1.线程池中空闲的线程线程线程处于什么状态?
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3.Qt——QThread源码浅析
线程池中空闲的线程处于什么状态?
一:阻塞状态,线程并没有销毁,也没有得到CPU时间片执行;
源码追踪:
for (;;) {
...
workQueue.take();
...
}
public E take()...{
...
while (count.get() == 0) { / /这里就是任务队列中的消息数量
notEmpty.await();
}
...
}
public final void await()...{
...
LockSupport.park(this);
...
}
继续往下:
public static void park(Object blocker) {
Thread t = Thread.currentThread();
setBlocker(t, blocker);
U.park(false, 0L);
setBlocker(t, null);
}
private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
//线程调用该方法,线程将一直阻塞直到超时,结束结束或者是源码中断条件出现。
public native void park(boolean isAbsolute,线程线程 long time);
上面就是java线程池中阻塞的源码追踪;
二.对比object的wait()方法:
@FastNative
public final native void wait(long timeout, int nanos) throws InterruptedException;
还有Thread的sleep() 方法:
@FastNative
private static native void sleep(Object lock, long millis, int nanos)throws...;
可见,线程池中使用的阻塞方式并不是Object中的wait(),也不是Thread.sleep() ;
这3个方法最终实现都是通过c&c++实现的native方法.
三.在<<Java虚拟机(第二版)>>中,对线程状态有以下介绍:
.4.3 状态转换
Java语言定义了5种线程状态,在任意一个时间点,结束结束一个线程只能有且只有其中的源码聊天mtk源码一种
状态,这5种状态分别如下。线程线程
1)新建(New):创建后尚未启动的结束结束线程处于这种状态。
2)运行(Runable):Runable包括了操作系统线程状态中的源码Running和Ready,也就是线程线程处于此
状态的线程有可能正在执行,也有可能正在等待着CPU为它分配执行时间。结束结束
3)无限期等待(Waiting):处于这种状态的源码线程不会被分配CPU执行时间,它们要等待被
其他线程显式地唤醒。线程线程以下方法会让线程陷入无限期的结束结束等待状态:
●没有设置Timeout参数的Object.wait()方法。
●没有设置Timeout参数的源码视频三端源码Thread.join()方法。
●LockSupport.park()方法。
4)限期等待(Timed Waiting):处于这种状态的线程也不会被分配CPU执行时间,不过无
须等待被其他线程显式地唤醒,在一定时间之后它们会由系统自动唤醒。以下方法会让线程
进入限期等待状态:
●Thread.sleep()方法。
●设置了Timeout参数的Object.wait()方法。
●设置了Timeout参数的web在线封装源码Thread.join()方法。
●LockSupport.parkNanos()方法。
●LockSupport.parkUntil()方法。
5)阻塞(Blocked):线程被阻塞了,“阻塞状态”与“等待状态”的区别是:“阻塞状态”在等
待着获取到一个排他锁,这个事件将在另外一个线程放弃这个锁的时候发生;而“等待状
态”则是在等待一段时间,或者唤醒动作的发生。在程序等待进入同步区域的视频论坛php源码时候,线程将
进入这种状态。
结束(Terminated):已终止线程的线程状态,线程已经结束执行。
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Option Explicit
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Private Declare Function GetTickCount Lib "kernel" () As Long
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Public myThreadleft As New cls_thread, myThreadright As New cls_thread, myThreadbottom As New cls_thread
Sub Main()
Load Form1
Form1.Show
End Sub
Public Sub Fillleft()
Static Bkgcolor As Long
Dim LongTick As Long, Longcounter As Long
On Error Resume Next
For Longcounter = 0 To
DoEvents
Bkgcolor = Longcounter Mod
Form1.Picture1.BackColor = RGB(Bkgcolor, 0, 0)
LongTick = GetTickCount
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Wend
Next
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End Sub
Public Sub Fillright()
Static Bkgcolor As Long
Dim LongTickValue As Long, Longcounter As Long
On Error Resume Next
For Longcounter = 0 To
DoEvents
Bkgcolor = Longcounter Mod
Form1.Picture2.BackColor = RGB(0, Bkgcolor, 0)
LongTickValue = GetTickCount
While GetTickCount - LongTickValue <
Wend
Next
Set myThreadright = Nothing
End Sub
Public Sub Fillbottom()
Static Bkgcolor As Long
Dim LongTick As Long, Longcounter As Long
On Error Resume Next
