277 lines
12 KiB
Ada
277 lines
12 KiB
Ada
------------------------------------------------------------------------------
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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 . S T A G E S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2005, 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 2, or (at your option) any later ver- --
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-- sion. GNARL 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. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNARL; see file COPYING. If not, write --
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-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
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-- Boston, MA 02110-1301, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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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 represents the high level tasking interface used by the
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-- compiler to expand Ada 95 tasking constructs into simpler run time calls
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-- (aka GNARLI, GNU Ada Run-time Library Interface)
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-- Note: Only the compiler is allowed to use this interface, by generating
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-- direct calls to it, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes
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-- in exp_ch9.adb and possibly exp_ch7.adb
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with System.Task_Info;
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-- used for Task_Info_Type
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with System.Parameters;
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-- used for Size_Type
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package System.Tasking.Stages is
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pragma Elaborate_Body;
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-- The compiler will expand in the GNAT tree the following construct:
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-- task type T (Discr : Integer);
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-- task body T is
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-- ...declarations, possibly some controlled...
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-- begin
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-- ...B...;
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-- end T;
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-- T1 : T (1);
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-- as follows:
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-- enter_master.all;
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-- _chain : aliased activation_chain;
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-- activation_chainIP (_chain);
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-- task type t (discr : integer);
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-- tE : aliased boolean := false;
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-- tZ : size_type := unspecified_size;
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-- type tV (discr : integer) is limited record
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-- _task_id : task_id;
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-- end record;
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-- procedure tB (_task : access tV);
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-- freeze tV [
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-- procedure tVIP (_init : in out tV; _master : master_id;
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-- _chain : in out activation_chain; _task_id : in task_image_type;
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-- discr : integer) is
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-- begin
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-- _init.discr := discr;
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-- _init._task_id := null;
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-- create_task (unspecified_priority, tZ,
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-- unspecified_task_info, 0, _master,
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-- task_procedure_access!(tB'address),
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-- _init'address, tE'unchecked_access, _chain, _task_id, _init.
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-- _task_id);
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-- return;
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-- end tVIP;
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-- ]
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-- procedure tB (_task : access tV) is
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-- discr : integer renames _task.discr;
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-- procedure _clean is
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-- begin
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-- abort_defer.all;
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-- complete_task;
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-- finalize_list (F14b);
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-- abort_undefer.all;
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-- return;
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-- end _clean;
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-- begin
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-- abort_undefer.all;
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-- ...declarations...
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-- complete_activation;
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-- ...B...;
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-- return;
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-- at end
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-- _clean;
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-- end tB;
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-- tE := true;
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-- t1 : t (1);
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-- _master : constant master_id := current_master.all;
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-- t1S : task_image_type := new string'"t1";
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-- task_image_typeIP (t1, _master, _chain, t1S, 1);
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-- activate_tasks (_chain'unchecked_access);
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procedure Abort_Tasks (Tasks : Task_List);
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-- Compiler interface only. Do not call from within the RTS. Initiate
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-- abort, however, the actual abort is done by abortee by means of
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-- Abort_Handler and Abort_Undefer
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--
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-- source code:
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-- Abort T1, T2;
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-- code expansion:
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-- abort_tasks (task_list'(t1._task_id, t2._task_id));
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procedure Activate_Tasks (Chain_Access : Activation_Chain_Access);
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-- Compiler interface only. Do not call from within the RTS.
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-- This must be called by the creator of a chain of one or more new tasks,
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-- to activate them. The chain is a linked list that up to this point is
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-- only known to the task that created them, though the individual tasks
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-- are already in the All_Tasks_List.
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--
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-- The compiler builds the chain in LIFO order (as a stack). Another
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-- version of this procedure had code to reverse the chain, so as to
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-- activate the tasks in the order of declaration. This might be nice, but
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-- it is not needed if priority-based scheduling is supported, since all
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-- the activated tasks synchronize on the activators lock before they
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-- start activating and so they should start activating in priority order.
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procedure Complete_Activation;
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-- Compiler interface only. Do not call from within the RTS.
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-- This should be called from the task body at the end of
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-- the elaboration code for its declarative part.
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-- Decrement the count of tasks to be activated by the activator and
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-- wake it up so it can check to see if all tasks have been activated.
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-- Except for the environment task, which should never call this procedure,
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-- T.Activator should only be null iff T has completed activation.
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procedure Complete_Master;
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-- Compiler interface only. Do not call from within the RTS. This must
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-- be called on exit from any master where Enter_Master was called.
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-- Assume abort is deferred at this point.
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procedure Complete_Task;
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-- Compiler interface only. Do not call from within the RTS.
