--- a/hotspot/src/share/vm/gc/g1/concurrentMarkThread.cpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/concurrentMarkThread.cpp	Thu Mar 17 11:18:52 2016 -0700
@@ -98,11 +98,11 @@
   G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
      GCTraceConcTimeImpl<LogLevel::Info,  LogTag::_gc, LogTag::_marking>(title),
      _cm(cm) {
-    _cm->register_concurrent_phase_start(title);
+    _cm->gc_timer_cm()->register_gc_concurrent_start(title);
   }
 
   ~G1ConcPhaseTimer() {
-    _cm->register_concurrent_phase_end();
+    _cm->gc_timer_cm()->register_gc_concurrent_end();
   }
 };
 
@@ -119,6 +119,10 @@
       break;
     }
 
+    GCIdMark gc_id_mark;
+
+    cm()->concurrent_cycle_start();
+
     assert(GCId::current() != GCId::undefined(), "GC id should have been set up by the initial mark GC.");
 
     GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
@@ -279,7 +283,8 @@
     {
       SuspendibleThreadSetJoiner sts_join;
       g1h->increment_old_marking_cycles_completed(true /* concurrent */);
-      g1h->register_concurrent_cycle_end();
+
+      cm()->concurrent_cycle_end();
     }
   }
   _cm->root_regions()->cancel_scan();

--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.cpp	Thu Mar 17 11:18:52 2016 -0700
@@ -1769,15 +1769,12 @@
   _expand_heap_after_alloc_failure(true),
   _old_marking_cycles_started(0),
   _old_marking_cycles_completed(0),
-  _heap_summary_sent(false),
   _in_cset_fast_test(),
   _dirty_cards_region_list(NULL),
   _worker_cset_start_region(NULL),
   _worker_cset_start_region_time_stamp(NULL),
   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
-  _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
-  _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
-  _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
+  _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
 
   _workers = new WorkGang("GC Thread", ParallelGCThreads,
                           /* are_GC_task_threads */true,
@@ -2318,52 +2315,6 @@
   FullGCCount_lock->notify_all();
 }
 
-void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
-  GCIdMarkAndRestore conc_gc_id_mark;
-  collector_state()->set_concurrent_cycle_started(true);
-  _gc_timer_cm->register_gc_start(start_time);
-
-  _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
-  trace_heap_before_gc(_gc_tracer_cm);
-  _cmThread->set_gc_id(GCId::current());
-}
-
-void G1CollectedHeap::register_concurrent_cycle_end() {
-  if (collector_state()->concurrent_cycle_started()) {
-    GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
-    if (_cm->has_aborted()) {
-      _gc_tracer_cm->report_concurrent_mode_failure();
-
-      // ConcurrentGCTimer will be ended as well.
-      _cm->register_concurrent_gc_end_and_stop_timer();
-    } else {
-      _gc_timer_cm->register_gc_end();
-    }
-
-    _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
-
-    // Clear state variables to prepare for the next concurrent cycle.
-    collector_state()->set_concurrent_cycle_started(false);
-    _heap_summary_sent = false;
-  }
-}
-
-void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
-  if (collector_state()->concurrent_cycle_started()) {
-    // This function can be called when:
-    //  the cleanup pause is run
-    //  the concurrent cycle is aborted before the cleanup pause.
-    //  the concurrent cycle is aborted after the cleanup pause,
-    //   but before the concurrent cycle end has been registered.
-    // Make sure that we only send the heap information once.
-    if (!_heap_summary_sent) {
-      GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
-      trace_heap_after_gc(_gc_tracer_cm);
-      _heap_summary_sent = true;
-    }
-  }
-}
-
 void G1CollectedHeap::collect(GCCause::Cause cause) {
   assert_heap_not_locked();
 
@@ -2854,12 +2805,14 @@
 
   size_t eden_used_bytes = young_list->eden_used_bytes();
   size_t survivor_used_bytes = young_list->survivor_used_bytes();
+  size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
 
   size_t eden_capacity_bytes =
     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
 
