8338202: Shenandoah: Improve handshake closure labels

Backport-of: ba69ed7c58fcf99ed18dfd8840125ddcac9460bb

Author: Satyen Subramaniam

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

@@ -806,7 +806,7 @@ void ShenandoahConcurrentGC::op_weak_roots() {
   // Perform handshake to flush out dead oops
   {
     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
-    heap->rendezvous_threads();
+    heap->rendezvous_threads("Shenandoah Concurrent Weak Roots");
   }
 }
 

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

@@ -186,7 +186,7 @@ class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {
   SATBMarkQueueSet& _qset;
 public:
   ShenandoahFlushSATBHandshakeClosure(SATBMarkQueueSet& qset) :
-    HandshakeClosure("Shenandoah Flush SATB Handshake"),
+    HandshakeClosure("Shenandoah Flush SATB"),
     _qset(qset) {}
 
   void do_thread(Thread* thread) {

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

@@ -1568,12 +1568,12 @@ class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionCl
 
 class ShenandoahRendezvousClosure : public HandshakeClosure {
 public:
-  inline ShenandoahRendezvousClosure() : HandshakeClosure("ShenandoahRendezvous") {}
+  inline ShenandoahRendezvousClosure(const char* name) : HandshakeClosure(name) {}
   inline void do_thread(Thread* thread) {}
 };
 
-void ShenandoahHeap::rendezvous_threads() {
-  ShenandoahRendezvousClosure cl;
+void ShenandoahHeap::rendezvous_threads(const char* name) {
+  ShenandoahRendezvousClosure cl(name);
   Handshake::execute(&cl);
 }
 

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

@@ -374,7 +374,7 @@ class ShenandoahHeap : public CollectedHeap {
   void update_heap_region_states(bool concurrent);
   void rebuild_free_set(bool concurrent);
 
-  void rendezvous_threads();
+  void rendezvous_threads(const char* name);
   void recycle_trash();
 public:
   void notify_gc_progress()    { _progress_last_gc.set();   }

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

@@ -171,7 +171,7 @@ void ShenandoahUnload::unload() {
   // Make sure stale metadata and nmethods are no longer observable
   {
     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_rendezvous);
-    heap->rendezvous_threads();
+    heap->rendezvous_threads("Shenandoah Class Unloading");
   }
 
   // Purge stale metadata and nmethods that were unlinked