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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.5.1/] [gcc/] [ada/] [s-taprob.adb] - Blame information for rev 300

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1 281 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
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--                                                                          --
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--      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     --
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--                                                                          --
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--                                  B o d y                                 --
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--                                                                          --
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--             Copyright (C) 1991-1994, Florida State University            --
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--                     Copyright (C) 1995-2008, AdaCore                     --
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--                                                                          --
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-- GNARL is free software; you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
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-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
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-- for  more details.  You should have  received  a copy of the GNU General --
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-- Public License  distributed with GNARL; see file COPYING.  If not, write --
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-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
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-- Boston, MA 02110-1301, USA.                                              --
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--                                                                          --
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-- As a special exception,  if other files  instantiate  generics from this --
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-- unit, or you link  this unit with other files  to produce an executable, --
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-- this  unit  does not  by itself cause  the resulting  executable  to  be --
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-- covered  by the  GNU  General  Public  License.  This exception does not --
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-- however invalidate  any other reasons why  the executable file  might be --
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-- covered by the  GNU Public License.                                      --
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--                                                                          --
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-- GNARL was developed by the GNARL team at Florida State University.       --
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-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
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--                                                                          --
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------------------------------------------------------------------------------
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pragma Polling (Off);
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--  Turn off polling, we do not want ATC polling to take place during
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--  tasking operations. It causes infinite loops and other problems.
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with System.Task_Primitives.Operations;
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with System.Parameters;
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with System.Traces;
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with System.Soft_Links.Tasking;
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package body System.Tasking.Protected_Objects is
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   use System.Task_Primitives.Operations;
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   use System.Traces;
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   ----------------
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   -- Local Data --
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   ----------------
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   Locking_Policy : Character;
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   pragma Import (C, Locking_Policy, "__gl_locking_policy");
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   -------------------------
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   -- Finalize_Protection --
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   -------------------------
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   procedure Finalize_Protection (Object : in out Protection) is
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   begin
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      Finalize_Lock (Object.L'Unrestricted_Access);
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   end Finalize_Protection;
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   ---------------------------
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   -- Initialize_Protection --
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   ---------------------------
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   procedure Initialize_Protection
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     (Object           : Protection_Access;
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      Ceiling_Priority : Integer)
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   is
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      Init_Priority : Integer := Ceiling_Priority;
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   begin
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      if Init_Priority = Unspecified_Priority then
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         Init_Priority  := System.Priority'Last;
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      end if;
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      Initialize_Lock (Init_Priority, Object.L'Access);
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      Object.Ceiling := System.Any_Priority (Init_Priority);
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      Object.New_Ceiling := System.Any_Priority (Init_Priority);
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      Object.Owner := Null_Task;
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   end Initialize_Protection;
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   -----------------
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   -- Get_Ceiling --
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   -----------------
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   function Get_Ceiling
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     (Object : Protection_Access) return System.Any_Priority is
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   begin
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      return Object.New_Ceiling;
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   end Get_Ceiling;
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   ----------
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   -- Lock --
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   ----------
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   procedure Lock (Object : Protection_Access) is
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      Ceiling_Violation : Boolean;
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   begin
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      --  The lock is made without deferring abort
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      --  Therefore the abort has to be deferred before calling this routine.
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      --  This means that the compiler has to generate a Defer_Abort call
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      --  before the call to Lock.
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      --  The caller is responsible for undeferring abort, and compiler
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      --  generated calls must be protected with cleanup handlers to ensure
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      --  that abort is undeferred in all cases.
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      --  If pragma Detect_Blocking is active then, as described in the ARM
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      --  9.5.1, par. 15, we must check whether this is an external call on a
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      --  protected subprogram with the same target object as that of the
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      --  protected action that is currently in progress (i.e., if the caller
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      --  is already the protected object's owner). If this is the case hence
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      --  Program_Error must be raised.
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      if Detect_Blocking and then Object.Owner = Self then
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         raise Program_Error;
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      end if;
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      Write_Lock (Object.L'Access, Ceiling_Violation);
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      if Parameters.Runtime_Traces then
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         Send_Trace_Info (PO_Lock);
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      end if;
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      if Ceiling_Violation then
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         raise Program_Error;
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      end if;
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      --  We are entering in a protected action, so that we increase the
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      --  protected object nesting level (if pragma Detect_Blocking is
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      --  active), and update the protected object's owner.
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      if Detect_Blocking then
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         declare
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            Self_Id : constant Task_Id := Self;
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         begin
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            --  Update the protected object's owner
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            Object.Owner := Self_Id;
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            --  Increase protected object nesting level
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            Self_Id.Common.Protected_Action_Nesting :=
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              Self_Id.Common.Protected_Action_Nesting + 1;
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         end;
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      end if;
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   end Lock;
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   --------------------
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   -- Lock_Read_Only --
157
   --------------------
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159
   procedure Lock_Read_Only (Object : Protection_Access) is
160
      Ceiling_Violation : Boolean;
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162
   begin
163
      --  If pragma Detect_Blocking is active then, as described in the ARM
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      --  9.5.1, par. 15, we must check whether this is an external call on
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      --  protected subprogram with the same target object as that of the
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      --  protected action that is currently in progress (i.e., if the caller
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      --  is already the protected object's owner). If this is the case hence
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      --  Program_Error must be raised.
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      --
170
      --  Note that in this case (getting read access), several tasks may have
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      --  read ownership of the protected object, so that this method of
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      --  storing the (single) protected object's owner does not work reliably
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      --  for read locks. However, this is the approach taken for two major
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      --  reasons: first, this function is not currently being used (it is
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      --  provided for possible future use), and second, it largely simplifies
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      --  the implementation.
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178
      if Detect_Blocking and then Object.Owner = Self then
179
         raise Program_Error;
180
      end if;
181
 
