gcc/ada/s-tposen.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --               GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS                --
   4 --                                                                          --
   5 --              SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY               --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --         Copyright (C) 1998-2002, 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. It is --
  30 -- now maintained by Ada Core Technologies, Inc. (http://www.gnat.com).     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 pragma Style_Checks (All_Checks);
  35 --  Turn off subprogram ordering check, since restricted GNARLI
  36 --  subprograms are gathered together at end.
  37
  38 --  This package provides an optimized version of Protected_Objects.Operations
  39 --  and Protected_Objects.Entries making the following assumptions:
  40 --
  41 --  PO have only one entry
  42 --  There is only one caller at a time (No_Entry_Queue)
  43 --  There is no dynamic priority support (No_Dynamic_Priorities)
  44 --  No Abort Statements
  45 --    (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
  46 --  PO are at library level
  47 --  No Requeue
  48 --  None of the tasks will terminate (no need for finalization)
  49 --
  50 --  This interface is intended to be used in the ravenscar and restricted
  51 --  profiles, the compiler is responsible for ensuring that the conditions
  52 --  mentioned above are respected, except for the No_Entry_Queue restriction
  53 --  that is checked dynamically in this package, since the check cannot be
  54 --  performed at compile time, and is relatively cheap (see PO_Do_Or_Queue,
  55 --  PO_Service_Entry).
  56
  57 pragma Polling (Off);
  58 --  Turn off polling, we do not want polling to take place during tasking
  59 --  operations. It can cause  infinite loops and other problems.
  60
  61 pragma Suppress (All_Checks);
  62
  63 with System.Task_Primitives.Operations;
  64 --  used for Self
  65 --           Finalize_Lock
  66 --           Write_Lock
  67 --           Unlock
  68
  69 with Ada.Exceptions;
  70 --  used for Exception_Id;
  71
  72 with System.Parameters;
  73 --  used for Single_Lock
  74
  75 package body System.Tasking.Protected_Objects.Single_Entry is
  76
  77    package STPO renames System.Task_Primitives.Operations;
  78
  79    use Parameters;
  80
  81    -----------------------
  82    -- Local Subprograms --
  83    -----------------------
  84
  85    procedure Send_Program_Error
  86      (Self_Id    : Task_ID;
  87       Entry_Call : Entry_Call_Link);
  88    pragma Inline (Send_Program_Error);
  89    --  Raise Program_Error in the caller of the specified entry call
  90
  91    --------------------------
  92    -- Entry Calls Handling --
  93    --------------------------
  94
  95    procedure Wakeup_Entry_Caller
  96      (Self_ID    : Task_ID;
  97       Entry_Call : Entry_Call_Link;
  98       New_State  : Entry_Call_State);
  99    pragma Inline (Wakeup_Entry_Caller);
 100    --  This is called at the end of service of an entry call,
 101    --  to abort the caller if he is in an abortable part, and
 102    --  to wake up the caller if he is on Entry_Caller_Sleep.
 103    --  Call it holding the lock of Entry_Call.Self.
 104    --
 105    --  Timed_Call or Simple_Call:
 106    --    The caller is waiting on Entry_Caller_Sleep, in
 107    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 108
 109    procedure Wait_For_Completion (Entry_Call : Entry_Call_Link);
 110    pragma Inline (Wait_For_Completion);
 111    --  This procedure suspends the calling task until the specified entry call
 112    --  has either been completed or cancelled. On exit, the call will not be
 113    --  queued. This waits for calls on protected entries.
 114    --  Call this only when holding Self_ID locked.
 115
 116    procedure Wait_For_Completion_With_Timeout
 117      (Entry_Call  : Entry_Call_Link;
 118       Wakeup_Time : Duration;
 119       Mode        : Delay_Modes);
 120    --  Same as Wait_For_Completion but it waits for a timeout with the value
 121    --  specified in Wakeup_Time as well.
 122
 123    procedure Check_Exception
 124      (Self_ID : Task_ID;
 125       Entry_Call : Entry_Call_Link);
 126    pragma Inline (Check_Exception);
 127    --  Raise any pending exception from the Entry_Call.
 128    --  This should be called at the end of every compiler interface procedure
 129    --  that implements an entry call.
 130    --  The caller should not be holding any locks, or there will be deadlock.
