gcc/ada/s-tarest.ads

   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 . R E S T R I C T E D . S T A G E S      --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-1999, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNARL was developed by the GNARL team at Florida State University. It is --
  31 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
  32 -- State University (http://www.gnat.com).                                  --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 --  This is a simplified version of the System.Tasking.Stages package,
  37 --  intended to be used in a restricted run time.
  38
  39 --  This package represents the high level tasking interface used by the
  40 --  compiler to expand Ada 95 tasking constructs into simpler run time calls
  41 --  (aka GNARLI, GNU Ada Run-time Library Interface)
  42
  43 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  44 --  Any changes to this interface may require corresponding compiler changes
  45 --  in exp_ch9.adb and possibly exp_ch7.adb
  46
  47 --  The restricted GNARLI is also composed of System.Protected_Objects and
  48 --  System.Protected_Objects.Single_Entry
  49
  50 with System.Task_Info;
  51 --  used for Task_Info_Type
  52
  53 with System.Parameters;
  54 --  used for Size_Type
  55
  56 package System.Tasking.Restricted.Stages is
  57    pragma Elaborate_Body;
  58
  59    ---------------------------------
  60    -- Compiler Interface (GNARLI) --
  61    ---------------------------------
  62
  63    --  The compiler will expand in the GNAT tree the following construct:
  64    --
  65    --   task type T (Discr : Integer);
  66    --
  67    --   task body T is
  68    --      ...declarations, possibly some controlled...
  69    --   begin
  70    --      ...B...;
  71    --   end T;
  72    --
  73    --   T1 : T (1);
  74    --
  75    --  as follows:
  76    --
  77    --   task type t (discr : integer);
  78    --   tE : aliased boolean := false;
  79    --   tZ : size_type := unspecified_size;
  80    --   type tV (discr : integer) is limited record
  81    --      _task_id : task_id;
  82    --   end record;
  83    --   procedure tB (_task : access tV);
  84    --   freeze tV [
  85    --      procedure _init_proc (_init : in out tV; _master : master_id;
  86    --        _chain : in out activation_chain; _task_id : in task_image_type;
  87    --        discr : integer) is
  88    --      begin
  89    --         _init.discr := discr;
  90    --         _init._task_id := null;
  91    --         create_restricted_task (unspecified_priority, tZ,
  92    --           unspecified_task_info, task_procedure_access!(tB'address),
  93    --           _init'address, tE'unchecked_access, _chain, _task_id, _init.
  94    --           _task_id);
  95    --         return;
  96    --      end _init_proc;
  97    --   ]
  98    --
  99    --   _chain : aliased activation_chain;
 100    --   _init_proc (_chain);
 101    --
 102    --   procedure tB (_task : access tV) is
 103    --      discr : integer renames _task.discr;
 104    --
 105    --      procedure _clean is
 106    --      begin
 107    --         complete_restricted_task;
 108    --         finalize_list (F14b);
 109    --         return;
 110    --      end _clean;
 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    --   t1I : task_image_type := new string'"t1";
 123    --   _init_proc (t1, 3, _chain, t1I, 1);
 124    --
 125    --   activate_restricted_tasks (_chain'unchecked_access);
 126
 127    procedure Create_Restricted_Task
 128      (Priority      : Integer;
 129       Size          : System.Parameters.Size_Type;
 130       Task_Info     : System.Task_Info.Task_Info_Type;
 131       State         : Task_Procedure_Access;
 132       Discriminants : System.Address;
 133       Elaborated    : Access_Boolean;
 134       Chain         : in out Activation_Chain;
 135       Task_Image    : System.Task_Info.Task_Image_Type;
 136       Created_Task  : out Task_ID);
 137    --  Compiler interface only. Do not call from within the RTS.
 138    --  This must be called to create a new task.
 139    --
 140    --  Priority is the task's priority (assumed to be in the
 141    --   System.Any_Priority'Range)
 142    --  Size is the stack size of the task to create
 143    --  Task_Info is the task info associated with the created task, or
 144    --   Unspecified_Task_Info if none.
 145    --  State is the compiler generated task's procedure body
 146    --  Discriminants is a pointer to a limited record whose discriminants
 147    --   are those of the task to create. This parameter should be passed as
 148    --   the single argument to State.
 149    --  Elaborated is a pointer to a Boolean that must be set to true on exit
 150    --   if the task could be successfully elaborated.
 151    --  Chain is a linked list of task that needs to be created. On exit,
 152    --   Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID
 153    --   will be Created_Task (e.g the created task will be linked at the front
 154    --   of Chain).
 155    --  Task_Image is a pointer to a string created by the compiler that the
 156    --   run time can store to ease the debugging and the
 157    --   Ada.Task_Identification facility.
 158    --  Created_Task is the resulting task.
 159    --
 160    --  This procedure can raise Storage_Error if the task creation failed.
 161
 162    procedure Activate_Restricted_Tasks
 163      (Chain_Access : Activation_Chain_Access);
 164    --  Compiler interface only. Do not call from within the RTS.
 165    --  This must be called by the creator of a chain of one or more new tasks,
 166    --  to activate them. The chain is a linked list that up to this point is
 167    --  only known to the task that created them, though the individual tasks
 168    --  are already in the All_Tasks_List.
 169    --
 170    --  The compiler builds the chain in LIFO order (as a stack). Another
 171    --  version of this procedure had code to reverse the chain, so as to
 172    --  activate the tasks in the order of declaration. This might be nice, but
 173    --  it is not needed if priority-based scheduling is supported, since all
 174    --  the activated tasks synchronize on the activators lock before they
 175    --  start activating and so they should start activating in priority order.
 176
 177    procedure Complete_Restricted_Activation;
 178    --  Compiler interface only. Do not call from within the RTS.
 179    --  This should be called from the task body at the end of
 180    --  the elaboration code for its declarative part.
 181    --  Decrement the count of tasks to be activated by the activator and
 182    --  wake it up so it can check to see if all tasks have been activated.
 183    --  Except for the environment task, which should never call this procedure,
 184    --  T.Activator should only be null iff T has completed activation.
 185
 186    procedure Complete_Restricted_Task;
 187    --  Compiler interface only. Do not call from within the RTS.
 188    --  This should be called from an implicit at-end handler
 189    --  associated with the task body, when it completes.
 190    --  From this point, the current task will become not callable.
 191    --  If the current task have not completed activation, this should be done
 192    --  now in order to wake up the activator (the environment task).
 193
 194    function Restricted_Terminated (T : Task_ID) return Boolean;
 195    --  Compiler interface only. Do not call from within the RTS.
 196    --  This is called by the compiler to implement the 'Terminated attribute.
 197    --
 198    --  source code:
 199    --     T1'Terminated
 200    --
 201    --  code expansion:
 202    --     restricted_terminated (t1._task_id)
 203
 204    procedure Finalize_Global_Tasks;
 205    --  This is needed to support the compiler interface; it will only be called
 206    --  by the Environment task in the binder generated file (by adafinal).
 207    --  Instead, it will cause the Environment to block forever, since none of
 208    --  the dependent tasks are expected to terminate
 209
 210 end System.Tasking.Restricted.Stages;