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标题: java死锁（Java-level deadlock） [打印本页]

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作者: 钜形不锈钢水箱    时间: 2022-9-16 17:20
标题: java死锁（Java-level deadlock）
java-level deadlock

如下代码可以模拟java死锁。注意：当出现死锁时，应用程序是无响应的。错误信息：
Found one Java-level deadlock:
=============================
"Thread-1":
  waiting to lock monitor 0x000000001c773158 (object 0x000000076bbc06b8, a java.util.concurrent.Concurren
tHashMap),
  which is held by "Thread-0"
"Thread-0":
  waiting to lock monitor 0x000000001c774548 (object 0x000000076bbc06f8, a java.lang.Object),
  which is held by "Thread-1"
 
deadlock demo及deadlock信息

上代码：

1. import java.util.concurrent.ConcurrentHashMap;
2. import static java.util.concurrent.TimeUnit.SECONDS;
4. public class TestDeadlockMain {
6.     private static final ConcurrentHashMap<String, String> concurrentHashMap1 = new ConcurrentHashMap<>(128);
7.     private static final Object concurrentHashMap2 = new Object();
9.     public static void main(String[] args) {
10.         new Thread(() -> {
11.             synchronized (concurrentHashMap1) {
13.                 // 模拟逻辑执行
14.                 try {
15.                     SECONDS.sleep(1L);
16.                 } catch (InterruptedException e) {
17.                     e.printStackTrace();
18.                 }
20.                 synchronized (concurrentHashMap2) {
21.                     // 模拟逻辑执行
22.                     System.out.println("test deadlock");
23.                 }
24.             }
25.         }).start();
26.         new Thread(() -> {
27.             synchronized (concurrentHashMap2) {
28.                 synchronized (concurrentHashMap1) {
29.                     // 模拟逻辑执行
30.                     try {
31.                         SECONDS.sleep(1L);
32.                     } catch (InterruptedException e) {
33.                         e.printStackTrace();
34.                     }
35.                 }
36.             }
37.         }).start();
38.         new Thread(()->{
39.             while (true){
40.                 System.out.println(System.currentTimeMillis());
41.                 try {
42.                     SECONDS.sleep(1);
43.                 } catch (InterruptedException e) {
44.                     e.printStackTrace();
45.                 }
46.             }
47.         }).start();
48.     }
50. }

复制代码

 
 
运行程序，通过控制台日志是无法看到死锁信息的。只能看到第三个线程在间隔1s不停的打日志，却无法看到另外两个线程在干啥。
如果是所调用的程序有用户界面的话，就会看到长时间无响应或超时的现象。
至于这个demo呢，我们可以借助IDEA的Terminal窗口。执行jps -l 命令，找到当前执行的java程序的进程pid。 接下来执行 jstack pid 命令，查看JVM里的线程快照信息。
如下贴出来Terminal窗口的内容：

