gcc/ada/s-taskin.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --                        S Y S T E M . T A S K I N G                       --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2003, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 pragma Polling (Off);
  35 --  Turn off polling, we do not want ATC polling to take place during
  36 --  tasking operations. It causes infinite loops and other problems.
  37
  38 with System.Task_Primitives.Operations;
  39 --  used for Self
  40
  41 with Unchecked_Deallocation;
  42 --  To recover from failure of ATCB initialization.
  43
  44 with System.Storage_Elements;
  45 --  Needed for initializing Stack_Info.Size
  46
  47 with System.Parameters;
  48 --  Used for Adjust_Storage_Size
  49
  50 package body System.Tasking is
  51
  52    package STPO renames System.Task_Primitives.Operations;
  53
  54    procedure Free is new
  55      Unchecked_Deallocation (Ada_Task_Control_Block, Task_ID);
  56
  57    ----------
  58    -- Self --
  59    ----------
  60
  61    function Self return Task_ID renames STPO.Self;
  62
  63    ---------------------
  64    -- Initialize_ATCB --
  65    ---------------------
  66
  67    procedure Initialize_ATCB
  68      (Self_ID          : Task_ID;
  69       Task_Entry_Point : Task_Procedure_Access;
  70       Task_Arg         : System.Address;
  71       Parent           : Task_ID;
  72       Elaborated       : Access_Boolean;
  73       Base_Priority    : System.Any_Priority;
  74       Task_Info        : System.Task_Info.Task_Info_Type;
  75       Stack_Size       : System.Parameters.Size_Type;
  76       T                : in out Task_ID;
  77       Success          : out Boolean) is
  78    begin
  79       T.Common.State := Unactivated;
  80
  81       --  Initialize T.Common.LL
  82
  83       STPO.Initialize_TCB (T, Success);
  84
  85       if not Success then
  86          Free (T);
  87          return;
  88       end if;
  89
  90       T.Common.Parent := Parent;
  91       T.Common.Base_Priority := Base_Priority;
  92       T.Common.Current_Priority := 0;
  93       T.Common.Call := null;
  94       T.Common.Task_Arg := Task_Arg;
  95       T.Common.Task_Entry_Point := Task_Entry_Point;
  96       T.Common.Activator := Self_ID;
  97       T.Common.Wait_Count := 0;
  98       T.Common.Elaborated := Elaborated;
  99       T.Common.Activation_Failed := False;
 100       T.Common.Task_Info := Task_Info;
 101
 102       if T.Common.Parent = null then
 103          --  For the environment task, the adjusted stack size is
 104          --  meaningless. For example, an unspecified Stack_Size means
 105          --  that the stack size is determined by the environment, or
 106          --  can grow dynamically. The Stack_Checking algorithm
 107          --  therefore needs to use the requested size, or 0 in
 108          --  case of an unknown size.
 109
 110          T.Common.Compiler_Data.Pri_Stack_Info.Size :=
 111             Storage_Elements.Storage_Offset (Stack_Size);
 112
 113       else
 114          T.Common.Compiler_Data.Pri_Stack_Info.Size :=
 115            Storage_Elements.Storage_Offset
 116              (Parameters.Adjust_Storage_Size (Stack_Size));
 117       end if;
 118
 119       --  Link the task into the list of all tasks.
 120
 121       T.Common.All_Tasks_Link := All_Tasks_List;
 122       All_Tasks_List := T;
 123    end Initialize_ATCB;
 124
 125    Main_Task_Image : constant String := "main_task";
 126    --  Image of environment task.
 127
 128    Main_Priority : Integer;
 129    pragma Import (C, Main_Priority, "__gl_main_priority");
 130    --  Priority for main task. Note that this is of type Integer, not
 131    --  Priority, because we use the value -1 to indicate the default
 132    --  main priority, and that is of course not in Priority'range.
 133
 134    ----------------------------
 135    -- Tasking Initialization --
 136    ----------------------------
 137
 138    --  This block constitutes the first part of the initialization of the
 139    --  GNARL. This includes creating data structures to make the initial thread
 140    --  into the environment task. The last part of the initialization is done
 141    --  in System.Tasking.Initialization or System.Tasking.Restricted.Stages.
 142    --  All the initializations used to be in Tasking.Initialization, but this
 143    --  is no longer possible with the run time simplification (including
 144    --  optimized PO and the restricted run time) since one cannot rely on
 145    --  System.Tasking.Initialization being present, as was done before.
 146
 147 begin
 148    declare
 149       T             : Task_ID;
 150       Success       : Boolean;
 151       Base_Priority : Any_Priority;
 152
 153    begin
 154       --  Initialize Environment Task
 155
 156       if Main_Priority = Unspecified_Priority then
 157          Base_Priority := Default_Priority;
 158       else
 159          Base_Priority := Priority (Main_Priority);
 160       end if;
 161
 162       Success := True;
 163       T := STPO.New_ATCB (0);
 164       Initialize_ATCB
 165         (null, null, Null_Address, Null_Task, null, Base_Priority,
 166          Task_Info.Unspecified_Task_Info, 0, T, Success);
 167       pragma Assert (Success);
 168
 169       STPO.Initialize (T);
 170       STPO.Set_Priority (T, T.Common.Base_Priority);
 171       T.Common.State := Runnable;
 172       T.Common.Task_Image_Len := Main_Task_Image'Length;
 173       T.Common.Task_Image (Main_Task_Image'Range) := Main_Task_Image;
 174
 175       --  Only initialize the first element since others are not relevant
 176       --  in ravenscar mode. Rest of the initialization is done in Init_RTS.
 177
 178       T.Entry_Calls (1).Self := T;
 179    end;
 180 end System.Tasking;