使用 jstack或者jconsole查看死锁状态

淩亂°似流年 2023-02-20 06:47 36阅读 0赞

1,有时候运行程序时会出现代码死锁，可以通过jstack进行查看，

1.1 死锁代码如下：

import lombok.extern.slf4j.Slf4j;
    
    import static cn.itcast.n2.util.Sleeper.sleep;
    
    @Slf4j(topic = "c.TestDeadLock")
    public class TestDeadLock {
        public static void main(String[] args) {
            test1();
        }
    
        private static void test1() {
            Object A = new Object();
            Object B = new Object();
            Thread t1 = new Thread(() -> {
                synchronized (A) {
                    log.debug("lock A");
                    sleep(1);
                    synchronized (B) {
                        log.debug("lock B");
                        log.debug("操作...");
                    }
                }
            }, "t1");
    
            Thread t2 = new Thread(() -> {
                synchronized (B) {
                    log.debug("lock B");
                    sleep(0.5);
                    synchronized (A) {
                        log.debug("lock A");
                        log.debug("操作...");
                    }
                }
            }, "t2");
            t1.start();
            t2.start();
        }
    }

1.2 ，通过jstack查看堆栈信息，通过deadlock关键字查询：

D:\bigdata\java_concurrent\juc_itcast>jstack 31540
    2020-06-24 10:07:25
    Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.121-b13 mixed mode):
    
    "DestroyJavaVM" #14 prio=5 os_prio=0 tid=0x00000000031d3800 nid=0x796c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "t2" #13 prio=5 os_prio=0 tid=0x000000001ff24000 nid=0x8c1c waiting for monitor entry [0x000000002044f000]
       java.lang.Thread.State: BLOCKED (on object monitor)
            at cn.itcast.n4.deadlock.TestDeadLock.lambda$test1$1(TestDeadLock.java:32)
            - waiting to lock <0x000000076c6001b8> (a java.lang.Object)
            - locked <0x000000076c6001c8> (a java.lang.Object)
            at cn.itcast.n4.deadlock.TestDeadLock$$Lambda$2/1321640594.run(Unknown Source)
            at java.lang.Thread.run(Thread.java:745)
    
    "t1" #12 prio=5 os_prio=0 tid=0x000000001ff21000 nid=0x7318 waiting for monitor entry [0x000000002034f000]
       java.lang.Thread.State: BLOCKED (on object monitor)
            at cn.itcast.n4.deadlock.TestDeadLock.lambda$test1$0(TestDeadLock.java:21)
            - waiting to lock <0x000000076c6001c8> (a java.lang.Object)
            - locked <0x000000076c6001b8> (a java.lang.Object)
            at cn.itcast.n4.deadlock.TestDeadLock$$Lambda$1/381707837.run(Unknown Source)
            at java.lang.Thread.run(Thread.java:745)
    
    "Service Thread" #11 daemon prio=9 os_prio=0 tid=0x000000001edb2800 nid=0x65e8 runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C1 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x000000001ed13000 nid=0x7d4c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000000001ed00000 nid=0x6f58 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000000001ecf9800 nid=0x8eac waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000000001ecf8800 nid=0xa7c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000000001ecba000 nid=0x8494 runnable [0x000000001f39e000]
       java.lang.Thread.State: RUNNABLE
            at java.net.SocketInputStream.socketRead0(Native Method)
            at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
            at java.net.SocketInputStream.read(SocketInputStream.java:171)
            at java.net.SocketInputStream.read(SocketInputStream.java:141)
            at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
            at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
            at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
            - locked <0x000000076ba4b800> (a java.io.InputStreamReader)
            at java.io.InputStreamReader.read(InputStreamReader.java:184)
            at java.io.BufferedReader.fill(BufferedReader.java:161)
            at java.io.BufferedReader.readLine(BufferedReader.java:324)
            - locked <0x000000076ba4b800> (a java.io.InputStreamReader)
            at java.io.BufferedReader.readLine(BufferedReader.java:389)
            at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)
    
    "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001eb7b000 nid=0x2f6c waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001eb79000 nid=0x8768 runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
    "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000000001eb60800 nid=0x3d74 in Object.wait() [0x000000001f03f000]
       java.lang.Thread.State: WAITING (on object monitor)
            at java.lang.Object.wait(Native Method)
            - waiting on <0x000000076b788ec8> (a java.lang.ref.ReferenceQueue$Lock)
            at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
            - locked <0x000000076b788ec8> (a java.lang.ref.ReferenceQueue$Lock)
            at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
            at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
    
    "Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x00000000032ca000 nid=0x67e8 in Object.wait() [0x000000001eb3e000]
       java.lang.Thread.State: WAITING (on object monitor)
            at java.lang.Object.wait(Native Method)
            - waiting on <0x000000076b786b68> (a java.lang.ref.Reference$Lock)
            at java.lang.Object.wait(Object.java:502)
            at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
            - locked <0x000000076b786b68> (a java.lang.ref.Reference$Lock)
            at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
    
    "VM Thread" os_prio=2 tid=0x000000001cc79800 nid=0x1b0c runnable
    
    "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00000000031e9000 nid=0x8828 runnable
    
    "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00000000031ea800 nid=0x598 runnable
    
    "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00000000031ec000 nid=0x5b24 runnable
    
    "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00000000031ee800 nid=0x59b4 runnable
    
    "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x00000000031f1000 nid=0x6008 runnable
    
    "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x00000000031f2000 nid=0x898c runnable
    
    "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x00000000031f5800 nid=0x5e90 runnable
    
    "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x00000000031f6800 nid=0x8380 runnable
    
    "VM Periodic Task Thread" os_prio=2 tid=0x000000001ee0c800 nid=0x70c8 waiting on condition
    
    JNI global references: 334
    
    
    Found one Java-level deadlock:
    =============================
    "t2":
      waiting to lock monitor 0x000000001cc835c8 (object 0x000000076c6001b8, a java.lang.Object),
      which is held by "t1"
    "t1":
      waiting to lock monitor 0x000000001cc81368 (object 0x000000076c6001c8, a java.lang.Object),
      which is held by "t2"
    
    Java stack information for the threads listed above:
    ===================================================
    "t2":
            at cn.itcast.n4.deadlock.TestDeadLock.lambda$test1$1(TestDeadLock.java:32)
            - waiting to lock <0x000000076c6001b8> (a java.lang.Object)
            - locked <0x000000076c6001c8> (a java.lang.Object)
            at cn.itcast.n4.deadlock.TestDeadLock$$Lambda$2/1321640594.run(Unknown Source)
            at java.lang.Thread.run(Thread.java:745)
    "t1":
            at cn.itcast.n4.deadlock.TestDeadLock.lambda$test1$0(TestDeadLock.java:21)
            - waiting to lock <0x000000076c6001c8> (a java.lang.Object)
            - locked <0x000000076c6001b8> (a java.lang.Object)
            at cn.itcast.n4.deadlock.TestDeadLock$$Lambda$1/381707837.run(Unknown Source)
            at java.lang.Thread.run(Thread.java:745)
    
    Found 1 deadlock.

最后一行，可以很快速判断出来出现死锁的位置

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2.使用jconsole查看死锁线程信息：

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