gcc/ada/s-tarest.adb

   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 --                                  B o d y                                 --
   8 --                                                                          --
   9 --         Copyright (C) 1999-2004, 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 pragma Style_Checks (All_Checks);
  35 --  Turn off subprogram alpha order check, since we group soft link
  36 --  bodies and also separate off subprograms for restricted GNARLI.
  37
  38 --  This is a simplified version of the System.Tasking.Stages package,
  39 --  intended to be used in a restricted run time.
  40
  41 --  This package represents the high level tasking interface used by the
  42 --  compiler to expand Ada 95 tasking constructs into simpler run time calls.
  43
  44 pragma Polling (Off);
  45 --  Turn off polling, we do not want ATC polling to take place during
  46 --  tasking operations. It causes infinite loops and other problems.
  47
  48 with System.Parameters;
  49 --  used for Size_Type
  50 --           Single_Lock
  51
  52 with System.Task_Info;
  53 --  used for Task_Info_Type
  54
  55 with System.Task_Primitives.Operations;
  56 --  used for Enter_Task
  57 --           Write_Lock
  58 --           Unlock
  59 --           Wakeup
  60 --           Get_Priority
  61
  62 with System.Soft_Links;
  63 --  used for the non-tasking routines (*_NT) that refer to global data.
  64 --  They are needed here before the tasking run time has been elaborated.
  65 --  used for Create_TSD
  66 --  This package also provides initialization routines for task specific data.
  67 --  The GNARL must call these to be sure that all non-tasking
  68 --  Ada constructs will work.
  69
  70 with System.Secondary_Stack;
  71 --  used for SS_Init;
  72
  73 with System.Storage_Elements;
  74 --  used for Storage_Array;
  75
  76 package body System.Tasking.Restricted.Stages is
  77
  78    package STPO renames System.Task_Primitives.Operations;
  79    package SSL  renames System.Soft_Links;
  80    package SSE  renames System.Storage_Elements;
  81    package SST  renames System.Secondary_Stack;
  82
  83    use Parameters;
  84    use Task_Primitives.Operations;
  85    use Task_Info;
  86
  87    Global_Task_Lock : aliased System.Task_Primitives.RTS_Lock;
  88    --  This is a global lock; it is used to execute in mutual exclusion
  89    --  from all other tasks. It is only used by Task_Lock and Task_Unlock.
  90
  91    -----------------------------------------------------------------
  92    -- Tasking versions of services needed by non-tasking programs --
  93    -----------------------------------------------------------------
  94
  95    procedure Task_Lock;
  96    --  Locks out other tasks. Preceding a section of code by Task_Lock and
  97    --  following it by Task_Unlock creates a critical region. This is used
  98    --  for ensuring that a region of non-tasking code (such as code used to
  99    --  allocate memory) is tasking safe. Note that it is valid for calls to
 100    --  Task_Lock/Task_Unlock to be nested, and this must work properly, i.e.
 101    --  only the corresponding outer level Task_Unlock will actually unlock.
 102
 103    procedure Task_Unlock;
 104    --  Releases lock previously set by call to Task_Lock. In the nested case,
 105    --  all nested locks must be released before other tasks competing for the
 106    --  tasking lock are released.
 107
 108    --  See s-tasini.adb for more information on the following functions.
 109
 110    function Get_Jmpbuf_Address return Address;
 111    procedure Set_Jmpbuf_Address (Addr : Address);
 112
 113    function Get_Sec_Stack_Addr return Address;
 114    procedure Set_Sec_Stack_Addr (Addr : Address);
 115
 116    function  Get_Machine_State_Addr return Address;
 117    procedure Set_Machine_State_Addr (Addr : Address);
 118
 119    function Get_Current_Excep return SSL.EOA;
 120
 121    procedure Timed_Delay_T (Time : Duration; Mode : Integer);
 122
 123    ------------------------
 124    --  Local Subprograms --
 125    ------------------------
 126
 127    procedure Task_Wrapper (Self_ID : Task_Id);
 128    --  This is the procedure that is called by the GNULL from the
 129    --  new context when a task is created. It waits for activation
 130    --  and then calls the task body procedure. When the task body
 131    --  procedure completes, it terminates the task.