   VirtualSpaceSummary heap_summary = create_heap_space_summary();
-  return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes, num_regions());
+  return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
+                       eden_capacity_bytes, survivor_used_bytes, num_regions());
 }
 
 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
@@ -2877,7 +2830,6 @@
   gc_tracer->report_metaspace_summary(when, metaspace_summary);
 }
 
-
 G1CollectedHeap* G1CollectedHeap::heap() {
   CollectedHeap* heap = Universe::heap();
   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
@@ -3250,7 +3202,7 @@
       // We are about to start a marking cycle, so we increment the
       // full collection counter.
       increment_old_marking_cycles_started();
-      register_concurrent_cycle_start(_gc_timer_stw->gc_start());
+      _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
     }
 
     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());

--- a/hotspot/src/share/vm/gc/g1/g1CollectedHeap.hpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectedHeap.hpp	Thu Mar 17 11:18:52 2016 -0700
@@ -73,11 +73,9 @@
 class G1ConcurrentMark;
 class ConcurrentMarkThread;
 class ConcurrentG1Refine;
-class ConcurrentGCTimer;
 class GenerationCounters;
 class STWGCTimer;
 class G1NewTracer;
-class G1OldTracer;
 class EvacuationFailedInfo;
 class nmethod;
 class Ticks;
@@ -270,8 +268,6 @@
   // concurrent cycles) we have completed.
   volatile uint _old_marking_cycles_completed;
 
-  bool _heap_summary_sent;
-
   // This is a non-product method that is helpful for testing. It is
   // called at the end of a GC and artificially expands the heap by
   // allocating a number of dead regions. This way we can induce very
@@ -622,10 +618,6 @@
     return _old_marking_cycles_completed;
   }
 
-  void register_concurrent_cycle_start(const Ticks& start_time);
-  void register_concurrent_cycle_end();
-  void trace_heap_after_concurrent_cycle();
-
   G1HRPrinter* hr_printer() { return &_hr_printer; }
 
   // Allocates a new heap region instance.
@@ -900,9 +892,7 @@
   ReferenceProcessor* _ref_processor_stw;
 
   STWGCTimer* _gc_timer_stw;
-  ConcurrentGCTimer* _gc_timer_cm;
 
-  G1OldTracer* _gc_tracer_cm;
   G1NewTracer* _gc_tracer_stw;
 
   // During reference object discovery, the _is_alive_non_header
@@ -1036,9 +1026,6 @@
   // The Concurrent Marking reference processor...
   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
 
-  ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
-  G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
-
   virtual size_t capacity() const;
   virtual size_t used() const;
   // This should be called when we're not holding the heap lock. The

--- a/hotspot/src/share/vm/gc/g1/g1CollectorState.hpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1CollectorState.hpp	Thu Mar 17 11:18:52 2016 -0700
@@ -72,7 +72,6 @@
   bool _in_marking_window;
   bool _in_marking_window_im;
 
-  bool _concurrent_cycle_started;
   bool _full_collection;
 
   public:
@@ -88,7 +87,6 @@
       _mark_in_progress(false),
       _in_marking_window(false),
       _in_marking_window_im(false),
-      _concurrent_cycle_started(false),
       _full_collection(false) {}
 
   // Setters
@@ -101,7 +99,6 @@
   void set_mark_in_progress(bool v) { _mark_in_progress = v; }
   void set_in_marking_window(bool v) { _in_marking_window = v; }
   void set_in_marking_window_im(bool v) { _in_marking_window_im = v; }
-  void set_concurrent_cycle_started(bool v) { _concurrent_cycle_started = v; }
   void set_full_collection(bool v) { _full_collection = v; }
 
