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/*
* Copyright (c) 2021, 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
* @bug 8268347
* @summary Nested locks optimization may create unbalanced monitor enter/exit code
*
* @run main/othervm -XX:-BackgroundCompilation
* -XX:CompileCommand=dontinline,TestNestedLocksElimination::foo
* -XX:CompileCommand=dontinline,TestNestedLocksElimination::getNext
* -XX:CompileCommand=dontinline,TestNestedLocksElimination::getHolder
* TestNestedLocksElimination
*/
import java.util.LinkedList;
public class TestNestedLocksElimination {
private LinkedList<char[]> buffers = new LinkedList<>();
private boolean complete = false;
private int bufferSize;
void foo(char[] ca) {
// Don't inline dummy method
}
// Don't inline
char[] getNext(int length, int count) {
if (this.buffers.isEmpty()) {
return new char[100];
}
char[] b = (char[]) this.buffers.getFirst();
if (count >= 100) {
this.complete = true;
this.buffers.clear(); // empty
}
return b;
}
synchronized boolean isComplete() {
return this.complete;
}
synchronized boolean availableSegment() {
return (buffers.isEmpty() == false);
}
// Don't inline
TestNestedLocksElimination getHolder(TestNestedLocksElimination s1, TestNestedLocksElimination s2, int count) {
return (count & 7) == 0 ? s2 : s1;
}
int test(TestNestedLocksElimination s1, TestNestedLocksElimination s2, int maxToSend) {
boolean isComplete = true;
boolean availableSegment = false;
int size = 0;
int count = 0;
do {
TestNestedLocksElimination s = getHolder(s1, s2, count++);
synchronized(s) {
isComplete = s.isComplete();
availableSegment = s.availableSegment();
}
synchronized (this) {
size = 0;
while (size < maxToSend) {
char[] b = null;
// This is outer Lock region for object 's'.
// Locks from following inlined methods are "nested"
// because they reference the same object.
synchronized(s) {
b = s.getNext(maxToSend - size, count);
// The next is bi-morphic call with both calls inlined.
// But one is synchronized and the other is not.
// Class check for bi-morphic call is loop invariant
// and will trigger loop unswitching.
// Loop unswitching will create two versions of loop
// with gollowing calls inlinined in both versions.
isComplete = s.isComplete();
// The next synchronized method availableSegment() is
// inlined and its Lock will be "coarsened" with Unlock
// in version of loop with inlined synchronized method
// isComplete().
// Nested Lock Optimization will mark only this Unlock
// as nested (as part of "nested" pair lock/unlock).
// Locks elimination will remove "coarsened" Lock from
// availableSegment() method leaving unmatched unlock.
availableSegment = s.availableSegment();
}
foo(b);
size += b.length;
}
}
} while (availableSegment == true || isComplete == false);
return size;
}
public static void main(String[] args) {
int count = 0;
int n = 0;
TestNestedLocksElimination t = new TestNestedLocksElimination();
TestNestedLocksElimination s1 = new TestNestedLocksElimination();
TestNestedLocksElimination s2 = new TestNestedLocksEliminationSub();
char[] c = new char[100];
while (n++ < 20_000) {
s1.buffers.add(c);
s2.buffers.add(c);
count += t.test(s1, s2, 10000);
}
System.out.println(" count: " + count);
}
}
class TestNestedLocksEliminationSub extends TestNestedLocksElimination {
public boolean isComplete() {
return true;
}
}
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