1、死锁案例
public class DeadLock {
final Object lockA = new Object();
public static void main(String[] args) {
DeadLock demo = new DeadLock();
demo.startLock();
}
public void startLock() {
ThreadA a = new ThreadA(lockA, lockB);
ThreadB b = new ThreadB(lockA, lockB);
a.start();
b.start();
}
}
class ThreadA extends Thread {
private Object lockA = null;
private Object lockB = null;
public ThreadA(Object a, Object b) {
this.lockA = a;
this.lockB = b;
}
public void run() {
synchronized (lockA) {
System.out.println("---- Thread A: locked A");
try {
sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lockB) {
System.out.println("---- Thread A: locked B");
}
}
System.out.println("---- Thread A: Finished");
}
}
class ThreadB extends Thread {
private Object lockA = null;
private Object lockB = null;
public ThreadB(Object a, Object b) {
this.lockA = a;
this.lockB = b;
}
public void run() {
synchronized (lockB) {
System.out.println("---- Thread B: locked B");
try {
sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lockA) {
System.out.println("Tread B: locked A");
}
}
System.out.println("---- Thread B: Finished");
}
}
2、死锁分析
打印Thread Dump
linux 环境kill -3 pid 或者jstack
windows环境 ctrl+fn+b
dump信息如下：
D:\test\deadlock>java DeadLock
---- Thread A: locked A
---- Thread B: locked B
2018-07-14 17:45:52
Full thread dump Java HotSpot(TM) Client VM (24.65-b04 mixed mode, sharing):
"DestroyJavaVM" prio=6 tid=0x02c4bc00 nid=0x1548 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
"Thread-1" prio=6 tid=0x02d2b400 nid=0x2b24 waiting for monitor entry [0x054bf000]
java.lang.Thread.State: BLOCKED (on object monitor)
at ThreadB.run(DeadLock.java:64)
- waiting to lock <0x252811c0> (a java.lang.Object)
- locked <0x252811c8> (a java.lang.Object)
"Thread-0" prio=6 tid=0x02d2ac00 nid=0x3640 waiting for monitor entry [0x0542f000]
java.lang.Thread.State: BLOCKED (on object monitor)
at ThreadA.run(DeadLock.java:37)
- waiting to lock <0x252811c8> (a java.lang.Object)
- locked <0x252811c0> (a java.lang.Object)
"Service Thread" daemon prio=6 tid=0x02cdd800 nid=0x4138 runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
"C1 CompilerThread0" daemon prio=10 tid=0x02cdc800 nid=0x2324 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
"Attach Listener" daemon prio=10 tid=0x02cdac00 nid=0x22dc runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
"Signal Dispatcher" daemon prio=10 tid=0x02d04800 nid=0x2fb0 waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
"Finalizer" daemon prio=8 tid=0x02c70000 nid=0x708 in Object.wait() [0x050cf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x25200fc8> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
- locked <0x25200fc8> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
"Reference Handler" daemon prio=10 tid=0x02c6e800 nid=0xf40 in Object.wait() [0x0503f000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x25200db0> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:503)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
- locked <0x25200db0> (a java.lang.ref.Reference$Lock)
"VM Thread" prio=10 tid=0x02c6d400 nid=0x1150 runnable
"VM Periodic Task Thread" prio=10 tid=0x02d16400 nid=0x3130 waiting on condition
JNI global references: 111
Found one Java-level deadlock:
=============================
"Thread-1":
waiting to lock monitor 0x02c73be4 (object 0x252811c0, a java.lang.Object),
which is held by "Thread-0"
"Thread-0":
waiting to lock monitor 0x02c75704 (object 0x252811c8, a java.lang.Object),
which is held by "Thread-1"
Java stack information for the threads listed above:
===================================================
"Thread-1":
at ThreadB.run(DeadLock.java:64)
- waiting to lock <0x252811c0> (a java.lang.Object)
- locked <0x252811c8> (a java.lang.Object)
"Thread-0":
at ThreadA.run(DeadLock.java:37)
- waiting to lock <0x252811c8> (a java.lang.Object)
- locked <0x252811c0> (a java.lang.Object)
Found 1 deadlock.
Heap
def new generation total 4928K, used 867K [0x25200000, 0x25750000, 0x2a750000)
eden space 4416K, 19% used [0x25200000, 0x252d8fe0, 0x25650000)
from space 512K, 0% used [0x25650000, 0x25650000, 0x256d0000)
to space 512K, 0% used [0x256d0000, 0x256d0000, 0x25750000)
tenured generation total 10944K, used 0K [0x2a750000, 0x2b200000, 0x35200000)
the space 10944K, 0% used [0x2a750000, 0x2a750000, 0x2a750200, 0x2b200000)
compacting perm gen total 12288K, used 157K [0x35200000, 0x35e00000, 0x39200000)
the space 12288K, 1% used [0x35200000, 0x35227730, 0x35227800, 0x35e00000)
ro space 10240K, 44% used [0x39200000, 0x3967a688, 0x3967a800, 0x39c00000)
rw space 12288K, 52% used [0x39c00000, 0x3a254170, 0x3a254200, 0x3a800000)
