# HG changeset patch

# User thartmann

# Date 1468206230 -3600

#      Mon Jul 11 04:03:50 2016 +0100

# Node ID 7c89f7f3f2c57d64970cc2ae3a81d24765830118

# Parent  4b40867e627dd9043bc67a4795caa9834ef69478

8159244, PR3074: Partially initialized string object created by C2's string concat optimization may escape

Summary: Emit release barrier after String creation to prevent partially initialized object from escaping.

Reviewed-by: kvn

diff -r 4b40867e627d -r 7c89f7f3f2c5 src/share/vm/opto/stringopts.cpp

--- openjdk/hotspot/src/share/vm/opto/stringopts.cpp	Fri Jun 17 11:31:24 2016 +0200

+++ openjdk/hotspot/src/share/vm/opto/stringopts.cpp	Mon Jul 11 04:03:50 2016 +0100

@@ -1,5 +1,5 @@

 /*

- * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.

+ * Copyright (c) 2009, 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

@@ -1640,6 +1640,12 @@

       kit.store_String_length(kit.control(), result, length);

     }

     kit.store_String_value(kit.control(), result, char_array);

+

+    // The value field is final. Emit a barrier here to ensure that the effect

+    // of the initialization is committed to memory before any code publishes

+    // a reference to the newly constructed object (see Parse::do_exits()).

+    assert(AllocateNode::Ideal_allocation(result, _gvn) != NULL, "should be newly allocated");

+    kit.insert_mem_bar(Op_MemBarRelease, result);

   } else {

     result = C->top();

   }

diff -r 4b40867e627d -r 7c89f7f3f2c5 test/compiler/stringopts/TestStringObjectInitialization.java

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000

+++ openjdk/hotspot/test/compiler/stringopts/TestStringObjectInitialization.java	Mon Jul 11 04:03:50 2016 +0100

@@ -0,0 +1,78 @@

+/*

+ * 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.

+ */

+

+

+import java.util.Arrays;

+

+/*

+ * @test

+ * @bug 8159244

+ * @requires vm.gc == "Parallel" | vm.gc == "null"

+ * @summary Verifies that no partially initialized String object escapes from

+ *          C2's String concat optimization in a highly concurrent setting.

+ *          This test triggers the bug in about 1 out of 10 runs.

+ * @compile -XDstringConcat=inline TestStringObjectInitialization.java

+ * @run main/othervm/timeout=300 -XX:+IgnoreUnrecognizedVMOptions -XX:-UseCompressedOops -XX:-CompactStrings

+ *                               -XX:-UseG1GC -XX:+UseParallelGC TestStringObjectInitialization

+ */

+public class TestStringObjectInitialization {

+

+    String myString;

+

+    public static void main(String[] args) throws Exception {

+        TestStringObjectInitialization t = new TestStringObjectInitialization();

+        // Create some threads that concurrently update 'myString'

+        for (int i = 0; i < 100; ++i) {

+            (new Thread(new Runner(t))).start();

+        }

+        Thread last = new Thread(new Runner(t));

+        last.start();

+        last.join();

+    }

+

+    private void add(String message) {

+        // String escapes to other threads here

+        myString += message;

+    }

+

+    public void run(String s, String[] sArray) {

+        // Trigger C2's string concatenation optimization

+        add(s + Arrays.toString(sArray) + " const ");

+    }

+}

+

+class Runner implements Runnable {

+    private TestStringObjectInitialization test;

+

+    public Runner(TestStringObjectInitialization t) {

+        test = t;

+    }

+

+    public void run(){

+        String[] array = {"a", "b", "c"};

+        for (int i = 0; i < 10000; ++i) {

+            test.run("a", array);

+        }

+    }

+}

+