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-- --
-- --
-- S Y S T E M . T A S K I N G . S T A G E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2021, 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 --
-- --
-- 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 --
-- <>. --
-- --
-- GNARL was developed by the GNARL team at Florida State University. --
-- Extensive contributions were provided by Ada Core Technologies, Inc. --
-- --
-- This package represents the high level tasking interface used by the
-- compiler to expand Ada 95 tasking constructs into simpler run time calls
-- (aka GNARLI, GNU Ada Run-time Library Interface)
-- Note: Only the compiler is allowed to use this interface, by generating
-- direct calls to it, via Rtsfind.
-- Any changes to this interface may require corresponding compiler changes
-- in exp_ch9.adb and possibly exp_ch7.adb
with System.Task_Info;
with System.Parameters;
with Ada.Real_Time;
package System.Tasking.Stages is
pragma Elaborate_Body;
-- The compiler will expand in the GNAT tree the following construct:
-- task type T (Discr : Integer);
-- task body T is
-- ...declarations, possibly some controlled...
-- begin
-- ...B...;
-- end T;
-- T1 : T (1);
-- as follows:
-- enter_master.all;
-- _chain : aliased activation_chain;
-- activation_chainIP (_chain);
-- task type t (discr : integer);
-- tE : aliased boolean := false;
-- tZ : size_type := unspecified_size;
-- type tV (discr : integer) is limited record
-- _task_id : task_id;
-- end record;
-- procedure tB (_task : access tV);
-- freeze tV [
-- procedure tVIP (_init : in out tV; _master : master_id;
-- _chain : in out activation_chain; _task_id : in task_image_type;
-- discr : integer) is
-- begin
-- _init.discr := discr;
-- _init._task_id := null;
-- create_task (unspecified_priority, tZ,
-- unspecified_task_info, unspecified_cpu,
-- ada__real_time__time_span_zero, 0, _master,
-- task_procedure_access!(tB'address), _init'address,
-- tE'unchecked_access, _chain, _task_id, _init._task_id);
-- return;
-- end tVIP;
-- ]
-- procedure tB (_task : access tV) is
-- discr : integer renames _task.discr;
-- procedure _clean is
-- begin
-- abort_defer.all;
-- complete_task;
-- finalize_list (F14b);
-- abort_undefer.all;
-- return;
-- end _clean;
-- begin
-- abort_undefer.all;
-- ...declarations...
-- complete_activation;
-- ...B...;
-- return;
-- at end
-- _clean;
-- end tB;
-- tE := true;
-- t1 : t (1);
-- _master : constant master_id := current_master.all;
-- t1S : task_image_type := new string'"t1";
-- task_image_typeIP (t1, _master, _chain, t1S, 1);
-- activate_tasks (_chain'unchecked_access);
procedure Abort_Tasks (Tasks : Task_List);
-- Compiler interface only. Do not call from within the RTS. Initiate
-- abort, however, the actual abort is done by abortee by means of
-- Abort_Handler and Abort_Undefer
-- source code:
-- Abort T1, T2;
-- code expansion:
-- abort_tasks (task_list'(t1._task_id, t2._task_id));
procedure Activate_Tasks (Chain_Access : Activation_Chain_Access);
-- Compiler interface only. Do not call from within the RTS.
-- This must be called by the creator of a chain of one or more new tasks,
-- to activate them. The chain is a linked list that up to this point is
-- only known to the task that created them, though the individual tasks
-- are already in the All_Tasks_List.
-- The compiler builds the chain in LIFO order (as a stack). Another
-- version of this procedure had code to reverse the chain, so as to
-- activate the tasks in the order of declaration. This might be nice, but
-- it is not needed if priority-based scheduling is supported, since all
-- the activated tasks synchronize on the activators lock before they
-- start activating and so they should start activating in priority order.
-- ??? Actually, the body of this package DOES reverse the chain, so I
-- don't understand the above comment.
procedure Complete_Activation;
-- Compiler interface only. Do not call from within the RTS.
-- This should be called from the task body at the end of
-- the elaboration code for its declarative part.
-- Decrement the count of tasks to be activated by the activator and
-- wake it up so it can check to see if all tasks have been activated.
-- Except for the environment task, which should never call this procedure,
-- T.Activator should only be null iff T has completed activation.
procedure Complete_Master;
-- Compiler interface only. Do not call from within the RTS. This must
-- be called on exit from any master where Enter_Master was called.
-- Assume abort is deferred at this point.
procedure Complete_Task;
-- Compiler interface only. Do not call from within the RTS.
-- This should be called from an implicit at-end handler
-- associated with the task body, when it completes.
-- From this point, the current task will become not callable.
-- If the current task have not completed activation, this should be done
-- now in order to wake up the activator (the environment task).
procedure Create_Task
(Priority : Integer;
Stack_Size : System.Parameters.Size_Type;
Secondary_Stack_Size : System.Parameters.Size_Type;
Task_Info : System.Task_Info.Task_Info_Type;
CPU : Integer;
Relative_Deadline : Ada.Real_Time.Time_Span;
Domain : Dispatching_Domain_Access;
Num_Entries : Task_Entry_Index;
Master : Master_Level;
State : Task_Procedure_Access;
Discriminants : System.Address;
Elaborated : Access_Boolean;
Chain : in out Activation_Chain;
Task_Image : String;
Created_Task : out Task_Id);
-- Compiler interface only. Do not call from within the RTS.
