gcc/ada/libgnarl/s-tasren.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 N D E Z V O U S            --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2018, 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 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT 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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNARL was developed by the GNARL team at Florida State University.       --
  28 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  33 --  Any changes to this interface may require corresponding compiler changes.
  34
  35 with Ada.Exceptions;
  36
  37 with System.Tasking.Protected_Objects.Entries;
  38
  39 package System.Tasking.Rendezvous is
  40
  41    package STPE renames System.Tasking.Protected_Objects.Entries;
  42
  43    procedure Task_Entry_Call
  44      (Acceptor              : Task_Id;
  45       E                     : Task_Entry_Index;
  46       Uninterpreted_Data    : System.Address;
  47       Mode                  : Call_Modes;
  48       Rendezvous_Successful : out Boolean);
  49    --  General entry call used to implement ATC or conditional entry calls.
  50    --  Compiler interface only. Do not call from within the RTS.
  51    --  Acceptor is the ID of the acceptor task.
  52    --  E is the entry index requested.
  53    --  Uninterpreted_Data represents the parameters of the entry. It is
  54    --  constructed by the compiler for the caller and the callee; therefore,
  55    --  the run time never needs to decode this data.
  56    --  Mode can be either Asynchronous_Call (ATC) or Conditional_Call.
  57    --  Rendezvous_Successful is set to True on return if the call was serviced.
  58
  59    procedure Timed_Task_Entry_Call
  60      (Acceptor              : Task_Id;
  61       E                     : Task_Entry_Index;
  62       Uninterpreted_Data    : System.Address;
  63       Timeout               : Duration;
  64       Mode                  : Delay_Modes;
  65       Rendezvous_Successful : out Boolean);
  66    --  Timed entry call without using ATC.
  67    --  Compiler interface only. Do not call from within the RTS.
  68    --  See Task_Entry_Call for details on Acceptor, E and Uninterpreted_Data.
  69    --  Timeout is the value of the time out.
  70    --  Mode determines whether the delay is relative or absolute.
  71
  72    procedure Call_Simple
  73      (Acceptor           : Task_Id;
  74       E                  : Task_Entry_Index;
  75       Uninterpreted_Data : System.Address);
  76    --  Simple entry call.
  77    --  Compiler interface only. Do not call from within the RTS.
  78    --
  79    --  source:
  80    --     T.E1 (Params);
  81    --
  82    --  expansion:
  83    --    declare
  84    --       P : parms := (parm1, parm2, parm3);
  85    --       X : Task_Entry_Index := 1;
  86    --    begin
  87    --       Call_Simple (t._task_id, X, P'Address);
  88    --       parm1 := P.param1;
  89    --       parm2 := P.param2;
  90    --       ...
  91    --    end;
  92
  93    procedure Cancel_Task_Entry_Call (Cancelled : out Boolean);
  94    --  Cancel pending asynchronous task entry call.
  95    --  Compiler interface only. Do not call from within the RTS.
  96    --  See Exp_Ch9.Expand_N_Asynchronous_Select for code expansion.
  97
  98    procedure Requeue_Task_Entry
  99      (Acceptor   : Task_Id;
 100       E          : Task_Entry_Index;
 101       With_Abort : Boolean);
 102    --  Requeue from a task entry to a task entry.
 103    --  Compiler interface only. Do not call from within the RTS.
 104    --  The code generation for task entry requeues is different from that for
 105    --  protected entry requeues. There is a "goto" that skips around the call
 106    --  to Complete_Rendezvous, so that Requeue_Task_Entry must also do the work
 107    --  of Complete_Rendezvous. The difference is that it does not report that
 108    --  the call's State = Done.
 109    --
 110    --  source:
 111    --     accept e1 do
 112    --       ...A...
 113    --       requeue e2;
 114    --       ...B...
 115    --     end e1;
 116    --
 117    --  expansion:
 118    --     A62b : address;
 119    --     L61b : label
 120    --     begin
 121    --        accept_call (1, A62b);
 122    --        ...A...