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-- This should be called from an implicit at-end handler
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-- associated with the task body, when it completes.
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-- From this point, the current task will become not callable.
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-- If the current task have not completed activation, this should be done
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-- now in order to wake up the activator (the environment task).
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procedure Create_Task
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(Priority : Integer;
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Size : System.Parameters.Size_Type;
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Task_Info : System.Task_Info.Task_Info_Type;
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Num_Entries : Task_Entry_Index;
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Master : Master_Level;
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State : Task_Procedure_Access;
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Discriminants : System.Address;
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Elaborated : Access_Boolean;
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Chain : in out Activation_Chain;
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Task_Image : String;
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Created_Task : out Task_Id);
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-- Compiler interface only. Do not call from within the RTS.
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-- This must be called to create a new task.
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--
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-- Priority is the task's priority (assumed to be in the
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-- System.Any_Priority'Range)
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-- Size is the stack size of the task to create
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-- Task_Info is the task info associated with the created task, or
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-- Unspecified_Task_Info if none.
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-- State is the compiler generated task's procedure body
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-- Discriminants is a pointer to a limited record whose discriminants
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-- are those of the task to create. This parameter should be passed as
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-- the single argument to State.
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-- Elaborated is a pointer to a Boolean that must be set to true on exit
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-- if the task could be sucessfully elaborated.
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-- Chain is a linked list of task that needs to be created. On exit,
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-- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID
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-- will be Created_Task (e.g the created task will be linked at the front
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-- of Chain).
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-- Task_Image is a string created by the compiler that the
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-- run time can store to ease the debugging and the
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-- Ada.Task_Identification facility.
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-- Created_Task is the resulting task.
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--
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-- This procedure can raise Storage_Error if the task creation failed.
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function Current_Master return Master_Level;
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-- Compiler interface only.
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-- This is called to obtain the current master nesting level.
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procedure Enter_Master;
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-- Compiler interface only. Do not call from within the RTS.
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-- This must be called on entry to any "master" where a task,
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-- or access type designating objects containing tasks, may be
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-- declared.
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procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain);
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-- Compiler interface only. Do not call from within the RTS.
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-- This must be called by the compiler-generated code for an allocator if
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-- the allocated object contains tasks, if the allocator exits without
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-- calling Activate_Tasks for a given activation chains, as can happen if
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-- an exception occurs during initialization of the object.
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--
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-- This should be called ONLY for tasks created via an allocator. Recovery
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-- of storage for unactivated local task declarations is done by
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-- Complete_Master and Complete_Task.
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--
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-- We remove each task from Chain and All_Tasks_List before we free the
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-- storage of its ATCB.
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--
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-- In other places where we recover the storage of unactivated tasks, we
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-- need to clean out the entry queues, but here that should not be
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-- necessary, since these tasks should not have been visible to any other
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-- tasks, and so no task should be able to queue a call on their entries.
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--
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-- Just in case somebody misuses this subprogram, there is a check to
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-- verify this condition.
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procedure Finalize_Global_Tasks;
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-- This should be called to complete the execution of the environment task
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-- and shut down the tasking runtime system. It is the equivalent of
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-- Complete_Task, but for the environment task.
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--
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-- The environment task must first call Complete_Master, to wait for user
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-- tasks that depend on library-level packages to terminate. It then calls
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-- Abort_Dependents to abort the "independent" library-level server tasks
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-- that are created implicitly by the RTS packages (signal and timer server
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-- tasks), and then waits for them to terminate. Then, it calls
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-- Vulnerable_Complete_Task.
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--
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-- It currently also executes the global finalization list, and then resets
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-- the "soft links".
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procedure Free_Task (T : Task_Id);
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-- Recover all runtime system storage associated with the task T, but only
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-- if T has terminated. Do nothing in the other case. It is called from
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-- Unchecked_Deallocation, for objects that are or contain tasks.
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function Terminated (T : Task_Id) return Boolean;
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-- This is called by the compiler to implement the 'Terminated attribute.
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-- Though is not required to be so by the ARM, we choose to synchronize
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-- with the task's ATCB, so that this is more useful for polling the state
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-- of a task, and so that it becomes an abort completion point for the
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-- calling task (via Undefer_Abort).
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--
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-- source code:
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-- T1'Terminated
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--
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-- code expansion:
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-- terminated (t1._task_id)
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procedure Terminate_Task (Self_ID : Task_Id);
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-- Terminate the calling task.
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-- This should only be called by the Task_Wrapper procedure, and to
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-- deallocate storage associate with foreign tasks.
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end System.Tasking.Stages;
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