--- a/hotspot/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Tue Sep 24 14:46:29 2013 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Mon Sep 30 12:43:59 2013 +0200
@@ -83,7 +83,9 @@
   for (uint i = 0; i < n_workers(); i++) {
     _cset_rs_update_cl[i] = NULL;
   }
-  _prev_period_summary.initialize(this, n_workers());
+  if (G1SummarizeRSetStats) {
+    _prev_period_summary.initialize(this);
+  }
 }
 
 G1RemSet::~G1RemSet() {
@@ -728,7 +730,7 @@
 
 void G1RemSet::print_periodic_summary_info(const char* header) {
   G1RemSetSummary current;
-  current.initialize(this, n_workers());
+  current.initialize(this);
 
   _prev_period_summary.subtract_from(&current);
   print_summary_info(&_prev_period_summary, header);
@@ -738,7 +740,7 @@
 
 void G1RemSet::print_summary_info() {
   G1RemSetSummary current;
-  current.initialize(this, n_workers());
+  current.initialize(this);
 
   print_summary_info(&current, " Cumulative RS summary");
 }

--- a/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.cpp	Tue Sep 24 14:46:29 2013 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.cpp	Mon Sep 30 12:43:59 2013 +0200
@@ -77,12 +77,12 @@
   return _rs_threads_vtimes[thread];
 }
 
-void G1RemSetSummary::initialize(G1RemSet* remset, uint num_workers) {
+void G1RemSetSummary::initialize(G1RemSet* remset) {
   assert(_rs_threads_vtimes == NULL, "just checking");
   assert(remset != NULL, "just checking");
 
   _remset = remset;
-  _num_vtimes = num_workers;
+  _num_vtimes = ConcurrentG1Refine::thread_num();
   _rs_threads_vtimes = NEW_C_HEAP_ARRAY(double, _num_vtimes, mtGC);
   memset(_rs_threads_vtimes, 0, sizeof(double) * _num_vtimes);
 

--- a/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.hpp	Tue Sep 24 14:46:29 2013 +0200
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1RemSetSummary.hpp	Mon Sep 30 12:43:59 2013 +0200
@@ -84,7 +84,7 @@
   void subtract_from(G1RemSetSummary* other);
 
   // initialize and get the first sampling
-  void initialize(G1RemSet* remset, uint num_workers);
+  void initialize(G1RemSet* remset);
 
   void print_on(outputStream* out);
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/gc/g1/TestSummarizeRSetStatsThreads.java	Mon Sep 30 12:43:59 2013 +0200
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2013, 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 TestSummarizeRSetStatsThreads
+ * @bug 8025441
+ * @summary Ensure that various values of worker threads/concurrent
+ * refinement threads do not crash the VM.
+ * @key gc
+ * @library /testlibrary
+ */
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import com.oracle.java.testlibrary.ProcessTools;
+import com.oracle.java.testlibrary.OutputAnalyzer;
+
+public class TestSummarizeRSetStatsThreads {
+
+  private static void runTest(int refinementThreads, int workerThreads) throws Exception {
+    ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-XX:+UseG1GC",
+                                                              "-XX:+UnlockDiagnosticVMOptions",
+                                                              "-XX:+G1SummarizeRSetStats",
+                                                              "-XX:G1ConcRefinementThreads=" + refinementThreads,
+                                                              "-XX:ParallelGCThreads=" + workerThreads,
+                                                              "-version");
+
+    OutputAnalyzer output = new OutputAnalyzer(pb.start());
+
+    // check output to contain the string "Concurrent RS threads times (s)" followed by
+    // the correct number of values in the next line.
+
+    // a zero in refinement thread numbers indicates that the value in ParallelGCThreads should be used.
+    // Additionally use at least one thread.
+    int expectedNumRefinementThreads = refinementThreads == 0 ? workerThreads : refinementThreads;
+    expectedNumRefinementThreads = Math.max(1, expectedNumRefinementThreads);
+    // create the pattern made up of n copies of a floating point number pattern
+    String numberPattern = String.format("%0" + expectedNumRefinementThreads + "d", 0)
+      .replace("0", "\\s+\\d+\\.\\d+");
+    String pattern = "Concurrent RS threads times \\(s\\)$" + numberPattern + "$";
+    Matcher m = Pattern.compile(pattern, Pattern.MULTILINE).matcher(output.getStdout());
+
+    if (!m.find()) {
+      throw new Exception("Could not find correct output for concurrent RS threads times in stdout," +
+        " should match the pattern \"" + pattern + "\", but stdout is \n" + output.getStdout());
+    }
+    output.shouldHaveExitValue(0);
+  }
+
+  public static void main(String[] args) throws Exception {
+    if (!TestSummarizeRSetStatsTools.testingG1GC()) {
+      return;
+    }
+    // different valid combinations of number of refinement and gc worker threads
+    runTest(0, 0);
+    runTest(0, 5);
+    runTest(5, 0);
+    runTest(10, 10);
+    runTest(1, 2);
+    runTest(4, 3);
+  }
+}