gcc/ada/s-tpopsp-rtems.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --    S Y S T E M . T A S K _ P R I M I T I V E S . O P E R A T I O N S .   --
   6 --                              S P E C I F I C                             --
   7 --                                                                          --
   8 --                                  B o d y                                 --
   9 --                                                                          --
  10 --                             $Revision: 1.2 $
  11 --                                                                          --
  12 --            Copyright (C) 1991-2003, Florida State University             --
  13 --            Copyright (C) 2008-2012, Free Software Foundation, Inc.       --
  14 --                                                                          --
  15 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  16 -- terms of the  GNU General Public License as published  by the Free Soft- --
  17 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  18 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  19 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  20 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  21 --                                                                          --
  22 -- As a special exception under Section 7 of GPL version 3, you are granted --
  23 -- additional permissions described in the GCC Runtime Library Exception,   --
  24 -- version 3.1, as published by the Free Software Foundation.               --
  25 --                                                                          --
  26 -- You should have received a copy of the GNU General Public License and    --
  27 -- a copy of the GCC Runtime Library Exception along with this program;     --
  28 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  29 -- <http://www.gnu.org/licenses/>.                                          --
  30 --                                                                          --
  31 -- GNARL was developed by the GNARL team at Florida State University. It is --
  32 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
  33 -- State University (http://www.gnat.com).                                  --
  34 --                                                                          --
  35 ------------------------------------------------------------------------------
  36
  37 --  This is a RTEMS version of this package which uses a special
  38 --  variable for Ada self which is context switched implicitly by RTEMS.
  39 --
  40 --  This is the same as the POSIX version except that an RTEMS variable
  41 --  is used instead of a POSIX key.
  42
  43 separate (System.Task_Primitives.Operations)
  44 package body Specific is
  45
  46    --  The following gives the Ada run-time direct access to a variable
  47    --  context switched by RTEMS at the lowest level.
  48
  49    ATCB_Key : System.Address;
  50    pragma Import (C, ATCB_Key, "rtems_ada_self");
  51
  52    ----------------
  53    -- Initialize --
  54    ----------------
  55
  56    procedure Initialize (Environment_Task : Task_Id) is
  57       pragma Warnings (Off, Environment_Task);
  58
  59    begin
  60       ATCB_Key := To_Address (Environment_Task);
  61    end Initialize;
  62
  63    -------------------
  64    -- Is_Valid_Task --
  65    -------------------
  66
  67    function Is_Valid_Task return Boolean is
  68    begin
  69       return ATCB_Key /= System.Null_Address;
  70    end Is_Valid_Task;
  71
  72    ---------
  73    -- Set --
  74    ---------
  75
  76    procedure Set (Self_Id : Task_Id) is
  77    begin
  78       ATCB_Key := To_Address (Self_Id);
  79    end Set;
  80
  81    ----------
  82    -- Self --
  83    ----------
  84
  85    --  To make Ada tasks and C threads interoperate better, we have added some
  86    --  functionality to Self. Suppose a C main program (with threads) calls an
  87    --  Ada procedure and the Ada procedure calls the tasking runtime system.
  88    --  Eventually, a call will be made to self. Since the call is not coming
  89    --  from an Ada task, there will be no corresponding ATCB.
  90
  91    --  What we do in Self is to catch references that do not come from
  92    --  recognized Ada tasks, and create an ATCB for the calling thread.
  93
  94    --  The new ATCB will be "detached" from the normal Ada task master
  95    --  hierarchy, much like the existing implicitly created signal-server
  96    --  tasks.
  97
  98    function Self return Task_Id is
  99       Result : System.Address;
 100
 101    begin
 102       Result := ATCB_Key;
 103
 104       --  If the key value is Null, then it is a non-Ada task.
 105
 106       if Result /= System.Null_Address then
 107          return To_Task_Id (Result);
 108       else
 109          return Register_Foreign_Thread;
 110       end if;
 111    end Self;
 112
 113 end Specific;