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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . T A S K I N G . U T I L I T I E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2020, Free Software Foundation, Inc. --
-- --
-- GNARL is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNARL was developed by the GNARL team at Florida State University. --
-- Extensive contributions were provided by Ada Core Technologies, Inc. --
-- --
------------------------------------------------------------------------------
-- This package provides RTS Internal Declarations.
-- These declarations are not part of the GNARLI
with Ada.Unchecked_Conversion;
with System.Task_Primitives;
package System.Tasking.Utilities is
function ATCB_To_Address is new
Ada.Unchecked_Conversion (Task_Id, System.Task_Primitives.Task_Address);
---------------------------------
-- Task_Stage Related routines --
---------------------------------
function Make_Independent return Boolean;
-- Move the current task to the outermost level (level 2) of the master
-- hierarchy of the environment task. That is one level further out
-- than normal tasks defined in library-level packages (level 3). The
-- environment task will wait for level 3 tasks to terminate normally,
-- then it will abort all the level 2 tasks. See Finalize_Global_Tasks
-- procedure for more information.
--
-- This is a dangerous operation, and should never be used on nested tasks
-- or tasks that depend on any objects that might be finalized earlier than
-- the termination of the environment task. It is primarily for internal
-- use by the GNARL, to prevent such internal server tasks from preventing
-- a partition from terminating.
--
-- Also note that the run time assumes that the parent of an independent
-- task is the environment task. If this is not the case, Make_Independent
-- will change the task's parent. This assumption is particularly
-- important for master level completion and for the computation of
-- Independent_Task_Count.
--
-- NOTE WELL: Make_Independent should be called before the task reaches its
-- "begin", like this:
--
-- task body Some_Independent_Task is
-- ...
-- Ignore : constant Boolean := Make_Independent;
-- ...
-- begin
--
-- The return value is meaningless; the only reason this is a function is
-- to get around the Ada limitation that makes a procedure call
-- syntactically illegal before the "begin".
--
-- Calling it before "begin" ensures that the call completes before the
-- activating task can proceed. This is important for preventing race
-- conditions. For example, if the environment task reaches
-- Finalize_Global_Tasks before some task has finished Make_Independent,
-- the program can hang.
--
-- Note also that if a package declares independent tasks, it should not
-- initialize its package-body data after "begin" of the package, because
-- that's where the tasks are activated. Initializing such data before the
-- task activation helps prevent the tasks from accessing uninitialized
-- data.
Independent_Task_Count : Natural := 0;
-- Number of independent tasks. This counter is incremented each time
-- Make_Independent is called. Note that if a server task terminates,
-- this counter will not be decremented. Since Make_Independent locks
-- the environment task (because every independent task depends on it),
-- this counter is protected by the environment task's lock.
---------------------------------
-- Task Abort Related Routines --
---------------------------------
procedure Cancel_Queued_Entry_Calls (T : Task_Id);
-- Cancel any entry calls queued on target task.
-- Call this while holding T's lock.
procedure Exit_One_ATC_Level (Self_ID : Task_Id);
pragma Inline (Exit_One_ATC_Level);
-- Call only with abort deferred and holding lock of Self_ID.
-- This is a bit of common code for all entry calls.
-- The effect is to exit one level of ATC nesting.
procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id);
-- Similar to Locked_Abort_To_Level (Self_ID, T, Level_Completed_Task),
-- but:
-- (1) caller should be holding no locks
-- (2) may be called for tasks that have not yet been activated
-- (3) always aborts whole task
procedure Abort_Tasks (Tasks : Task_List);
-- Abort_Tasks is called to initiate abort, however, the actual
-- aborting is done by aborted task by means of Abort_Handler
procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean);
-- Update counts to indicate current task is either terminated or
-- accepting on a terminate alternative. Call holding no locks except
-- Global_Task_Lock when calling from Terminate_Task.
end System.Tasking.Utilities;
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