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, Free Software Foundation, Inc.            --
  14 --                                                                          --
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  20 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
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  22 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
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  24 -- Boston, MA 02110-1301, USA.                                              --
  25 --                                                                          --
  26 -- As a special exception,  if other files  instantiate  generics from this --
  27 -- unit, or you link  this unit with other files  to produce an executable, --
  28 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  29 -- covered  by the  GNU  General  Public  License.  This exception does not --
  30 -- however invalidate  any other reasons why  the executable file  might be --
  31 -- covered by the  GNU Public License.                                      --
  32 --                                                                          --
  33 -- GNARL was developed by the GNARL team at Florida State University. It is --
  34 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
  35 -- State University (http://www.gnat.com).                                  --
  36 --                                                                          --
  37 ------------------------------------------------------------------------------
  38
  39 --  This is a RTEMS version of this package which uses a special
  40 --  variable for Ada self which is context switched implicitly by RTEMS.
  41 --
  42 --  This is the same as the POSIX version except that an RTEMS variable
  43 --  is used instead of a POSIX key.
  44
  45 separate (System.Task_Primitives.Operations)
  46 package body Specific is
  47
  48    --  The following gives the Ada run-time direct access to a variable
  49    --  context switched by RTEMS at the lowest level.
  50
  51    RTEMS_Ada_Self : System.Address;
  52    pragma Import (C, RTEMS_Ada_Self, "rtems_ada_self");
  53
  54    ----------------
  55    -- Initialize --
  56    ----------------
  57
  58    procedure Initialize (Environment_Task : Task_Id) is
  59       pragma Warnings (Off, Environment_Task);
  60
  61    begin
  62       ATCB_Key := No_Key;
  63       RTEMS_Ada_Self := To_Address (Environment_Task);
  64    end Initialize;
  65
  66    -------------------
  67    -- Is_Valid_Task --
  68    -------------------
  69
  70    function Is_Valid_Task return Boolean is
  71    begin
  72       return RTEMS_Ada_Self /= System.Null_Address;
  73    end Is_Valid_Task;
  74
  75    ---------
  76    -- Set --
  77    ---------
  78
  79    procedure Set (Self_Id : Task_Id) is
  80    begin
  81       RTEMS_Ada_Self := To_Address (Self_Id);
  82    end Set;
  83
  84    ----------
  85    -- Self --
  86    ----------
  87
  88    --  To make Ada tasks and C threads interoperate better, we have added some
  89    --  functionality to Self. Suppose a C main program (with threads) calls an
  90    --  Ada procedure and the Ada procedure calls the tasking runtime system.
  91    --  Eventually, a call will be made to self. Since the call is not coming
  92    --  from an Ada task, there will be no corresponding ATCB.
  93
  94    --  What we do in Self is to catch references that do not come from
  95    --  recognized Ada tasks, and create an ATCB for the calling thread.
  96
  97    --  The new ATCB will be "detached" from the normal Ada task master
  98    --  hierarchy, much like the existing implicitly created signal-server
  99    --  tasks.
 100
 101    function Self return Task_Id is
 102       Result : System.Address;
 103
 104    begin
 105       Result := RTEMS_Ada_Self;
 106
 107       --  If the key value is Null, then it is a non-Ada task.
 108
 109       if Result /= System.Null_Address then
 110          return To_Task_Id (Result);
 111       else
 112          return Register_Foreign_Thread;
 113       end if;
 114    end Self;
 115
 116 end Specific;