diff -r 1258121876f8 -r 8e875c964f41 src/share/vm/jfr/leakprofiler/sampling/objectSampler.hpp
--- a/src/share/vm/jfr/leakprofiler/sampling/objectSampler.hpp	Fri Sep 27 13:23:32 2019 +0800
+++ b/src/share/vm/jfr/leakprofiler/sampling/objectSampler.hpp	Wed Oct 09 16:11:58 2019 +0800
@@ -28,7 +28,10 @@
 #include "memory/allocation.hpp"
 #include "jfr/utilities/jfrTime.hpp"
 
+typedef u8 traceid;
+
 class BoolObjectClosure;
+class JfrStackTrace;
 class OopClosure;
 class ObjectSample;
 class ObjectSampler;
@@ -40,11 +43,13 @@
 // making sure the samples are evenly distributed as
 // new entries are added and removed.
 class ObjectSampler : public CHeapObj<mtTracing> {
+  friend class EventEmitter;
+  friend class JfrRecorderService;
   friend class LeakProfiler;
-  friend class ObjectSampleCheckpoint;
   friend class StartOperation;
   friend class StopOperation;
-  friend class EmitEventOperation;
+  friend class ObjectSampleCheckpoint;
+  friend class WriteObjectSampleStacktrace;
  private:
   SamplePriorityQueue* _priority_queue;
   SampleList* _list;
@@ -52,20 +57,33 @@
   size_t _total_allocated;
   size_t _threshold;
   size_t _size;
-  volatile int _tryLock;
   bool _dead_samples;
 
+  // Lifecycle
   explicit ObjectSampler(size_t size);
   ~ObjectSampler();
+  static bool create(size_t size);
+  static bool is_created();
+  static ObjectSampler* sampler();
+  static void destroy();
 
-  void add(HeapWord* object, size_t size, JavaThread* thread);
+  // For operations that require exclusive access (non-safepoint)
+  static ObjectSampler* acquire();
+  static void release();
+
+  // Stacktrace
+  static void fill_stacktrace(JfrStackTrace* stacktrace, JavaThread* thread);
+  traceid stacktrace_id(const JfrStackTrace* stacktrace, JavaThread* thread);
+
+  // Sampling
+  static void sample(HeapWord* object, size_t size, JavaThread* thread);
+  void add(HeapWord* object, size_t size, traceid thread_id, JfrStackTrace* stacktrace, JavaThread* thread);
+  void scavenge();
   void remove_dead(ObjectSample* sample);
-  void scavenge();
 
   // Called by GC
-  void oops_do(BoolObjectClosure* is_alive, OopClosure* f);
+  static void oops_do(BoolObjectClosure* is_alive, OopClosure* f);
 
- public:
   const ObjectSample* item_at(int index) const;
   ObjectSample* item_at(int index);
   int item_count() const;