Java死锁的排查
2016-09-08 19:12
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先弄个死锁的代码例子:
public class DeadLock implements Runnable {
private int flagCurrent = -1;
private static int flagThread1 = 0;
private static int flagThread2 = 1;
private static Object object1 = new Integer(1);
private static Object object2 = new Double(2);
@Override
public void run() {
System.out.println("CurrentThread" + flagCurrent);
if (flagCurrent == flagThread1) {// 线程1进
synchronized (object1) {// 线程1先锁定object1(期间要等500ms去锁定object2)
try {
Thread.sleep(500);
} catch (final Exception e) {
e.printStackTrace();
}
// 此时线程2已经锁定object2,需要【等待】线程2释放object2,然后线程1锁定object2释放object2,再释放object1
// 死锁发生:线程1等待线程2释放object2,线程1才释放object1;线程2等待线程1释放object1,线程2才释放object2;
synchronized (object2) {
System.out.println("1");
}
}
}
if (flagCurrent == flagThread2) {// 线程2进
synchronized (object2) {// 线程2先锁定object2(期间要等500ms去锁定object1)
try {
Thread.sleep(500);
} catch (final Exception e) {
e.printStackTrace();
}
// 此时线程1已经锁定object1,需要【等待】线程1释放object1,然后线程2锁定object1释放object1,再释放object2
// 死锁发生:线程1等待线程2释放object2,线程1才释放object1;线程2等待线程1释放object1,线程2才释放object2;
synchronized (object1) {
System.out.println("0");
}
}
}
}
public static void main(final String[] args) {
final DeadLock runnableThread1 = new DeadLock();
final DeadLock runnableThread2 = new DeadLock();
runnableThread1.flagCurrent = flagThread1;
runnableThread2.flagCurrent = flagThread2;
new Thread(runnableThread1, "runnableThread1").start();
new Thread(runnableThread2, "runnableThread2").start();
}
}
查找死锁的2个方法:
1.用Jconsole
切换到线程那个选项卡,左下角有个死锁检查:
2.用Jstack
先jps 找出对应的代号,再Jstack -l 代号,就可看见了
public class DeadLock implements Runnable {
private int flagCurrent = -1;
private static int flagThread1 = 0;
private static int flagThread2 = 1;
private static Object object1 = new Integer(1);
private static Object object2 = new Double(2);
@Override
public void run() {
System.out.println("CurrentThread" + flagCurrent);
if (flagCurrent == flagThread1) {// 线程1进
synchronized (object1) {// 线程1先锁定object1(期间要等500ms去锁定object2)
try {
Thread.sleep(500);
} catch (final Exception e) {
e.printStackTrace();
}
// 此时线程2已经锁定object2,需要【等待】线程2释放object2,然后线程1锁定object2释放object2,再释放object1
// 死锁发生:线程1等待线程2释放object2,线程1才释放object1;线程2等待线程1释放object1,线程2才释放object2;
synchronized (object2) {
System.out.println("1");
}
}
}
if (flagCurrent == flagThread2) {// 线程2进
synchronized (object2) {// 线程2先锁定object2(期间要等500ms去锁定object1)
try {
Thread.sleep(500);
} catch (final Exception e) {
e.printStackTrace();
}
// 此时线程1已经锁定object1,需要【等待】线程1释放object1,然后线程2锁定object1释放object1,再释放object2
// 死锁发生:线程1等待线程2释放object2,线程1才释放object1;线程2等待线程1释放object1,线程2才释放object2;
synchronized (object1) {
System.out.println("0");
}
}
}
}
public static void main(final String[] args) {
final DeadLock runnableThread1 = new DeadLock();
final DeadLock runnableThread2 = new DeadLock();
runnableThread1.flagCurrent = flagThread1;
runnableThread2.flagCurrent = flagThread2;
new Thread(runnableThread1, "runnableThread1").start();
new Thread(runnableThread2, "runnableThread2").start();
}
}
查找死锁的2个方法:
1.用Jconsole
切换到线程那个选项卡,左下角有个死锁检查:
2.用Jstack
先jps 找出对应的代号,再Jstack -l 代号,就可看见了
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