gcc/ada/s-taprob.ads

   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 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2011, 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 --  This package provides necessary definitions to handle simple (i.e without
  33 --  entries) protected objects.
  34
  35 --  All the routines that handle protected objects with entries have been moved
  36 --  to two children: Entries and Operations. Note that Entries only contains
  37 --  the type declaration and the OO primitives. This is needed to avoid
  38 --  circular dependency.
  39
  40 --  This package is part of the high level tasking interface used by the
  41 --  compiler to expand Ada 95 tasking constructs into simpler run time calls
  42 --  (aka GNARLI, GNU Ada Run-time Library Interface)
  43
  44 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  45 --  Any changes to this interface may require corresponding compiler changes
  46 --  in exp_ch9.adb and possibly exp_ch7.adb and exp_attr.adb
  47
  48 package System.Tasking.Protected_Objects is
  49    pragma Elaborate_Body;
  50
  51    ---------------------------------
  52    -- Compiler Interface (GNARLI) --
  53    ---------------------------------
  54
  55    --  The compiler will expand in the GNAT tree the following construct:
  56
  57    --  protected PO is
  58    --     procedure P;
  59    --  private
  60    --     open : boolean := false;
  61    --  end PO;
  62
  63    --  protected body PO is
  64    --     procedure P is
  65    --        ...variable declarations...
  66    --     begin
  67    --        ...B...
  68    --     end P;
  69    --  end PO;
  70
  71    --  as follows:
  72
  73    --  protected type poT is
  74    --     procedure p;
  75    --  private
  76    --     open : boolean := false;
  77    --  end poT;
  78    --  type poTV is limited record
  79    --     open : boolean := false;
  80    --     _object : aliased protection;
  81    --  end record;
  82    --  procedure poPT__pN (_object : in out poTV);
  83    --  procedure poPT__pP (_object : in out poTV);
  84    --  freeze poTV [
  85    --     procedure poTVI (_init : in out poTV) is
  86    --     begin
  87    --        _init.open := false;
  88    --        object-init-proc (_init._object);
  89    --        initialize_protection (_init._object'unchecked_access,
  90    --          unspecified_priority);
  91    --        return;
  92    --     end _init_proc;
  93    --  ]
  94    --  po : poT;
  95    --  poTVI (poTV!(po));
  96
  97    --  procedure poPT__pN (_object : in out poTV) is
  98    --     poR : protection renames _object._object;
  99    --     openP : boolean renames _object.open;
 100    --     ...variable declarations...
 101    --  begin
 102    --     ...B...
 103    --     return;
 104    --  end poPT__pN;
 105
 106    --  procedure poPT__pP (_object : in out poTV) is
 107    --     procedure _clean is
 108    --     begin
 109    --        unlock (_object._object'unchecked_access);
 110    --        return;
 111    --     end _clean;
 112    --  begin
 113    --     lock (_object._object'unchecked_access);
 114    --     B2b : begin
 115    --        poPT__pN (_object);
 116    --     at end
 117    --        _clean;
 118    --     end B2b;
 119    --     return;
 120    --  end poPT__pP;
 121
 122    Null_Protected_Entry : constant := Null_Entry;
 123
 124    Max_Protected_Entry : constant := Max_Entry;
 125
 126    type Protected_Entry_Index is new Entry_Index
 127      range Null_Protected_Entry .. Max_Protected_Entry;
 128
 129    type Barrier_Function_Pointer is access
 130      function
 131        (O    : System.Address;
 132         E    : Protected_Entry_Index)
 133         return Boolean;
 134    --  Pointer to a function which evaluates the barrier of a protected
 135    --  entry body. O is a pointer to the compiler-generated record
 136    --  representing the protected object, and E is the index of the
 137    --  entry serviced by the body.
 138
 139    type Entry_Action_Pointer is access
 140      procedure
 141        (O : System.Address;
 142         P : System.Address;
 143         E : Protected_Entry_Index);
 144    --  Pointer to a procedure which executes the sequence of statements
 145    --  of a protected entry body. O is a pointer to the compiler-generated
 146    --  record representing the protected object, P is a pointer to the
 147    --  record of entry parameters, and E is the index of the
 148    --  entry serviced by the body.
