高性能大容量SOCKET并发(5):锁和对象分离
高性能大容量SOCKET并发(五):锁和对象分离
锁和对象一起封装的危险
在多线程编写中,绝大多数编码风格喜欢把锁和要访问的对象封装在同一个对象,释放对象的时候也释放锁,这样会造成死锁。我们写一个测试例子,我们创建一个锁,把锁锁住,然后再创建一个线程,一直不停的等待锁返回,然后我们把锁释放,这时线程就死锁,代码如下:
定义接口:
type TLockObject = class; TLockTestThread = class; TForm1 = class(TForm) btn1: TButton; mmoLockThreadTest: TMemo; procedure btn1Click(Sender: TObject); procedure FormCreate(Sender: TObject); private FLockTestThread: TLockTestThread; FLockObject: TLockObject; public { Public declarations } end; TLockTestThread = class(TThread) private FLockObject: TLockObject; public procedure Execute; override; procedure AddLockLog; property LockObject: TLockObject read FLockObject write FLockObject; end; TLockObject = class(TObject) private FLock: TCriticalSection; public constructor Create; virtual; destructor Destroy; override; procedure Lock; procedure UnLock; end; var Form1: TForm1;在Form1创建的时候创建锁,并把锁锁住,创建一个线程等待锁返回:procedure TForm1.FormCreate(Sender: TObject); begin FLockObject := TLockObject.Create; FLockObject.Lock; FLockTestThread := TLockTestThread.Create(True); FLockTestThread.LockObject := FLockObject; FLockTestThread.FreeOnTerminate := True; FLockTestThread.Resume; end;线程的执行方法一直等待锁返回,并写一条日志。由于是窗体创建的时候,锁已经锁住了,因此线程会一直等待:procedure TLockTestThread.AddLockLog; begin Form1.mmoLockThreadTest.Lines.Add('Lock') end; procedure TLockTestThread.Execute; begin inherited; while not Terminated do begin FLockObject.Lock; Synchronize(AddLockLog); end; end;这时线程会一直等待,如果我们把FLockObject释放,线程也会一直等待,造成死锁。procedure TForm1.btn1Click(Sender: TObject); begin FLockObject.Lock; FLockObject.Free; FLockObject := nil; end;
锁和对象分离
有了上面的基础之后,我们就需要把锁和对象分离,在IOCPDemoSvr例子代码中TSocketHandle我们用一个结构体来管理锁和对象,锁在创建之后只有等TSocketHandle释放之后再释放,主要代码是TSocketHandles类,定义单元:
{* 客户端对应Socket管理对象 *} TSocketHandles = class(TObject) private {* 正在使用列表管理对象 *} FList: TList; {* 不再使用列表管理对象 *} FIdleList: TList; {* 锁 *} FLock: TCriticalSection; {* 获取某一个 *} function GetItems(const AIndex: Integer): PClientSocket; {* 获取总个数 *} function GetCount: Integer; {* 清除 *} procedure Clear; public constructor Create; virtual; destructor Destroy; override; {* 加锁 *} procedure Lock; {* 解锁 *} procedure UnLock; {* 添加一个对象 *} function Add(ASocketHandle: TSocketHandle): Integer; {* 删除 *} procedure Delete(const AIndex: Integer); overload; procedure Delete(ASocketHandle: TSocketHandle); overload; property Items[const AIndex: Integer]: PClientSocket read GetItems; default; property Count: Integer read GetCount; end;实现单元:{ TSocketHandles } constructor TSocketHandles.Create; begin FList := TList.Create; FIdleList := TList.Create; FLock := TCriticalSection.Create; end; destructor TSocketHandles.Destroy; begin Clear; FList.Free; FIdleList.Free; FLock.Free; inherited; end; function TSocketHandles.GetItems(const AIndex: Integer): PClientSocket; begin Result := FList[AIndex]; end; function TSocketHandles.GetCount: Integer; begin Result := FList.Count; end; procedure TSocketHandles.Clear; var i: Integer; ClientSocket: PClientSocket; begin for i := 0 to Count - 1 do begin ClientSocket := Items[i]; ClientSocket.Lock.Free; ClientSocket.SocketHandle.Free; Dispose(ClientSocket); end; FList.Clear; for i := 0 to FIdleList.Count - 1 do begin ClientSocket := FIdleList[i]; ClientSocket.Lock.Free; //释放锁 Dispose(ClientSocket); end; FIdleList.Clear; end; procedure TSocketHandles.Lock; begin FLock.Enter; end; procedure TSocketHandles.UnLock; begin FLock.Leave; end; function TSocketHandles.Add(ASocketHandle: TSocketHandle): Integer; var ClientSocket: PClientSocket; begin if FIdleList.Count > 0 then //先在空余中查找 begin ClientSocket := FIdleList[0]; FIdleList.Delete(0); end else //否则创建一个 begin New(ClientSocket); ClientSocket.Lock := TCriticalSection.Create; end; ClientSocket.SocketHandle := ASocketHandle; ASocketHandle.FLock := ClientSocket.Lock; Result := FList.Add(ClientSocket); end; procedure TSocketHandles.Delete(const AIndex: Integer); var ClientSocket: PClientSocket; begin ClientSocket := FList[AIndex]; ClientSocket.Lock.Enter; try ClientSocket.SocketHandle.Free; ClientSocket.SocketHandle := nil; finally ClientSocket.Lock.Leave; end; FList.Delete(AIndex); if FIdleList.Count > MAX_IDLELOCK then //如果达到最大空闲个数,则释放 Dispose(ClientSocket) else FIdleList.Add(ClientSocket); end; procedure TSocketHandles.Delete(ASocketHandle: TSocketHandle); var i, iIndex: Integer; begin iIndex := -1; for i := 0 to Count - 1 do begin if Items[i].SocketHandle = ASocketHandle then begin iIndex := i; Break; end; end; if iIndex <> -1 then begin Delete(iIndex); end; end;IOCPDemoSvr下载地址:http://download.csdn.net/detail/sqldebug_fan/4510076
免责声明:此代码只是为了演示IOCP编程,仅用于学习和研究,切勿用于商业用途。水平有限,错误在所难免,欢迎指正和指导。邮箱地址:fansheng_hx@163.com