 132
 133    procedure Terminate_Task (Self_ID : Task_Id);
 134    --  Terminate the calling task.
 135    --  This should only be called by the Task_Wrapper procedure.
 136
 137    procedure Init_RTS;
 138    --  This procedure performs the initialization of the GNARL.
 139    --  It consists of initializing the environment task, global locks, and
 140    --  installing tasking versions of certain operations used by the compiler.
 141    --  Init_RTS is called during elaboration.
 142
 143    ---------------
 144    -- Task_Lock --
 145    ---------------
 146
 147    procedure Task_Lock is
 148    begin
 149       STPO.Write_Lock (Global_Task_Lock'Access, Global_Lock => True);
 150    end Task_Lock;
 151
 152    -----------------
 153    -- Task_Unlock --
 154    -----------------
 155
 156    procedure Task_Unlock is
 157    begin
 158       STPO.Unlock (Global_Task_Lock'Access, Global_Lock => True);
 159    end Task_Unlock;
 160
 161    ----------------------
 162    -- Soft-Link Bodies --
 163    ----------------------
 164
 165    function Get_Current_Excep return SSL.EOA is
 166    begin
 167       return STPO.Self.Common.Compiler_Data.Current_Excep'Access;
 168    end Get_Current_Excep;
 169
 170    function Get_Jmpbuf_Address return  Address is
 171    begin
 172       return STPO.Self.Common.Compiler_Data.Jmpbuf_Address;
 173    end Get_Jmpbuf_Address;
 174
 175    function Get_Machine_State_Addr return Address is
 176    begin
 177       return STPO.Self.Common.Compiler_Data.Machine_State_Addr;
 178    end Get_Machine_State_Addr;
 179
 180    function Get_Sec_Stack_Addr return  Address is
 181    begin
 182       return STPO.Self.Common.Compiler_Data.Sec_Stack_Addr;
 183    end Get_Sec_Stack_Addr;
 184
 185    procedure Set_Jmpbuf_Address (Addr : Address) is
 186    begin
 187       STPO.Self.Common.Compiler_Data.Jmpbuf_Address := Addr;
 188    end Set_Jmpbuf_Address;
 189
 190    procedure Set_Machine_State_Addr (Addr : Address) is
 191    begin
 192       STPO.Self.Common.Compiler_Data.Machine_State_Addr := Addr;
 193    end Set_Machine_State_Addr;
 194
 195    procedure Set_Sec_Stack_Addr (Addr : Address) is
 196    begin
 197       STPO.Self.Common.Compiler_Data.Sec_Stack_Addr := Addr;
 198    end Set_Sec_Stack_Addr;
 199
 200    ------------------
 201    -- Task_Wrapper --
 202    ------------------
 203
 204    --  The task wrapper is a procedure that is called first for each task
 205    --  task body, and which in turn calls the compiler-generated task body
 206    --  procedure. The wrapper's main job is to do initialization for the task.
 207
 208    --  The variable ID in the task wrapper is used to implement the Self
 209    --  function on targets where there is a fast way to find the stack base
 210    --  of the current thread, since it should be at a fixed offset from the
 211    --  stack base.
 212
 213    procedure Task_Wrapper (Self_ID : Task_Id) is
 214       ID : Task_Id := Self_ID;
 215       pragma Volatile (ID);
 216
 217       pragma Warnings (Off, ID);
 218       --  Turn off warnings (stand alone volatile constant has to be
 219       --  imported, so we cannot just make ID constant).
 220
 221       --  Do not delete this variable.
 222       --  In some targets, we need this variable to implement a fast Self.
 223
 224       use type System.Parameters.Size_Type;
 225       use type SSE.Storage_Offset;
 226
 227       Secondary_Stack : aliased SSE.Storage_Array
 228         (1 .. Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size *
 229            SSE.Storage_Offset (Parameters.Sec_Stack_Ratio) / 100);
 230       Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
 231
 232    begin
 233       if not Parameters.Sec_Stack_Dynamic then
 234          Self_ID.Common.Compiler_Data.Sec_Stack_Addr :=
 235            Secondary_Stack'Address;
 236          SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
 237       end if;
 238
 239       --  Initialize low-level TCB components, that
 240       --  cannot be initialized by the creator.
