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死锁检测及其测试用例

news 2025/8/30 12:29:18

1)实现

package com.next1b.nextsvr.util.deadlockcheck;import com.next1b.nextsvr.util.log.Log;import java.lang.management.*;
import java.util.HashMap;
import java.util.Map;/*** 查找死锁,打印死锁上下文*/
public final class DeadLockCheckThread extends Thread {private final static int MAX_DEPTH = 255;// 最大检测等待时间private static final int MaxCheckPeriodMs = 5000;// 当前线程是否还在运行private volatile boolean running = true;// jmx线程对象private final ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();// 多久检测一次死锁private int sleepIdleMs = 1000;public DeadLockCheckThread() {super("DeadLockCheckThread");// 守护线程this.setDaemon(true);}@Overridepublic void run() {while (running) {try {// 检测到了死锁if (checkDeadLock()) { // 核心方法，检测死锁sleepIdleMs = 1000; // 检测到了，则改为下次1s后再进行下次检测} else {sleepIdleMs += 1000; // 没检测到，则加大下次检测的时间,就不要那么频繁了if (sleepIdleMs > MaxCheckPeriodMs) {sleepIdleMs = MaxCheckPeriodMs;}}// 休眠一会sleepIdle(sleepIdleMs);} catch (Throwable e) {Log.logException(e);}}}/*** 关闭*/public void shutdown() {running = false;}/*** 检测死锁*/private boolean checkDeadLock() {// step1:返回死锁的线程Id列表long[] deadlockedThreadIds = threadMXBean.findDeadlockedThreads();if (null == deadlockedThreadIds) {return false; // 说明没找到死锁}// step2:走到这里，说明找到了死锁// 构建死锁线程信息映射 <threadId, ThreadInfo>Map<Long, ThreadInfo> deadLockedThreadId2ThreadInfoMap = new HashMap<>();ThreadInfo[] threadInfos = threadMXBean.getThreadInfo(deadlockedThreadIds, threadMXBean.isObjectMonitorUsageSupported(), threadMXBean.isSynchronizerUsageSupported());for (ThreadInfo threadInfo : threadInfos) {try {if (null != threadInfo&& threadInfo.getLockOwnerId() != -1) { // getLockOwnerId == -1,不在等待被其他线程拥有的锁. 肯定不是环的一部分。deadLockedThreadId2ThreadInfoMap.put(threadInfo.getThreadId(), threadInfo);}} catch (Exception e) {Log.logException(e);}}// step3:检测死锁环，打印下死锁信息while (!deadLockedThreadId2ThreadInfoMap.isEmpty()) {// 检查死锁Map<Long, ThreadInfo> threadId2ThreadInfoCycleMap = new HashMap<>();// 先拿到第一个线程信息ThreadInfo threadInfo = deadLockedThreadId2ThreadInfoMap.entrySet().iterator().next().getValue();do {if (null != threadId2ThreadInfoCycleMap.put(threadInfo.getThreadId(), threadInfo)) { // 环找到了，说明有死锁了// 打印发现的死锁信息StringBuilder sb = new StringBuilder();// 打印的时候把挂在环上的线程也打出来。for (ThreadInfo info : threadId2ThreadInfoCycleMap.values()) {fillThreadInfo(info, sb);}Log.logErr("\n----------DEAD LOCK BEGIN----------\n" + sb + "----------DEADLOCK END----------");// 打断当前的do while循环，执行外层的while循环并尝试寻找下一个死锁.break;}} while ((threadInfo = deadLockedThreadId2ThreadInfoMap.get(threadInfo.getLockOwnerId())) != null);// 删除已经被处理的线程。cycle是完整的环，或者是那些等待的环已被打破剩下的孤立枝节。deadLockedThreadId2ThreadInfoMap.keySet().removeAll(threadId2ThreadInfoCycleMap.keySet());}return true;}/*** @param threadInfo 死锁环中线程的信息* @param sb 线程信息*/private void fillThreadInfo(ThreadInfo threadInfo, StringBuilder sb) {// 当前死锁的线程信息sb.append("ThreadName=").append(threadInfo.getThreadName()).append(" ThreadId=").append( threadInfo.getThreadId()).append(" ThreadState=").append(threadInfo.getThreadState());String lockOwnerStr = "";if (threadInfo.getLockOwnerName() != null) {lockOwnerStr = threadInfo.getLockOwnerName() + "\" ThreadId=" + threadInfo.getLockOwnerId();}if (threadInfo.isSuspended()) {sb.append(" (suspended)");}if (threadInfo.isInNative()) {sb.append(" (in native)");}sb.append('\n');StackTraceElement[] stackTrace = threadInfo.getStackTrace();int i = 0;for (; i < stackTrace.length && i < MAX_DEPTH; i++) {for (MonitorInfo mi : threadInfo.getLockedMonitors()) {if (mi.getLockedStackDepth() == i) {sb.append("ERROR\t- SuccessLock:"); // 当前拿到的锁的信息sb.append(mi);sb.append('\n');}}if (i == 0 && threadInfo.getLockInfo() != null) {State ts = threadInfo.getThreadState();switch (ts) {case BLOCKED:sb.append("ERROR\t- FailLock:"); // 当前无法获得的锁信息sb.append(getLockOwnerStr(threadInfo, lockOwnerStr));sb.append('\n');break;case WAITING:sb.append("ERROR\t- waiting on:");sb.append(getLockOwnerStr(threadInfo, lockOwnerStr));sb.append('\n');break;case TIMED_WAITING:sb.append("ERROR\t- timed waiting on:");sb.append(getLockOwnerStr(threadInfo, lockOwnerStr));sb.append('\n');break;default:}}StackTraceElement ste = stackTrace[i];sb.append("ERROR\t- ").append(ste.toString()).append("\n"); // 发现死锁的代码位置}if (i < stackTrace.length) {sb.append("ERROR\t...");sb.append('\n');}// 获取当前获得的重入锁LockInfo[] locks = threadInfo.getLockedSynchronizers();if (locks.length > 0) {sb.append("ERROR\n\tNumber of LockedSynchronizer = ").append(locks.length);sb.append('\n');for (LockInfo li : locks) {sb.append("ERROR\t- ").append(li);sb.append('\n');}}sb.append("\n\n");}private String getLockOwnerStr(ThreadInfo  threadInfo, String lockOwnerStr) {return threadInfo.getLockInfo() + " CurOwnerThread:" + lockOwnerStr; // 当前持有的线程}/*** 挂起当前线程一段时间。*/private synchronized void sleepIdle(long ms) {try {this.wait(ms);} catch (Exception e) {Log.logException(e);}}
}

2)测试用例

package com.example.variable;import com.example.variable.deadlock.DeadLockCheckThread;
import com.example.variable.deadlock.Student;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;@SpringBootTest
class DeadLockCheckTests {private final DeadLockCheckThread deadLockCheckThread = new DeadLockCheckThread();@BeforeEachvoid setUp() {deadLockCheckThread.start();}@Testpublic void test() throws Exception {Object lock1 = new Object();Student lock2 = new Student();new Thread(()->{synchronized (lock1){try {Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}synchronized (lock2){System.out.println("thread1 run");}}}, "thread1").start();new Thread(()->{synchronized (lock2){try {Thread.sleep(2000);} catch (InterruptedException e) {throw new RuntimeException(e);}synchronized (lock1){System.out.println("thread2 run");}}}, "thread2").start();Thread.sleep(Long.MAX_VALUE);}}

3)效果