并发(九):检查死锁与Locked ownable synchronizers
来源:互联网 发布:苹果免费office软件 编辑:程序博客网 时间:2024/06/10 23:13
通过jstack可快速检查线程的死锁信息,用法如下:
# 获取JVM ID(JAVA 进程ID),通过参数lv可以获取更详细的JAVA方法调用信息jps -lv# 得到JVM ID后,执行jstack命令,这里假定为123# 将结果重定向到文件,更便于查看jstack -l 123 >> d:/123.txt
翻到页底,可发现明显的死锁信息:
Java stack information for the threads listed above:==================================================="Thread-1": at com.mirana.concurrent.LockedOwnThread.run(LockedOwnThread.java:47) - waiting to lock <0x000000076c5806f8> (a java.lang.Class for java.lang.Object) - locked <0x000000076c636568> (a java.lang.Class for com.mirana.concurrent.LockedOwnThread) - locked <0x000000076c6392f0> (a com.mirana.concurrent.LockedOwnThread)"Thread-0": at com.mirana.concurrent.LockedOwnThread$AThread.run(LockedOwnThread.java:27) - waiting to lock <0x000000076c636568> (a java.lang.Class for com.mirana.concurrent.LockedOwnThread) - locked <0x000000076c5806f8> (a java.lang.Class for java.lang.Object)Found 1 deadlock.
从输出信息中,可明显发觉两个线程彼此锁定了对方需要的锁(0x000000076c636568与0x000000076c5806f8)。
在打印的堆栈信息中,我们还发现了如下信息:
"Thread-0" #11 prio=5 os_prio=0 tid=0x000000001e902000 nid=0x5b34c waiting for monitor entry [0x000000001f5bf000] java.lang.Thread.State: BLOCKED (on object monitor) at com.mirana.concurrent.LockedOwnThread$AThread.run(LockedOwnThread.java:27) - waiting to lock <0x000000076c636538> (a java.lang.Class for com.mirana.concurrent.LockedOwnThread) - locked <0x000000076c5806f8> (a java.lang.Class for java.lang.Object) Locked ownable synchronizers: - None
Locked ownable synchronizers是个什么东东?按照官方定义
一个可持有的同步器多半是线程独有并且使用了AbstractOwnableSynchronizer(或是其子类)去实现它的同步特性,ReentrantLock与ReentrantReadWriteLock就是JAVA平台提供的两个例子。
我们将程序改为如下形式,依旧为死锁形式:```javastatic class AThread extends Thread { private ReentrantLock lock1; private ReentrantLock lock2; /** * @param lock1 * @param lock2 */ public AThread(ReentrantLock lock1, ReentrantLock lock2) { super(); this.lock1 = lock1; this.lock2 = lock2; } public void run() { try { lock1.lock(); Thread.sleep(3000); // 必须获取两个锁后才执行操作 lock2.lock(); System.out.println("A: I have all Locks!"); } catch (InterruptedException e) { e.printStackTrace(); } finally { lock2.unlock(); lock1.unlock(); } }}static class BThread extends Thread { private ReentrantLock lock1; private ReentrantLock lock2; /** * @param lock1 * @param lock2 */ public BThread(ReentrantLock lock1, ReentrantLock lock2) { super(); this.lock1 = lock1; this.lock2 = lock2; } public void run() { try { lock2.lock(); Thread.sleep(1000); // 必须获取两个锁后才执行操作 lock1.lock(); System.out.println("B: I have all Locks!"); } catch (InterruptedException e) { e.printStackTrace(); } finally { lock1.unlock(); lock2.unlock(); } }}// 测试程序主函数public static void main(String[] args) throws InterruptedException { final ReentrantLock lock1 = new ReentrantLock(); final ReentrantLock lock2 = new ReentrantLock(); new AThread(lock1, lock2).start(); new BThread(lock1, lock2).start();}<div class="se-preview-section-delimiter"></div>
最后打印线程的堆栈信息,出现的内容如下:
"Thread-1" #12 prio=5 os_prio=0 tid=0x000000001ef5a000 nid=0x1c2c waiting on condition [0x000000001fcbf000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x000000076c637ca0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199) at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209) at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285) at com.mirana.concurrent.LockedOwnThread$BThread.run(LockedOwnThread.java:70) Locked ownable synchronizers: - <0x000000076c637cd0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
发现ReentrantLock与内置锁有如下3点不同:
1. 等待的对象不同,内置锁是“monitor entry”(监视器进入点),而ReentrantLock是“condition”(条件);
2. 线程的状态不同,内置锁是“BLOCKED”,而ReentrantLock是“WAITING”;
3. 锁定的同步器不同,内置锁没有,而ReentrantLock则指向持有的同步器;
结论
通过jstack可快速检查到死锁情况,并能给出冲突的锁与监测对象,另外,内置锁对象与ReentrantLock在运行中表现出截然不同的状态。
阅读全文
0 0
- 并发(九):检查死锁与Locked ownable synchronizers
- Java并发编程-Synchronizers
- 死锁小示例与检查方法
- 【Java并发编程】之九:死锁(含代码)
- 【Java并发编程】之九:死锁(含代码)
- 【Java并发编程】之九:死锁(含代码)
- 【Java并发编程】之九:死锁(含代码)
- 【Java并发编程】之九:死锁(含代码)(r)
- 【Java并发编程】之九:死锁(含代码)
- 第六章 并发:死锁与饥饿
- Java并发与多线程(1) 死锁是什么
- Java多线程与并发(三)之死锁
- Oracle中检查死锁
- SQL Server 检查死锁
- 如何检查oracle死锁
- SQL Server 检查死锁
- 数据库死锁检查、解锁
- 检查死锁的问题
- Hibernate缓存机制
- easyUI的学习--在线教程,工具选择安装配置过程(一)
- Foxmail不能收取163邮件的解决办法
- 【Away3D代码解读】(五):动画模块及骨骼动画
- python ctypes常用方法
- 并发(九):检查死锁与Locked ownable synchronizers
- Mybatis第二篇【CRUD、分页】
- Hibernate使用查询
- Idea Maven 报错 Cannot reconnect
- ZooKeeper
- PHP——post(实例)
- mybatis注解一对多如何传递多个参数
- Linux进程间通信——使用共享内存
- Windows快捷键总结