 131
 132    procedure PO_Do_Or_Queue
 133      (Self_Id    : Task_ID;
 134       Object     : Protection_Entry_Access;
 135       Entry_Call : Entry_Call_Link);
 136    --  This procedure executes or queues an entry call, depending
 137    --  on the status of the corresponding barrier. It assumes that the
 138    --  specified object is locked.
 139
 140    ---------------------
 141    -- Check_Exception --
 142    ---------------------
 143
 144    procedure Check_Exception
 145      (Self_ID    : Task_ID;
 146       Entry_Call : Entry_Call_Link)
 147    is
 148       pragma Warnings (Off, Self_ID);
 149
 150       procedure Internal_Raise (X : Ada.Exceptions.Exception_Id);
 151       pragma Import (C, Internal_Raise, "__gnat_raise_with_msg");
 152
 153       use type Ada.Exceptions.Exception_Id;
 154
 155       E : constant Ada.Exceptions.Exception_Id :=
 156         Entry_Call.Exception_To_Raise;
 157
 158    begin
 159       if E /= Ada.Exceptions.Null_Id then
 160          Internal_Raise (E);
 161       end if;
 162    end Check_Exception;
 163
 164    ------------------------
 165    -- Send_Program_Error --
 166    ------------------------
 167
 168    procedure Send_Program_Error
 169      (Self_Id    : Task_ID;
 170       Entry_Call : Entry_Call_Link)
 171    is
 172       Caller : constant Task_ID := Entry_Call.Self;
 173    begin
 174       Entry_Call.Exception_To_Raise := Program_Error'Identity;
 175
 176       if Single_Lock then
 177          STPO.Lock_RTS;
 178       end if;
 179
 180       STPO.Write_Lock (Caller);
 181       Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 182       STPO.Unlock (Caller);
 183
 184       if Single_Lock then
 185          STPO.Unlock_RTS;
 186       end if;
 187    end Send_Program_Error;
 188
 189    -------------------------
 190    -- Wait_For_Completion --
 191    -------------------------
 192
 193    procedure Wait_For_Completion (Entry_Call : Entry_Call_Link) is
 194       Self_Id : constant Task_ID := Entry_Call.Self;
 195    begin
 196       Self_Id.Common.State := Entry_Caller_Sleep;
 197       STPO.Sleep (Self_Id, Entry_Caller_Sleep);
 198       Self_Id.Common.State := Runnable;
 199    end Wait_For_Completion;
 200
 201    --------------------------------------
 202    -- Wait_For_Completion_With_Timeout --
 203    --------------------------------------
 204
 205    procedure Wait_For_Completion_With_Timeout
 206      (Entry_Call  : Entry_Call_Link;
 207       Wakeup_Time : Duration;
 208       Mode        : Delay_Modes)
 209    is
 210       Self_Id  : constant Task_ID := Entry_Call.Self;
 211       Timedout : Boolean;
 212       Yielded  : Boolean;
 213
 214       use type Ada.Exceptions.Exception_Id;
 215
 216    begin
 217       --  This procedure waits for the entry call to be served, with a timeout.
 218       --  It tries to cancel the call if the timeout expires before the call is
 219       --  served.
 220
 221       --  If we wake up from the timed sleep operation here, it may be for the
 222       --  following possible reasons:
 223
 224       --  1) The entry call is done being served.
 225       --  2) The timeout has expired (Timedout = True)
 226
 227       --  Once the timeout has expired we may need to continue to wait if the
 228       --  call is already being serviced. In that case, we want to go back to
 229       --  sleep, but without any timeout. The variable Timedout is used to
 230       --  control this. If the Timedout flag is set, we do not need to Sleep
 231       --  with a timeout. We just sleep until we get a wakeup for some status
 232       --  change.
 233
 234       pragma Assert (Entry_Call.Mode = Timed_Call);
 235       Self_Id.Common.State := Entry_Caller_Sleep;
 236
 237       STPO.Timed_Sleep
 238         (Self_Id, Wakeup_Time, Mode, Entry_Caller_Sleep, Timedout, Yielded);
 239
 240       if Timedout then
 241          Entry_Call.State := Cancelled;
 242       else
 243          Entry_Call.State := Done;
 244       end if;
 245
 246       Self_Id.Common.State := Runnable;
 247    end Wait_For_Completion_With_Timeout;
 248
 249    -------------------------
 250    -- Wakeup_Entry_Caller --
 251    -------------------------
 252
 253    --  This is called at the end of service of an entry call, to abort the
 254    --  caller if he is in an abortable part, and to wake up the caller if it
 255    --  is on Entry_Caller_Sleep. It assumes that the call is already off-queue.
