Task Ada交会互同步

我有这样的代码：

task body Task1Type is
begin
    Put_Line("Task1 Part1");
    Task2.Part1Ready;
    accept Part1Ready;
    Put_Line("Task1 Part2");
end;

task body Task2Type is
begin
    Put_Line("Task2 Part1");
    Task1.Part1Ready;
    accept Part1Ready;
    Put_Line("Task2 Part2");
end;

protected Readiness is
   procedure Task_1_Ready;
   entry Wait_Until_Task_1_Ready;

   procedure Task_2_Ready;
   entry Wait_Until_Task_2_Ready;
private
   Task_1_Is_Ready : Boolean := False;
   Task_2_Is_Ready : Boolean := False;
end Readiness;

protected body Readiness is
   procedure Task_1_Ready is
   begin
      Task_1_Is_Ready := True;
   end Task_1_Ready;

   entry Wait_Until_Task_1_Ready when Task_1_Is_Ready is
   begin
      null;
   end Wait_Until_Task_1_Ready;

   procedure Task_2_Ready is
   begin
      Task_2_Is_Ready := True;
   end Task_2_Ready;

   entry Wait_Until_Task_2_Ready when Task_2_Is_Ready is
   begin
      null;
   end Wait_Until_Task_2_Ready;
end Readiness;

---

我的逻辑告诉我，每个任务中的part2必须在两个任务都完成task1之后运行。但事实并非如此。我错在哪里？

当

Task1

调用

Task2.Part1Ready

时，它会阻塞，直到

Task2

发出

接受Part1Ready

。同样，当

Task2

调用

Task1.Part1Ready

时，它会阻塞，直到

Task1

发出

接受Part1Ready

这被称为“致命拥抱”，意味着两项任务都无法继续。解决此问题的一种方法是使用受保护对象，可能如下所示：

task body Task1Type is
begin
    Put_Line("Task1 Part1");
    Task2.Part1Ready;
    accept Part1Ready;
    Put_Line("Task1 Part2");
end;

task body Task2Type is
begin
    Put_Line("Task2 Part1");
    Task1.Part1Ready;
    accept Part1Ready;
    Put_Line("Task2 Part2");
end;

protected Readiness is
   procedure Task_1_Ready;
   entry Wait_Until_Task_1_Ready;

   procedure Task_2_Ready;
   entry Wait_Until_Task_2_Ready;
private
   Task_1_Is_Ready : Boolean := False;
   Task_2_Is_Ready : Boolean := False;
end Readiness;

protected body Readiness is
   procedure Task_1_Ready is
   begin
      Task_1_Is_Ready := True;
   end Task_1_Ready;

   entry Wait_Until_Task_1_Ready when Task_1_Is_Ready is
   begin
      null;
   end Wait_Until_Task_1_Ready;

   procedure Task_2_Ready is
   begin
      Task_2_Is_Ready := True;
   end Task_2_Ready;

   entry Wait_Until_Task_2_Ready when Task_2_Is_Ready is
   begin
      null;
   end Wait_Until_Task_2_Ready;
end Readiness;

然后去掉

Part1Ready

任务条目，替换

task body Task1Type is begin
   Put_Line("Task1 Part1");
   Task2.Part1Ready;
   accept Part1Ready;
   Put_Line("Task1 Part2”);
end;

与

在

Task2Type

中反之亦然