jstack使用

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2014-08 ( 2)
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都知道jstack是干嘛的

本文讲如何看它的输出内容：

1. synchronized

已经进入临界区，sleep，在边界等待

 
    @Test
    public void testSync() {
        final String s = "test";
        Runnable task = new Runnable() {

            public void run() {
                synchronized (s) {
                    try {
                        Thread.sleep(60 * 1000);
                    } catch (InterruptedException e) {
                        //这里直接抓住就不要深究了
                        e.printStackTrace();
                    }
                }
            }
        };
        Thread t = new Thread(task, "test-thread");
        t.start();

        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        synchronized (s) {
            System.out.println("end....");
        }
    }

这个用例简单说就是，先起一个线程“test-thread"，取得对象s上的锁，然后sleep 1min。

然后主线程尝试获取s上的锁，当然就会被阻塞住了（1min），通过jstack取得信息如下：

"test-thread" prio=6 tid=0x000000000749e800 nid=0x10f4 waiting on condition [0x000000000787f000]
   java.lang.Thread.State: TIMED_WAITING (sleeping) //处于TIMED_WAITING状态，等待某个条件
        at java.lang.Thread.sleep(Native Method)
        at com.snowm.test.concurrent.TestInnerImplements$1.run(TestInnerImplements.java:17)
        - locked <0x000000077f454e80> (a java.lang.String) //已经对一个String对象加锁（已进入临界区）
        at java.lang.Thread.run(Thread.java:662)
 
   Locked ownable synchronizers:
        - None 
 
"main" prio=6 tid=0x000000000027c000 nid=0x188c waiting for monitor entry [0x000000000260e000]
   java.lang.Thread.State: BLOCKED (on object monitor) //处于BLOCKED状态，是synchronized干的
        at com.snowm.test.concurrent.TestInnerImplements.testSync(TestInnerImplements.java:34)
        - waiting to lock <0x000000077f454e80> (a java.lang.String) //在等待对一个String对象加锁（还在边界）
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
 
   Locked ownable synchronizers:
        - None

重入，以及wait()

    @Test
    public void testSyncReentryWait() {
        final String s = "test";
        synchronized (s) {
            synchronized (s) {
                try {
                    s.wait();
                } catch (InterruptedException e) {
                    // 这里直接抓住就不要深究了
                    e.printStackTrace();
                }
            }
        }
    }

"main" prio=6 tid=0x000000000018c000 nid=0x2624 in Object.wait() [0x00000000024de000]
   java.lang.Thread.State: WAITING (on object monitor)//处于WAITING状态，是Object.wait()干的
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000077f455268> (a java.lang.String)//在等一个String对象的信号
        at java.lang.Object.wait(Object.java:485)
        at com.snowm.test.concurrent.TestInnerImplements.testSyncReentryWait(TestInnerImplements.java:44)
        - locked <0x000000077f455268> (a java.lang.String)//又对这个String对象加锁（地址一样）
        - locked <0x000000077f455268> (a java.lang.String)//已经对一个String对象加锁
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 
   Locked ownable synchronizers:
 
        - None

wait(time)

    @Test
    public void testSyncWaittime() {
        final String s = "test";
        synchronized (s) {
            try {
                s.wait(60 * 1000);
            } catch (InterruptedException e) {
                // 这里直接抓住就不要深究了
                e.printStackTrace();
            }
        }
    }

"main" prio=6 tid=0x000000000051c000 nid=0x148c in Object.wait() [0x00000000026ae000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000077f456018> (a java.lang.String)
        at com.snowm.test.concurrent.TestInnerImplements.testSyncWaittime(TestInnerImplements.java:62)
        - locked <0x000000077f456018> (a java.lang.String)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

   Locked ownable synchronizers:
        - None

2. ReentrantLock

已经进入临界区，在边界等待

    @Test
    public void testReentrantLock() {
        final ReentrantLock lock = new ReentrantLock();
        Runnable task = new Runnable() {

            public void run() {
                lock.lock();
                try {
                    Thread.sleep(60*1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    lock.unlock();
                }
            }
        };
        Thread t = new Thread(task, "test-thread");
        t.start();