 149
 150    type Entry_Body is record
 151       Barrier : Barrier_Function_Pointer;
 152       Action  : Entry_Action_Pointer;
 153    end record;
 154    --  The compiler-generated code passes objects of this type to the GNARL
 155    --  to allow it to access the executable code of an entry body.
 156
 157    type Entry_Body_Access is access all Entry_Body;
 158
 159    type Protection is limited private;
 160    --  This type contains the GNARL state of a protected object. The
 161    --  application-defined portion of the state (i.e. private objects)
 162    --  is maintained by the compiler-generated code.
 163    --  Note that there are now 2 Protection types. One for the simple
 164    --  case (no entries) and one for the general case that needs the whole
 165    --  Finalization mechanism.
 166    --  This split helps in the case of restricted run time where we want to
 167    --  minimize the size of the code.
 168
 169    type Protection_Access is access all Protection;
 170
 171    Null_PO : constant Protection_Access := null;
 172
 173    function Get_Ceiling
 174      (Object : Protection_Access) return System.Any_Priority;
 175    --  Returns the new ceiling priority of the protected object
 176
 177    procedure Initialize_Protection
 178      (Object           : Protection_Access;
 179       Ceiling_Priority : Integer);
 180    --  Initialize the Object parameter so that it can be used by the runtime
 181    --  to keep track of the runtime state of a protected object.
 182
 183    procedure Lock (Object : Protection_Access);
 184    --  Lock a protected object for write access. Upon return, the caller
 185    --  owns the lock to this object, and no other call to Lock or
 186    --  Lock_Read_Only with the same argument will return until the
 187    --  corresponding call to Unlock has been made by the caller.
 188
 189    procedure Lock_Read_Only (Object : Protection_Access);
 190    --  Lock a protected object for read access. Upon return, the caller
 191    --  owns the lock for read access, and no other calls to Lock with the
 192    --  same argument will return until the corresponding call to Unlock
 193    --  has been made by the caller. Other calls to Lock_Read_Only may (but
 194    --  need not) return before the call to Unlock, and the corresponding
 195    --  callers will also own the lock for read access.
 196
 197    procedure Set_Ceiling
 198      (Object : Protection_Access;
 199       Prio   : System.Any_Priority);
 200    --  Sets the new ceiling priority of the protected object
 201
 202    procedure Unlock (Object : Protection_Access);
 203    --  Relinquish ownership of the lock for the object represented by
 204    --  the Object parameter. If this ownership was for write access, or
 205    --  if it was for read access where there are no other read access
 206    --  locks outstanding, one (or more, in the case of Lock_Read_Only)
 207    --  of the tasks waiting on this lock (if any) will be given the
 208    --  lock and allowed to return from the Lock or Lock_Read_Only call.
 209
 210 private
 211    type Protection is record
 212       L : aliased Task_Primitives.Lock;
 213       --  Lock used to ensure mutual exclusive access to the protected object
 214
 215       Ceiling : System.Any_Priority;
 216       --  Ceiling priority associated to the protected object
 217
 218       New_Ceiling : System.Any_Priority;
 219       --  New ceiling priority associated to the protected object. In case
 220       --  of assignment of a new ceiling priority to the protected object the
 221       --  frontend generates a call to set_ceiling to save the new value in
 222       --  this field. After such assignment this value can be read by means
 223       --  of the 'Priority attribute, which generates a call to get_ceiling.
 224       --  However, the ceiling of the protected object will not be changed
 225       --  until completion of the protected action in which the assignment
 226       --  has been executed (AARM D.5.2 (10/2)).
 227
 228       Owner : Task_Id;
 229       --  This field contains the protected object's owner. Null_Task
 230       --  indicates that the protected object is not currently being used.
 231       --  This information is used for detecting the type of potentially
 232       --  blocking operations described in the ARM 9.5.1, par. 15 (external
 233       --  calls on a protected subprogram with the same target object as that
 234       --  of the protected action).
 235    end record;
 236
 237    procedure Finalize_Protection (Object : in out Protection);
 238    --  Clean up a Protection object (in particular, finalize the associated
 239    --  Lock object). The compiler generates calls automatically to this
 240    --  procedure
 241
 242 end System.Tasking.Protected_Objects;