 256
 257    --  (This enforces the rule that a task must be off-queue if its state is
 258    --  Done or Cancelled.) Call it holding the lock of Entry_Call.Self.
 259
 260    --  Timed_Call or Simple_Call:
 261    --    The caller is waiting on Entry_Caller_Sleep, in
 262    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 263
 264    --  Conditional_Call:
 265    --    The caller might be in Wait_For_Completion,
 266    --    waiting for a rendezvous (possibly requeued without abort)
 267    --    to complete.
 268
 269    procedure Wakeup_Entry_Caller
 270      (Self_ID    : Task_ID;
 271       Entry_Call : Entry_Call_Link;
 272       New_State  : Entry_Call_State)
 273    is
 274       pragma Warnings (Off, Self_ID);
 275
 276       Caller : constant Task_ID := Entry_Call.Self;
 277
 278    begin
 279       pragma Assert (New_State = Done or else New_State = Cancelled);
 280       pragma Assert
 281         (Caller.Common.State /= Terminated and then
 282          Caller.Common.State /= Unactivated);
 283
 284       Entry_Call.State := New_State;
 285       STPO.Wakeup (Caller, Entry_Caller_Sleep);
 286    end Wakeup_Entry_Caller;
 287
 288    -----------------------
 289    -- Restricted GNARLI --
 290    -----------------------
 291
 292    --------------------------------
 293    -- Complete_Single_Entry_Body --
 294    --------------------------------
 295
 296    procedure Complete_Single_Entry_Body (Object : Protection_Entry_Access) is
 297       pragma Warnings (Off, Object);
 298
 299    begin
 300       --  Nothing needs to do (Object.Call_In_Progress.Exception_To_Raise
 301       --  has already been set to Null_Id).
 302
 303       null;
 304    end Complete_Single_Entry_Body;
 305
 306    --------------------------------------------
 307    -- Exceptional_Complete_Single_Entry_Body --
 308    --------------------------------------------
 309
 310    procedure Exceptional_Complete_Single_Entry_Body
 311      (Object : Protection_Entry_Access;
 312       Ex     : Ada.Exceptions.Exception_Id) is
 313    begin
 314       Object.Call_In_Progress.Exception_To_Raise := Ex;
 315    end Exceptional_Complete_Single_Entry_Body;
 316
 317    ---------------------------------
 318    -- Initialize_Protection_Entry --
 319    ---------------------------------
 320
 321    procedure Initialize_Protection_Entry
 322      (Object            : Protection_Entry_Access;
 323       Ceiling_Priority  : Integer;
 324       Compiler_Info     : System.Address;
 325       Entry_Body        : Entry_Body_Access)
 326    is
 327       Init_Priority : Integer := Ceiling_Priority;
 328    begin
 329       if Init_Priority = Unspecified_Priority then
 330          Init_Priority := System.Priority'Last;
 331       end if;
 332
 333       STPO.Initialize_Lock (Init_Priority, Object.L'Access);
 334       Object.Ceiling := System.Any_Priority (Init_Priority);
 335       Object.Compiler_Info := Compiler_Info;
 336       Object.Call_In_Progress := null;
 337       Object.Entry_Body := Entry_Body;
 338       Object.Entry_Queue := null;
 339    end Initialize_Protection_Entry;
 340
 341    ----------------
 342    -- Lock_Entry --
 343    ----------------
 344
 345    --  Compiler interface only.
 346    --  Do not call this procedure from within the run-time system.
 347
 348    procedure Lock_Entry (Object : Protection_Entry_Access) is
 349       Ceiling_Violation : Boolean;
 350    begin
 351       STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
 352
 353       if Ceiling_Violation then
 354          raise Program_Error;
 355       end if;
 356    end Lock_Entry;
 357
 358    --------------------------
 359    -- Lock_Read_Only_Entry --
 360    --------------------------
 361
 362    --  Compiler interface only.
 363    --  Do not call this procedure from within the runtime system.
