gcc/ada/s-tposen.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                  --
   4 --                                                                          --
   5 --             SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY                --
   6 --                                                                          --
   7 --                                B o d y                                   --
   8 --                                                                          --
   9 --         Copyright (C) 1998-2009, 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 pragma Style_Checks (All_Checks);
  33 --  Turn off subprogram ordering check, since restricted GNARLI subprograms are
  34 --  gathered together at end.
  35
  36 --  This package provides an optimized version of Protected_Objects.Operations
  37 --  and Protected_Objects.Entries making the following assumptions:
  38
  39 --    PO has only one entry
  40 --    There is only one caller at a time (No_Entry_Queue)
  41 --    There is no dynamic priority support (No_Dynamic_Priorities)
  42 --    No Abort Statements
  43 --     (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
  44 --    PO are at library level
  45 --    No Requeue
  46 --    None of the tasks will terminate (no need for finalization)
  47
  48 --  This interface is intended to be used in the ravenscar and restricted
  49 --  profiles, the compiler is responsible for ensuring that the conditions
  50 --  mentioned above are respected, except for the No_Entry_Queue restriction
  51 --  that is checked dynamically in this package, since the check cannot be
  52 --  performed at compile time, and is relatively cheap (see PO_Do_Or_Queue,
  53 --  Service_Entry).
  54
  55 pragma Polling (Off);
  56 --  Turn off polling, we do not want polling to take place during tasking
  57 --  operations. It can cause  infinite loops and other problems.
  58
  59 pragma Suppress (All_Checks);
  60 --  Why is this required ???
  61
  62 with Ada.Exceptions;
  63
  64 with System.Task_Primitives.Operations;
  65 with System.Parameters;
  66
  67 package body System.Tasking.Protected_Objects.Single_Entry is
  68
  69    package STPO renames System.Task_Primitives.Operations;
  70
  71    use Parameters;
  72
  73    -----------------------
  74    -- Local Subprograms --
  75    -----------------------
  76
  77    procedure Send_Program_Error
  78      (Self_Id    : Task_Id;
  79       Entry_Call : Entry_Call_Link);
  80    pragma Inline (Send_Program_Error);
  81    --  Raise Program_Error in the caller of the specified entry call
  82
  83    --------------------------
  84    -- Entry Calls Handling --
  85    --------------------------
  86
  87    procedure Wakeup_Entry_Caller
  88      (Self_ID    : Task_Id;
  89       Entry_Call : Entry_Call_Link;
  90       New_State  : Entry_Call_State);
  91    pragma Inline (Wakeup_Entry_Caller);
  92    --  This is called at the end of service of an entry call,
  93    --  to abort the caller if he is in an abortable part, and
  94    --  to wake up the caller if he is on Entry_Caller_Sleep.
  95    --  Call it holding the lock of Entry_Call.Self.
  96    --
  97    --  Timed_Call or Simple_Call:
  98    --    The caller is waiting on Entry_Caller_Sleep, in
  99    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 100
 101    procedure Wait_For_Completion (Entry_Call : Entry_Call_Link);
 102    pragma Inline (Wait_For_Completion);
 103    --  This procedure suspends the calling task until the specified entry call
 104    --  has either been completed or cancelled. On exit, the call will not be
 105    --  queued. This waits for calls on protected entries.
 106    --  Call this only when holding Self_ID locked.
 107
 108    procedure Wait_For_Completion_With_Timeout
 109      (Entry_Call  : Entry_Call_Link;
 110       Wakeup_Time : Duration;
 111       Mode        : Delay_Modes);
 112    --  Same as Wait_For_Completion but it waits for a timeout with the value
 113    --  specified in Wakeup_Time as well.
 114
 115    procedure Check_Exception
 116      (Self_ID : Task_Id;
 117       Entry_Call : Entry_Call_Link);
 118    pragma Inline (Check_Exception);
 119    --  Raise any pending exception from the Entry_Call.
 120    --  This should be called at the end of every compiler interface procedure
 121    --  that implements an entry call.
 122    --  The caller should not be holding any locks, or there will be deadlock.
 123
 124    procedure PO_Do_Or_Queue
 125      (Self_Id    : Task_Id;
 126       Object     : Protection_Entry_Access;
 127       Entry_Call : Entry_Call_Link);
 128    --  This procedure executes or queues an entry call, depending
 129    --  on the status of the corresponding barrier. It assumes that the
 130    --  specified object is locked.
