ThreadState

浅析android 线程状态

java的6种线程状态定义在/java/lang/Thread.java中:

https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.State.html

//Thread.java
public class Thread implements Runnable {
    ...
    public enum State {
        /**
         * The thread has been created, but has never been started.
         */
        NEW,
        /**
         * The thread may be run.
         */
        RUNNABLE,
        /**
         * The thread is blocked and waiting for a lock.
         */
        BLOCKED,
        /**
         * The thread is waiting.
         */
        WAITING,
        /**
         * The thread is waiting for a specified amount of time.
         */
        TIMED_WAITING,
        /**
         * The thread has been terminated.
         */
        TERMINATED
    }
    ...
}

在VMThread.java中, 可以看到下面的代码， native thread有10种状态, 对应着java thread的6种状态.

//VMThread.java
    /**
     * Holds a mapping from native Thread statuses to Java one. Required for
     * translating back the result of getStatus().
     */
    static final Thread.State[] STATE_MAP = new Thread.State[] {
        Thread.State.TERMINATED,     // ZOMBIE
        Thread.State.RUNNABLE,       // RUNNING
        Thread.State.TIMED_WAITING,  // TIMED_WAIT
        Thread.State.BLOCKED,        // MONITOR
        Thread.State.WAITING,        // WAIT
        Thread.State.NEW,            // INITIALIZING
        Thread.State.NEW,            // STARTING
        Thread.State.RUNNABLE,       // NATIVE
        Thread.State.WAITING,        // VMWAIT
        Thread.State.RUNNABLE        // SUSPENDED
    };

在之前的文章中， 已经分析了android thread的底层实现其实就是linux下的pthread. 我们再看一下native层的Thread.cpp, 有这段代码:

const char* dvmGetThreadStatusStr(ThreadStatus status)
{
    switch (status) {
        case THREAD_ZOMBIE:         return "ZOMBIE";
        case THREAD_RUNNING:        return "RUNNABLE";
        case THREAD_TIMED_WAIT:     return "TIMED_WAIT";
        case THREAD_MONITOR:        return "MONITOR";
        case THREAD_WAIT:           return "WAIT";
        case THREAD_INITIALIZING:   return "INITIALIZING";
        case THREAD_STARTING:       return "STARTING";
        case THREAD_NATIVE:         return "NATIVE";
        case THREAD_VMWAIT:         return "VMWAIT";
        case THREAD_SUSPENDED:      return "SUSPENDED";
        default:                    return "UNKNOWN";
    }
}

实际上， 写入traces.txt中的线程状态值就是这个函数返回的字符串. 所以我们就知道了如下的事实:

"main" prio=5 tid=1 MONITOR  其实就是java中的BLOCKED状态.
"Timer-0" daemon prio=5 tid=23 TIMED_WAIT 其实就是java中的TIMED_WAITING状态
"QMThreadPool #3" daemon prio=3 tid=22 WAIT 其实就是java中的WAITING状态
"WifiManager" prio=5 tid=20 NATIVE 其实就是java中的RUNNABLE状态
"Signal Catcher" daemon prio=5 tid=3 RUNNABLE 其实就是java中的RUNNABLE状态