线程同步之lock学习

在应用程序中使用多个线程的一个好处是每个线程都可以异步执行。然而，线程的异步特性意味着必须协调对资源（如文件句柄、网络连接和内存）的访问。否则，两个或更多的线程可能在同一时间访问相同的资源，而每个线程都不知道其他线程的操作。结果将产生不可预知的数据损坏。这个时候我们就需要lock上场了。

Lock的作用

Lock获取给定对象的互斥锁，保证相应的代码块运行时，不会被其他线程中断;直到该对象被释放时其他线程才能访问相应的代码块；

Lock实现本质

通过System.Threading.Monitor的enter和exit方法实现的

代码实例如下

 

View Code

 

 1 public void PrintByInnerObj(object greating)
 2        { 
 3            Console.WriteLine(greating+"-- before lock");           
 4            object obj = new object();           
 5            lock(obj)
 6            {
 7                Console.WriteLine(greating + "-- is locking");
 8                Console.WriteLine(greating.ToString());
 9                System.Threading.Thread.Sleep(10000);
10            }
11            Console.WriteLine(greating + "--  has unlock");
12        }

 

 对应的MSIL代码如下

 

public   void  PrintByInnerObj( object  greating)
 2          { 
 3              Console.WriteLine(greating + " -- before lock " );           
 4               object  obj  =   new   object ();           
 5               lock (obj)
 6              {
 7                  Console.WriteLine(greating  +   " -- is locking " );
 8                  Console.WriteLine(greating.ToString());
 9                  System.Threading.Thread.Sleep( 10000 );
10              }
11              Console.WriteLine(greating  +   " --  has unlock " );
12          }

 

Lock的锁定范围

Lock的参数必须为引用类型的对象，该对象代表了锁定的范围，对象不同锁定的范围也不同。 

锁定参数为待锁定代码块内声明的对象，锁定范围为该代码块

 

View Code

 

 1 public void PrintByInnerObj(objectgreating)
 2 
 3 { 
 4 
 5 Console.WriteLine(greating+"-- before lock"); 
 6 
 7 object obj=newobject(); 
 8 
 9 lock(obj)
10 
11 {
12 
13 Console.WriteLine(greating+"-- is locking");
14 
15 Console.WriteLine(greating.ToString());
16 
17 System.Threading.Thread.Sleep(10000);
18 
19 }
20 
21 Console.WriteLine(greating+"-- has unlock");
22 
23 }

 

 

锁定参数为待锁定代码块所在类的私有字段，锁定范围为该类具体的一个实例

 

1  .method   public   hidebysig   instance   void   PrintByInnerObj( object  greating)  cil   managed
 2  {
 3     //  Code size       116 (0x74)
 4     .maxstack    2
 5     .locals   init  ([ 0 ]  object  obj,
 6             [ 1 ]  bool   ' <>s__LockTaken0 ' ,
 7             [ 2 ]  object  CS$ 2 $ 0000 ,
 8             [ 3 ]  bool  CS$ 4 $ 0001 )
 9     IL_0000:    nop
10     IL_0001:    ldarg.1
11     IL_0002:    ldstr        " -- before lock "
12     IL_0007:    call         string  [mscorlib]System.String::Concat( object ,
13                                                                 object )
14     IL_000c:    call         void  [mscorlib]System.Console::WriteLine( string )
15     IL_0011:    nop
16     IL_0012:    newobj       instance   void  [mscorlib]System.Object::.ctor()
17     IL_0017:    stloc.0
18     IL_0018:    ldc.i4.0
19     IL_0019:    stloc.1
20    .try
21    {
22       IL_001a:    ldloc.0
23       IL_001b:    dup
24       IL_001c:    stloc.2
25       IL_001d:    ldloca.s     ' <>s__LockTaken0 '
26       IL_001f:    call         void  [mscorlib]System.Threading.Monitor::Enter( object ,
27                                                                           bool &)
28       IL_0024:    nop
29       IL_0025:    nop
30       IL_0026:    ldarg.1
31       IL_0027:    ldstr        " -- is locking "
32       IL_002c:    call         string  [mscorlib]System.String::Concat( object ,
33                                                                   object )
34       IL_0031:    call         void  [mscorlib]System.Console::WriteLine( string )
35       IL_0036:    nop
36       IL_0037:    ldarg.1
37       IL_0038:    callvirt     instance   string  [mscorlib]System.Object::ToString()
38       IL_003d:    call         void  [mscorlib]System.Console::WriteLine( string )
39       IL_0042:    nop
40       IL_0043:    ldc.i4       0x2710
41       IL_0048:    call         void  [mscorlib]System.Threading.Thread::Sleep( int32 )
42       IL_004d:    nop
43       IL_004e:    nop
44       IL_004f:    leave .s    IL_0061
45    }   //  end .try
46    finally
47    {
48       IL_0051:    ldloc.1
49       IL_0052:    ldc.i4.0
50       IL_0053:   ceq
51       IL_0055:    stloc.3
52       IL_0056:    ldloc.3
53       IL_0057:    brtrue.s    IL_0060
54       IL_0059:    ldloc.2
55       IL_005a:    call         void  [mscorlib]System.Threading.Monitor::Exit( object )
56       IL_005f:    nop
57       IL_0060:    endfinally
58    }   //  end handler
59     IL_0061:    nop
60     IL_0062:    ldarg.1
61     IL_0063:    ldstr        " --  has unlock "
62     IL_0068:    call         string  [mscorlib]System.String::Concat( object ,
63                                                                 object )
64     IL_006d:    call         void  [mscorlib]System.Console::WriteLine( string )
65     IL_0072:    nop
66     IL_0073:    ret
67  }  //  end of method MyLockTest::PrintByInnerObj

 

锁定参数为待锁定代码块所在类的私有静态字段，锁定范围为该类所有的实例

 

 1  public   void  PrintByInnerObj(objectgreating)
 2 
 3  { 
 4 
 5  Console.WriteLine(greating + " -- before lock " ); 
 6 
 7  object  obj = newobject(); 
 8 
 9  lock (obj)
10 
11  {
12 
13  Console.WriteLine(greating + " -- is locking " );
14 
15  Console.WriteLine(greating.ToString());
16 
17  System.Threading.Thread.Sleep( 10000 );
18 
19  }
20 
21  Console.WriteLine(greating + " -- has unlock " );
22 
23  }

 

锁定参数为某一字符串，锁定范围为与该字符串值相等的所有字符串

 

public   void  PrintByInstanceObj(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " ); 
 6  
 7   lock  (instanceObj)
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   System.Threading.Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " -- has unlock " );
20  
21   }

 

锁定参数为this，锁定范围为所有能访问到this的地方

 

1   public   void  PrintLockByStaticObj(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " ); 
 6  
 7   lock  (staticObj)
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " -- has unlock " );
20  
21   }

 

锁定参数为某个类的System.Type的实例，锁定范围为所有的地方

 

锁定public的实例字段，锁定范围同锁定this

 

 1   public   void  PrintLockByStringObj(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " ); 
 6  
 7   lock  (stringObj)
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   System.Threading.Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " --has unlock " );
20  
21   }
22  
23  
24   public   void  PrintLockByString(objectgreating)
25  
26   {
27  
28   Console.WriteLine(greating + " -- before lock " ); 
29  
30   lock  ( " lock " )
31  
32   {
33  
34   Console.WriteLine(greating + " -- is locking " );
35  
36   Console.WriteLine(greating.ToString());
37  
38   System.Threading.Thread.Sleep( 10000 );
39  
40   }
41  
42   Console.WriteLine(greating + " --has unlock " );
43  
44   } 

 

锁定参数为public的静态字段，锁定范围与锁定system.type相同

 1   public   void  PrintLockByThis(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " ); 
 6  
 7   lock  ( this )
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   System.Threading.Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " --has unlock " );
20  
21   }

 

 

整个类的代码如下

 

1   public   void  PrintLockByPublicInstanceObj(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " );
 6  
 7   lock  (publicInstanceObj)
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   System.Threading.Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " --has unlock " );
20  
21   }

 

  1   public   void  PrintLockByPublicStaticObj(objectgreating)
 2  
 3   {
 4  
 5   Console.WriteLine(greating + " -- before lock " );
 6  
 7   lock  (publicStaticObj)
 8  
 9   {
10  
11   Console.WriteLine(greating + " -- is locking " );
12  
13   Console.WriteLine(greating.ToString());
14  
15   System.Threading.Thread.Sleep( 10000 );
16  
17   }
18  
19   Console.WriteLine(greating + " --has unlock " );
20  
21   }

整个类的代码如下

 

