gcc/ada/s-tarest.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --     S Y S T E M . T A S K I N G . R E S T R I C T E D . S T A G E S      --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2008, 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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 --  This is a simplified version of the System.Tasking.Stages package,
  35 --  intended to be used in a restricted run time.
  36
  37 --  This package represents the high level tasking interface used by the
  38 --  compiler to expand Ada 95 tasking constructs into simpler run time calls
  39 --  (aka GNARLI, GNU Ada Run-time Library Interface)
  40
  41 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  42 --  Any changes to this interface may require corresponding compiler changes
  43 --  in exp_ch9.adb and possibly exp_ch7.adb
  44
  45 --  The restricted GNARLI is also composed of System.Protected_Objects and
  46 --  System.Protected_Objects.Single_Entry
  47
  48 with System.Task_Info;
  49 with System.Parameters;
  50
  51 package System.Tasking.Restricted.Stages is
  52    pragma Elaborate_Body;
  53
  54    ---------------------------------
  55    -- Compiler Interface (GNARLI) --
  56    ---------------------------------
  57
  58    --  The compiler will expand in the GNAT tree the following construct:
  59
  60    --   task type T (Discr : Integer);
  61
  62    --   task body T is
  63    --      ...declarations, possibly some controlled...
  64    --   begin
  65    --      ...B...;
  66    --   end T;
  67
  68    --   T1 : T (1);
  69
  70    --  as follows:
  71
  72    --   task type t (discr : integer);
  73    --   tE : aliased boolean := false;
  74    --   tZ : size_type := unspecified_size;
  75
  76    --   type tV (discr : integer) is limited record
  77    --      _task_id : task_id;
  78    --      _atcb : aliased system__tasking__ada_task_control_block (0);
  79    --   end record;
  80
  81    --   procedure tB (_task : access tV);
  82    --   freeze tV [
  83    --      procedure tVIP (_init : in out tV; _master : master_id;
  84    --        _chain : in out activation_chain; _task_name : in string;
  85    --        discr : integer) is
  86    --      begin
  87    --         _init.discr := discr;
  88    --         _init._task_id := null;
  89    --         system__tasking__ada_task_control_blockIP (_init._atcb, 0);
  90    --         _init._task_id := _init._atcb'unchecked_access;
  91    --         create_restricted_task (unspecified_priority, tZ,
  92    --           unspecified_task_info, task_procedure_access!(tB'address),
  93    --           _init'address, tE'unchecked_access, _chain, _task_name, _init.
  94    --           _task_id);
  95    --         return;
  96    --      end tVIP;
  97
  98    --   _chain : aliased activation_chain;
  99    --   activation_chainIP (_chain);
 100
 101    --   procedure tB (_task : access tV) is
 102    --      discr : integer renames _task.discr;
 103
 104    --      procedure _clean is
 105    --      begin
 106    --         complete_restricted_task;
 107    --         finalize_list (F14b);
 108    --         return;
 109    --      end _clean;
 110
 111    --   begin
 112    --      ...declarations...
 113    --      complete_restricted_activation;
 114    --      ...B...;
 115    --      return;
 116    --   at end
 117    --      _clean;
 118    --   end tB;
 119
 120    --   tE := true;
 121    --   t1 : t (1);
 122    --   t1S : constant String := "t1";
 123    --   tIP (t1, 3, _chain, t1S, 1);
 124
 125    --   activate_restricted_tasks (_chain'unchecked_access);
 126
 127    procedure Create_Restricted_Task
 128      (Priority      : Integer;
 129       Stack_Address : System.Address;
 130       Size          : System.Parameters.Size_Type;
 131       Task_Info     : System.Task_Info.Task_Info_Type;
 132       State         : Task_Procedure_Access;
 133       Discriminants : System.Address;
 134       Elaborated    : Access_Boolean;
 135       Chain         : in out Activation_Chain;
 136       Task_Image    : String;
 137       Created_Task  : Task_Id);
 138    --  Compiler interface only. Do not call from within the RTS.
