gomp-20050608-branch/gcc/ada/s-tpoben.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                  --
   4 --                                                                          --
   5 --      S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S .   --
   6 --                               E N T R I E S                              --
   7 --                                                                          --
   8 --                                  B o d y                                 --
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  10 --         Copyright (C) 1998-2005, Free Software Foundation, Inc.          --
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  12 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
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  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
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  21 -- Boston, MA 02110-1301, USA.                                              --
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  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNARL was developed by the GNARL team at Florida State University.       --
  31 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This package contains all the simple primitives related to protected
  36 --  objects with entries (i.e init, lock, unlock).
  37
  38 --  The handling of protected objects with no entries is done in
  39 --  System.Tasking.Protected_Objects, the complex routines for protected
  40 --  objects with entries in System.Tasking.Protected_Objects.Operations.
  41
  42 --  The split between Entries and Operations is needed to break circular
  43 --  dependencies inside the run time.
  44
  45 --  Note: the compiler generates direct calls to this interface, via Rtsfind
  46
  47 with Ada.Exceptions;
  48 --  Used for Exception_Occurrence_Access
  49 --           Raise_Exception
  50
  51 with System.Task_Primitives.Operations;
  52 --  Used for Initialize_Lock
  53 --           Write_Lock
  54 --           Unlock
  55 --           Get_Priority
  56 --           Wakeup
  57
  58 with System.Tasking.Initialization;
  59 --  Used for Defer_Abort,
  60 --           Undefer_Abort,
  61 --           Change_Base_Priority
  62
  63 pragma Elaborate_All (System.Tasking.Initialization);
  64 --  This insures that tasking is initialized if any protected objects are
  65 --  created.
  66
  67 with System.Parameters;
  68 --  Used for Single_Lock
  69
  70 package body System.Tasking.Protected_Objects.Entries is
  71
  72    package STPO renames System.Task_Primitives.Operations;
  73
  74    use Parameters;
  75    use Task_Primitives.Operations;
  76    use Ada.Exceptions;
  77
  78    ----------------
  79    -- Local Data --
  80    ----------------
  81
  82    Locking_Policy : Character;
  83    pragma Import (C, Locking_Policy, "__gl_locking_policy");
  84
  85    --------------
  86    -- Finalize --
  87    --------------
  88
  89    procedure Finalize (Object : in out Protection_Entries) is
  90       Entry_Call        : Entry_Call_Link;
  91       Caller            : Task_Id;
  92       Ceiling_Violation : Boolean;
  93       Self_ID           : constant Task_Id := STPO.Self;
  94       Old_Base_Priority : System.Any_Priority;
  95
  96    begin
  97       if Object.Finalized then
  98          return;
  99       end if;
 100
 101       STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
 102
 103       if Single_Lock then
 104          Lock_RTS;
 105       end if;
 106
 107       if Ceiling_Violation then
 108
 109          --  Dip our own priority down to ceiling of lock. See similar code in
 110          --  Tasking.Entry_Calls.Lock_Server.
 111
 112          STPO.Write_Lock (Self_ID);
 113          Old_Base_Priority := Self_ID.Common.Base_Priority;
 114          Self_ID.New_Base_Priority := Object.Ceiling;
 115          Initialization.Change_Base_Priority (Self_ID);
 116          STPO.Unlock (Self_ID);
 117
 118          if Single_Lock then
 119             Unlock_RTS;
 120          end if;
 121
 122          STPO.Write_Lock (Object.L'Unrestricted_Access, Ceiling_Violation);
 123
 124          if Ceiling_Violation then
 125             Raise_Exception (Program_Error'Identity, "Ceiling Violation");
 126          end if;
 127
 128          if Single_Lock then
 129             Lock_RTS;
 130          end if;
 131
 132          Object.Old_Base_Priority := Old_Base_Priority;
 133          Object.Pending_Action := True;
 134       end if;
 135