 241
 242       Enter_Task (Self_ID);
 243
 244       --  Call the task body procedure.
 245
 246       begin
 247          --  We are separating the following portion of the code in order to
 248          --  place the exception handlers in a different block.
 249          --  In this way we do not call Set_Jmpbuf_Address (which needs
 250          --  Self) before we set Self in Enter_Task.
 251          --  Note that in the case of Ravenscar HI-E where there are no
 252          --  exception handlers, the exception handler is suppressed.
 253
 254          --  Call the task body procedure.
 255
 256          Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
 257          Terminate_Task (Self_ID);
 258
 259       exception
 260          when others =>
 261             Terminate_Task (Self_ID);
 262       end;
 263    end Task_Wrapper;
 264
 265    -------------------
 266    -- Timed_Delay_T --
 267    -------------------
 268
 269    procedure Timed_Delay_T (Time : Duration; Mode : Integer) is
 270    begin
 271       STPO.Timed_Delay (STPO.Self, Time, Mode);
 272    end Timed_Delay_T;
 273
 274    -----------------------
 275    -- Restricted GNARLI --
 276    -----------------------
 277
 278    -------------------------------
 279    -- Activate_Restricted_Tasks --
 280    -------------------------------
 281
 282    --  Note that locks of activator and activated task are both locked
 283    --  here. This is necessary because C.State and Self.Wait_Count
 284    --  have to be synchronized. This is safe from deadlock because
 285    --  the activator is always created before the activated task.
 286    --  That satisfies our in-order-of-creation ATCB locking policy.
 287
 288    procedure Activate_Restricted_Tasks
 289      (Chain_Access : Activation_Chain_Access)
 290    is
 291       Self_ID       : constant Task_Id := STPO.Self;
 292       C             : Task_Id;
 293       Activate_Prio : System.Any_Priority;
 294       Success       : Boolean;
 295
 296    begin
 297       pragma Assert (Self_ID = Environment_Task);
 298       pragma Assert (Self_ID.Common.Wait_Count = 0);
 299
 300       if Single_Lock then
 301          Lock_RTS;
 302       end if;
 303
 304       --  Lock self, to prevent activated tasks
 305       --  from racing ahead before we finish activating the chain.
 306
 307       Write_Lock (Self_ID);
 308
 309       --  Activate all the tasks in the chain.
 310       --  Creation of the thread of control was deferred until
 311       --  activation. So create it now.
 312
 313       C := Chain_Access.T_ID;
 314
 315       while C /= null loop
 316          if C.Common.State /= Terminated then
 317             pragma Assert (C.Common.State = Unactivated);
 318
 319             Write_Lock (C);
 320
 321             if C.Common.Base_Priority < Get_Priority (Self_ID) then
 322                Activate_Prio := Get_Priority (Self_ID);
 323             else
 324                Activate_Prio := C.Common.Base_Priority;
 325             end if;
 326
 327             STPO.Create_Task
 328               (C, Task_Wrapper'Address,
 329                Parameters.Size_Type
 330                  (C.Common.Compiler_Data.Pri_Stack_Info.Size),
 331                Activate_Prio, Success);
 332
 333             Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
 334
 335             if Success then
 336                C.Common.State := Runnable;
 337             else
 338                raise Program_Error;
 339             end if;
 340
 341             Unlock (C);
 342          end if;
 343
 344          C := C.Common.Activation_Link;
 345       end loop;
 346
 347       Self_ID.Common.State := Activator_Sleep;
 348
 349       --  Wait for the activated tasks to complete activation.
 350       --  It is unsafe to abort any of these tasks until the count goes to
 351       --  zero.
 352
 353       loop
 354          exit when Self_ID.Common.Wait_Count = 0;
 355          Sleep (Self_ID, Activator_Sleep);
 356       end loop;
 357
 358       Self_ID.Common.State := Runnable;
 359       Unlock (Self_ID);
 360
 361       if Single_Lock then
 362          Unlock_RTS;
 363       end if;
 364
 365       --  Remove the tasks from the chain.