 131
 132    ---------------------
 133    -- Check_Exception --
 134    ---------------------
 135
 136    procedure Check_Exception
 137      (Self_ID    : Task_Id;
 138       Entry_Call : Entry_Call_Link)
 139    is
 140       pragma Warnings (Off, Self_ID);
 141
 142       procedure Internal_Raise (X : Ada.Exceptions.Exception_Id);
 143       pragma Import (C, Internal_Raise, "__gnat_raise_with_msg");
 144
 145       use type Ada.Exceptions.Exception_Id;
 146
 147       E : constant Ada.Exceptions.Exception_Id :=
 148             Entry_Call.Exception_To_Raise;
 149
 150    begin
 151       if E /= Ada.Exceptions.Null_Id then
 152          Internal_Raise (E);
 153       end if;
 154    end Check_Exception;
 155
 156    ------------------------
 157    -- Send_Program_Error --
 158    ------------------------
 159
 160    procedure Send_Program_Error
 161      (Self_Id    : Task_Id;
 162       Entry_Call : Entry_Call_Link)
 163    is
 164       Caller : constant Task_Id := Entry_Call.Self;
 165    begin
 166       Entry_Call.Exception_To_Raise := Program_Error'Identity;
 167
 168       if Single_Lock then
 169          STPO.Lock_RTS;
 170       end if;
 171
 172       STPO.Write_Lock (Caller);
 173       Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 174       STPO.Unlock (Caller);
 175
 176       if Single_Lock then
 177          STPO.Unlock_RTS;
 178       end if;
 179    end Send_Program_Error;
 180
 181    -------------------------
 182    -- Wait_For_Completion --
 183    -------------------------
 184
 185    procedure Wait_For_Completion (Entry_Call : Entry_Call_Link) is
 186       Self_Id : constant Task_Id := Entry_Call.Self;
 187    begin
 188       Self_Id.Common.State := Entry_Caller_Sleep;
 189       STPO.Sleep (Self_Id, Entry_Caller_Sleep);
 190       Self_Id.Common.State := Runnable;
 191    end Wait_For_Completion;
 192
 193    --------------------------------------
 194    -- Wait_For_Completion_With_Timeout --
 195    --------------------------------------
 196
 197    procedure Wait_For_Completion_With_Timeout
 198      (Entry_Call  : Entry_Call_Link;
 199       Wakeup_Time : Duration;
 200       Mode        : Delay_Modes)
 201    is
 202       Self_Id  : constant Task_Id := Entry_Call.Self;
 203       Timedout : Boolean;
 204
 205       Yielded  : Boolean;
 206       pragma Unreferenced (Yielded);
 207
 208       use type Ada.Exceptions.Exception_Id;
 209
 210    begin
 211       --  This procedure waits for the entry call to be served, with a timeout.
 212       --  It tries to cancel the call if the timeout expires before the call is
 213       --  served.
 214
 215       --  If we wake up from the timed sleep operation here, it may be for the
 216       --  following possible reasons:
 217
 218       --  1) The entry call is done being served.
 219       --  2) The timeout has expired (Timedout = True)
 220
 221       --  Once the timeout has expired we may need to continue to wait if the
 222       --  call is already being serviced. In that case, we want to go back to
 223       --  sleep, but without any timeout. The variable Timedout is used to
 224       --  control this. If the Timedout flag is set, we do not need to Sleep
 225       --  with a timeout. We just sleep until we get a wakeup for some status
 226       --  change.
 227
 228       pragma Assert (Entry_Call.Mode = Timed_Call);
 229       Self_Id.Common.State := Entry_Caller_Sleep;
 230
 231       STPO.Timed_Sleep
 232         (Self_Id, Wakeup_Time, Mode, Entry_Caller_Sleep, Timedout, Yielded);
 233
 234       Entry_Call.State := (if Timedout then Cancelled else Done);
 235       Self_Id.Common.State := Runnable;
 236    end Wait_For_Completion_With_Timeout;
 237
 238    -------------------------
 239    -- Wakeup_Entry_Caller --
 240    -------------------------
 241
 242    --  This is called at the end of service of an entry call, to abort the
 243    --  caller if he is in an abortable part, and to wake up the caller if it
 244    --  is on Entry_Caller_Sleep. It assumes that the call is already off-queue.
 245
 246    --  (This enforces the rule that a task must be off-queue if its state is
 247    --  Done or Cancelled.) Call it holding the lock of Entry_Call.Self.