 136       --  Send program_error to all tasks still queued on this object
 137
 138       for E in Object.Entry_Queues'Range loop
 139          Entry_Call := Object.Entry_Queues (E).Head;
 140
 141          while Entry_Call /= null loop
 142             Caller := Entry_Call.Self;
 143             Entry_Call.Exception_To_Raise := Program_Error'Identity;
 144
 145             STPO.Write_Lock (Caller);
 146             Initialization.Wakeup_Entry_Caller (Self_ID, Entry_Call, Done);
 147             STPO.Unlock (Caller);
 148
 149             exit when Entry_Call = Object.Entry_Queues (E).Tail;
 150             Entry_Call := Entry_Call.Next;
 151          end loop;
 152       end loop;
 153
 154       Object.Finalized := True;
 155
 156       if Single_Lock then
 157          Unlock_RTS;
 158       end if;
 159
 160       STPO.Unlock (Object.L'Unrestricted_Access);
 161
 162       STPO.Finalize_Lock (Object.L'Unrestricted_Access);
 163    end Finalize;
 164
 165    -------------------------------------
 166    -- Has_Interrupt_Or_Attach_Handler --
 167    -------------------------------------
 168
 169    function Has_Interrupt_Or_Attach_Handler
 170      (Object : Protection_Entries_Access)
 171       return   Boolean
 172    is
 173       pragma Warnings (Off, Object);
 174    begin
 175       return False;
 176    end Has_Interrupt_Or_Attach_Handler;
 177
 178    -----------------------------------
 179    -- Initialize_Protection_Entries --
 180    -----------------------------------
 181
 182    procedure Initialize_Protection_Entries
 183      (Object            : Protection_Entries_Access;
 184       Ceiling_Priority  : Integer;
 185       Compiler_Info     : System.Address;
 186       Entry_Bodies      : Protected_Entry_Body_Access;
 187       Find_Body_Index   : Find_Body_Index_Access)
 188    is
 189       Init_Priority : Integer := Ceiling_Priority;
 190       Self_ID       : constant Task_Id := STPO.Self;
 191
 192    begin
 193       if Init_Priority = Unspecified_Priority then
 194          Init_Priority  := System.Priority'Last;
 195       end if;
 196
 197       if Locking_Policy = 'C'
 198         and then Has_Interrupt_Or_Attach_Handler (Object)
 199         and then Init_Priority not in System.Interrupt_Priority
 200       then
 201          --  Required by C.3.1(11)
 202
 203          raise Program_Error;
 204       end if;
 205
 206       Initialization.Defer_Abort (Self_ID);
 207       Initialize_Lock (Init_Priority, Object.L'Access);
 208       Initialization.Undefer_Abort (Self_ID);
 209       Object.Ceiling := System.Any_Priority (Init_Priority);
 210       Object.Owner := Null_Task;
 211       Object.Compiler_Info := Compiler_Info;
 212       Object.Pending_Action := False;
 213       Object.Call_In_Progress := null;
 214       Object.Entry_Bodies := Entry_Bodies;
 215       Object.Find_Body_Index :=  Find_Body_Index;
 216
 217       for E in Object.Entry_Queues'Range loop
 218          Object.Entry_Queues (E).Head := null;
 219          Object.Entry_Queues (E).Tail := null;
 220       end loop;
 221    end Initialize_Protection_Entries;
 222
 223    ------------------
 224    -- Lock_Entries --
 225    ------------------
 226
 227    procedure Lock_Entries
 228      (Object : Protection_Entries_Access; Ceiling_Violation : out Boolean)
 229    is
 230    begin
 231       if Object.Finalized then
 232          Raise_Exception
 233            (Program_Error'Identity, "Protected Object is finalized");
 234       end if;
 235
 236       --  If pragma Detect_Blocking is active then, as described in the ARM
 237       --  9.5.1, par. 15, we must check whether this is an external call on a
 238       --  protected subprogram with the same target object as that of the
 239       --  protected action that is currently in progress (i.e., if the caller
 240       --  is already the protected object's owner). If this is the case hence
 241       --  Program_Error must be raised.
 242
 243       if Detect_Blocking and then Object.Owner = Self then
 244          raise Program_Error;
 245       end if;
 246
 247       --  The lock is made without defering abort
 248
 249       --  Therefore the abort has to be deferred before calling this routine.
 250       --  This means that the compiler has to generate a Defer_Abort call
 251       --  before the call to Lock.
 252
 253       --  The caller is responsible for undeferring abort, and compiler
 254       --  generated calls must be protected with cleanup handlers to ensure
 255       --  that abort is undeferred in all cases.