 366
 367       Chain_Access.T_ID := null;
 368    end Activate_Restricted_Tasks;
 369
 370    ------------------------------------
 371    -- Complete_Restricted_Activation --
 372    ------------------------------------
 373
 374    --  As in several other places, the locks of the activator and activated
 375    --  task are both locked here. This follows our deadlock prevention lock
 376    --  ordering policy, since the activated task must be created after the
 377    --  activator.
 378
 379    procedure Complete_Restricted_Activation is
 380       Self_ID   : constant Task_Id := STPO.Self;
 381       Activator : constant Task_Id := Self_ID.Common.Activator;
 382
 383    begin
 384       if Single_Lock then
 385          Lock_RTS;
 386       end if;
 387
 388       Write_Lock (Activator);
 389       Write_Lock (Self_ID);
 390
 391       --  Remove dangling reference to Activator,
 392       --  since a task may outlive its activator.
 393
 394       Self_ID.Common.Activator := null;
 395
 396       --  Wake up the activator, if it is waiting for a chain
 397       --  of tasks to activate, and we are the last in the chain
 398       --  to complete activation
 399
 400       if Activator.Common.State = Activator_Sleep then
 401          Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
 402
 403          if Activator.Common.Wait_Count = 0 then
 404             Wakeup (Activator, Activator_Sleep);
 405          end if;
 406       end if;
 407
 408       Unlock (Self_ID);
 409       Unlock (Activator);
 410
 411       if Single_Lock then
 412          Unlock_RTS;
 413       end if;
 414
 415       --  After the activation, active priority should be the same
 416       --  as base priority. We must unlock the Activator first,
 417       --  though, since it should not wait if we have lower priority.
 418
 419       if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
 420          Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
 421       end if;
 422    end Complete_Restricted_Activation;
 423
 424    ------------------------------
 425    -- Complete_Restricted_Task --
 426    ------------------------------
 427
 428    procedure Complete_Restricted_Task is
 429    begin
 430       STPO.Self.Common.State := Terminated;
 431    end Complete_Restricted_Task;
 432
 433    ----------------------------
 434    -- Create_Restricted_Task --
 435    ----------------------------
 436
 437    procedure Create_Restricted_Task
 438      (Priority      : Integer;
 439       Size          : System.Parameters.Size_Type;
 440       Task_Info     : System.Task_Info.Task_Info_Type;
 441       State         : Task_Procedure_Access;
 442       Discriminants : System.Address;
 443       Elaborated    : Access_Boolean;
 444       Chain         : in out Activation_Chain;
 445       Task_Image    : String;
 446       Created_Task  : out Task_Id)
 447    is
 448       T             : Task_Id;
 449       Self_ID       : constant Task_Id := STPO.Self;
 450       Base_Priority : System.Any_Priority;
 451       Success       : Boolean;
 452
 453    begin
 454       if Priority = Unspecified_Priority then
 455          Base_Priority := Self_ID.Common.Base_Priority;
 456       else
 457          Base_Priority := System.Any_Priority (Priority);
 458       end if;
 459
 460       T := New_ATCB (0);
 461
 462       if Single_Lock then
 463          Lock_RTS;
 464       end if;
 465
 466       Write_Lock (Self_ID);
 467
 468       --  With no task hierarchy, the parent of all non-Environment tasks that
 469       --  are created must be the Environment task
 470
 471       Initialize_ATCB
 472         (Self_ID, State, Discriminants, Self_ID, Elaborated, Base_Priority,
 473          Task_Info, Size, T, Success);
 474
 475       --  If we do our job right then there should never be any failures,
 476       --  which was probably said about the Titanic; so just to be safe,
 477       --  let's retain this code for now
 478
 479       if not Success then
 480          Unlock (Self_ID);
 481
 482          if Single_Lock then
 483             Unlock_RTS;
 484          end if;
 485
 486          raise Program_Error;
 487       end if;
 488
 489       T.Entry_Calls (1).Self := T;
 490
 491       T.Common.Task_Image_Len :=
 492         Integer'Min (T.Common.Task_Image'Length, Task_Image'Length);
 493       T.Common.Task_Image (1 .. T.Common.Task_Image_Len) := Task_Image;
 494
 495       Unlock (Self_ID);
 496
 497       if Single_Lock then
 498          Unlock_RTS;
 499       end if;
 500
 501       --  Create TSD as early as possible in the creation of a task, since it
 502       --  may be used by the operation of Ada code within the task.
