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------------------------------------------------------------------------------

--                                                                          --

--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --

--                                                                          --

--                 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) 1992-2011, 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 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;

      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;

      Build_Entry_Names : Boolean);

   --  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)

   --  Size is the stack size of the task to create

   --  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.

   --  Build_Entry_Names is a flag which controls the allocation of the data

   --   structure which stores all entry names.

   --

   --  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.

   procedure Set_Entry_Name

     (T   : Task_Id;

      Pos : Task_Entry_Index;

      Val : String_Access);

   --  This is called by the compiler to map a string which denotes an entry

   --  name to a task entry index.

   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;