Thread相关学习之二 - JavaThread&JV

线程生命周期

JavaThread生命周期

线程生命周期就在上述的6个状态中流转，如下图：

Snip20180703_22.png

JVMTIThreadState定义

不过在jvmti.xml中，看到了jvmti(JVM Tool Interface)定义的相关ThreadState，看下：

<constants id="jvmtiThreadState" label="Thread State Flags" kind="bits">
      <constant id="JVMTI_THREAD_STATE_ALIVE" num="0x0001">
        Thread is alive. Zero if thread is new (not started) or terminated.
      </constant>
      <constant id="JVMTI_THREAD_STATE_TERMINATED" num="0x0002">
        Thread has completed execution.
      </constant>
      <constant id="JVMTI_THREAD_STATE_RUNNABLE" num="0x0004">
        Thread is runnable.
      </constant>
      <constant id="JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER" num="0x0400">
        Thread is waiting to enter a synchronization block/method or,
            after an <code>Object.wait()</code>, waiting to re-enter a 
            synchronization block/method.
      </constant>
      <constant id="JVMTI_THREAD_STATE_WAITING" num="0x0080">
        Thread is waiting.
      </constant>
      <constant id="JVMTI_THREAD_STATE_WAITING_INDEFINITELY" num="0x0010">
        Thread is waiting without a timeout.
            For example, <code>Object.wait()</code>.
      </constant>
      <constant id="JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT" num="0x0020">
        Thread is waiting with a maximum time to wait specified.
            For example, <code>Object.wait(long)</code>.
      </constant>
      <constant id="JVMTI_THREAD_STATE_SLEEPING" num="0x0040">
        Thread is sleeping -- <code>Thread.sleep(long)</code>.
      </constant>
      <constant id="JVMTI_THREAD_STATE_IN_OBJECT_WAIT" num="0x0100">
        Thread is waiting on an object monitor -- <code>Object.wait</code>.
      </constant>
      <constant id="JVMTI_THREAD_STATE_PARKED" num="0x0200">
        Thread is parked, for example: <code>LockSupport.park</code>,
            <code>LockSupport.parkUtil</code> and <code>LockSupport.parkNanos</code>.
      </constant>
      <constant id="JVMTI_THREAD_STATE_SUSPENDED" num="0x100000">
        Thread suspended.
        <code>java.lang.Thread.suspend()</code>
        or a <jvmti/> suspend function 
            (such as <functionlink id="SuspendThread"></functionlink>) 
            has been called on the thread. If this bit
        is set, the other bits refer to the thread state before suspension.
      </constant>
      <constant id="JVMTI_THREAD_STATE_INTERRUPTED" num="0x200000">
        Thread has been interrupted.
      </constant>
      <constant id="JVMTI_THREAD_STATE_IN_NATIVE" num="0x400000">
            Thread is in native code--that is, a native method is running
            which has not called back into the VM or Java programming
            language code.
            <p/>
            This flag is not set when running VM compiled Java programming
            language code nor is it set when running VM code or
            VM support code. Native VM interface functions, such as JNI and
            <jvmti/> functions, may be implemented as VM code.
      </constant>
      <constant id="JVMTI_THREAD_STATE_VENDOR_1" num="0x10000000">
            Defined by VM vendor.
      </constant>
      <constant id="JVMTI_THREAD_STATE_VENDOR_2" num="0x20000000">
            Defined by VM vendor.
      </constant>
      <constant id="JVMTI_THREAD_STATE_VENDOR_3" num="0x40000000">
            Defined by VM vendor.
      </constant>
    </constants>

可以看到，这里使用十六进制表示一个具体的ThreadState值。整理一下：

Thread State Flags
Constant	Value	Description
JVMTI_THREAD_STATE_ALIVE	0x0001	Thread is alive. Zero if thread is new (not started) or terminated.
JVMTI_THREAD_STATE_TERMINATED	0x0002	Thread has completed execution.
JVMTI_THREAD_STATE_RUNNABLE	0x0004	Thread is runnable.
JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER	0x0400	Thread is waiting to enter a synchronization block/method or, after an Object.wait(), waiting to re-enter a synchronization block/method.
JVMTI_THREAD_STATE_WAITING	0x0080	Thread is waiting.
JVMTI_THREAD_STATE_WAITING_INDEFINITELY	0x0010	Thread is waiting without a timeout. For example, Object.wait().
JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT	0x0020	Thread is waiting with a maximum time to wait specified. For example, Object.wait(long).
JVMTI_THREAD_STATE_SLEEPING	0x0040	Thread is sleeping -- Thread.sleep(long).
JVMTI_THREAD_STATE_IN_OBJECT_WAIT	0x0100	Thread is waiting on an object monitor -- Object.wait.
JVMTI_THREAD_STATE_PARKED	0x0200	Thread is parked, for example: LockSupport.park, LockSupport.parkUtil and LockSupport.parkNanos.
JVMTI_THREAD_STATE_SUSPENDED	0x100000	Thread suspended. java.lang.Thread.suspend() or a JVM TI suspend function (such as [SuspendThread](file:///home/alanjin/gitspace/jdk10/hotspot/src/share/vm/prims/jvmti.xml#SuspendThread)) has been called on the thread. If this bit is set, the other bits refer to the thread state before suspension.
JVMTI_THREAD_STATE_INTERRUPTED	0x200000	Thread has been interrupted.
JVMTI_THREAD_STATE_IN_NATIVE	0x400000	Thread is in native code--that is, a native method is running which has not called back into the VM or Java programming language code. This flag is not set when running VM compiled Java programming language code nor is it set when running VM code or VM support code. Native VM interface functions, such as JNI and JVM TI functions, may be implemented as VM code.
JVMTI_THREAD_STATE_VENDOR_1	0x10000000	Defined by VM vendor.
JVMTI_THREAD_STATE_VENDOR_2	0x20000000	Defined by VM vendor.
JVMTI_THREAD_STATE_VENDOR_3	0x40000000	Defined by VM vendor.

注意其中的值都是16进制数据，而实际上是用位（bit）来组合计算的。