--- a/jaxp/src/java.xml/share/classes/com/sun/org/apache/xalan/internal/xsltc/compiler/Stylesheet.java	Thu Oct 20 18:38:09 2016 +0000
+++ b/jaxp/src/java.xml/share/classes/com/sun/org/apache/xalan/internal/xsltc/compiler/Stylesheet.java	Fri Oct 21 02:53:22 2016 +0300
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2016, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -31,6 +31,7 @@
 import com.sun.org.apache.bcel.internal.generic.GETSTATIC;
 import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
 import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;
+import com.sun.org.apache.bcel.internal.generic.INVOKESTATIC;
 import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;
 import com.sun.org.apache.bcel.internal.generic.ISTORE;
 import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
@@ -1252,6 +1253,10 @@
                                 classGen.getConstantPool());
         transf.addException("com.sun.org.apache.xalan.internal.xsltc.TransletException");
 
+        // call resetPrefixIndex at the beginning of transform
+        final int check = cpg.addMethodref(BASIS_LIBRARY_CLASS, "resetPrefixIndex", "()V");
+        il.append(new INVOKESTATIC(check));
+
         // Define and initialize current with the root node
         final LocalVariableGen current =
             transf.addLocalVariable("current",

--- a/jaxp/src/java.xml/share/classes/com/sun/org/apache/xalan/internal/xsltc/runtime/BasisLibrary.java	Thu Oct 20 18:38:09 2016 +0000
+++ b/jaxp/src/java.xml/share/classes/com/sun/org/apache/xalan/internal/xsltc/runtime/BasisLibrary.java	Fri Oct 21 02:53:22 2016 +0300
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2016, Oracle and/or its affiliates. All rights reserved.
  */
 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -31,6 +31,7 @@
 import java.text.NumberFormat;
 import java.util.Locale;
 import java.util.ResourceBundle;
+import java.util.concurrent.atomic.AtomicInteger;
 import javax.xml.transform.dom.DOMSource;
 
 import com.sun.org.apache.xalan.internal.xsltc.DOM;
@@ -1533,16 +1534,25 @@
     }
 
     /**
-     * This function is used in the execution of xsl:element
+     * These functions are used in the execution of xsl:element to generate
+     * and reset namespace prefix index local to current transformation process
      */
-    private static int prefixIndex = 0;
-
     public static String generatePrefix() {
-        synchronized (BasisLibrary.class) {
-            return ("ns" + prefixIndex++);
-        }
+        return ("ns" + threadLocalPrefixIndex.get().getAndIncrement());
+    }
+
+    public static void resetPrefixIndex() {
+        threadLocalPrefixIndex.get().set(0);
     }
 
+    private static final ThreadLocal<AtomicInteger> threadLocalPrefixIndex =
+        new ThreadLocal<AtomicInteger>() {
+            @Override
+            protected AtomicInteger initialValue() {
+                return new AtomicInteger();
+            }
+        };
+
     public static final String RUN_TIME_INTERNAL_ERR =
                                            "RUN_TIME_INTERNAL_ERR";
     public static final String RUN_TIME_COPY_ERR =

