Question

我有调用任务A的任务B 在一些品脱任务B被终止但任务A不知道并且现在调用终止任务B。
由于任务B已终止，因此从任务A调用它会终止任务A。

如何检查任务B是否已终止任务A？

如果重要，我正在使用GNAT Programming Studio 我可以在终止之前创建一个由B设置的全局变量，但我宁愿从B找出A的状态。

Answer 1

您可以查看B＆＃39;已终止，请参阅RM 9.9

if not B'Terminated then
   -- do something
end if;

Answer 2

以下示例使用“已终止”属性允许主任务确定何时完成一组任务。

------------------------------------------------------------------
-- Parallel Array Filling --
------------------------------------------------------------------
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Numerics.Discrete_Random;
with Ada.Calendar; use Ada.Calendar;

procedure Array_Fill is
   Start_Time : Time := Clock;
   Num_Tasks  : constant := 8;
   Slice_Size : constant Natural := 8_388_608;
   Max_Size   : constant Natural :=  Num_Tasks * Slice_Size -1;
   subtype Values is Natural range 0..10_000;

   type Big_Array is array(Natural range 0..Max_Size) of Integer;
   type Big_Access is access Big_Array;

   -- Instantiate the generic package Ada.Numerics.Discrete_Random
   -- to produce random numbers in the range of the subtype Values
   -- defined above
   package Rand_Nums is new Ada.Numerics.Discrete_Random(Values);
   use Rand_Nums;

   -- dynamically allocate the integer array, initializing all array
   -- elements to the lowest valid value for type Integer
   The_Array  : Big_Access := new Big_Array'(Others => Integer'First);

   task type Filler is
      -- Set_Low is a synchronization point between the main task and
      -- an instance of the task type Filler. This point allows the main
      -- task to send an integer value >= 0 directly to the Filler task
      Entry Set_Low(Item : in Natural);
   end Filler;

   task body Filler is
      Id         : Natural;
      Low_Index  : Natural;
      High_Index : Natural;
      Seed       : Generator;
   begin
      Reset(Seed);

      -- the Filler task waits for the main task to send a value to the
      -- entry Set_Low.
      accept Set_Low(Item : in Natural) do
         Id := Item;
      end Set_Low;

      Low_Index := Id * Slice_Size;
      High_Index := Low_Index + (Slice_Size - 1);

      for I in Low_Index..High_Index loop
         The_Array(I) := Random(Seed);
      end loop;
   end Filler;

   -- create an array type containing Num_Tasks of Filler tasks;
   type Task_List is array(Natural range 0..Num_tasks - 1) of Filler;

   -- Create an instance of the task array. The tasks start as soon
   -- as this array is created
   List       : Task_List;

begin -- begin the execution of the main task
   -- Send ID values to each instance of the Filler task in the array
   -- List.
   for I in Task_List'Range loop
      List(I).Set_Low(I);
   end loop;

   loop -- waits for all the tasks to terminate
      if List(0)'Terminated and then
        List(1)'Terminated and then
        List(2)'Terminated and then
        List(3)'Terminated and then
        List(4)'Terminated and then
        List(5)'Terminated and then
        List(6)'Terminated and then
        List(7)'Terminated then
         exit;  -- exit this loop
      end if;
   end loop;

   Put_Line("Elapsed time " & Duration'Image(Clock - Start_Time) & " seconds");
end Array_Fill;

如何检查Ada中的任务是否终止

2 个答案: