1 /*
2 * Copyright (c) 2004, 2006, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 package sun.jvm.hotspot.runtime;
26
27 import sun.jvm.hotspot.debugger.*;
28 import sun.jvm.hotspot.memory.*;
29 import sun.jvm.hotspot.oops.*;
30 import java.io.*;
31 import java.util.*;
32 import java.util.Map.Entry;
33
34 /** Prints information about Java-level deadlocks in supplied 'tty'. */
35
36 public class DeadlockDetector {
37
38 public static void print(PrintStream tty) {
39 print(tty, true);
40 }
41
42 /** prints zero or more deadlocks into 'tty' taking current
43 snapshot of Java threads and locks */
44 public static void print(PrintStream tty, boolean concurrentLocks) {
45 tty.println("Deadlock Detection:");
46 tty.println();
47
48 int globalDfn = 0, thisDfn;
49 int numberOfDeadlocks = 0;
50 JavaThread currentThread = null, previousThread = null;
51 ObjectMonitor waitingToLockMonitor = null;
52 Oop waitingToLockBlocker = null;
53
54 threads = VM.getVM().getThreads();
55 heap = VM.getVM().getObjectHeap();
56 createThreadTable();
57
58 Iterator i = threadTable.entrySet().iterator();
59 while (i.hasNext()) {
60 Entry e = (Entry)i.next();
61 if (dfn(e) >= 0) {
62 // this thread was already visited
63 continue;
64 }
65
66 thisDfn = globalDfn;
67 JavaThread thread = (JavaThread)e.getKey();
68 previousThread = thread;
69
70 // When there is a deadlock, all the monitors involved in the dependency
71 // cycle must be contended and heavyweight. So we only care about the
72 // heavyweight monitor a thread is waiting to lock.
73 try {
74 waitingToLockMonitor = thread.getCurrentPendingMonitor();
75 } catch (RuntimeException re) {
76 tty.println("This version of HotSpot VM doesn't support deadlock detection.");
77 return;
78 }
79
80 Klass abstractOwnableSyncKlass = null;
81 if (concurrentLocks) {
82 waitingToLockBlocker = thread.getCurrentParkBlocker();
83 SystemDictionary sysDict = VM.getVM().getSystemDictionary();
84 abstractOwnableSyncKlass = sysDict.getAbstractOwnableSynchronizerKlass();
85 }
86
87 while (waitingToLockMonitor != null ||
88 waitingToLockBlocker != null) {
89 if (waitingToLockMonitor != null) {
90 currentThread = threads.owningThreadFromMonitor(waitingToLockMonitor);
91 } else {
92 if (concurrentLocks) {
93 if (waitingToLockBlocker.isA(abstractOwnableSyncKlass)) {
94 Oop threadOop = OopUtilities.abstractOwnableSynchronizerGetOwnerThread(waitingToLockBlocker);
95 if (threadOop != null) {
96 currentThread = OopUtilities.threadOopGetJavaThread(threadOop);
97 }
98 }
99 }
100 }
101 if (currentThread == null) {
102 // No dependency on another thread
103 break;
104 }
105 if (dfn(currentThread) < 0) {
106 // First visit to this thread
107 threadTable.put(currentThread, new Integer(globalDfn++));
108 } else if (dfn(currentThread) < thisDfn) {
109 // Thread already visited, and not on a (new) cycle
110 break;
111 } else if (currentThread == previousThread) {
112 // Self-loop, ignore
113 break;
114 } else {
115 // We have a (new) cycle
116 numberOfDeadlocks ++;
117 printOneDeadlock(tty, currentThread, concurrentLocks);
118 break;
119 }
120 previousThread = currentThread;
121 waitingToLockMonitor = (ObjectMonitor)currentThread.getCurrentPendingMonitor();
122 if (concurrentLocks) {
123 waitingToLockBlocker = currentThread.getCurrentParkBlocker();
124 }
125 }
126 }
127
128 switch (numberOfDeadlocks) {
129 case 0:
130 tty.println("No deadlocks found.");
131 break;
132 case 1:
133 tty.println("Found a total of 1 deadlock.");
134 break;
135 default:
136 tty.println("Found a total of " + numberOfDeadlocks + " deadlocks.");
137 break;
138 }
139 tty.println();
140 }
141
142 //-- Internals only below this point
143 private static Threads threads;
144 private static ObjectHeap heap;
145 private static HashMap threadTable;
146
147 private static void createThreadTable() {
148 threadTable = new HashMap();
149 for (JavaThread cur = threads.first(); cur != null; cur = cur.next()) {
150 // initialize dfn for each thread to -1
151 threadTable.put(cur, new Integer(-1));
152 }
153 }
154
155 private static int dfn(JavaThread thread) {
156 Object obj = threadTable.get(thread);
157 if (obj != null) {
158 return ((Integer)obj).intValue();
159 }
160 return -1;
161 }
162
163 private static int dfn(Entry e) {
164 return ((Integer)e.getValue()).intValue();
165 }
166
167 private static void printOneDeadlock(PrintStream tty, JavaThread thread,
168 boolean concurrentLocks) {
169 tty.println("Found one Java-level deadlock:");
170 tty.println("=============================");
171 ObjectMonitor waitingToLockMonitor = null;
172 Oop waitingToLockBlocker = null;
173 JavaThread currentThread = thread;
174 do {
175 tty.println();
176 tty.println("\"" + currentThread.getThreadName() + "\":");
177 waitingToLockMonitor = currentThread.getCurrentPendingMonitor();
178 if (waitingToLockMonitor != null) {
179 tty.print(" waiting to lock Monitor@" + waitingToLockMonitor.getAddress());
180 OopHandle obj = waitingToLockMonitor.object();
181 Oop oop = heap.newOop(obj);
182 if (obj != null) {
183 tty.print(" (Object@");
184 Oop.printOopAddressOn(oop, tty);
185 tty.print(", a " + oop.getKlass().getName().asString() + ")" );
186 tty.print(",\n which is held by");
187 } else {
188 // No Java object associated - a raw monitor
189 tty.print(" (raw monitor),\n which is held by");
190 }
191 currentThread = threads.owningThreadFromMonitor(waitingToLockMonitor);
192 tty.print(" \"" + currentThread.getThreadName() + "\"");
193 } else if (concurrentLocks) {
194 waitingToLockBlocker = currentThread.getCurrentParkBlocker();
195 tty.print(" waiting for ownable synchronizer ");
196 Oop.printOopAddressOn(waitingToLockBlocker, tty);
197 tty.print(", (a " + waitingToLockBlocker.getKlass().getName().asString() + ")" );
198 Oop threadOop = OopUtilities.abstractOwnableSynchronizerGetOwnerThread(waitingToLockBlocker);
199 currentThread = OopUtilities.threadOopGetJavaThread(threadOop);
200 tty.print(",\n which is held by");
201 tty.print(" \"" + currentThread.getThreadName() + "\"");
202 }
203 } while (!currentThread.equals(thread));
204 tty.println();
205 tty.println();
206 }
207 }