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comparison agent/src/os/win32/Monitor.cpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include <stdio.h>
26 #include <assert.h>
27 #include "Monitor.hpp"
28
29 Monitor::Monitor() {
30 _lock_count = -1; // No threads have entered the critical section
31 _owner = NULL;
32 _lock_event = CreateEvent(NULL, false, false, NULL);
33 _wait_event = CreateEvent(NULL, true, false, NULL);
34 _counter = 0;
35 _tickets = 0;
36 _waiters = 0;
37 }
38
39 Monitor::~Monitor() {
40 assert(_owner == NULL); // Otherwise, owned monitor being deleted
41 assert(_lock_count == -1); // Otherwise, monitor being deleted with non -1 lock count
42 CloseHandle(_lock_event);
43 CloseHandle(_wait_event);
44 }
45
46 void
47 Monitor::lock() {
48 if (InterlockedIncrement(&_lock_count) == 0) {
49 // Success, we now own the lock
50 } else {
51 DWORD dwRet = WaitForSingleObject((HANDLE)_lock_event, INFINITE);
52 assert(dwRet == WAIT_OBJECT_0); // Unexpected return value from WaitForSingleObject
53 }
54 assert(owner() == NULL); // Otherwise, lock count and owner are inconsistent
55 setOwner(GetCurrentThread());
56 }
57
58 void
59 Monitor::unlock() {
60 setOwner(NULL);
61 if (InterlockedDecrement(&_lock_count) >= 0) {
62 // Wake a waiting thread up
63 DWORD dwRet = SetEvent(_lock_event);
64 assert(dwRet != 0); // Unexpected return value from SetEvent
65 }
66 }
67
68 bool
69 Monitor::wait(long timeout) {
70 assert(owner() != NULL);
71 assert(owner() == GetCurrentThread());
72
73 // 0 means forever. Convert to Windows specific code.
74 DWORD timeout_value = (timeout == 0) ? INFINITE : timeout;
75 DWORD which;
76
77 long c = _counter;
78 bool retry = false;
79
80 _waiters++;
81 // Loop until condition variable is signaled. The event object is
82 // set whenever the condition variable is signaled, and tickets will
83 // reflect the number of threads which have been notified. The counter
84 // field is used to make sure we don't respond to notifications that
85 // have occurred *before* we started waiting, and is incremented each
86 // time the condition variable is signaled.
87
88 while (true) {
89
90 // Leave critical region
91 unlock();
92
93 // If this is a retry, let other low-priority threads have a chance
94 // to run. Make sure that we sleep outside of the critical section.
95 if (retry) {
96 Sleep(1);
97 } else {
98 retry = true;
99 }
100
101 which = WaitForSingleObject(_wait_event, timeout_value);
102 // Enter critical section
103 lock();
104
105 if (_tickets != 0 && _counter != c) break;
106
107 if (which == WAIT_TIMEOUT) {
108 --_waiters;
109 return true;
110 }
111 }
112 _waiters--;
113
114 // If this was the last thread to be notified, then we need to reset
115 // the event object.
116 if (--_tickets == 0) {
117 ResetEvent(_wait_event);
118 }
119
120 return false;
121 }
122
123 // Notify a single thread waiting on this monitor
124 bool
125 Monitor::notify() {
126 assert(ownedBySelf()); // Otherwise, notify on unknown thread
127
128 if (_waiters > _tickets) {
129 if (!SetEvent(_wait_event)) {
130 return false;
131 }
132 _tickets++;
133 _counter++;
134 }
135
136 return true;
137 }
138
139 // Notify all threads waiting on this monitor
140 bool
141 Monitor::notifyAll() {
142 assert(ownedBySelf()); // Otherwise, notifyAll on unknown thread
143
144 if (_waiters > 0) {
145 if (!SetEvent(_wait_event)) {
146 return false;
147 }
148 _tickets = _waiters;
149 _counter++;
150 }
151
152 return true;
153 }
154
155 HANDLE
156 Monitor::owner() {
157 return _owner;
158 }
159
160 void
161 Monitor::setOwner(HANDLE owner) {
162 if (owner != NULL) {
163 assert(_owner == NULL); // Setting owner thread of already owned monitor
164 assert(owner == GetCurrentThread()); // Else should not be doing this
165 } else {
166 HANDLE oldOwner = _owner;
167 assert(oldOwner != NULL); // Removing the owner thread of an unowned mutex
168 assert(oldOwner == GetCurrentThread());
169 }
170 _owner = owner;
171 }
172
173 bool
174 Monitor::ownedBySelf() {
175 return (_owner == GetCurrentThread());
176 }