For Longcounter = 0 To
DoEvents
Bkgcolor = Longcounter Mod
Form1.Picture3.BackColor = RGB(0, 0, Bkgcolor)
LongTick = GetTickCount
While GetTickCount - LongTick <
Wend
Next
Set myThreadright = Nothing
End Sub
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Option Explicit
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Private Declare Function CreateThread Lib "kernel" (ByVal lpThreadAttributes As Any, ByVal dwStackSize As Long, ByVal lpStartAddress As Long, lpParameter As Any, ByVal dwCreationFlags As Long, LpthreadId As Long) As Long
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Private Declare Function TerminateThread Lib "kernel" (ByVal hThread As Long, ByVal dwExitCode As Long) As Long
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Private Declare Function ResumeThread Lib "kernel" (ByVal hThread As Long) As Long
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Private Declare Function SuspendThread Lib "kernel" (ByVal hThread As Long) As Long
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Private Type udtThread
Handle As Long
Enabled As Boolean
End Type
Private meTheard As udtThread
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Public Sub Initialize(ByVal LongPointFunction As Long)
Dim LongStackSize As Long, LongCreationFlags As Long, LpthreadId As Long, LongNull As Long
On Error Resume Next
LongNull = 0
LongStackSize = 0
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meTheard.Handle = CreateThread(LongNull, LongStackSize, ByVal LongPointFunction, LongNull, LongCreationFlags, LpthreadId)
If meTheard.Handle = LongNull Then
MsgBox "线ç¨å建失败ï¼", , "é误"
End If
End Sub
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Public Property Get ThreadEnabled() As Boolean
On Error Resume Next
Enabled = meTheard.Enabled
End Property
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Public Property Let ThreadEnabled(ByVal Newvalue As Boolean)
On Error Resume Next
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ResumeThread meTheard.Handle
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If meTheard.Enabled Then
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meTheard.Enabled = False
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End Property
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Private Sub Class_Terminate()
On Error Resume Next
Call TerminateThread(meTheard.Handle, 0)
End Sub
Qt——QThread源码浅析
在探索Qt的多线程处理中,QThread类的实现源码历经变迁。在Qt4.0.1和Qt5.6.2版本中,尽管QThread类的c语言switch源码声明相似,但run()函数的实现有所不同。从Qt4.4开始,QThread不再是抽象类,这标志着一些关键调整。
QThread::start()函数在不同版本中的核心代码保持基本一致,其中Q_D()宏定义是一个预处理宏,用于获取QThread的私有数据。_beginthreadex()函数则是创建线程的核心,调用QThreadPrivate::start(this),即执行run()函数并发出started()信号。
QThread::run()函数在Qt4.4后的版本中,不再强制要求重写,而是可以通过start启动事件循环。在Qt5.6.2版本中,run函数的定义更灵活,可以根据需要进行操作。
关于线程停止,QThread提供了quit()、exit()和terminate()三种方式。quit()和exit(0)等效,用于事件循环中停止线程,而terminate()则立即终止线程,但不推荐使用,因为它可能引发不稳定行为。
总结起来,QThread的核心功能包括线程的创建、run函数的执行以及线程的结束控制。从Qt4.4版本开始,QThread的使用变得更加灵活,可以根据需要选择是否重写run函数,以及如何正确地停止线程。不同版本间的细微差别需要开发者注意,以确保代码的兼容性和稳定性。