   // Getters
@@ -114,7 +111,6 @@
   bool mark_in_progress() const { return _mark_in_progress; }
   bool in_marking_window() const { return _in_marking_window; }
   bool in_marking_window_im() const { return _in_marking_window_im; }
-  bool concurrent_cycle_started() const { return _concurrent_cycle_started; }
   bool full_collection() const { return _full_collection; }
 
   // Composite booleans (clients worry about flickering)

--- a/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.cpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.cpp	Thu Mar 17 11:18:52 2016 -0700
@@ -377,7 +377,8 @@
   _has_aborted(false),
   _restart_for_overflow(false),
   _concurrent_marking_in_progress(false),
-  _concurrent_phase_status(ConcPhaseNotStarted),
+  _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
+  _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
 
   // _verbose_level set below
 
@@ -1011,44 +1012,24 @@
   }
 }
 
-void G1ConcurrentMark::register_concurrent_phase_start(const char* title) {
-  uint old_val = 0;
-  do {
-    old_val = Atomic::cmpxchg(ConcPhaseStarted, &_concurrent_phase_status, ConcPhaseNotStarted);
-  } while (old_val != ConcPhaseNotStarted);
-  _g1h->gc_timer_cm()->register_gc_concurrent_start(title);
+void G1ConcurrentMark::concurrent_cycle_start() {
+  _gc_timer_cm->register_gc_start();
+
+  _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
+
+  _g1h->trace_heap_before_gc(_gc_tracer_cm);
 }
 
-void G1ConcurrentMark::register_concurrent_phase_end_common(bool end_timer) {
-  if (_concurrent_phase_status == ConcPhaseNotStarted) {
-    return;
+void G1ConcurrentMark::concurrent_cycle_end() {
+  _g1h->trace_heap_after_gc(_gc_tracer_cm);
+
+  if (has_aborted()) {
+    _gc_tracer_cm->report_concurrent_mode_failure();
   }
 
-  uint old_val = Atomic::cmpxchg(ConcPhaseStopping, &_concurrent_phase_status, ConcPhaseStarted);
-  if (old_val == ConcPhaseStarted) {
-    _g1h->gc_timer_cm()->register_gc_concurrent_end();
-    // If 'end_timer' is true, we came here to end timer which needs concurrent phase ended.
-    // We need to end it before changing the status to 'ConcPhaseNotStarted' to prevent
-    // starting a new concurrent phase by 'ConcurrentMarkThread'.
-    if (end_timer) {
-      _g1h->gc_timer_cm()->register_gc_end();
-    }
-    old_val = Atomic::cmpxchg(ConcPhaseNotStarted, &_concurrent_phase_status, ConcPhaseStopping);
-    assert(old_val == ConcPhaseStopping, "Should not have changed since we entered this scope.");
-  } else {
-    do {
-      // Let other thread finish changing '_concurrent_phase_status' to 'ConcPhaseNotStarted'.
-      os::naked_short_sleep(1);
-    } while (_concurrent_phase_status != ConcPhaseNotStarted);
-  }
-}
-
-void G1ConcurrentMark::register_concurrent_phase_end() {
-  register_concurrent_phase_end_common(false);
-}
-
-void G1ConcurrentMark::register_concurrent_gc_end_and_stop_timer() {
-  register_concurrent_phase_end_common(true);
+  _gc_timer_cm->register_gc_end();
+
+  _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
 }
 
 void G1ConcurrentMark::mark_from_roots() {
@@ -1127,7 +1108,7 @@
     reset_marking_state();
   } else {
     {
-      GCTraceTime(Debug, gc) trace("Aggregate Data", g1h->gc_timer_cm());
+      GCTraceTime(Debug, gc) trace("Aggregate Data", _gc_timer_cm);
 
       // Aggregate the per-task counting data that we have accumulated
       // while marking.
@@ -1166,7 +1147,7 @@
   g1p->record_concurrent_mark_remark_end();
 
