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5netbsdtasinf.ads
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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . T A S K _ I N F O --
-- --
-- S p e c --
-- --
-- --
-- Copyright (C) 1992-2000 Free Software Foundation, Inc. --
-- --
-- GNAT 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. 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; 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. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains the definitions and routines associated with the
-- implementation of the Task_Info pragma.
-- This is the NetBSD (native) version of this module.
with System.OS_Interface;
with Unchecked_Deallocation;
package System.Task_Info is
pragma Elaborate_Body;
-- To ensure that a body is allowed
-----------------------------------------------------
-- Binding of Tasks to LWPs and LWPs to processors --
-----------------------------------------------------
-- The NetBSD implementation of the GNU Low-Level Interface (GNULLI)
-- implements each Ada task as a NetBSD thread. The NetBSD thread
-- library distributes threads across one or more LWPs (Light Weight
-- Process) that are members of the same process. NetBSD distributes
-- processes and LWPs across the available CPUs on a given machine. The
-- pragma Task_Info provides the mechanism to control the distribution
-- of tasks to LWPs, and LWPs to processors.
-- Each thread has a number of attributes that dictate it's scheduling.
-- These attributes are:
--
-- New_LWP: whether a new LWP is created for this thread.
--
-- Bound_To_LWP: whether the thread is bound to a specific LWP
-- for its entire lifetime.
--
-- CPU: the CPU number associated to the LWP
--
-- The Task_Info pragma:
-- pragma Task_Info (EXPRESSION);
-- allows the specification on a task by task basis of a value of type
-- System.Task_Info.Task_Info_Type to be passed to a task when it is
-- created. The specification of this type, and the effect on the task
-- that is created is target dependent.
-- The Task_Info pragma appears within a task definition (compare the
-- definition and implementation of pragma Priority). If no such pragma
-- appears, then the value Task_Info_Unspecified is passed. If a pragma
-- is present, then it supplies an alternative value. If the argument of
-- the pragma is a discriminant reference, then the value can be set on
-- a task by task basis by supplying the appropriate discriminant value.
-- Note that this means that the type used for Task_Info_Type must be
-- suitable for use as a discriminant (i.e. a scalar or access type).
-----------------------
-- Thread Attributes --
-----------------------
subtype CPU_Number is System.OS_Interface.processorid_t;
CPU_UNCHANGED : constant CPU_Number := System.OS_Interface.PBIND_QUERY;
-- Do not bind the LWP to a specific processor
ANY_CPU : constant CPU_Number := System.OS_Interface.PBIND_NONE;
-- Bind the LWP to any processor
Invalid_CPU_Number : exception;
type Thread_Attributes (New_LWP : Boolean) is record
Bound_To_LWP : Boolean := True;
case New_LWP is
when False =>
null;
when True =>
CPU : CPU_Number := CPU_UNCHANGED;
end case;
end record;
Default_Thread_Attributes : constant Thread_Attributes := (False, True);
function Unbound_Thread_Attributes
return Thread_Attributes;
function Bound_Thread_Attributes
return Thread_Attributes;
function Bound_Thread_Attributes (CPU : CPU_Number)
return Thread_Attributes;
type Task_Info_Type is access all Thread_Attributes;
function New_Unbound_Thread_Attributes
return Task_Info_Type;
function New_Bound_Thread_Attributes
return Task_Info_Type;
function New_Bound_Thread_Attributes (CPU : CPU_Number)
return Task_Info_Type;
type Task_Image_Type is access String;
-- Used to generate a meaningful identifier for tasks that are variables
-- and components of variables.
procedure Free_Task_Image is new
Unchecked_Deallocation (String, Task_Image_Type);
Unspecified_Task_Info : constant Task_Info_Type := null;
end System.Task_Info;