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jaxp/test/javax/xml/jaxp/unittest/transform/NamespacePrefixTest.java	Fri Oct 21 02:53:22 2016 +0300
@@ -0,0 +1,193 @@
+/*
+ * Copyright (c) 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
+ * 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.
+ */
+
+package transform;
+
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import javax.xml.transform.Source;
+import javax.xml.transform.Templates;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.stream.StreamResult;
+import javax.xml.transform.stream.StreamSource;
+
+import org.testng.annotations.Test;
+import static org.testng.Assert.assertTrue;
+import static jaxp.library.JAXPTestUtilities.runWithAllPerm;
+
+/*
+ * @test
+ * @bug 8167179
+ * @library /javax/xml/jaxp/libs
+ * @run testng/othervm -DrunSecMngr=true transform.NamespacePrefixTest
+ * @run testng/othervm transform.NamespacePrefixTest
+ * @summary This class tests the generation of namespace prefixes
+ */
+public class NamespacePrefixTest {
+
+    @Test
+    public void testReuseTemplates() throws Exception {
+        final TransformerFactory tf = TransformerFactory.newInstance();
+        final Source xslsrc = new StreamSource(new StringReader(XSL));
+        final Templates tmpl = tf.newTemplates(xslsrc);
+        for (int i = 0; i < TRANSF_COUNT; i++) {
+            checkResult(doTransformation(tmpl.newTransformer()));
+        }
+    }
+
+    @Test
+    public void testReuseTransformer() throws Exception {
+        final TransformerFactory tf = TransformerFactory.newInstance();
+        final Source xslsrc = new StreamSource(new StringReader(XSL));
+        final Transformer t = tf.newTransformer(xslsrc);
+        for (int i = 0; i < TRANSF_COUNT; i++) {
+            checkResult(doTransformation(t));
+        }
+    }
+
+    @Test
+    public void testConcurrentTransformations() throws Exception {
+        final TransformerFactory tf = TransformerFactory.newInstance();
+        final Source xslsrc = new StreamSource(new StringReader(XSL));
+        final Templates tmpl = tf.newTemplates(xslsrc);
+        concurrentTestPassed.set(true);
+
+        // Execute multiple TestWorker tasks
+        for (int id = 0; id < THREADS_COUNT; id++) {
+            EXECUTOR.execute(new TransformerThread(tmpl.newTransformer(), id));
+        }
+        // Initiate shutdown of previously submitted task
+        runWithAllPerm(EXECUTOR::shutdown);
+        // Wait for termination of submitted tasks
+        if (!EXECUTOR.awaitTermination(THREADS_COUNT, TimeUnit.SECONDS)) {
+            // If not all tasks terminates during the time out force them to shutdown
+            runWithAllPerm(EXECUTOR::shutdownNow);
+        }
+        // Check if all transformation threads generated the correct namespace prefix
+        assertTrue(concurrentTestPassed.get());
+    }
+
+    // Do one transformation with the provided transformer
+    private static String doTransformation(Transformer t) throws Exception {
+        StringWriter resWriter = new StringWriter();
+        Source xmlSrc = new StreamSource(new StringReader(XML));
+        t.transform(xmlSrc, new StreamResult(resWriter));
+        return resWriter.toString();
+    }
+
+    // Check if the transformation result string contains the
+    // element with the exact namespace prefix generated.
+    private static void checkResult(String result) {
+        // Check prefix of 'Element2' element, it should always be the same
+        assertTrue(result.contains(EXPECTED_CONTENT));
+    }
+
+    // Check if the transformation result string contains the element with
+    // the exact namespace prefix generated by current thread.
+    // If the expected prefix is not found and there was no failures observed by
+    // other test threads then mark concurrent test as failed.
+    private static void checkThreadResult(String result, int id) {
+        boolean res = result.contains(EXPECTED_CONTENT);
+        System.out.printf("%d: transformation result: %s%n", id, res ? "Pass" : "Fail");
+        if (!res) {
+            System.out.printf("%d result:%s%n", id, result);
+        }
+        concurrentTestPassed.compareAndSet(true, res);
+    }
+
+    // TransformerThread task that does the transformation similar
+    // to testReuseTransformer test method
+    private class TransformerThread implements Runnable {
+
+        private final Transformer transformer;
+        private final int id;
+
+        TransformerThread(Transformer transformer, int id) {
+            this.transformer = transformer;
+            this.id = id;
+        }
+
+        @Override
+        public void run() {
+            try {
+                System.out.printf("%d: waiting for barrier%n", id);
+                //Synchronize startup of all tasks
+                BARRIER.await();
+                System.out.printf("%d: starting transformation%n", id);
+                checkThreadResult(doTransformation(transformer), id);
+            } catch (Exception ex) {
+                throw new RuntimeException("TransformerThread " + id + " failed", ex);
+            }
+        }
+    }
+
+    // Number of subsequent transformations
+    private static final int TRANSF_COUNT = 10;
+
+    // Number of transformer threads running concurently
+    private static final int THREADS_COUNT = 10;
+
+    // Variable for storing the concurrent transformation test result. It is
+    // updated by transformer threads
+    private static final AtomicBoolean concurrentTestPassed = new AtomicBoolean(true);
+
+    // Cyclic barrier for threads startup synchronization
+    private static final CyclicBarrier BARRIER = new CyclicBarrier(THREADS_COUNT);
+
+    // Thread pool
+    private static final ExecutorService EXECUTOR = Executors.newCachedThreadPool();
+
+    // XSL that transforms XML and produces unique namespace prefixes for each element
+    private final static String XSL = "<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\">\n"
+            + " <xsl:template match=\"node()|@*\" priority=\"1\">\n"
+            + "     <xsl:copy>\n"
+            + "       <xsl:apply-templates select=\"node()|@*\"/>\n"
+            + "     </xsl:copy>\n"
+            + " </xsl:template>\n"
+            + " <xsl:template match=\"*\" priority=\"2\">\n"
+            + "  <xsl:element name=\"{name()}\" namespace=\"{namespace-uri()}\">\n"
+            + "   <xsl:apply-templates select=\"node()|@*\"/>\n"
+            + "  </xsl:element>\n"
+            + " </xsl:template>\n"
+            + "</xsl:stylesheet>";
+
+    // Simple XML content with root and two child elements
+    private final static String XML = "<TestRoot xmlns=\"test.xmlns\">\n"
+            + "  <Element1 xmlns=\"test.xmlns\">\n"
+            + "  </Element1>\n"
+            + "  <Element2 xmlns=\"test.xmlns\">\n"
+            + "  </Element2>\n"
+            + "</TestRoot>";
+
+    // With thread local namespace prefix index each transformation result should
+    // be the same and contain the same prefix for Element2
+    private final static String EXPECTED_CONTENT = "</ns2:Element2>";
+
+}