   G1CMIsAliveClosure is_alive(g1h);
-  g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
+  _gc_tracer_cm->report_object_count_after_gc(&is_alive);
 }
 
 // Base class of the closures that finalize and verify the
@@ -1755,8 +1736,6 @@
   // sure we update the old gen/space data.
   g1h->g1mm()->update_sizes();
   g1h->allocation_context_stats().update_after_mark();
-
-  g1h->trace_heap_after_concurrent_cycle();
 }
 
 void G1ConcurrentMark::complete_cleanup() {
@@ -2048,7 +2027,7 @@
   // Inner scope to exclude the cleaning of the string and symbol
   // tables from the displayed time.
   {
-    GCTraceTime(Debug, gc) trace("Reference Processing", g1h->gc_timer_cm());
+    GCTraceTime(Debug, gc) trace("Reference Processing", _gc_timer_cm);
 
     ReferenceProcessor* rp = g1h->ref_processor_cm();
 
@@ -2105,8 +2084,8 @@
                                           &g1_keep_alive,
                                           &g1_drain_mark_stack,
                                           executor,
-                                          g1h->gc_timer_cm());
-    g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
+                                          _gc_timer_cm);
+    _gc_tracer_cm->report_gc_reference_stats(stats);
 
     // The do_oop work routines of the keep_alive and drain_marking_stack
     // oop closures will set the has_overflown flag if we overflow the
@@ -2138,24 +2117,24 @@
 
   // Unload Klasses, String, Symbols, Code Cache, etc.
   {
-    GCTraceTime(Debug, gc) trace("Unloading", g1h->gc_timer_cm());
+    GCTraceTime(Debug, gc) trace("Unloading", _gc_timer_cm);
 
     if (ClassUnloadingWithConcurrentMark) {
       bool purged_classes;
 
       {
-        GCTraceTime(Trace, gc) trace("System Dictionary Unloading", g1h->gc_timer_cm());
+        GCTraceTime(Trace, gc) trace("System Dictionary Unloading", _gc_timer_cm);
         purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
       }
 
       {
-        GCTraceTime(Trace, gc) trace("Parallel Unloading", g1h->gc_timer_cm());
+        GCTraceTime(Trace, gc) trace("Parallel Unloading", _gc_timer_cm);
         weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
       }
     }
 
     if (G1StringDedup::is_enabled()) {
-      GCTraceTime(Trace, gc) trace("String Deduplication Unlink", g1h->gc_timer_cm());
+      GCTraceTime(Trace, gc) trace("String Deduplication Unlink", _gc_timer_cm);
       G1StringDedup::unlink(&g1_is_alive);
     }
   }
@@ -2276,7 +2255,7 @@
   HandleMark   hm;
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 
-  GCTraceTime(Debug, gc) trace("Finalize Marking", g1h->gc_timer_cm());
+  GCTraceTime(Debug, gc) trace("Finalize Marking", _gc_timer_cm);
 
   g1h->ensure_parsability(false);
 
@@ -2632,10 +2611,6 @@
   satb_mq_set.set_active_all_threads(
                                  false, /* new active value */
                                  satb_mq_set.is_active() /* expected_active */);
-
-  _g1h->trace_heap_after_concurrent_cycle();
-
-  _g1h->register_concurrent_cycle_end();
 }
 
 static void print_ms_time_info(const char* prefix, const char* name,

--- a/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.hpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/g1ConcurrentMark.hpp	Thu Mar 17 11:18:52 2016 -0700
@@ -34,6 +34,8 @@
 class G1CMBitMap;
 class G1CMTask;
 class G1ConcurrentMark;
+class ConcurrentGCTimer;
+class G1OldTracer;
 typedef GenericTaskQueue<oop, mtGC>              G1CMTaskQueue;
 typedef GenericTaskQueueSet<G1CMTaskQueue, mtGC> G1CMTaskQueueSet;
 
@@ -349,17 +351,9 @@
   // time of remark.
   volatile bool           _concurrent_marking_in_progress;
 