1. D:\SourceProject\account\target\test-classes\com\emaxcard\jvm>jps -l
2. 24912
3. 21556 org.jetbrains.jps.cmdline.Launcher
4. 28840 com.emaxcard.jvm.TestDeadlockMain
5. 30328 sun.tools.jps.Jps
6. 13644 org.jetbrains.idea.maven.server.RemoteMavenServer
8. D:\SourceProject\account\target\test-classes\com\emaxcard\jvm>jstack 28840
9. 2022-08-24 20:56:11
10. Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.40-b25 mixed mode):
12. "DestroyJavaVM" #14 prio=5 os_prio=0 tid=0x0000000002a58800 nid=0x6bf4 waiting on condition [0x0000000000
13. 000000]
14.    java.lang.Thread.State: RUNNABLE
16. "Thread-1" #13 prio=5 os_prio=0 tid=0x000000001fdba800 nid=0x4f88 waiting for monitor entry [0x0000000020
17. e1f000]
18.    java.lang.Thread.State: BLOCKED (on object monitor)
19.         at com.emaxcard.jvm.TestDeadlockMain.lambda$main$1(TestDeadlockMain.java:41)
20.         - waiting to lock <0x000000076bbc06b8> (a java.util.concurrent.ConcurrentHashMap)
21.         - locked <0x000000076bbc06f8> (a java.lang.Object)
22.         at com.emaxcard.jvm.TestDeadlockMain$$Lambda$2/654845766.run(Unknown Source)
23.         at java.lang.Thread.run(Thread.java:745)
25. "Thread-0" #12 prio=5 os_prio=0 tid=0x000000001fcf8000 nid=0x6ecc waiting for monitor entry [0x0000000020
26. d1e000]
27.    java.lang.Thread.State: BLOCKED (on object monitor)
28.         at com.emaxcard.jvm.TestDeadlockMain.lambda$main$0(TestDeadlockMain.java:33)
29.         - waiting to lock <0x000000076bbc06f8> (a java.lang.Object)
30.         - locked <0x000000076bbc06b8> (a java.util.concurrent.ConcurrentHashMap)
31.         at com.emaxcard.jvm.TestDeadlockMain$$Lambda$1/2101842856.run(Unknown Source)
32.         at java.lang.Thread.run(Thread.java:745)
34. "Service Thread" #11 daemon prio=9 os_prio=0 tid=0x000000001f53d800 nid=0x72d0 runnable [0x00000000000000
35. 00]
36.    java.lang.Thread.State: RUNNABLE
38. "C1 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x000000001f4ea800 nid=0x948 waiting on condition [0
39. x0000000000000000]
40.    java.lang.Thread.State: RUNNABLE
42. "C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000000001f4e8000 nid=0x5ed0 waiting on condition [0
43. x0000000000000000]
44.    java.lang.Thread.State: RUNNABLE
46. "C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000000001f4e3000 nid=0x6130 waiting on condition [0
47. x0000000000000000]
48.    java.lang.Thread.State: RUNNABLE
50. "C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000000001f4e0800 nid=0x6804 waiting on condition [0
51. x0000000000000000]
52.    java.lang.Thread.State: RUNNABLE
54. "Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000000001f4a8000 nid=0x52bc runnable [0x000000001f6
55. 4e000]
56.    java.lang.Thread.State: RUNNABLE
57.         at java.net.SocketInputStream.socketRead0(Native Method)
58.         at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
59.         at java.net.SocketInputStream.read(SocketInputStream.java:170)
60.         at java.net.SocketInputStream.read(SocketInputStream.java:141)
61.         at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
62.         at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
63.         at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
64.         - locked <0x000000076bce5ac8> (a java.io.InputStreamReader)
65.         at java.io.InputStreamReader.read(InputStreamReader.java:184)
66.         at java.io.BufferedReader.fill(BufferedReader.java:161)
67.         at java.io.BufferedReader.readLine(BufferedReader.java:324)
68.         - locked <0x000000076bce5ac8> (a java.io.InputStreamReader)
69.         at java.io.BufferedReader.readLine(BufferedReader.java:389)
70.         at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:61)
72. "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001e7d2000 nid=0x6478 waiting on condition [0x00
73. 00000000000000]
74.    java.lang.Thread.State: RUNNABLE
76. "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001e7d1800 nid=0x5e4c runnable [0x000000000000
77. 0000]
78.    java.lang.Thread.State: RUNNABLE
80. "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000000001c774800 nid=0x5df0 in Object.wait() [0x000000001e73
81. e000]
82.    java.lang.Thread.State: WAITING (on object monitor)
83.         at java.lang.Object.wait(Native Method)
84.         - waiting on <0x000000076b306f58> (a java.lang.ref.ReferenceQueue$Lock)
85.         at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
86.         - locked <0x000000076b306f58> (a java.lang.ref.ReferenceQueue$Lock)
87.         at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
88.         at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
90. "Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x000000001c76e000 nid=0x6828 in Object.wait() [0x000
91. 000001e63f000]
92.    java.lang.Thread.State: WAITING (on object monitor)
93.         at java.lang.Object.wait(Native Method)
94.         - waiting on <0x000000076b306998> (a java.lang.ref.Reference$Lock)
95.         at java.lang.Object.wait(Object.java:502)
96.         at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157)
97.         - locked <0x000000076b306998> (a java.lang.ref.Reference$Lock)
99. "VM Thread" os_prio=2 tid=0x000000001c76a000 nid=0x3384 runnable
101. "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000002a72000 nid=0x6d44 runnable
103. "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000002a73800 nid=0x61c8 runnable
105. "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000002a75000 nid=0x6a00 runnable
107. "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000002a77800 nid=0x5e6c runnable
109. "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x0000000002a7a000 nid=0x480c runnable
111. "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x0000000002a7b000 nid=0x497c runnable
113. "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x0000000002a7e000 nid=0x13f8 runnable
115. "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x0000000002a7f800 nid=0x40b4 runnable
117. "VM Periodic Task Thread" os_prio=2 tid=0x000000001f53e800 nid=0x7314 waiting on condition
119. JNI global references: 330
122. Found one Java-level deadlock:
123. =============================
124. "Thread-1":
125.   waiting to lock monitor 0x000000001c773158 (object 0x000000076bbc06b8, a java.util.concurrent.Concurren
126. tHashMap),
127.   which is held by "Thread-0"
128. "Thread-0":
129.   waiting to lock monitor 0x000000001c774548 (object 0x000000076bbc06f8, a java.lang.Object),
130.   which is held by "Thread-1"
132. Java stack information for the threads listed above:
133. ===================================================
134. "Thread-1":
135.         at com.emaxcard.jvm.TestDeadlockMain.lambda$main$1(TestDeadlockMain.java:41)
136.         - waiting to lock <0x000000076bbc06b8> (a java.util.concurrent.ConcurrentHashMap)
137.         - locked <0x000000076bbc06f8> (a java.lang.Object)
138.         at com.emaxcard.jvm.TestDeadlockMain$$Lambda$2/654845766.run(Unknown Source)
139.         at java.lang.Thread.run(Thread.java:745)
140. "Thread-0":
141.         at com.emaxcard.jvm.TestDeadlockMain.lambda$main$0(TestDeadlockMain.java:33)
142.         - waiting to lock <0x000000076bbc06f8> (a java.lang.Object)
143.         - locked <0x000000076bbc06b8> (a java.util.concurrent.ConcurrentHashMap)
144.         at com.emaxcard.jvm.TestDeadlockMain$$Lambda$1/2101842856.run(Unknown Source)
145.         at java.lang.Thread.run(Thread.java:745)
147. Found 1 deadlock.

复制代码

 
 
jstack简介

• jstack命令用于打印指定Java进程、核心文件或远程调试服务器的Java线程的Java堆栈跟踪信息[1]。
  
• jstack命令可以生成JVM当前时刻的线程快照。线程快照是当前JVM内每一条线程正在执行的方法堆栈的集合，生成线程快照的主要目的是定位线程出现长时间停顿的原因，如线程间死锁、死循环、请求外部资源导致的长时间等待等。
  
• 如果java程序崩溃生成core文件，jstack工具可以用来获得core文件的java stack和native stack的信息，从而可以轻松地知道java程序是如何崩溃和在程序何处发生问题。
  
• 当指定的进程在64位Java虚拟机上运行时，可能需要指定-J-d64选项，例如:jstack -J-d64 -m pid。
  
• 该命令可能在未来的版本中不可用！！！
  

语法

jstack [ options ] pid

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