 503
 504       SSL.Create_TSD (T.Common.Compiler_Data);
 505       T.Common.Activation_Link := Chain.T_ID;
 506       Chain.T_ID   := T;
 507       Created_Task := T;
 508    end Create_Restricted_Task;
 509
 510    ---------------------------
 511    -- Finalize_Global_Tasks --
 512    ---------------------------
 513
 514    --  This is needed to support the compiler interface; it will only be called
 515    --  by the Environment task. Instead, it will cause the Environment to block
 516    --  forever, since none of the dependent tasks are expected to terminate
 517
 518    procedure Finalize_Global_Tasks is
 519       Self_ID : constant Task_Id := STPO.Self;
 520
 521    begin
 522       pragma Assert (Self_ID = STPO.Environment_Task);
 523
 524       if Single_Lock then
 525          Lock_RTS;
 526       end if;
 527
 528       Write_Lock (Self_ID);
 529       Sleep (Self_ID, Master_Completion_Sleep);
 530       Unlock (Self_ID);
 531
 532       if Single_Lock then
 533          Unlock_RTS;
 534       end if;
 535
 536       --  Should never return from Master Completion Sleep
 537
 538       raise Program_Error;
 539    end Finalize_Global_Tasks;
 540
 541    ---------------------------
 542    -- Restricted_Terminated --
 543    ---------------------------
 544
 545    function Restricted_Terminated (T : Task_Id) return Boolean is
 546    begin
 547       return T.Common.State = Terminated;
 548    end Restricted_Terminated;
 549
 550    --------------------
 551    -- Terminate_Task --
 552    --------------------
 553
 554    procedure Terminate_Task (Self_ID : Task_Id) is
 555    begin
 556       Self_ID.Common.State := Terminated;
 557    end Terminate_Task;
 558
 559    --------------
 560    -- Init_RTS --
 561    --------------
 562
 563    procedure Init_RTS is
 564    begin
 565       --  Initialize lock used to implement mutual exclusion between all tasks
 566
 567       STPO.Initialize_Lock (Global_Task_Lock'Access, STPO.Global_Task_Level);
 568
 569       --  Notify that the tasking run time has been elaborated so that
 570       --  the tasking version of the soft links can be used.
 571
 572       SSL.Lock_Task              := Task_Lock'Access;
 573       SSL.Unlock_Task            := Task_Unlock'Access;
 574
 575       SSL.Get_Jmpbuf_Address     := Get_Jmpbuf_Address'Access;
 576       SSL.Set_Jmpbuf_Address     := Set_Jmpbuf_Address'Access;
 577       SSL.Get_Machine_State_Addr := Get_Machine_State_Addr'Access;
 578       SSL.Set_Machine_State_Addr := Set_Machine_State_Addr'Access;
 579       SSL.Get_Current_Excep      := Get_Current_Excep'Access;
 580       SSL.Set_Jmpbuf_Address     (SSL.Get_Jmpbuf_Address_NT);
 581       SSL.Set_Machine_State_Addr (SSL.Get_Machine_State_Addr_NT);
 582
 583       SSL.Get_Sec_Stack_Addr     := Get_Sec_Stack_Addr'Access;
 584       SSL.Set_Sec_Stack_Addr     := Set_Sec_Stack_Addr'Access;
 585
 586       --  No need to create a new Secondary Stack, since we will use the
 587       --  default one created in s-secsta.adb
 588
 589       Set_Sec_Stack_Addr (SSL.Get_Sec_Stack_Addr_NT);
 590
 591       SSL.Timed_Delay            := Timed_Delay_T'Access;
 592       SSL.Adafinal               := Finalize_Global_Tasks'Access;
 593    end Init_RTS;
 594
 595 begin
 596    Init_RTS;
 597 end System.Tasking.Restricted.Stages;