-  // There would be a race between ConcurrentMarkThread and VMThread(ConcurrentMark::abort())
-  // to call ConcurrentGCTimer::register_gc_concurrent_end().
-  // And this variable is used to keep track of concurrent phase.
-  volatile uint           _concurrent_phase_status;
-  // Concurrent phase is not yet started.
-  static const uint       ConcPhaseNotStarted = 0;
-  // Concurrent phase is started.
-  static const uint       ConcPhaseStarted = 1;
-  // Caller thread of ConcurrentGCTimer::register_gc_concurrent_end() is ending concurrent phase.
-  // So other thread should wait until the status to be changed to ConcPhaseNotStarted.
-  static const uint       ConcPhaseStopping = 2;
+  ConcurrentGCTimer*      _gc_timer_cm;
+
+  G1OldTracer*            _gc_tracer_cm;
 
   // All of these times are in ms
   NumberSeq _init_times;
@@ -530,10 +524,8 @@
     _concurrent_marking_in_progress = false;
   }
 
-  void register_concurrent_phase_start(const char* title);
-  void register_concurrent_phase_end();
-  // Ends both concurrent phase and timer.
-  void register_concurrent_gc_end_and_stop_timer();
+  void concurrent_cycle_start();
+  void concurrent_cycle_end();
 
   void update_accum_task_vtime(int i, double vtime) {
     _accum_task_vtime[i] += vtime;
@@ -735,6 +727,9 @@
     return _completed_initialization;
   }
 
+  ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
+  G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
+
 protected:
   // Clear all the per-task bitmaps and arrays used to store the
   // counting data.

--- a/hotspot/src/share/vm/gc/g1/vm_operations_g1.cpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/g1/vm_operations_g1.cpp	Thu Mar 17 11:18:52 2016 -0700
@@ -216,7 +216,7 @@
   GCIdMark gc_id_mark(_gc_id);
   GCTraceCPUTime tcpu;
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
-  GCTraceTime(Info, gc) t(_printGCMessage, g1h->gc_timer_cm(), GCCause::_no_gc, true);
+  GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
   IsGCActiveMark x;
   _cl->do_void();
 }

--- a/hotspot/src/share/vm/gc/shared/gcTrace.cpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/shared/gcTrace.cpp	Thu Mar 17 11:18:52 2016 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -242,4 +242,12 @@
                                 prediction_active);
 }
 
+void G1OldTracer::report_gc_start_impl(GCCause::Cause cause, const Ticks& timestamp) {
+  _shared_gc_info.set_start_timestamp(timestamp);
+}
+
+void G1OldTracer::set_gc_cause(GCCause::Cause cause) {
+  _shared_gc_info.set_cause(cause);
+}
+
 #endif

--- a/hotspot/src/share/vm/gc/shared/gcTrace.hpp	Tue Mar 08 13:17:30 2016 +0100
+++ b/hotspot/src/share/vm/gc/shared/gcTrace.hpp	Thu Mar 17 11:18:52 2016 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -126,7 +126,7 @@
 
  protected:
   GCTracer(GCName name) : _shared_gc_info(name) {}
-  void report_gc_start_impl(GCCause::Cause cause, const Ticks& timestamp);
+  virtual void report_gc_start_impl(GCCause::Cause cause, const Ticks& timestamp);
   virtual void report_gc_end_impl(const Ticks& timestamp, TimePartitions* time_partitions);
 
  private:
@@ -297,8 +297,11 @@
 };
 
 class G1OldTracer : public OldGCTracer {
+ protected:
+  void report_gc_start_impl(GCCause::Cause cause, const Ticks& timestamp);
  public:
   G1OldTracer() : OldGCTracer(G1Old) {}
+  void set_gc_cause(GCCause::Cause cause);
 };
 
 #endif // SHARE_VM_GC_SHARED_GCTRACE_HPP