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 --          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 --  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 --  used for Task_Info_Type
  50
  51 with System.Parameters;
  52 --  used for Size_Type
  53
  54 package System.Tasking.Restricted.Stages is
  55    pragma Elaborate_Body;
  56
  57    ---------------------------------
  58    -- Compiler Interface (GNARLI) --
  59    ---------------------------------
  60
  61    --  The compiler will expand in the GNAT tree the following construct:
  62
  63    --   task type T (Discr : Integer);
  64
  65    --   task body T is
  66    --      ...declarations, possibly some controlled...
  67    --   begin
  68    --      ...B...;
  69    --   end T;
  70
  71    --   T1 : T (1);
  72
  73    --  as follows:
  74
  75    --   task type t (discr : integer);
  76    --   tE : aliased boolean := false;
  77    --   tZ : size_type := unspecified_size;
  78    --   type tV (discr : integer) is limited record
  79    --      _task_id : task_id;
  80    --   end record;
  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    --         create_restricted_task (unspecified_priority, tZ,
  90    --           unspecified_task_info, task_procedure_access!(tB'address),
  91    --           _init'address, tE'unchecked_access, _chain, _task_name, _init.
  92    --           _task_id);
  93    --         return;
  94    --      end tVIP;
  95    --   ]
  96
  97    --   _chain : aliased activation_chain;
  98    --   activation_chainIP (_chain);
  99
 100    --   procedure tB (_task : access tV) is
 101    --      discr : integer renames _task.discr;
 102    --
 103    --      procedure _clean is
 104    --      begin
 105    --         complete_restricted_task;
 106    --         finalize_list (F14b);
 107    --         return;
 108    --      end _clean;
 109    --   begin
 110    --      ...declarations...
 111    --      complete_restricted_activation;
 112    --      ...B...;
 113    --      return;
 114    --   at end
 115    --      _clean;
 116    --   end tB;
 117
 118    --   tE := true;
 119    --   t1 : t (1);
 120    --   t1S : constant String := "t1";
 121    --   tIP (t1, 3, _chain, t1S, 1);
 122
 123    --   activate_restricted_tasks (_chain'unchecked_access);
 124
 125    procedure Create_Restricted_Task
 126      (Priority      : Integer;
 127       Size          : System.Parameters.Size_Type;
 128       Task_Info     : System.Task_Info.Task_Info_Type;
 129       State         : Task_Procedure_Access;
 130       Discriminants : System.Address;
 131       Elaborated    : Access_Boolean;
 132       Chain         : in out Activation_Chain;
 133       Task_Image    : String;
 134       Created_Task  : out Task_ID);
 135    --  Compiler interface only. Do not call from within the RTS.
 136    --  This must be called to create a new task.
 137    --
 138    --  Priority is the task's priority (assumed to be in the
 139    --   System.Any_Priority'Range)
 140    --  Size is the stack size of the task to create
 141    --  Task_Info is the task info associated with the created task, or
 142    --   Unspecified_Task_Info if none.
 143    --  State is the compiler generated task's procedure body
 144    --  Discriminants is a pointer to a limited record whose discriminants
 145    --   are those of the task to create. This parameter should be passed as
 146    --   the single argument to State.
 147    --  Elaborated is a pointer to a Boolean that must be set to true on exit
 148    --   if the task could be sucessfully elaborated.
 149    --  Chain is a linked list of task that needs to be created. On exit,
 150    --   Created_Task.Activation_Link will be Chain.T_ID, and Chain.T_ID
 151    --   will be Created_Task (e.g the created task will be linked at the front
 152    --   of Chain).
 153    --  Task_Image is a string created by the compiler that the
 154    --   run time can store to ease the debugging and the
 155    --   Ada.Task_Identification facility.
 156    --  Created_Task is the resulting task.
 157    --
 158    --  This procedure can raise Storage_Error if the task creation failed.
 159
 160    procedure Activate_Restricted_Tasks
 161      (Chain_Access : Activation_Chain_Access);
 162    --  Compiler interface only. Do not call from within the RTS.
 163    --  This must be called by the creator of a chain of one or more new tasks,
 164    --  to activate them. The chain is a linked list that up to this point is
 165    --  only known to the task that created them, though the individual tasks
 166    --  are already in the All_Tasks_List.
 167    --
 168    --  The compiler builds the chain in LIFO order (as a stack). Another
 169    --  version of this procedure had code to reverse the chain, so as to
 170    --  activate the tasks in the order of declaration. This might be nice, but
 171    --  it is not needed if priority-based scheduling is supported, since all
 172    --  the activated tasks synchronize on the activators lock before they
 173    --  start activating and so they should start activating in priority order.
 174
 175    procedure Complete_Restricted_Activation;
 176    --  Compiler interface only. Do not call from within the RTS.
 177    --  This should be called from the task body at the end of
 178    --  the elaboration code for its declarative part.
 179    --  Decrement the count of tasks to be activated by the activator and
 180    --  wake it up so it can check to see if all tasks have been activated.
 181    --  Except for the environment task, which should never call this procedure,
 182    --  T.Activator should only be null iff T has completed activation.
 183
 184    procedure Complete_Restricted_Task;
 185    --  Compiler interface only. Do not call from within the RTS.
 186    --  This should be called from an implicit at-end handler
 187    --  associated with the task body, when it completes.
 188    --  From this point, the current task will become not callable.
 189    --  If the current task have not completed activation, this should be done
 190    --  now in order to wake up the activator (the environment task).
 191
 192    function Restricted_Terminated (T : Task_ID) return Boolean;
 193    --  Compiler interface only. Do not call from within the RTS.
 194    --  This is called by the compiler to implement the 'Terminated attribute.
 195    --
 196    --  source code:
 197    --     T1'Terminated
 198    --
 199    --  code expansion:
 200    --     restricted_terminated (t1._task_id)
 201
 202    procedure Finalize_Global_Tasks;
 203    --  This is needed to support the compiler interface; it will only be called
 204    --  by the Environment task in the binder generated file (by adafinal).
 205    --  Instead, it will cause the Environment to block forever, since none of
 206    --  the dependent tasks are expected to terminate
 207
 208 end System.Tasking.Restricted.Stages;