 248
 249    --  Timed_Call or Simple_Call:
 250    --    The caller is waiting on Entry_Caller_Sleep, in
 251    --    Wait_For_Completion, or Wait_For_Completion_With_Timeout.
 252
 253    --  Conditional_Call:
 254    --    The caller might be in Wait_For_Completion,
 255    --    waiting for a rendezvous (possibly requeued without abort)
 256    --    to complete.
 257
 258    procedure Wakeup_Entry_Caller
 259      (Self_ID    : Task_Id;
 260       Entry_Call : Entry_Call_Link;
 261       New_State  : Entry_Call_State)
 262    is
 263       pragma Warnings (Off, Self_ID);
 264
 265       Caller : constant Task_Id := Entry_Call.Self;
 266
 267    begin
 268       pragma Assert (New_State = Done or else New_State = Cancelled);
 269       pragma Assert
 270         (Caller.Common.State /= Terminated and then
 271          Caller.Common.State /= Unactivated);
 272
 273       Entry_Call.State := New_State;
 274       STPO.Wakeup (Caller, Entry_Caller_Sleep);
 275    end Wakeup_Entry_Caller;
 276
 277    -----------------------
 278    -- Restricted GNARLI --
 279    -----------------------
 280
 281    --------------------------------
 282    -- Complete_Single_Entry_Body --
 283    --------------------------------
 284
 285    procedure Complete_Single_Entry_Body (Object : Protection_Entry_Access) is
 286       pragma Warnings (Off, Object);
 287
 288    begin
 289       --  Nothing needs to do (Object.Call_In_Progress.Exception_To_Raise
 290       --  has already been set to Null_Id).
 291
 292       null;
 293    end Complete_Single_Entry_Body;
 294
 295    --------------------------------------------
 296    -- Exceptional_Complete_Single_Entry_Body --
 297    --------------------------------------------
 298
 299    procedure Exceptional_Complete_Single_Entry_Body
 300      (Object : Protection_Entry_Access;
 301       Ex     : Ada.Exceptions.Exception_Id) is
 302    begin
 303       Object.Call_In_Progress.Exception_To_Raise := Ex;
 304    end Exceptional_Complete_Single_Entry_Body;
 305
 306    ---------------------------------
 307    -- Initialize_Protection_Entry --
 308    ---------------------------------
 309
 310    procedure Initialize_Protection_Entry
 311      (Object            : Protection_Entry_Access;
 312       Ceiling_Priority  : Integer;
 313       Compiler_Info     : System.Address;
 314       Entry_Body        : Entry_Body_Access)
 315    is
 316    begin
 317       Initialize_Protection (Object.Common'Access, Ceiling_Priority);
 318
 319       Object.Compiler_Info := Compiler_Info;
 320       Object.Call_In_Progress := null;
 321       Object.Entry_Body := Entry_Body;
 322       Object.Entry_Queue := null;
 323    end Initialize_Protection_Entry;
 324
 325    ----------------
 326    -- Lock_Entry --
 327    ----------------
 328
 329    --  Compiler interface only.
 330    --  Do not call this procedure from within the run-time system.
 331
 332    procedure Lock_Entry (Object : Protection_Entry_Access) is
 333    begin
 334       Lock (Object.Common'Access);
 335    end Lock_Entry;
 336
 337    --------------------------
 338    -- Lock_Read_Only_Entry --
 339    --------------------------
 340
 341    --  Compiler interface only
 342
 343    --  Do not call this procedure from within the runtime system
 344
 345    procedure Lock_Read_Only_Entry (Object : Protection_Entry_Access) is
 346    begin
 347       Lock_Read_Only (Object.Common'Access);
 348    end Lock_Read_Only_Entry;
 349
 350    --------------------
 351    -- PO_Do_Or_Queue --
 352    --------------------
 353
 354    procedure PO_Do_Or_Queue
 355      (Self_Id    : Task_Id;
 356       Object     : Protection_Entry_Access;
 357       Entry_Call : Entry_Call_Link)
 358    is
 359       Barrier_Value : Boolean;
 360
 361    begin
 362       --  When the Action procedure for an entry body returns, it must be
 363       --  completed (having called [Exceptional_]Complete_Entry_Body).
 364
 365       Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1);
 366
 367       if Barrier_Value then
 368          if Object.Call_In_Progress /= null then
 369
 370             --  This violates the No_Entry_Queue restriction, send
 371             --  Program_Error to the caller.
