc/shenandoah/shenandoahUnload.cpp

@@ -133,12 +133,6 @@ void ShenandoahUnload::prepare() {
   DependencyContext::cleaning_start();
 }
 
-class ShenandoahRendezvousClosure : public HandshakeClosure {
-public:
-  inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
-  inline void do_thread(Thread* thread) {}
-};
-
 void ShenandoahUnload::unload() {
   ShenandoahHeap* heap = ShenandoahHeap::heap();
   assert(ClassUnloading, "Filtered by caller");
@@ -172,8 +166,7 @@ void ShenandoahUnload::unload() {
   // Make sure stale metadata and nmethods are no longer observable
   {
     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_rendezvous);
-    ShenandoahRendezvousClosure cl;
-    Handshake::execute(&cl);
+    heap->rendezvous_threads();
   }
 
   // Purge stale metadata and nmethods that were unlinked