130 lines
6.7 KiB
Ada
130 lines
6.7 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- S Y S T E M . T A S K I N G . U T I L I T I E S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2014, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package provides RTS Internal Declarations.
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-- These declarations are not part of the GNARLI
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with Ada.Unchecked_Conversion;
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with System.Task_Primitives;
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package System.Tasking.Utilities is
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function ATCB_To_Address is new
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Ada.Unchecked_Conversion (Task_Id, System.Task_Primitives.Task_Address);
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---------------------------------
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-- Task_Stage Related routines --
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---------------------------------
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function Make_Independent return Boolean;
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-- Move the current task to the outermost level (level 2) of the master
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-- hierarchy of the environment task. That is one level further out
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-- than normal tasks defined in library-level packages (level 3). The
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-- environment task will wait for level 3 tasks to terminate normally,
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-- then it will abort all the level 2 tasks. See Finalize_Global_Tasks
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-- procedure for more information.
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--
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-- This is a dangerous operation, and should never be used on nested tasks
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-- or tasks that depend on any objects that might be finalized earlier than
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-- the termination of the environment task. It is for internal use by the
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-- GNARL, to prevent such internal server tasks from preventing a partition
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-- from terminating.
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--
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-- Also note that the run time assumes that the parent of an independent
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-- task is the environment task. If this is not the case, Make_Independent
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-- will change the task's parent. This assumption is particularly
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-- important for master level completion and for the computation of
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-- Independent_Task_Count.
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--
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-- NOTE WELL: Make_Independent should be called before the task reaches its
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-- "begin", like this:
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--
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-- task body Some_Independent_Task is
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-- ...
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-- Ignore : constant Boolean := Make_Independent;
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-- ...
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-- begin
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--
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-- The return value is meaningless; the only reason this is a function is
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-- to get around the Ada limitation that makes a procedure call
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-- syntactically illegal before the "begin".
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--
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-- Calling it before "begin" ensures that the call completes before the
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-- activating task can proceed. This is important for preventing race
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-- conditions. For example, if the environment task reaches
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-- Finalize_Global_Tasks before some task has finished Make_Independent,
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-- the program can hang.
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--
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-- Note also that if a package declares independent tasks, it should not
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-- initialize its package-body data after "begin" of the package, because
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-- that's where the tasks are activated. Initializing such data before the
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-- task activation helps prevent the tasks from accessing uninitialized
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-- data.
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Independent_Task_Count : Natural := 0;
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-- Number of independent tasks. This counter is incremented each time
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-- Make_Independent is called. Note that if a server task terminates,
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-- this counter will not be decremented. Since Make_Independent locks
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-- the environment task (because every independent task depends on it),
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-- this counter is protected by the environment task's lock.
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---------------------------------
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-- Task Abort Related Routines --
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---------------------------------
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procedure Cancel_Queued_Entry_Calls (T : Task_Id);
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-- Cancel any entry calls queued on target task.
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-- Call this while holding T's lock (or RTS_Lock in Single_Lock mode).
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procedure Exit_One_ATC_Level (Self_ID : Task_Id);
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pragma Inline (Exit_One_ATC_Level);
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-- Call only with abort deferred and holding lock of Self_ID.
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-- This is a bit of common code for all entry calls.
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-- The effect is to exit one level of ATC nesting.
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procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id);
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-- Similar to Locked_Abort_To_Level (Self_ID, T, 0), but:
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-- (1) caller should be holding no locks
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-- (2) may be called for tasks that have not yet been activated
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-- (3) always aborts whole task
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procedure Abort_Tasks (Tasks : Task_List);
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-- Abort_Tasks is called to initiate abort, however, the actual
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-- aborting is done by aborted task by means of Abort_Handler
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procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean);
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-- Update counts to indicate current task is either terminated or
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-- accepting on a terminate alternative. Call holding no locks except
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-- Global_Task_Lock when calling from Terminate_Task, and RTS_Lock when
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-- Single_Lock is True.
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end System.Tasking.Utilities;
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