.NET线程同步
关键字 C#,线程,同步
在处理.net线程同步问题,有许多办法,这里所将谈到的是特定代码区的同步.
这些特定的代码区是方法中重要的代码段,他们可以改变对象的状态,或者更新另一个资源.
Monitor类用于同步代码去,其方式是使用Monitor.Enter()方法获得一个锁,然后使用Monitor.Exit()方法释放该锁.
示例如下:
using System;
using System.Threading;
namespace EnterExit
{
public class EnterExit
{
private int result=0;
public EnterExit()
{
}
public void NonCriticalSection()
{
Console.WriteLine("Enter Threah"+Thread.CurrentThread.GetHashCode());
for(int i=1;i<=5;i++)
{
Console.WriteLine("Result="+result++ +" ThreadID"+Thread.CurrentThread.GetHashCode());
Thread.Sleep(1000);
}
Console.WriteLine("Exiting Threah"+Thread.CurrentThread.GetHashCode());
}
public void CriticalSection()
{
Monitor.Enter(this);
Console.WriteLine("Enter Threah"+Thread.CurrentThread.GetHashCode());
for(int i=1;i<=5;i++)
{
Console.WriteLine("Result="+result++ +" ThreadID"+Thread.CurrentThread.GetHashCode());
Thread.Sleep(1000);
}
Console.WriteLine("Exiting Threah"+Thread.CurrentThread.GetHashCode());
Monitor.Exit(this);
}
public static void Main(String[] args)
{
EnterExit e=new EnterExit();
if(args.Length>0)
{
Thread nt1=new Thread(new ThreadStart(e.NonCriticalSection));
nt1.Start();
Thread nt2=new Thread(new ThreadStart(e.NonCriticalSection));
nt2.Start();
}
else
{
Thread ct1=new Thread(new ThreadStart(e.CriticalSection));
ct1.Start();
Thread ct2=new Thread(new ThreadStart(e.CriticalSection));
ct2.Start();
}
}
}
}
运行结果:
Enter Threah 1
Result=0 Thread1
Result=1 Thread1
Result=2 Thread1
Result=3 Thread1
Result=4 Thread1
Exiting Thread1
Enter Threah 2
Result=5 Thread2
Result=6 Thread2
Result=7 Thread2
Result=8 Thread2
Result=9 Thread2
Exiting Thread2
------------------------------------------------------------------------------
Monitor类的TryEnter()方法非常类似于Enter()方法,他试图获得对象的独占锁,不过它不会象Enter()方法那样暂停. 如果线程成功进入,则TryEnter()方法返回True.
TryEnter()有3种重载方法,其中两个都带有超时参数,表示等待锁定的时间.
using System;
using System.Threading;
namespace MonitorTryEnter
{
public class TryEnter
{
public TryEnter()
{
}
public void CriticalSection()
{
bool b=Monitor.TryEnter(this,1000);
Console.WriteLine("Thread "+Thread.CurrentThread.GetHashCode()+" TryEnter Value "+b);
for(int i=1;i<=3;i++)
{
Thread.Sleep(1000);
Console.WriteLine(i+" "+Thread.CurrentThread.GetHashCode()+" ");
}
Monitor.Exit(this);
}
public static void Main()
{
TryEnter a=new TryEnter();
Thread t1=new Thread(new ThreadStart(a.CriticalSection));
Thread t2=new Thread(new ThreadStart(a.CriticalSection));
t1.Start();
t2.Start();
}
}
}
运行结果:
在可能发生竞争,但不希望线程睡眠某个未指定的时间时,就可以使用TryEnter().
----------------------------------------------------------------------------------------------------------------
另一个同步策略是手控技术,System.Threading命名空间中的一些可以用于手控同步的类。ManualResetEvent类用来使线程处于等待状态,它有2种状态:有信号(True)或无信号(False)。还有2个重要方法:Reset()和Set()。
下面代码说明Reset()方法的用法:
using System;
using System.Threading;
namespace ManualReset
{
class Reset
{
[STAThread]
static void Main()
{
ManualResetEvent manRE;
manRE=new ManualResetEvent(true); // 赋给信号量
bool state=manRE.WaitOne(1000,true);
Console.WriteLine("ManualResetEvent After first waitone "+state);
manRE.Reset(); //设置ManualResetEvent状态为无信号量
state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After second waitone "+state);
}
}
}
运行结果:
下面代码说明Set()方法的用法:
using System;
using System.Threading;
namespace ManualSet
{
class Set
{
[STAThread]
static void Main(string[] args)
{
ManualResetEvent manRE;
manRE=new ManualResetEvent(false);
Console.WriteLine("Before waitone");
bool state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After first waitone "+state);
manRE.Set(); //将其状态设为有信号量
Thread.Sleep(3000);
state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After second waitone "+state);
}
}
}
运行结果:
在处理.net线程同步问题,有许多办法,这里所将谈到的是特定代码区的同步.