 123    --        requeue_task_entry (tTV!(t)._task_id, 2, false);
 124    --        goto L61b;
 125    --        ...B...
 126    --        complete_rendezvous;
 127    --        <<L61b>>
 128    --     exception
 129    --        when others =>
 130    --           exceptional_complete_rendezvous (current_exception);
 131    --     end;
 132
 133    procedure Requeue_Protected_To_Task_Entry
 134      (Object     : STPE.Protection_Entries_Access;
 135       Acceptor   : Task_Id;
 136       E          : Task_Entry_Index;
 137       With_Abort : Boolean);
 138    --  Requeue from a protected entry to a task entry.
 139    --  Compiler interface only. Do not call from within the RTS.
 140    --
 141    --  source:
 142    --     entry e2 when b is
 143    --     begin
 144    --        b := false;
 145    --        ...A...
 146    --        requeue t.e2;
 147    --     end e2;
 148    --
 149    --  expansion:
 150    --     procedure rPT__E14b (O : address; P : address; E :
 151    --       protected_entry_index) is
 152    --        type rTVP is access rTV;
 153    --        freeze rTVP []
 154    --        _object : rTVP := rTVP!(O);
 155    --     begin
 156    --        declare
 157    --           rR : protection renames _object._object;
 158    --           vP : integer renames _object.v;
 159    --           bP : boolean renames _object.b;
 160    --        begin
 161    --           b := false;
 162    --           ...A...
 163    --           requeue_protected_to_task_entry (rR'unchecked_access, tTV!(t).
 164    --             _task_id, 2, false);
 165    --           return;
 166    --        end;
 167    --        complete_entry_body (_object._object'unchecked_access, objectF =>
 168    --          0);
 169    --        return;
 170    --     exception
 171    --        when others =>
 172    --           abort_undefer.all;
 173    --           exceptional_complete_entry_body (_object._object'
 174    --             unchecked_access, current_exception, objectF => 0);
 175    --           return;
 176    --     end rPT__E14b;
 177
 178    procedure Selective_Wait
 179      (Open_Accepts       : Accept_List_Access;
 180       Select_Mode        : Select_Modes;
 181       Uninterpreted_Data : out System.Address;
 182       Index              : out Select_Index);
 183    --  Implement select statement.
 184    --  Compiler interface only. Do not call from within the RTS.
 185    --  See comments on Accept_Call.
 186    --
 187    --  source:
 188    --     select accept e1 do
 189    --           ...A...
 190    --        end e1;
 191    --        ...B...
 192    --     or accept e2;
 193    --        ...C...
 194    --     end select;
 195    --
 196    --  expansion:
 197    --     A32b : address;
 198    --     declare
 199    --        A37b : T36b;
 200    --        A37b (1) := (null_body => false, s => 1);
 201    --        A37b (2) := (null_body => true, s => 2);
 202    --        S0 : aliased T36b := accept_list'A37b;
 203    --        J1 : select_index := 0;
 204    --        procedure e1A is
 205    --        begin
 206    --           abort_undefer.all;
 207    --           ...A...
 208    --           <<L31b>>
 209    --           complete_rendezvous;
 210    --        exception
 211    --           when all others =>
 212    --              exceptional_complete_rendezvous (get_gnat_exception);
 213    --        end e1A;
 214    --     begin
 215    --        selective_wait (S0'unchecked_access, simple_mode, A32b, J1);
 216    --        case J1 is
 217    --           when 0 =>
 218    --              goto L3;
 219    --           when 1 =>
 220    --              e1A;
 221    --              goto L1;
 222    --           when 2 =>
 223    --              goto L2;
 224    --           when others =>
 225    --              goto L3;
 226    --        end case;
 227    --        <<L1>>
 228    --        ...B...
 229    --        goto L3;
 230    --        <<L2>>
 231    --        ...C...
