gcc/ada/s-taprob.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 . P R O T E C T E D _ O B J E C T S     --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --             Copyright (C) 1991-1994, Florida State University            --
  10 --                   Copyright (C) 1995-2005, AdaCore                       --
  11 --                                                                          --
  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- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  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 --
  19 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  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 pragma Polling (Off);
  36 --  Turn off polling, we do not want ATC polling to take place during
  37 --  tasking operations. It causes infinite loops and other problems.
  38
  39 with System.Task_Primitives.Operations;
  40 --  used for Write_Lock
  41 --           Unlock
  42 --           Self
  43
  44 with System.Parameters;
  45 --  used for Runtime_Traces
  46
  47 with System.Traces;
  48 --  used for Send_Trace_Info
  49
  50 with System.Soft_Links.Tasking;
  51 --  Used for Init_Tasking_Soft_Links
  52
  53 package body System.Tasking.Protected_Objects is
  54
  55    use System.Task_Primitives.Operations;
  56    use System.Traces;
  57
  58    -------------------------
  59    -- Finalize_Protection --
  60    -------------------------
  61
  62    procedure Finalize_Protection (Object : in out Protection) is
  63    begin
  64       Finalize_Lock (Object.L'Unrestricted_Access);
  65    end Finalize_Protection;
  66
  67    ---------------------------
  68    -- Initialize_Protection --
  69    ---------------------------
  70
  71    procedure Initialize_Protection
  72      (Object           : Protection_Access;
  73       Ceiling_Priority : Integer)
  74    is
  75       Init_Priority : Integer := Ceiling_Priority;
  76
  77    begin
  78       if Init_Priority = Unspecified_Priority then
  79          Init_Priority  := System.Priority'Last;
  80       end if;
  81
  82       Initialize_Lock (Init_Priority, Object.L'Access);
  83       Object.Ceiling := System.Any_Priority (Init_Priority);
  84       Object.Owner := Null_Task;
  85    end Initialize_Protection;
  86
  87    ----------
  88    -- Lock --
  89    ----------
  90
  91    procedure Lock (Object : Protection_Access) is
  92       Ceiling_Violation : Boolean;
  93
  94    begin
  95       --  The lock is made without defering abort
  96
  97       --  Therefore the abort has to be deferred before calling this routine.
  98       --  This means that the compiler has to generate a Defer_Abort call
  99       --  before the call to Lock.
 100
 101       --  The caller is responsible for undeferring abort, and compiler
 102       --  generated calls must be protected with cleanup handlers to ensure
 103       --  that abort is undeferred in all cases.
 104
 105       --  If pragma Detect_Blocking is active then, as described in the ARM
 106       --  9.5.1, par. 15, we must check whether this is an external call on a
 107       --  protected subprogram with the same target object as that of the
 108       --  protected action that is currently in progress (i.e., if the caller
 109       --  is already the protected object's owner). If this is the case hence
 110       --  Program_Error must be raised.
 111
 112       if Detect_Blocking and then Object.Owner = Self then
 113          raise Program_Error;
 114       end if;
 115
 116       Write_Lock (Object.L'Access, Ceiling_Violation);
 117
 118       if Parameters.Runtime_Traces then
 119          Send_Trace_Info (PO_Lock);
 120       end if;
 121
 122       if Ceiling_Violation then
 123          raise Program_Error;
 124       end if;
 125
 126       --  We are entering in a protected action, so that we increase the
 127       --  protected object nesting level (if pragma Detect_Blocking is
 128       --  active), and update the protected object's owner.
 129
 130       if Detect_Blocking then
 131          declare
 132             Self_Id : constant Task_Id := Self;
 133          begin
 134             --  Update the protected object's owner
 135
 136             Object.Owner := Self_Id;
 137
 138             --  Increase protected object nesting level
 139
 140             Self_Id.Common.Protected_Action_Nesting :=
 141               Self_Id.Common.Protected_Action_Nesting + 1;
 142          end;
 143       end if;
 144    end Lock;
 145
 146    --------------------
 147    -- Lock_Read_Only --
 148    --------------------
 149
 150    procedure Lock_Read_Only (Object : Protection_Access) is
 151       Ceiling_Violation : Boolean;
 152
 153    begin
 154       --  If pragma Detect_Blocking is active then, as described in the ARM
 155       --  9.5.1, par. 15, we must check whether this is an external call on
 156       --  protected subprogram with the same target object as that of the
 157       --  protected action that is currently in progress (i.e., if the caller
 158       --  is already the protected object's owner). If this is the case hence
 159       --  Program_Error must be raised.
 160       --
 161       --  Note that in this case (getting read access), several tasks may have
 162       --  read ownership of the protected object, so that this method of
 163       --  storing the (single) protected object's owner does not work reliably
 164       --  for read locks. However, this is the approach taken for two major
 165       --  reasosn: first, this function is not currently being used (it is
 166       --  provided for possible future use), and second, it largely simplifies
 167       --  the implementation.
 168
 169       if Detect_Blocking and then Object.Owner = Self then
 170          raise Program_Error;
 171       end if;
 172
 173       Read_Lock (Object.L'Access, Ceiling_Violation);
 174
 175       if Parameters.Runtime_Traces then
 176          Send_Trace_Info (PO_Lock);
 177       end if;
 178
 179       if Ceiling_Violation then
 180          raise Program_Error;
 181       end if;
 182
 183       --  We are entering in a protected action, so we increase the protected
 184       --  object nesting level (if pragma Detect_Blocking is active).
 185
 186       if Detect_Blocking then
 187          declare
 188             Self_Id : constant Task_Id := Self;
 189          begin
 190             --  Update the protected object's owner
 191
 192             Object.Owner := Self_Id;
 193
 194             --  Increase protected object nesting level
 195
 196             Self_Id.Common.Protected_Action_Nesting :=
 197               Self_Id.Common.Protected_Action_Nesting + 1;
 198          end;
 199       end if;
 200    end Lock_Read_Only;
 201
 202    ------------
 203    -- Unlock --
 204    ------------
 205
 206    procedure Unlock (Object : Protection_Access) is
 207    begin
 208       --  We are exiting from a protected action, so that we decrease the
 209       --  protected object nesting level (if pragma Detect_Blocking is
 210       --  active), and remove ownership of the protected object.
 211
 212       if Detect_Blocking then
 213          declare
 214             Self_Id : constant Task_Id := Self;
 215
 216          begin
 217             --  Calls to this procedure can only take place when being within
 218             --  a protected action and when the caller is the protected
 219             --  object's owner.
 220
 221             pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
 222                              and then Object.Owner = Self_Id);
 223
 224             --  Remove ownership of the protected object
 225
 226             Object.Owner := Null_Task;
 227
 228             --  We are exiting from a protected action, so we decrease the
 229             --  protected object nesting level.
 230
 231             Self_Id.Common.Protected_Action_Nesting :=
 232               Self_Id.Common.Protected_Action_Nesting - 1;
 233          end;
 234       end if;
 235
 236       Unlock (Object.L'Access);
 237
 238       if Parameters.Runtime_Traces then
 239          Send_Trace_Info (PO_Unlock);
 240       end if;
 241    end Unlock;
 242
 243 begin
 244    --  Ensure that tasking soft links are set when using protected objects
 245
 246    System.Soft_Links.Tasking.Init_Tasking_Soft_Links;
 247 end System.Tasking.Protected_Objects;