 364
 365    procedure Lock_Read_Only_Entry (Object : Protection_Entry_Access) is
 366       Ceiling_Violation : Boolean;
 367    begin
 368       STPO.Read_Lock (Object.L'Access, Ceiling_Violation);
 369
 370       if Ceiling_Violation then
 371          raise Program_Error;
 372       end if;
 373    end Lock_Read_Only_Entry;
 374
 375    --------------------
 376    -- PO_Do_Or_Queue --
 377    --------------------
 378
 379    procedure PO_Do_Or_Queue
 380      (Self_Id    : Task_ID;
 381       Object     : Protection_Entry_Access;
 382       Entry_Call : Entry_Call_Link)
 383    is
 384       Barrier_Value : Boolean;
 385    begin
 386       --  When the Action procedure for an entry body returns, it must be
 387       --  completed (having called [Exceptional_]Complete_Entry_Body).
 388
 389       Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1);
 390
 391       if Barrier_Value then
 392          if Object.Call_In_Progress /= null then
 393             --  This violates the No_Entry_Queue restriction, send
 394             --  Program_Error to the caller.
 395
 396             Send_Program_Error (Self_Id, Entry_Call);
 397             return;
 398          end if;
 399
 400          Object.Call_In_Progress := Entry_Call;
 401          Object.Entry_Body.Action
 402            (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
 403          Object.Call_In_Progress := null;
 404
 405          if Single_Lock then
 406             STPO.Lock_RTS;
 407          end if;
 408
 409          STPO.Write_Lock (Entry_Call.Self);
 410          Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 411          STPO.Unlock (Entry_Call.Self);
 412
 413          if Single_Lock then
 414             STPO.Unlock_RTS;
 415          end if;
 416
 417       elsif Entry_Call.Mode /= Conditional_Call then
 418          Object.Entry_Queue := Entry_Call;
 419       else
 420          --  Conditional_Call
 421
 422          if Single_Lock then
 423             STPO.Lock_RTS;
 424          end if;
 425
 426          STPO.Write_Lock (Entry_Call.Self);
 427          Wakeup_Entry_Caller (Self_Id, Entry_Call, Cancelled);
 428          STPO.Unlock (Entry_Call.Self);
 429
 430          if Single_Lock then
 431             STPO.Unlock_RTS;
 432          end if;
 433       end if;
 434
 435    exception
 436       when others =>
 437          Send_Program_Error
 438            (Self_Id, Entry_Call);
 439    end PO_Do_Or_Queue;
 440
 441    ----------------------------
 442    -- Protected_Single_Count --
 443    ----------------------------
 444
 445    function Protected_Count_Entry (Object : Protection_Entry) return Natural is
 446    begin
 447       if Object.Call_In_Progress /= null then
 448          return 1;
 449       else
 450          return 0;
 451       end if;
 452    end Protected_Count_Entry;
 453
 454    ---------------------------------
 455    -- Protected_Single_Entry_Call --
 456    ---------------------------------
 457
 458    procedure Protected_Single_Entry_Call
 459      (Object             : Protection_Entry_Access;
 460       Uninterpreted_Data : System.Address;
 461       Mode               : Call_Modes)
 462    is
 463       Self_Id           : constant Task_ID := STPO.Self;
 464       Entry_Call        : Entry_Call_Record renames Self_Id.Entry_Calls (1);
 465       Ceiling_Violation : Boolean;
 466
 467    begin
 468       STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
 469
 470       if Ceiling_Violation then
 471          raise Program_Error;
 472       end if;
 473
 474       Entry_Call.Mode := Mode;
 475       Entry_Call.State := Now_Abortable;
 476       Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
 477       Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
 478
 479       PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
 480       Unlock_Entry (Object);
 481
 482       --  The call is either `Done' or not. It cannot be cancelled since there
 483       --  is no ATC construct.
