+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNU ADA 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 --
--- --
--- $Revision: 1.2.10.1 $
--- --
--- Copyright (C) 1992-1999, 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 2, or (at your option) any later ver- --
--- sion. GNARL 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. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNARL; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- As a special exception, if other files instantiate generics from this --
--- unit, or you link this unit with other files to produce an executable, --
--- this unit does not by itself cause the resulting executable to be --
--- covered by the GNU General Public License. This exception does not --
--- however invalidate any other reasons why the executable file might be --
--- covered by the GNU Public License. --
--- --
--- 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;
--- used for Task_Info_Type
-
-with System.Parameters;
--- used for Size_Type
-
-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;
- -- _init_proc (_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 _init_proc (_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, 0, _master,
- -- task_procedure_access!(tB'address),
- -- _init'address, tE'unchecked_access, _chain, _task_id, _init.
- -- _task_id);
- -- return;
- -- end _init_proc;
- -- ]
- --
- -- 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;
- -- t1I : task_image_type := new string'"t1";
- -- _init_proc (t1, _master, _chain, t1I, 1);
- --
- -- activate_tasks (_chain'unchecked_access);
-
- procedure Abort_Tasks (Tasks : Task_List);
- -- Compiler interface only. Do not call from within the RTS.
- -- Initiate abortion, however, the actual abortion 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.
-
- 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;
- 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 : System.Task_Info.Task_Image_Type;
- 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 the
- -- System.Any_Priority'Range)
- -- 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.
- -- 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 pointer to 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.
-
- 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)
-
-end System.Tasking.Stages;
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