 139    --  This must be called to create a new task.
 140    --
 141    --  Priority is the task's priority (assumed to be in the
 142    --  System.Any_Priority'Range)
 143    --
 144    --  Stack_Address is the start address of the stack associated to the task,
 145    --  in case it has been preallocated by the compiler; it is equal to
 146    --  Null_Address when the stack needs to be allocated by the underlying
 147    --  operating system.
 148    --
 149    --  Size is the stack size of the task to create
 150    --
 151    --  Task_Info is the task info associated with the created task, or
 152    --  Unspecified_Task_Info if none.
 153    --
 154    --  State is the compiler generated task's procedure body
 155    --
 156    --  Discriminants is a pointer to a limited record whose discriminants are
 157    --  those of the task to create. This parameter should be passed as the
 158    --  single argument to State.
 159    --
 160    --  Elaborated is a pointer to a Boolean that must be set to true on exit
 161    --  if the task could be successfully elaborated.
 162    --
 163    --  Chain is a linked list of task that needs to be created. On exit,
 164    --  Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID will be
 165    --  Created_Task (the created task will be linked at the front of Chain).
 166    --
 167    --  Task_Image is a string created by the compiler that the run time can
 168    --  store to ease the debugging and the Ada.Task_Identification facility.
 169    --
 170    --  Created_Task is the resulting task.
 171    --
 172    --  This procedure can raise Storage_Error if the task creation fails
 173
 174    procedure Activate_Restricted_Tasks
 175      (Chain_Access : Activation_Chain_Access);
 176    --  Compiler interface only. Do not call from within the RTS.
 177    --  This must be called by the creator of a chain of one or more new tasks,
 178    --  to activate them. The chain is a linked list that up to this point is
 179    --  only known to the task that created them, though the individual tasks
 180    --  are already in the All_Tasks_List.
 181    --
 182    --  The compiler builds the chain in LIFO order (as a stack). Another
 183    --  version of this procedure had code to reverse the chain, so as to
 184    --  activate the tasks in the order of declaration. This might be nice, but
 185    --  it is not needed if priority-based scheduling is supported, since all
 186    --  the activated tasks synchronize on the activators lock before they start
 187    --  activating and so they should start activating in priority order.
 188
 189    procedure Complete_Restricted_Activation;
 190    --  Compiler interface only. Do not call from within the RTS. This should be
 191    --  called from the task body at the end of the elaboration code for its
 192    --  declarative part. Decrement the count of tasks to be activated by the
 193    --  activator and wake it up so it can check to see if all tasks have been
 194    --  activated. Except for the environment task, which should never call this
 195    --  procedure, T.Activator should only be null iff T has completed
 196    --  activation.
 197
 198    procedure Complete_Restricted_Task;
 199    --  Compiler interface only. Do not call from within the RTS. This should be
 200    --  called from an implicit at-end handler associated with the task body,
 201    --  when it completes. From this point, the current task will become not
 202    --  callable. If the current task have not completed activation, this should
 203    --  be done now in order to wake up the activator (the environment task).
 204
 205    function Restricted_Terminated (T : Task_Id) return Boolean;
 206    --  Compiler interface only. Do not call from within the RTS. This is called
 207    --  by the compiler to implement the 'Terminated attribute.
 208    --
 209    --  source code:
 210    --     T1'Terminated
 211    --
 212    --  code expansion:
 213    --     restricted_terminated (t1._task_id)
 214
 215    procedure Finalize_Global_Tasks;
 216    --  This is needed to support the compiler interface; it will only be called
 217    --  by the Environment task in the binder generated file (by adafinal).
 218    --  Instead, it will cause the Environment to block forever, since none of
 219    --  the dependent tasks are expected to terminate
 220
 221 end System.Tasking.Restricted.Stages;