182
      Read_Lock (Object.L'Access, Ceiling_Violation);
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      if Parameters.Runtime_Traces then
185
         Send_Trace_Info (PO_Lock);
186
      end if;
187
 
188
      if Ceiling_Violation then
189
         raise Program_Error;
190
      end if;
191
 
192
      --  We are entering in a protected action, so we increase the protected
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      --  object nesting level (if pragma Detect_Blocking is active).
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195
      if Detect_Blocking then
196
         declare
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            Self_Id : constant Task_Id := Self;
198
         begin
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            --  Update the protected object's owner
200
 
201
            Object.Owner := Self_Id;
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203
            --  Increase protected object nesting level
204
 
205
            Self_Id.Common.Protected_Action_Nesting :=
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              Self_Id.Common.Protected_Action_Nesting + 1;
207
         end;
208
      end if;
209
   end Lock_Read_Only;
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211
   -----------------
212
   -- Set_Ceiling --
213
   -----------------
214
 
215
   procedure Set_Ceiling
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     (Object : Protection_Access;
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      Prio   : System.Any_Priority) is
218
   begin
219
      Object.New_Ceiling := Prio;
220
   end Set_Ceiling;
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   ------------
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   -- Unlock --
224
   ------------
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   procedure Unlock (Object : Protection_Access) is
227
   begin
228
      --  We are exiting from a protected action, so that we decrease the
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      --  protected object nesting level (if pragma Detect_Blocking is
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      --  active), and remove ownership of the protected object.
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232
      if Detect_Blocking then
233
         declare
234
            Self_Id : constant Task_Id := Self;
235
 
236
         begin
237
            --  Calls to this procedure can only take place when being within
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            --  a protected action and when the caller is the protected
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            --  object's owner.
240
 
241
            pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
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                             and then Object.Owner = Self_Id);
243
 
244
            --  Remove ownership of the protected object
245
 
246
            Object.Owner := Null_Task;
247
 
248
            --  We are exiting from a protected action, so we decrease the
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            --  protected object nesting level.
250
 
251
            Self_Id.Common.Protected_Action_Nesting :=
252
              Self_Id.Common.Protected_Action_Nesting - 1;
253
         end;
254
      end if;
255
 
256
      --  Before releasing the mutex we must actually update its ceiling
257
      --  priority if it has been changed.
258
 
259
      if Object.New_Ceiling /= Object.Ceiling then
260
         if Locking_Policy = 'C' then
261
            System.Task_Primitives.Operations.Set_Ceiling
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              (Object.L'Access, Object.New_Ceiling);
263
         end if;
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265
         Object.Ceiling := Object.New_Ceiling;
266
      end if;
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268
      Unlock (Object.L'Access);
269
 
270
      if Parameters.Runtime_Traces then
271
         Send_Trace_Info (PO_Unlock);
272
      end if;
273
   end Unlock;
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275
begin
276
   --  Ensure that tasking is initialized, as well as tasking soft links
277
   --  when using protected objects.
278
 
279
   Tasking.Initialize;
280
   System.Soft_Links.Tasking.Init_Tasking_Soft_Links;
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end System.Tasking.Protected_Objects;

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