 372
 373             Send_Program_Error (Self_Id, Entry_Call);
 374             return;
 375          end if;
 376
 377          Object.Call_In_Progress := Entry_Call;
 378          Object.Entry_Body.Action
 379            (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
 380          Object.Call_In_Progress := null;
 381
 382          if Single_Lock then
 383             STPO.Lock_RTS;
 384          end if;
 385
 386          STPO.Write_Lock (Entry_Call.Self);
 387          Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 388          STPO.Unlock (Entry_Call.Self);
 389
 390          if Single_Lock then
 391             STPO.Unlock_RTS;
 392          end if;
 393
 394       elsif Entry_Call.Mode /= Conditional_Call then
 395          if Object.Entry_Queue /= null then
 396
 397             --  This violates the No_Entry_Queue restriction, send
 398             --  Program_Error to the caller.
 399
 400             Send_Program_Error (Self_Id, Entry_Call);
 401             return;
 402          else
 403             Object.Entry_Queue := Entry_Call;
 404          end if;
 405
 406       else
 407          --  Conditional_Call
 408
 409          if Single_Lock then
 410             STPO.Lock_RTS;
 411          end if;
 412
 413          STPO.Write_Lock (Entry_Call.Self);
 414          Wakeup_Entry_Caller (Self_Id, Entry_Call, Cancelled);
 415          STPO.Unlock (Entry_Call.Self);
 416
 417          if Single_Lock then
 418             STPO.Unlock_RTS;
 419          end if;
 420       end if;
 421
 422    exception
 423       when others =>
 424          Send_Program_Error
 425            (Self_Id, Entry_Call);
 426    end PO_Do_Or_Queue;
 427
 428    ----------------------------
 429    -- Protected_Single_Count --
 430    ----------------------------
 431
 432    function Protected_Count_Entry (Object : Protection_Entry) return Natural is
 433    begin
 434       if Object.Entry_Queue /= null then
 435          return 1;
 436       else
 437          return 0;
 438       end if;
 439    end Protected_Count_Entry;
 440
 441    ---------------------------------
 442    -- Protected_Single_Entry_Call --
 443    ---------------------------------
 444
 445    procedure Protected_Single_Entry_Call
 446      (Object             : Protection_Entry_Access;
 447       Uninterpreted_Data : System.Address;
 448       Mode               : Call_Modes)
 449    is
 450       Self_Id    : constant Task_Id := STPO.Self;
 451       Entry_Call : Entry_Call_Record renames Self_Id.Entry_Calls (1);
 452    begin
 453       --  If pragma Detect_Blocking is active then Program_Error must be
 454       --  raised if this potentially blocking operation is called from a
 455       --  protected action.
 456
 457       if Detect_Blocking
 458         and then Self_Id.Common.Protected_Action_Nesting > 0
 459       then
 460          raise Program_Error with "potentially blocking operation";
 461       end if;
 462
 463       Lock_Entry (Object);
 464
 465       Entry_Call.Mode := Mode;
 466       Entry_Call.State := Now_Abortable;
 467       Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
 468       Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
 469
 470       PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
 471       Unlock_Entry (Object);
 472
 473       --  The call is either `Done' or not. It cannot be cancelled since there
 474       --  is no ATC construct.
