我的应用程序中也有类似的情况:
public class Example {
private static A aClass = new A();
private static B bClass = new B();
public static void main(String[] args) {
new Thread(new Runnable() {
@Override
public void run() {
bClass.start();
}
}, ">>>>>>>>>>").start();
new Thread(new Runnable() {
@Override
public void run() {
aClass.start();
}
}, "__________").start();
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
detectDeadlock();
}
private static void detectDeadlock() {
ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
long[] threadIds = threadBean.findMonitorDeadlockedThreads();
int deadlockedThreads = threadIds != null? threadIds.length : 0;
System.out.println("Number of deadlocked threads: " + deadlockedThreads);
}
private static class A {
private final Object aLock = new Object();
public void start() {
System.out.println(Thread.currentThread()+ " " + "A-start; waiting for aLock");
synchronized (aLock) {
System.out.println(Thread.currentThread()+ " " + "A-start; acquired aLock");
bClass.synchronizedMethod();
}
System.out.println(Thread.currentThread()+ " " + "A-start; release aLock");
}
public void synchronizedMethod() {
System.out.println(Thread.currentThread()+ " " + "A-synchronizedMethod; waiting for aLock");
synchronized (aLock) {
System.out.println(Thread.currentThread()+ " " + "A-synchronizedMethod; acquired aLock");
}
System.out.println(Thread.currentThread()+ " " + "A-synchronizedMethod; release aLock");
}
}
private static class B {
private final Object bLock = new Object();
public void synchronizedMethod() {
System.out.println(Thread.currentThread()+ " " + "B-synchronizedMethod; waiting for bLock");
synchronized (bLock) {
System.out.println(Thread.currentThread()+ " " + "B-synchronizedMethod; acquired bLock");
}
System.out.println(Thread.currentThread()+ " " + "B-synchronizedMethod; release bLock");
}
public void start() {
System.out.println(Thread.currentThread() + " " + "B-Start; waiting for bLock");
synchronized (bLock) {
System.out.println(Thread.currentThread()+ " " + "B-Start; acquired bLock");
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
aClass.synchronizedMethod();
}
System.out.println(Thread.currentThread()+ " " + "B-Start; released bLock");
}
}
}
此代码片段的输出将如下所示:
Thread[>>>>>>>>>>,5,main] B-Start; waiting for bLock
Thread[>>>>>>>>>>,5,main] B-Start; acquired bLock
Thread[__________,5,main] A-start; waiting for aLock
Thread[__________,5,main] A-start; acquired aLock
Thread[__________,5,main] B-synchronizedMethod; waiting for bLock
Thread[>>>>>>>>>>,5,main] A-synchronizedMethod; waiting for aLock
Number of deadlocked threads: 2
我正在寻找有关这种僵局情况的一些指导。
您能告诉我如何避免这种僵局吗？
最佳答案
最后我选择使用由 A 和 B 实例共享的全局锁。
代码看起来像这样:
private static class Lock {
private static Lock lock = new Lock();
private Lock(){}
public static Lock getLock() {return lock;}
}
private static class A {
private final Object aLock = Lock.getLock();
// ...
}
private static class B {
private final Object bLock = Lock.getLock();
// ...
}
关于java - 寻求有关如何避免死锁的建议，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/53304022/