-- This must be called to create a new task.
-- Priority is the task's priority (assumed to be in range of type
-- System.Any_Priority)
-- Stack_Size is the stack size of the task to create
-- Secondary_Stack_Size is the size of the secondary stack to be used by
-- the task.
-- Task_Info is the task info associated with the created task, or
-- Unspecified_Task_Info if none.
-- CPU is the task affinity. Passed as an Integer because the undefined
-- value is not in the range of CPU_Range. Static range checks are
-- performed when analyzing the pragma, and dynamic ones are performed
-- before setting the affinity at run time.
-- Relative_Deadline is the relative deadline associated with the created
-- task by means of a pragma Relative_Deadline, or 0.0 if none.
-- Domain is the dispatching domain associated with the created task by
-- means of a Dispatching_Domain pragma or aspect, or null if none.
-- State is the compiler generated task's procedure body
-- Discriminants is a pointer to a limited record whose discriminants
-- are those of the task to create. This parameter should be passed as
-- the single argument to State.
-- Elaborated is a pointer to a Boolean that must be set to true on exit
-- if the task could be successfully elaborated.
-- Chain is a linked list of task that needs to be created. On exit,
-- Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID
-- will be Created_Task (e.g the created task will be linked at the front
-- of Chain).
-- Task_Image is a string created by the compiler that the
-- run time can store to ease the debugging and the
-- Ada.Task_Identification facility.
-- Created_Task is the resulting task.
-- This procedure can raise Storage_Error if the task creation failed.
function Current_Master return Master_Level;
-- Compiler interface only.
-- This is called to obtain the current master nesting level.
procedure Enter_Master;
-- Compiler interface only. Do not call from within the RTS.
-- This must be called on entry to any "master" where a task,
-- or access type designating objects containing tasks, may be
-- declared.
procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain);
-- Compiler interface only. Do not call from within the RTS.
-- This must be called by the compiler-generated code for an allocator if
-- the allocated object contains tasks, if the allocator exits without
-- calling Activate_Tasks for a given activation chains, as can happen if
-- an exception occurs during initialization of the object.
-- This should be called ONLY for tasks created via an allocator. Recovery
-- of storage for unactivated local task declarations is done by
-- Complete_Master and Complete_Task.
-- We remove each task from Chain and All_Tasks_List before we free the
-- storage of its ATCB.
-- In other places where we recover the storage of unactivated tasks, we
-- need to clean out the entry queues, but here that should not be
-- necessary, since these tasks should not have been visible to any other
-- tasks, and so no task should be able to queue a call on their entries.
-- Just in case somebody misuses this subprogram, there is a check to
-- verify this condition.
procedure Finalize_Global_Tasks;
-- This should be called to complete the execution of the environment task
-- and shut down the tasking runtime system. It is the equivalent of
-- Complete_Task, but for the environment task.
-- The environment task must first call Complete_Master, to wait for user
-- tasks that depend on library-level packages to terminate. It then calls
-- Abort_Dependents to abort the "independent" library-level server tasks
-- that are created implicitly by the RTS packages (signal and timer server
-- tasks), and then waits for them to terminate. Then, it calls
-- Vulnerable_Complete_Task.
-- It currently also executes the global finalization list, and then resets
-- the "soft links".
procedure Free_Task (T : Task_Id);
-- Recover all runtime system storage associated with the task T, but only
-- if T has terminated. Do nothing in the other case. It is called from
-- Unchecked_Deallocation, for objects that are or contain tasks.
procedure Move_Activation_Chain
(From, To : Activation_Chain_Access;
New_Master : Master_ID);
-- Compiler interface only. Do not call from within the RTS.
-- Move all tasks on From list to To list, and change their Master_Of_Task
-- to be New_Master. This is used to implement build-in-place function
-- returns. Tasks that are part of the return object are initially placed
-- on an activation chain local to the return statement, and their master
-- is the return statement, in case the return statement is left
-- prematurely (due to raising an exception, being aborted, or a goto or
-- exit statement). Once the return statement has completed successfully,
-- Move_Activation_Chain is called to move them to the caller's activation
-- chain, and change their master to the one passed in by the caller. If
-- that doesn't happen, they will never be activated, and will become
-- terminated on leaving the return statement.
function Terminated (T : Task_Id) return Boolean;
-- This is called by the compiler to implement the 'Terminated attribute.
-- Though is not required to be so by the ARM, we choose to synchronize
-- with the task's ATCB, so that this is more useful for polling the state
-- of a task, and so that it becomes an abort completion point for the
-- calling task (via Undefer_Abort).
-- source code:
-- T1'Terminated
-- code expansion:
-- terminated (t1._task_id)
procedure Terminate_Task (Self_ID : Task_Id);
-- Terminate the calling task.
-- This should only be called by the Task_Wrapper procedure, and to
-- deallocate storage associate with foreign tasks.
end System.Tasking.Stages;