CriticalSection的Enter/Leave次数问题

在用TCriticalSection来同步线程时，Enter/Leave的次数对结果有影响吗？不管Enter多少次，Leave一次后，别的线程就能进入了吗？

因为可能在写函数嵌套时，会遇到这样的情况：

var CS:TCriticalSection;procedure P1;begin CS.Enter; try ..... finally CS.Leave; end;end;procedure P2;begin CS.Enter; try ..... P1; ..... finally CS.Leave; end;end;

P2希望在调用CS.Leave前都是本线程拥有CS，但是在P1结束后，它调用了CS.Leave，这个时候，别的线程有机会获得CS吗？（如果能获得的话，那太复杂了，陷阱太多了。）

写一个Demo试试：

unit Unit3;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls,SyncObjs;type TThread1=class(TThread) public procedure Execute;override; procedure AddMsg; end; TThread2=class(TThread) public procedure Execute;override; procedure AddMsg; end; TForm3 = class(TForm) Memo1: TMemo; Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } Thread1:TThread1; Thread2:TThread2; public { Public declarations } end;var Form3: TForm3; CS:TCriticalSection;implementation{$R *.dfm}procedure TForm3.Button1Click(Sender: TObject);begin Thread1:=TThread1.Create; Thread2:=TThread2.Create;end;{ TThread1 }procedure TThread1.AddMsg;begin Form3.Memo1.Lines.Add('TThread1');end;procedure TThread1.Execute;begin while not Terminated do begin CS.Enter; CS.Enter; //故意Enter两次 try Self.Synchronize(AddMsg); finally CS.Leave; end; Sleep(100); end;end;{ TThread2 }procedure TThread2.AddMsg;begin Form3.Memo1.Lines.Add('TThread2'); ShowMessage('Catch it!');end;procedure TThread2.Execute;begin while not Terminated do begin CS.Enter; try Self.Synchronize(AddMsg); finally CS.Leave; end; Sleep(10); end;end;initialization CS:=TCriticalSection.Create;finalization CS.Free;end.

没有抓到TThread2的信息，可以安心了。