 484
 485       pragma Assert (Entry_Call.State /= Cancelled);
 486
 487       if Entry_Call.State /= Done then
 488          if Single_Lock then
 489             STPO.Lock_RTS;
 490          end if;
 491
 492          STPO.Write_Lock (Self_Id);
 493          Wait_For_Completion (Entry_Call'Access);
 494          STPO.Unlock (Self_Id);
 495
 496          if Single_Lock then
 497             STPO.Unlock_RTS;
 498          end if;
 499       end if;
 500
 501       Check_Exception (Self_Id, Entry_Call'Access);
 502    end Protected_Single_Entry_Call;
 503
 504    -----------------------------------
 505    -- Protected_Single_Entry_Caller --
 506    -----------------------------------
 507
 508    function Protected_Single_Entry_Caller
 509      (Object : Protection_Entry) return Task_ID is
 510    begin
 511       return Object.Call_In_Progress.Self;
 512    end Protected_Single_Entry_Caller;
 513
 514    -------------------
 515    -- Service_Entry --
 516    -------------------
 517
 518    procedure Service_Entry (Object : Protection_Entry_Access) is
 519       Self_Id       : constant Task_ID := STPO.Self;
 520       Entry_Call    : constant Entry_Call_Link := Object.Entry_Queue;
 521       Caller        : Task_ID;
 522       Barrier_Value : Boolean;
 523
 524    begin
 525       if Entry_Call /= null then
 526          Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1);
 527
 528          if Barrier_Value then
 529             if Object.Call_In_Progress /= null then
 530                --  This violates the No_Entry_Queue restriction, send
 531                --  Program_Error to the caller.
 532
 533                Send_Program_Error (Self_Id, Entry_Call);
 534                return;
 535             end if;
 536
 537             Object.Call_In_Progress := Entry_Call;
 538             Object.Entry_Body.Action
 539               (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
 540             Object.Call_In_Progress := null;
 541             Caller := Entry_Call.Self;
 542
 543             if Single_Lock then
 544                STPO.Lock_RTS;
 545             end if;
 546
 547             STPO.Write_Lock (Caller);
 548             Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 549             STPO.Unlock (Caller);
 550
 551             if Single_Lock then
 552                STPO.Unlock_RTS;
 553             end if;
 554          end if;
 555       end if;
 556
 557    exception
 558       when others =>
 559          Send_Program_Error (Self_Id, Entry_Call);
 560    end Service_Entry;
 561
 562    ---------------------------------------
 563    -- Timed_Protected_Single_Entry_Call --
 564    ---------------------------------------
 565
 566    --  Compiler interface only. Do not call from within the RTS.
 567
 568    procedure Timed_Protected_Single_Entry_Call
 569      (Object                : Protection_Entry_Access;
 570       Uninterpreted_Data    : System.Address;
 571       Timeout               : Duration;
 572       Mode                  : Delay_Modes;
 573       Entry_Call_Successful : out Boolean)
 574    is
 575       Self_Id           : constant Task_ID  := STPO.Self;
 576       Entry_Call        : Entry_Call_Record renames Self_Id.Entry_Calls (1);
 577       Ceiling_Violation : Boolean;
 578
 579    begin
 580       STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
 581
 582       if Ceiling_Violation then
 583          raise Program_Error;
 584       end if;
 585
 586       Entry_Call.Mode := Timed_Call;
 587       Entry_Call.State := Now_Abortable;
 588       Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
 589       Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
 590
 591       PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
 592       Unlock_Entry (Object);
 593
 594       --  Try to avoid waiting for completed calls.
 595       --  The call is either `Done' or not. It cannot be cancelled since there
 596       --  is no ATC construct and the timed wait has not started yet.
 597
 598       pragma Assert (Entry_Call.State /= Cancelled);
 599
 600       if Entry_Call.State = Done then
 601          Check_Exception (Self_Id, Entry_Call'Access);
 602          Entry_Call_Successful := True;
 603          return;
 604       end if;
 605
 606       if Single_Lock then
 607          STPO.Lock_RTS;
 608       else
 609          STPO.Write_Lock (Self_Id);
 610       end if;
 611
 612       Wait_For_Completion_With_Timeout (Entry_Call'Access, Timeout, Mode);
 613
 614       if Single_Lock then
 615          STPO.Unlock_RTS;
 616       else
 617          STPO.Unlock (Self_Id);
 618       end if;
 619
 620       pragma Assert (Entry_Call.State >= Done);
 621
 622       Check_Exception (Self_Id, Entry_Call'Access);
 623       Entry_Call_Successful := Entry_Call.State = Done;
 624    end Timed_Protected_Single_Entry_Call;
 625
 626    ------------------
 627    -- Unlock_Entry --
 628    ------------------
 629
 630    procedure Unlock_Entry (Object : Protection_Entry_Access) is
 631    begin
 632       STPO.Unlock (Object.L'Access);
 633    end Unlock_Entry;
 634
 635 end System.Tasking.Protected_Objects.Single_Entry;