这些特定的代码区是方法中重要的代码段,他们可以改变对象的状态,或者更新另一个资源.
Monitor类用于同步代码去,其方式是使用Monitor.Enter()方法获得一个锁,然后使用Monitor.Exit()方法释放该锁.
示例如下:
using System;
using System.Threading;
namespace EnterExit
{
public class EnterExit
{
private int result=0;
public EnterExit()
{
}
public void NonCriticalSection()
{
Console.WriteLine("Enter Threah"+Thread.CurrentThread.GetHashCode());
for(int i=1;i<=5;i++)
{
Console.WriteLine("Result="+result++ +" ThreadID"+Thread.CurrentThread.GetHashCode());
Thread.Sleep(1000);
}
Console.WriteLine("Exiting Threah"+Thread.CurrentThread.GetHashCode());
}
public void CriticalSection()
{
Monitor.Enter(this);
Console.WriteLine("Enter Threah"+Thread.CurrentThread.GetHashCode());
for(int i=1;i<=5;i++)
{
Console.WriteLine("Result="+result++ +" ThreadID"+Thread.CurrentThread.GetHashCode());
Thread.Sleep(1000);
}
Console.WriteLine("Exiting Threah"+Thread.CurrentThread.GetHashCode());
Monitor.Exit(this);
}
public static void Main(String[] args)
{
EnterExit e=new EnterExit();
if(args.Length>0)
{
Thread nt1=new Thread(new ThreadStart(e.NonCriticalSection));
nt1.Start();
Thread nt2=new Thread(new ThreadStart(e.NonCriticalSection));
nt2.Start();
}
else
{
Thread ct1=new Thread(new ThreadStart(e.CriticalSection));
ct1.Start();
Thread ct2=new Thread(new ThreadStart(e.CriticalSection));
ct2.Start();
}
}
}
}
运行结果:
Enter Threah 1
Result=0 Thread1
Result=1 Thread1
Result=2 Thread1
Result=3 Thread1
Result=4 Thread1
Exiting Thread1
Enter Threah 2
Result=5 Thread2
Result=6 Thread2
Result=7 Thread2
Result=8 Thread2
Result=9 Thread2
Exiting Thread2
------------------------------------------------------------------------------
Monitor类的TryEnter()方法非常类似于Enter()方法,他试图获得对象的独占锁,不过它不会象Enter()方法那样暂停. 如果线程成功进入,则TryEnter()方法返回True.
TryEnter()有3种重载方法,其中两个都带有超时参数,表示等待锁定的时间.
using System;
using System.Threading;
namespace MonitorTryEnter
{
public class TryEnter
{
public TryEnter()
{
}
public void CriticalSection()
{
bool b=Monitor.TryEnter(this,1000);
Console.WriteLine("Thread "+Thread.CurrentThread.GetHashCode()+" TryEnter Value "+b);
for(int i=1;i<=3;i++)
{
Thread.Sleep(1000);
Console.WriteLine(i+" "+Thread.CurrentThread.GetHashCode()+" ");
}
Monitor.Exit(this);
}
public static void Main()
{
TryEnter a=new TryEnter();
Thread t1=new Thread(new ThreadStart(a.CriticalSection));
Thread t2=new Thread(new ThreadStart(a.CriticalSection));
t1.Start();
t2.Start();
}
}
}
运行结果:
在可能发生竞争,但不希望线程睡眠某个未指定的时间时,就可以使用TryEnter().
----------------------------------------------------------------------------------------------------------------
另一个同步策略是手控技术,System.Threading命名空间中的一些可以用于手控同步的类。ManualResetEvent类用来使线程处于等待状态,它有2种状态:有信号(True)或无信号(False)。还有2个重要方法:Reset()和Set()。
下面代码说明Reset()方法的用法:
using System;
using System.Threading;
namespace ManualReset
{
class Reset
{
[STAThread]
static void Main()
{
ManualResetEvent manRE;
manRE=new ManualResetEvent(true); // 赋给信号量
bool state=manRE.WaitOne(1000,true);
Console.WriteLine("ManualResetEvent After first waitone "+state);
manRE.Reset(); //设置ManualResetEvent状态为无信号量
state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After second waitone "+state);
}
}
}
运行结果:
下面代码说明Set()方法的用法:
using System;
using System.Threading;
namespace ManualSet
{
class Set
{
[STAThread]
static void Main(string[] args)
{
ManualResetEvent manRE;
manRE=new ManualResetEvent(false);
Console.WriteLine("Before waitone");
bool state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After first waitone "+state);
manRE.Set(); //将其状态设为有信号量
Thread.Sleep(3000);
state=manRE.WaitOne(5000,true);
Console.WriteLine("ManualResetEvent After second waitone "+state);
}
}
}
运行结果: