C#多线程技术总结（同步）

二、串行（同步）：

1.lock、Monitor--注意锁定的对象必需是引用类型（string类型除外）

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
private static object syncObject = new object();

private static void TaskWork(object i)
{
Console.WriteLine("我是任务：{0}",i);
lock (syncObject)
{
Thread.Sleep(1000);
Console.WriteLine("我是任务：{0},线程ID:{1}",i,Thread.CurrentThread.ManagedThreadId);
}

try
{
Monitor.Enter(syncObject);
Console.WriteLine("我是任务：{0},线程ID:{1}", i, Thread.CurrentThread.ManagedThreadId);
}
finally
{
Monitor.Exit(syncObject);
}
}

//调用
Task.Factory.StartNew(TaskWork,1);
Task.Factory.StartNew(TaskWork, 2);
2.Interlocked

示例：

1
2
3
4
5
6
7
8
9
10
11
12
int i=1;
Interlocked.Increment(ref i); //增量+1=2;
Console.WriteLine("i当前的值：{0}", i);

Interlocked.Decrement(ref i); //减量-1=0;
Console.WriteLine("i当前的值：{0}", i);

Interlocked.Exchange(ref i, 2);//赋值=2;
Console.WriteLine("i当前的值：{0}",i);

Interlocked.CompareExchange(ref i, 10, 2);//比较交换值，当i=2时，则将i赋值为10；
Console.WriteLine("i当前的值：{0}", i);
3.Mutex--可以实现进程间的同步，甚至是两个远程进程间的同步

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
var t1 = new Task(() =>
{
Console.WriteLine("我是第一个任务！");
Mutex m = new Mutex(false, "test");
m.WaitOne();
Console.WriteLine("第一个任务完成！");
m.ReleaseMutex();
});

var t2 = new Task(() =>
{
Console.WriteLine("我是第二个任务！");
Mutex m = new Mutex(false, "test");
m.WaitOne();
Console.WriteLine("第二个任务完成！");
m.ReleaseMutex();
});

t1.Start();
t2.Start();
4.ReaderWriterLock 、ReaderWriterLockSlim--如果在某一时刻资源并没有获取写的独占权,那么可以获得多个读的访问权,单个写入的独占权,如果某一时刻已经获取了写入的独占权,那么其它读取的访问权必须进行等待.

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
static ReaderWriterLock rwLock = new ReaderWriterLock();

static void Read(object state)
{
Console.WriteLine("我是读线程，线程ID是：{0}",Thread.CurrentThread.ManagedThreadId);
rwLock.AcquireReaderLock(Timeout.Infinite);//无限期等待,需要显式调用ReleaseReaderLock释放锁
var readList = state as IEnumerable<int>;
foreach (int item in readList)
{
Console.WriteLine("读取当前的值为：{0}", item);
Thread.Sleep(500);
}
Console.WriteLine("读完成，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
rwLock.ReleaseReaderLock();

}

static void Write(object state)
{
Console.WriteLine("我是写线程，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
rwLock.AcquireWriterLock(Timeout.Infinite); //无限期等待,需要显式调用ReleaseWriterLock释放锁
var writeList = state as List<int>;
int lastCount=writeList.Count();
for (int i = lastCount; i <= 10+lastCount; i++)
{
writeList.Add(i);
Console.WriteLine("写入当前值：{0}",i);
Thread.Sleep(500);
}
Console.WriteLine("写完成，线程ID是：{0}", Thread.CurrentThread.ManagedThreadId);
rwLock.ReleaseWriterLock();
}

//调用：
var rwList = new List<int>();

var t1 = new Thread(Write);
var t2 = new Thread(Read);
var t3 = new Thread(Write);
var t4 = new Thread(Read);

t1.Start(rwList);
t2.Start(rwList);
t3.Start(rwList);
t4.Start(rwList);

5.SynchronizationAttribute--确保某个类的实例在同一时刻只能被一个线程访问，类的定义要求：A.类上必需标记SynchronizationAttribute特性，B.类必需继承自System.ContextBoundObject对象

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
[Synchronization(SynchronizationAttribute.REQUIRED,true)]
public class Account : System.ContextBoundObject
{
private static int _balance;
public int Blance
{
get
{
return _balance;
}
}

public Account()
{
_balance = 1000;
}

public void WithDraw(string name,object money)
{
if ((int)money <= _balance)
{
Thread.Sleep(2000);
_balance = _balance - (int)money;
Console.WriteLine("{0} 取钱成功！余额={1}", name, _balance);
}
else
{
Console.WriteLine("{0} 取钱失败！余额不足！", name);
}
}
}

//调用：
var account = new Account();
Parallel.Invoke(() =>
{
account.WithDraw("张三",600);

}, () =>
{
account.WithDraw("李四",600);
});
6.MethodImplAttribute--使整个方法上锁，直到方法返回，才释放锁

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
public class Account
{
private static int _balance;
public int Blance
{
get
{
return _balance;
}
}

public Account()
{
_balance = 1000;
}

[MethodImpl(MethodImplOptions.Synchronized)]
public void WithDraw(string name,object money)
{
if ((int)money <= _balance)
{
Thread.Sleep(2000);
_balance = _balance - (int)money;
Console.WriteLine("{0} 取钱成功！余额={1}", name, _balance);
}
else
{
Console.WriteLine("{0} 取钱失败！余额不足！", name);
}
}
}

//调用
var account = new Account();
Parallel.Invoke(() =>
{
account.WithDraw("张三",600);

}, () =>
{
account.WithDraw("李四",600);
});
7.AutoResetEvent、ManualResetEvent、ManualResetEventSlim--调用WaitOne、WaitAny或WaitAll来使线程等待事件,调用Set方法发送信号，事件将变为终止状态，等待的线程被唤醒

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
AutoResetEvent arEvent = new AutoResetEvent(false);//默认为无信号，处于非终止状态
Task.Factory.StartNew((o) => {
for (int i = 1; i <= 10; i++)
{
Console.WriteLine("循环第{0}次",i);
}
arEvent.Set();//发送信号，处于终止状态
},arEvent);

arEvent.WaitOne();//等待信号，收到信号后则继续下面的执行

Console.WriteLine("我是主线程，我继续执行！");
Console.Read();
8.Sempaphore、SemaphoreSlim（不可跨进程）--信号量，可实现线程、进程间同步

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
public class WashRoom
{
private readonly Semaphore sem;

public WashRoom(int maxUseableCount)
{
sem = new Semaphore(maxUseableCount, maxUseableCount, "WC");
}

public void Use(int i)
{
Task.Factory.StartNew(() =>
{
Console.WriteLine("第{0}个人等待进入", i);
// WaitOne:如果还有“空位”，则占位，如果没有空位，则等待；
sem.WaitOne();
Console.WriteLine("第{0}个人成功进入，使用中", i);
// 模拟线程执行了一些操作
Thread.Sleep(100);
Console.WriteLine("第{0}个人用完，离开了", i);
// Release:释放一个“空位”
sem.Release();
});
}
}

//调用：
var wc = new WashRoom(5);
for (int i = 1; i <= 7; i++)
{
wc.Use(i);
}
9.Barrier--屏障，使多个任务能够采用并行方式依据某种算法在多个阶段中协同工作，即：将一个阶段的事情分成多个线程来异步执行，执行完毕后再同时进入下一个阶段

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
int taskSize = 5;
Barrier barrier = new Barrier(taskSize, (b) =>
{
Console.WriteLine(string.Format("{0}当前阶段编号：{1}{0}", "-".PadRight(15, '-'), b.CurrentPhaseNumber));
});

var tasks = new Task[taskSize];

for (int i = 0; i < taskSize; i++)
{
tasks[i] = Task.Factory.StartNew((n) =>
{
Console.WriteLine("Task : #{0}   ---->  处理了第一部份数据。", n);
barrier.SignalAndWait();

Console.WriteLine("Task : #{0}   ---->  处理了第二部份数据。", n);
barrier.SignalAndWait();

Console.WriteLine("Task : #{0}   ---->  处理了第三部份数据。", n);
barrier.SignalAndWait();

}, i);
}

Task.WaitAll(tasks);
10.SpinLock--自旋锁,仅限锁定的时间较短

示例：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
SpinLock sLock = new SpinLock();
int num = 0;
Action action = () =>
{
bool lockTaken = false;
for (int i = 0; i < 10; i++)
{
lockTaken = false;
try
{
sLock.Enter(ref lockTaken);
Console.WriteLine("{0}+1={1} ---线程ID:[{2}]", num, ++num,Thread.CurrentThread.ManagedThreadId);
Thread.Sleep(new Random().Next(9));
}
finally
{
//真正获取之后，才释放
if (lockTaken) sLock.Exit();
}
}
};

//多线程调用：
Parallel.Invoke(action, action, action);
Console.WriteLine("合计：{0}", num);
11.SpinWait--自旋等待，轻量级

1
2
3
4
5
6
7
8
Thread.Sleep(1000);//线程等待1S;
Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));

SpinWait.SpinUntil(() => false, 1000);//自旋等待1S
Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));

Thread.SpinWait(100000);//指定CPU的循环次数，时间间隔处决于处理器的运行速度,一般不建议使用
Console.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));
12.CountdownEvent--与Sempaphore功能类似，但CountdownEvent支持动态调整信号计数

示例：

static void TimeLimitShopping(int custCount,int times,CountdownEvent countdown)
{
var customers = Enumerable.Range(1, custCount);
foreach (var customer in customers)
{
int currentCustomer = customer;
Task.Factory.StartNew(()=>
{
SpinWait.SpinUntil(() => false, 1000);
Console.WriteLine("第{0}波客户购买情况：Customer-{1}-已购买.", times, currentCustomer);
countdown.Signal();
});
//countdown.AddCount();
}
}

//调用：
var countdown = new CountdownEvent(5);
TimeLimitShopping(5, 1, countdown);
countdown.Wait();

countdown.Reset(10);
TimeLimitShopping(10, 2, countdown);
countdown.Wait();

countdown.Reset(20);
TimeLimitShopping(20, 3, countdown);
countdown.Wait();
最后分享在System.Collections.Concurrent命名空间下的几个并发集合类：

ConcurrentBag<T>：表示线程安全的无序集合；

ConcurrentDictionary<T>：表示线程安全的多个键值对集合；

ConcurrentQueue<T>：表示线程安全的先进先出集合；

ConcurrentStack<T>：表示线程安全的后进先出集合；

线程的几个状态(以下图片来源于这篇文章：http://www.cnblogs.com/edisonchou/p/4848131.html)：