1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
/*
* Copyright (c) 2004, 2008, 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
* @modules java.base/java.util.concurrent:open
* @bug 4992438 6633113
* @summary Checks that fairness setting is respected.
*/
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
public class Fairness {
private final static VarHandle underlyingTransferQueueAccess;
static {
try {
underlyingTransferQueueAccess =
MethodHandles.privateLookupIn(
SynchronousQueue.class,
MethodHandles.lookup()
).findVarHandle(
SynchronousQueue.class,
"transferer",
Class.forName(SynchronousQueue.class.getName() + "$Transferer")
);
} catch (Exception ex) {
throw new ExceptionInInitializerError(ex);
}
}
private static void testFairness(boolean fair, final SynchronousQueue<Integer> q)
throws Throwable
{
final LinkedTransferQueue<Integer> underlying =
(LinkedTransferQueue<Integer>)underlyingTransferQueueAccess.get(q);
final ReentrantLock lock = new ReentrantLock();
final Condition ready = lock.newCondition();
final int threadCount = 10;
final Throwable[] badness = new Throwable[1];
lock.lock();
for (int i = 0; i < threadCount; i++) {
final Integer I = i;
Thread t = new Thread() { public void run() {
try {
lock.lock();
ready.signal();
lock.unlock();
q.put(I);
} catch (Throwable t) { badness[0] = t; }}};
t.start();
ready.await();
// Wait until previous put:ing thread is provably parked
while (underlying.size() < (i + 1))
Thread.yield();
if (underlying.size() > (i + 1))
throw new Error("Unexpected number of waiting producers: " + i);
}
for (int i = 0; i < threadCount; i++) {
int j = q.take();
// Non-fair queues are lifo in our implementation
if (fair ? j != i : j != threadCount - 1 - i)
throw new Error(String.format("fair=%b i=%d j=%d%n",
fair, i, j));
}
if (badness[0] != null) throw new Error(badness[0]);
}
public static void main(String[] args) throws Throwable {
testFairness(false, new SynchronousQueue<>());
testFairness(false, new SynchronousQueue<>(false));
testFairness(true, new SynchronousQueue<>(true));
}
}
|