        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        lock.lock();
        try {
            System.out.println("end....");
        } finally {
            lock.unlock();
        }
    }

"test-thread" prio=6 tid=0x00000000075df800 nid=0x25c8 waiting on condition [0x00000000080ff000]

java.lang.Thread.State: TIMED_WAITING (sleeping)//sleep

at java.lang.Thread.sleep(Native Method)

at com.snowm.test.concurrent.TestInnerImplements$2.run(TestInnerImplements.java:63)

at java.lang.Thread.run(Thread.java:662)

Locked ownable synchronizers:

- <0x00000007d6e1b420> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)//锁住当前线程的同步器拥有者

"main" prio=6 tid=0x000000000053c000 nid=0x2274 waiting on condition [0x000000000264e000]

java.lang.Thread.State: WAITING (parking)//WAITING，unsafe.park()干的

at sun.misc.Unsafe.park(Native Method)

- parking to wait for <0x00000007d6e1b420> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)//parking在等待某个同步器（就是test-thread上那个锁同步器）

at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:842)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1178)

at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)

at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)

at com.snowm.test.concurrent.TestInnerImplements.testReentrantLock(TestInnerImplements.java:81)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

Locked ownable synchronizers:

- None

重入

    @Test
    public void testReentrantLockReentry() {
        final ReentrantLock lock = new ReentrantLock();
        lock.lock();
        lock.lock();
        try {
            Thread.sleep(60 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
            lock.unlock();
        }
    }

"main" prio=6 tid=0x000000000022c000 nid=0x1728 waiting on condition [0x00000000025de000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at com.snowm.test.concurrent.TestInnerImplements.testReentrantLockReentry(TestInnerImplements.java:93)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)

   Locked ownable synchronizers:
        - <0x00000007d6e1dc10> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)//锁住当前线程的同步器拥有者

await()

    @Test
    public void testReentrantLockAwait() {
        final ReentrantLock lock = new ReentrantLock();
        final Condition condition = lock.newCondition();
        lock.lock();
        try {
            condition.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

"main" prio=6 tid=0x00000000005bc000 nid=0x10f4 waiting on condition [0x000000000250e000]
   java.lang.Thread.State: WAITING (parking)//WAITING，Unsafe.park()干的
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000007d6e1f108> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)//parking在等待一个条件对象的信号
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1987)
        at com.snowm.test.concurrent.TestInnerImplements.testReentrantLockAwait(TestInnerImplements.java:132)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

   Locked ownable synchronizers:
        - None

await(time, timeUnit)

    @Test
    public void testReentrantLockAwaitTime() {
        final ReentrantLock lock = new ReentrantLock();
        final Condition condition = lock.newCondition();
        lock.lock();
        try {
            condition.await(60, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

"main" prio=6 tid=0x000000000036c000 nid=0x148c waiting on condition [0x00000000025be000]
   java.lang.Thread.State: TIMED_WAITING (parking)//WAITING, Unsafe.park()干的
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000007d6e20798> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)//parking在等待一个条件对象的信号
        at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:196)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2116)
        at com.snowm.test.concurrent.TestInnerImplements.testReentrantLockAwaitTime(TestInnerImplements.java:146)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

   Locked ownable synchronizers:
        - None

3. LockSupport.park

没有blocker

    @Test
    public void testPark() {
        LockSupport.park();
    }

"main" prio=6 tid=0x000000000055c000 nid=0x30c8 waiting on condition [0x000000000258e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:283)
        at com.snowm.test.concurrent.TestInnerImplements.testPark(TestInnerImplements.java:171)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

   Locked ownable synchronizers:
        - None

有blocker

    @Test
    public void testParkWithBlocker() {
        LockSupport.park(this);
    }

"main" prio=6 tid=0x000000000026c000 nid=0x2674 waiting on condition [0x000000000256e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000007d6e1d2e0> (a com.snowm.test.concurrent.TestInnerImplements)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
        at com.snowm.test.concurrent.TestInnerImplements.testParkWithBlocker(TestInnerImplements.java:176)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

   Locked ownable synchronizers:
        - None

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2014-08-13 16:52
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