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
|
/*
* Copyright (c) 2007, 2018, 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 nsk.share.locks;
import nsk.share.*;
/*
* DeadlockLocker - class used for deadlock creation
*
* To create deadlock second 'inner' instance of DeadlockLocker is required.
*
* Deadlock creation scenario:
* - object acquires its resource
* - notify 'inner' through Wicket step1 that resource is locked and 'inner' can try to acquire this object's resource
* - wait notification through Wicket step2 from 'inner' that 'inner' acquired its resource
* - call readyWicket.unlock to notify thread waiting deadlock creation
* - try acquire locked inner's resource, at the same time inner trying to acquire locked this object's resource - deadlock is created
*
* Subclasses should implement method doLock() taking in account described scenario.
*
* Objects of DeadlockLocker should not be created directly, to create deadlocked threads use class DeadlockMaker
*/
abstract public class DeadlockLocker {
protected DeadlockLocker inner;
protected Wicket step1;
protected Wicket step2;
// 'readyWicket' is used to notify DeadlockMacker that deadlock is almost created
protected Wicket readyWicket;
public DeadlockLocker(Wicket step1, Wicket step2, Wicket readyWicket) {
this.step1 = step1;
this.step2 = step2;
this.readyWicket = readyWicket;
}
public void setInner(DeadlockLocker inner) {
this.inner = inner;
}
protected void checkInnerLocker() {
if (inner == null) {
throw new IllegalStateException(getClass().getName() + " deadlockLocker's inner locker is null");
}
}
protected abstract void doLock();
abstract public Object getLock();
private int lockCount;
final public void lock() {
// call this method once
if (lockCount++ > 1)
return;
// check that inner locker was set
checkInnerLocker();
doLock();
}
}
|
