--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Fri Nov 28 09:33:48 2014 +0100
@@ -2257,6 +2257,7 @@
     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
     case GCCause::_g1_humongous_allocation: return true;
     case GCCause::_update_allocation_context_stats_inc: return true;
+    case GCCause::_wb_conc_mark:            return true;
     default:                                return false;
   }
 }

--- a/hotspot/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp	Fri Nov 28 09:33:48 2014 +0100
@@ -92,12 +92,8 @@
 
 void VM_G1IncCollectionPause::doit() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
-  assert(!_should_initiate_conc_mark ||
-  ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
-   (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
-    _gc_cause == GCCause::_g1_humongous_allocation ||
-    _gc_cause == GCCause::_update_allocation_context_stats_inc),
-      "only a GC locker, a System.gc(), stats update or a hum allocation induced GC should start a cycle");
+  assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),
+      "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");
 
   if (_word_size > 0) {
     // An allocation has been requested. So, try to do that first.

--- a/hotspot/src/share/vm/gc_interface/gcCause.cpp	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/src/share/vm/gc_interface/gcCause.cpp	Fri Nov 28 09:33:48 2014 +0100
@@ -54,6 +54,9 @@
     case _wb_young_gc:
       return "WhiteBox Initiated Young GC";
 
+    case _wb_conc_mark:
+      return "WhiteBox Initiated Concurrent Mark";
+
     case _update_allocation_context_stats_inc:
     case _update_allocation_context_stats_full:
       return "Update Allocation Context Stats";

--- a/hotspot/src/share/vm/gc_interface/gcCause.hpp	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/src/share/vm/gc_interface/gcCause.hpp	Fri Nov 28 09:33:48 2014 +0100
@@ -47,6 +47,7 @@
     _heap_inspection,
     _heap_dump,
     _wb_young_gc,
+    _wb_conc_mark,
     _update_allocation_context_stats_inc,
     _update_allocation_context_stats_full,
 

--- a/hotspot/src/share/vm/prims/whitebox.cpp	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/src/share/vm/prims/whitebox.cpp	Fri Nov 28 09:33:48 2014 +0100
@@ -49,6 +49,7 @@
 #if INCLUDE_ALL_GCS
 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
 #include "gc_implementation/g1/concurrentMark.hpp"
+#include "gc_implementation/g1/concurrentMarkThread.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/heapRegionRemSet.hpp"
 #endif // INCLUDE_ALL_GCS
@@ -266,8 +267,16 @@
 
 WB_ENTRY(jboolean, WB_G1InConcurrentMark(JNIEnv* env, jobject o))
   G1CollectedHeap* g1 = G1CollectedHeap::heap();
-  ConcurrentMark* cm = g1->concurrent_mark();
-  return cm->concurrent_marking_in_progress();
+  return g1->concurrent_mark()->cmThread()->during_cycle();
+WB_END
+
+WB_ENTRY(jboolean, WB_G1StartMarkCycle(JNIEnv* env, jobject o))
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+  if (!g1h->concurrent_mark()->cmThread()->during_cycle()) {
+    g1h->collect(GCCause::_wb_conc_mark);
+    return true;
+  }
+  return false;
 WB_END
 
 WB_ENTRY(jint, WB_G1RegionSize(JNIEnv* env, jobject o))
@@ -1106,6 +1115,7 @@
   {CC"g1IsHumongous",      CC"(Ljava/lang/Object;)Z", (void*)&WB_G1IsHumongous     },
   {CC"g1NumFreeRegions",   CC"()J",                   (void*)&WB_G1NumFreeRegions  },
   {CC"g1RegionSize",       CC"()I",                   (void*)&WB_G1RegionSize      },
+  {CC"g1StartConcMarkCycle",       CC"()Z",           (void*)&WB_G1StartMarkCycle  },
 #endif // INCLUDE_ALL_GCS
 #if INCLUDE_NMT
   {CC"NMTMalloc",           CC"(J)J",                 (void*)&WB_NMTMalloc          },

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/gc/whitebox/TestConcMarkCycleWB.java	Fri Nov 28 09:33:48 2014 +0100
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2014, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test TestConMarkCycleWB
+ * @bug 8065579
+ * @requires vm.gc=="null" | vm.gc=="G1"
+ * @library /testlibrary /testlibrary/whitebox
+ * @build ClassFileInstaller com.oracle.java.testlibrary.* sun.hotspot.WhiteBox TestConcMarkCycleWB
+ * @run main ClassFileInstaller sun.hotspot.WhiteBox
+ *                              sun.hotspot.WhiteBox$WhiteBoxPermission
+ * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -XX:+UseG1GC TestConcMarkCycleWB
+ * @summary Verifies that ConcurrentMarking-related WB works properly
+ */
+import static com.oracle.java.testlibrary.Asserts.assertFalse;
+import static com.oracle.java.testlibrary.Asserts.assertTrue;
+import sun.hotspot.WhiteBox;
+
+public class TestConcMarkCycleWB {
+
+    public static void main(String[] args) throws Exception {
+        WhiteBox wb = WhiteBox.getWhiteBox();
+
+        wb.youngGC();
+        assertTrue(wb.g1StartConcMarkCycle());
+        while (wb.g1InConcurrentMark()) {
+            Thread.sleep(5);
+        }
+
+        wb.fullGC();
+        assertTrue(wb.g1StartConcMarkCycle());
+        while (wb.g1InConcurrentMark()) {
+            Thread.sleep(5);
+        }
+        assertTrue(wb.g1StartConcMarkCycle());
+    }
+}

--- a/hotspot/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java	Thu Nov 27 21:02:13 2014 +0100
+++ b/hotspot/test/testlibrary/whitebox/sun/hotspot/WhiteBox.java	Fri Nov 28 09:33:48 2014 +0100
@@ -162,12 +162,16 @@
   public native long incMetaspaceCapacityUntilGC(long increment);
   public native long metaspaceCapacityUntilGC();
 
-  // force Young GC
+  // Force Young GC
   public native void youngGC();
 
-  // force Full GC
+  // Force Full GC
   public native void fullGC();
 
+  // Method tries to start concurrent mark cycle.
+  // It returns false if CM Thread is always in concurrent cycle.
+  public native boolean g1StartConcMarkCycle();
+
   // Tests on ReservedSpace/VirtualSpace classes
   public native int stressVirtualSpaceResize(long reservedSpaceSize, long magnitude, long iterations);
   public native void runMemoryUnitTests();