 475
 476       pragma Assert (Entry_Call.State /= Cancelled);
 477
 478       if Entry_Call.State /= Done then
 479          if Single_Lock then
 480             STPO.Lock_RTS;
 481          end if;
 482
 483          STPO.Write_Lock (Self_Id);
 484          Wait_For_Completion (Entry_Call'Access);
 485          STPO.Unlock (Self_Id);
 486
 487          if Single_Lock then
 488             STPO.Unlock_RTS;
 489          end if;
 490       end if;
 491
 492       Check_Exception (Self_Id, Entry_Call'Access);
 493    end Protected_Single_Entry_Call;
 494
 495    -----------------------------------
 496    -- Protected_Single_Entry_Caller --
 497    -----------------------------------
 498
 499    function Protected_Single_Entry_Caller
 500      (Object : Protection_Entry) return Task_Id is
 501    begin
 502       return Object.Call_In_Progress.Self;
 503    end Protected_Single_Entry_Caller;
 504
 505    -------------------
 506    -- Service_Entry --
 507    -------------------
 508
 509    procedure Service_Entry (Object : Protection_Entry_Access) is
 510       Self_Id    : constant Task_Id := STPO.Self;
 511       Entry_Call : constant Entry_Call_Link := Object.Entry_Queue;
 512       Caller     : Task_Id;
 513
 514    begin
 515       if Entry_Call /= null
 516         and then Object.Entry_Body.Barrier (Object.Compiler_Info, 1)
 517       then
 518          Object.Entry_Queue := null;
 519
 520          if Object.Call_In_Progress /= null then
 521
 522             --  Violation of No_Entry_Queue restriction, raise exception
 523
 524             Send_Program_Error (Self_Id, Entry_Call);
 525             Unlock_Entry (Object);
 526             return;
 527          end if;
 528
 529          Object.Call_In_Progress := Entry_Call;
 530          Object.Entry_Body.Action
 531            (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
 532          Object.Call_In_Progress := null;
 533          Caller := Entry_Call.Self;
 534          Unlock_Entry (Object);
 535
 536          if Single_Lock then
 537             STPO.Lock_RTS;
 538          end if;
 539
 540          STPO.Write_Lock (Caller);
 541          Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
 542          STPO.Unlock (Caller);
 543
 544          if Single_Lock then
 545             STPO.Unlock_RTS;
 546          end if;
 547
 548       else
 549          --  Just unlock the entry
 550
 551          Unlock_Entry (Object);
 552       end if;
 553
 554    exception
 555       when others =>
 556          Send_Program_Error (Self_Id, Entry_Call);
 557          Unlock_Entry (Object);
 558    end Service_Entry;
 559
 560    ---------------------------------------
 561    -- Timed_Protected_Single_Entry_Call --
 562    ---------------------------------------
 563
 564    --  Compiler interface only (do not call from within the RTS)
 565
 566    procedure Timed_Protected_Single_Entry_Call
 567      (Object                : Protection_Entry_Access;
 568       Uninterpreted_Data    : System.Address;
 569       Timeout               : Duration;
 570       Mode                  : Delay_Modes;
 571       Entry_Call_Successful : out Boolean)
 572    is
 573       Self_Id           : constant Task_Id  := STPO.Self;
 574       Entry_Call        : Entry_Call_Record renames Self_Id.Entry_Calls (1);
 575
 576    begin
 577       --  If pragma Detect_Blocking is active then Program_Error must be
 578       --  raised if this potentially blocking operation is called from a
 579       --  protected action.
 580
 581       if Detect_Blocking
 582         and then Self_Id.Common.Protected_Action_Nesting > 0
 583       then
 584          raise Program_Error with "potentially blocking operation";
 585       end if;
 586
 587       Lock (Object.Common'Access);
 588
 589       Entry_Call.Mode := Timed_Call;
 590       Entry_Call.State := Now_Abortable;
 591       Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
 592       Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
 593
 594       PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
 595       Unlock_Entry (Object);
 596
 597       --  Try to avoid waiting for completed calls.
 598       --  The call is either `Done' or not. It cannot be cancelled since there
 599       --  is no ATC construct and the timed wait has not started yet.
 600
 601       pragma Assert (Entry_Call.State /= Cancelled);
 602
 603       if Entry_Call.State = Done then
 604          Check_Exception (Self_Id, Entry_Call'Access);
 605          Entry_Call_Successful := True;
 606          return;
 607       end if;
 608
 609       if Single_Lock then
 610          STPO.Lock_RTS;
 611       else
 612          STPO.Write_Lock (Self_Id);
 613       end if;
 614
 615       Wait_For_Completion_With_Timeout (Entry_Call'Access, Timeout, Mode);
 616
 617       if Single_Lock then
 618          STPO.Unlock_RTS;
 619       else
 620          STPO.Unlock (Self_Id);
 621       end if;
 622
 623       pragma Assert (Entry_Call.State >= Done);
 624
 625       Check_Exception (Self_Id, Entry_Call'Access);
 626       Entry_Call_Successful := Entry_Call.State = Done;
 627    end Timed_Protected_Single_Entry_Call;
 628
 629    ------------------
 630    -- Unlock_Entry --
 631    ------------------
 632
 633    procedure Unlock_Entry (Object : Protection_Entry_Access) is
 634    begin
 635       Unlock (Object.Common'Access);
 636    end Unlock_Entry;
 637
 638 end System.Tasking.Protected_Objects.Single_Entry;