1   using  System;
  2   using  System.Collections.Generic;
  3   using  System.Linq;
  4   using  System.Text;
  5   using  System.Threading;
  6  
  7   namespace  LockCVolatileCA
  8   {
  9       public   class  MyLockTest
 10       {
 11           private   static   object  staticObj  =   new   object ();
 12           private   object  instanceObj  =   new   object ();
 13           public   static   object  publicStaticObj  =   new   object ();
 14           public   object  publicInstanceObj  =   new   object ();
 15           private   string  stringObj  =   " lock " ;
 16           private   static  Int32 i  =   new   int ()  ;
 17  
 18           public   void  PrintByInnerObj( object  greating)
 19          { 
 20              Console.WriteLine(greating + " -- before lock " );          
 21               object  obj  =   new   object ();           
 22               lock (obj)
 23              {
 24                  Console.WriteLine(greating  +   " -- is locking " );
 25                  Console.WriteLine(greating.ToString());
 26                  System.Threading.Thread.Sleep( 10000 );
 27              }
 28              Console.WriteLine(greating  +   " --  has unlock " );
 29          }
 30  
 31           public   void  PrintByInstanceObj( object  greating)
 32          {
 33              Console.WriteLine(greating  +   " -- before lock " );                    
 34               lock  (instanceObj)
 35              {
 36                  Console.WriteLine(greating  +   " -- is locking " );
 37                  Console.WriteLine(greating.ToString());
 38                  System.Threading.Thread.Sleep( 10000 );
 39              }
 40              Console.WriteLine(greating  +   " --  has unlock " );
 41          }
 42  
 43           public   void  PrintLockByStaticObj( object  greating)
 44          {
 45              Console.WriteLine(greating  +   " -- before lock " );           
 46               lock  (staticObj)
 47              {
 48                  Console.WriteLine(greating  +   " -- is locking " );
 49                  Console.WriteLine(greating.ToString());
 50                  Thread.Sleep( 10000 );
 51              }
 52              Console.WriteLine(greating  +   " -- has unlock " );
 53          }
 54  
 55           public   void  PrintLockByClass( object  greating)
 56          {
 57              Console.WriteLine(greating  +   " -- before lock " );         
 58               lock  ( typeof (MyLockTest))
 59              {
 60                  Console.WriteLine(greating  +   " -- is locking " );
 61                  Console.WriteLine(greating.ToString());
 62                  Thread.Sleep( 1000 );
 63              }
 64              Console.WriteLine(greating  +   " -- has unlock " );
 65          }
 66  
 67           public   void  PrintLockByThis( object  greating)
 68          {
 69              Console.WriteLine(greating  +   " -- before lock " );        
 70               lock  ( this )
 71              {
 72                  Console.WriteLine(greating  +   " -- is locking " );
 73                  Console.WriteLine(greating.ToString());
 74                  System.Threading.Thread.Sleep( 10000 );
 75              }
 76              Console.WriteLine(greating  +   " --has unlock " );
 77          }
 78  
 79           public   void  PrintLockByStringObj( object  greating)
 80          {
 81              Console.WriteLine(greating  +   " -- before lock " );       
 82               lock  (stringObj)
 83              {
 84                  Console.WriteLine(greating  +   " -- is locking " );
 85                  Console.WriteLine(greating.ToString());
 86                  System.Threading.Thread.Sleep( 10000 );
 87              }
 88              Console.WriteLine(greating  +   " --has unlock " );
 89          }
 90  
 91           public   void  PrintLockByString( object  greating)
 92          {
 93              Console.WriteLine(greating  +   " -- before lock " );         
 94               lock  ( " lock " )
 95              {
 96                  Console.WriteLine(greating  +   " -- is locking " );
 97                  Console.WriteLine(greating.ToString());
 98                  System.Threading.Thread.Sleep( 10000 );
 99              }
100              Console.WriteLine(greating  +   " --has unlock " );
101          }
102  
103           public   void  PrintLockByPublicStaticObj( object  greating)
104          {
105              Console.WriteLine(greating  +   " -- before lock " );           
106               lock  (publicStaticObj)
107              {
108                  Console.WriteLine(greating  +   " -- is locking " );
109                  Console.WriteLine(greating.ToString());
110                  System.Threading.Thread.Sleep( 10000 );
111              }
112              Console.WriteLine(greating  +   " --has unlock " );
113          }
114  
115           public   void  PrintLockByPublicInstanceObj( object  greating)
116          {
117              Console.WriteLine(greating  +   " -- before lock " );
118               lock  (publicInstanceObj)
119              {
120                  Console.WriteLine(greating  +   " -- is locking " );
121                  Console.WriteLine(greating.ToString());
122                  System.Threading.Thread.Sleep( 10000 );
123              }
124              Console.WriteLine(greating  +   " --has unlock " );
125          }       
126       }
127   }

 

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