 256
 257       pragma Assert (STPO.Self.Deferral_Level > 0);
 258       Write_Lock (Object.L'Access, Ceiling_Violation);
 259
 260       --  We are entering in a protected action, so that we increase the
 261       --  protected object nesting level (if pragma Detect_Blocking is
 262       --  active), and update the protected object's owner.
 263
 264       if Detect_Blocking then
 265          declare
 266             Self_Id : constant Task_Id := Self;
 267
 268          begin
 269             --  Update the protected object's owner
 270
 271             Object.Owner := Self_Id;
 272
 273             --  Increase protected object nesting level
 274
 275             Self_Id.Common.Protected_Action_Nesting :=
 276               Self_Id.Common.Protected_Action_Nesting + 1;
 277          end;
 278       end if;
 279
 280    end Lock_Entries;
 281
 282    procedure Lock_Entries (Object : Protection_Entries_Access) is
 283       Ceiling_Violation : Boolean;
 284
 285    begin
 286       Lock_Entries (Object, Ceiling_Violation);
 287
 288       if Ceiling_Violation then
 289          Raise_Exception (Program_Error'Identity, "Ceiling Violation");
 290       end if;
 291    end Lock_Entries;
 292
 293    ----------------------------
 294    -- Lock_Read_Only_Entries --
 295    ----------------------------
 296
 297    procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access) is
 298       Ceiling_Violation : Boolean;
 299
 300    begin
 301       if Object.Finalized then
 302          Raise_Exception
 303            (Program_Error'Identity, "Protected Object is finalized");
 304       end if;
 305
 306       --  If pragma Detect_Blocking is active then, as described in the ARM
 307       --  9.5.1, par. 15, we must check whether this is an external call on a
 308       --  protected subprogram with the same target object as that of the
 309       --  protected action that is currently in progress (i.e., if the caller
 310       --  is already the protected object's owner). If this is the case hence
 311       --  Program_Error must be raised.
 312
 313       --  Note that in this case (getting read access), several tasks may
 314       --  have read ownership of the protected object, so that this method of
 315       --  storing the (single) protected object's owner does not work
 316       --  reliably for read locks. However, this is the approach taken for two
 317       --  major reasosn: first, this function is not currently being used (it
 318       --  is provided for possible future use), and second, it largely
 319       --  simplifies the implementation.
 320
 321       if Detect_Blocking and then Object.Owner = Self then
 322          raise Program_Error;
 323       end if;
 324
 325       Read_Lock (Object.L'Access, Ceiling_Violation);
 326
 327       if Ceiling_Violation then
 328          Raise_Exception (Program_Error'Identity, "Ceiling Violation");
 329       end if;
 330
 331       --  We are entering in a protected action, so that we increase the
 332       --  protected object nesting level (if pragma Detect_Blocking is
 333       --  active), and update the protected object's owner.
 334
 335       if Detect_Blocking then
 336          declare
 337             Self_Id : constant Task_Id := Self;
 338
 339          begin
 340             --  Update the protected object's owner
 341
 342             Object.Owner := Self_Id;
 343
 344             --  Increase protected object nesting level
 345
 346             Self_Id.Common.Protected_Action_Nesting :=
 347               Self_Id.Common.Protected_Action_Nesting + 1;
 348          end;
 349       end if;
 350    end Lock_Read_Only_Entries;
 351
 352    --------------------
 353    -- Unlock_Entries --
 354    --------------------
 355
 356    procedure Unlock_Entries (Object : Protection_Entries_Access) is
 357    begin
 358       --  We are exiting from a protected action, so that we decrease the
 359       --  protected object nesting level (if pragma Detect_Blocking is
 360       --  active), and remove ownership of the protected object.
 361
 362       if Detect_Blocking then
 363          declare
 364             Self_Id : constant Task_Id := Self;
 365
 366          begin
 367             --  Calls to this procedure can only take place when being within
 368             --  a protected action and when the caller is the protected
 369             --  object's owner.
 370
 371             pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
 372                              and then Object.Owner = Self_Id);
 373
 374             --  Remove ownership of the protected object
 375
 376             Object.Owner := Null_Task;
 377
 378             Self_Id.Common.Protected_Action_Nesting :=
 379               Self_Id.Common.Protected_Action_Nesting - 1;
 380          end;
 381       end if;
 382
 383       Unlock (Object.L'Access);
 384    end Unlock_Entries;
 385
 386 end System.Tasking.Protected_Objects.Entries;