 232    --        goto L3;
 233    --        <<L3>>
 234    --     end;
 235
 236    procedure Timed_Selective_Wait
 237      (Open_Accepts       : Accept_List_Access;
 238       Select_Mode        : Select_Modes;
 239       Uninterpreted_Data : out System.Address;
 240       Timeout            : Duration;
 241       Mode               : Delay_Modes;
 242       Index              : out Select_Index);
 243    --  Selective wait with timeout without using ATC.
 244    --  Compiler interface only. Do not call from within the RTS.
 245
 246    procedure Accept_Call
 247      (E                  : Task_Entry_Index;
 248       Uninterpreted_Data : out System.Address);
 249    --  Accept an entry call.
 250    --  Compiler interface only. Do not call from within the RTS.
 251    --
 252    --  source:
 253    --              accept E do  ...A... end E;
 254    --  expansion:
 255    --              A27b : address;
 256    --              L26b : label
 257    --              begin
 258    --                 accept_call (1, A27b);
 259    --                 ...A...
 260    --                 complete_rendezvous;
 261    --              <<L26b>>
 262    --              exception
 263    --              when all others =>
 264    --                 exceptional_complete_rendezvous (get_gnat_exception);
 265    --              end;
 266    --
 267    --  The handler for Abort_Signal (*all* others) is to handle the case when
 268    --  the acceptor is aborted between Accept_Call and the corresponding
 269    --  Complete_Rendezvous call. We need to wake up the caller in this case.
 270    --
 271    --   See also Selective_Wait
 272
 273    procedure Accept_Trivial (E : Task_Entry_Index);
 274    --  Accept an entry call that has no parameters and no body.
 275    --  Compiler interface only. Do not call from within the RTS.
 276    --  This should only be called when there is no accept body, or the accept
 277    --  body is empty.
 278    --
 279    --  source:
 280    --               accept E;
 281    --  expansion:
 282    --               accept_trivial (1);
 283    --
 284    --  The compiler is also able to recognize the following and
 285    --  translate it the same way.
 286    --
 287    --     accept E do null; end E;
 288
 289    function Task_Count (E : Task_Entry_Index) return Natural;
 290    --  Return number of tasks waiting on the entry E (of current task)
 291    --  Compiler interface only. Do not call from within the RTS.
 292
 293    function Callable (T : Task_Id) return Boolean;
 294    --  Return T'Callable
 295    --  Compiler interface. Do not call from within the RTS, except for body of
 296    --  Ada.Task_Identification.
 297
 298    type Task_Entry_Nesting_Depth is new Task_Entry_Index
 299      range 0 .. Max_Task_Entry;
 300
 301    function Task_Entry_Caller (D : Task_Entry_Nesting_Depth) return Task_Id;
 302    --  Return E'Caller. This will only work if called from within an
 303    --  accept statement that is handling E, as required by the LRM (C.7.1(14)).
 304    --  Compiler interface only. Do not call from within the RTS.
 305
 306    procedure Complete_Rendezvous;
 307    --  Called by acceptor to wake up caller
 308
 309    procedure Exceptional_Complete_Rendezvous
 310      (Ex : Ada.Exceptions.Exception_Id);
 311    pragma No_Return (Exceptional_Complete_Rendezvous);
 312    --  Called by acceptor to mark the end of the current rendezvous and
 313    --  propagate an exception to the caller.
 314
 315    --  For internal use only:
 316
 317    function Task_Do_Or_Queue
 318      (Self_ID    : Task_Id;
 319       Entry_Call : Entry_Call_Link) return Boolean;
 320    --  Call this only with abort deferred and holding no locks, except
 321    --  the global RTS lock when Single_Lock is True which must be owned.
 322    --  Returns False iff the call cannot be served or queued, as is the
 323    --  case if the caller is not callable; i.e., a False return value
 324    --  indicates that Tasking_Error should be raised.
 325    --  Either initiate the entry call, such that the accepting task is
 326    --  free to execute the rendezvous, queue the call on the acceptor's
 327    --  queue, or cancel the call. Conditional calls that cannot be
 328    --  accepted immediately are cancelled.
 329
 330 end System.Tasking.Rendezvous;