gcc/ada/s-tpoben.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                  --
   4 --                                                                          --
   5 --                SYSTEM.TASKING.PROTECTED_OBJECTS.ENTRIES                  --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2012, 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 contains all simple primitives related to Protected_Objects
  33 --  with entries (i.e init, lock, unlock).
  34
  35 --  The handling of protected objects with no entries is done in
  36 --  System.Tasking.Protected_Objects, the complex routines for protected
  37 --  objects with entries in System.Tasking.Protected_Objects.Operations.
  38
  39 --  The split between Entries and Operations is needed to break circular
  40 --  dependencies inside the run time.
  41
  42 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  43 --  Any changes to this interface may require corresponding compiler changes.
  44
  45 with Ada.Finalization;
  46 with Ada.Unchecked_Conversion;
  47
  48 package System.Tasking.Protected_Objects.Entries is
  49    pragma Elaborate_Body;
  50
  51    subtype Positive_Protected_Entry_Index is
  52      Protected_Entry_Index range  1 .. Protected_Entry_Index'Last;
  53
  54    type Find_Body_Index_Access is access
  55      function
  56        (O : System.Address;
  57         E : Protected_Entry_Index)
  58         return Protected_Entry_Index;
  59
  60    type Protected_Entry_Body_Array is
  61      array (Positive_Protected_Entry_Index range <>) of Entry_Body;
  62    --  Contains executable code for all entry bodies of a protected type
  63
  64    type Protected_Entry_Body_Access is access all Protected_Entry_Body_Array;
  65
  66    type Protected_Entry_Queue_Array is
  67      array (Protected_Entry_Index range <>) of Entry_Queue;
  68
  69    --  The following declarations define an array that contains the string
  70    --  names of entries and entry family members, together with an associated
  71    --  access type.
  72
  73    type Protected_Entry_Names_Array is
  74      array (Entry_Index range <>) of String_Access;
  75
  76    type Protected_Entry_Names_Access is access all Protected_Entry_Names_Array;
  77
  78    --  The following type contains the GNARL state of a protected object.
  79    --  The application-defined portion of the state (i.e. private objects)
  80    --  is maintained by the compiler-generated code. Note that there is a
  81    --  simplified version of this type declared in System.Tasking.PO_Simple
  82    --  that handle the simple case (no entries).
  83
  84    type Protection_Entries (Num_Entries : Protected_Entry_Index) is new
  85      Ada.Finalization.Limited_Controlled
  86    with record
  87       L : aliased Task_Primitives.Lock;
  88       --  The underlying lock associated with a Protection_Entries. Note
  89       --  that you should never (un)lock Object.L directly, but instead
  90       --  use Lock_Entries/Unlock_Entries.
  91
  92       Compiler_Info : System.Address;
  93       --  Pointer to compiler-generated record representing protected object
  94
  95       Call_In_Progress : Entry_Call_Link;
  96       --  Pointer to the entry call being executed (if any)
  97
  98       Ceiling : System.Any_Priority;
  99       --  Ceiling priority associated with the protected object
 100
 101       New_Ceiling : System.Any_Priority;
 102       --  New ceiling priority associated to the protected object. In case
 103       --  of assignment of a new ceiling priority to the protected object the
 104       --  frontend generates a call to set_ceiling to save the new value in
 105       --  this field. After such assignment this value can be read by means
 106       --  of the 'Priority attribute, which generates a call to get_ceiling.
 107       --  However, the ceiling of the protected object will not be changed
 108       --  until completion of the protected action in which the assignment
 109       --  has been executed (AARM D.5.2 (10/2)).
 110
 111       Owner : Task_Id;
 112       --  This field contains the protected object's owner. Null_Task
 113       --  indicates that the protected object is not currently being used.
 114       --  This information is used for detecting the type of potentially
 115       --  blocking operations described in the ARM 9.5.1, par. 15 (external
 116       --  calls on a protected subprogram with the same target object as that
 117       --  of the protected action).
 118
 119       Old_Base_Priority : System.Any_Priority;
 120       --  Task's base priority when the protected operation was called
 121
 122       Pending_Action : Boolean;
 123       --  Flag indicating that priority has been dipped temporarily in order
 124       --  to avoid violating the priority ceiling of the lock associated with
 125       --  this protected object, in Lock_Server. The flag tells Unlock_Server
 126       --  or Unlock_And_Update_Server to restore the old priority to
 127       --  Old_Base_Priority. This is needed because of situations (bad
 128       --  language design?) where one needs to lock a PO but to do so would
 129       --  violate the priority ceiling. For example, this can happen when an
 130       --  entry call has been requeued to a lower-priority object, and the
 131       --  caller then tries to cancel the call while its own priority is
 132       --  higher than the ceiling of the new PO.
 133
 134       Finalized : Boolean := False;
 135       --  Set to True by Finalize to make this routine idempotent
 136
 137       Entry_Bodies : Protected_Entry_Body_Access;
 138       --  Pointer to an array containing the executable code for all entry
 139       --  bodies of a protected type.
 140
 141       Find_Body_Index : Find_Body_Index_Access;
 142       --  A function which maps the entry index in a call (which denotes the
 143       --  queue of the proper entry) into the body of the entry.
 144
 145       Entry_Queues : Protected_Entry_Queue_Array (1 .. Num_Entries);
 146
 147       Entry_Names : Protected_Entry_Names_Access := null;
 148       --  An array of string names which denotes entry [family member] names.
 149       --  The structure is indexed by protected entry index and contains Num_
 150       --  Entries components.
 151    end record;
 152
 153    --  No default initial values for this type, since call records will need to
 154    --  be re-initialized before every use.
 155
 156    type Protection_Entries_Access is access all Protection_Entries'Class;
 157    --  See comments in s-tassta.adb about the implicit call to Current_Master
 158    --  generated by this declaration.
 159
 160    function To_Address is
 161      new Ada.Unchecked_Conversion (Protection_Entries_Access, System.Address);
 162    function To_Protection is
 163      new Ada.Unchecked_Conversion (System.Address, Protection_Entries_Access);
 164
 165    function Get_Ceiling
 166      (Object : Protection_Entries_Access) return System.Any_Priority;
 167    --  Returns the new ceiling priority of the protected object
 168
 169    function Has_Interrupt_Or_Attach_Handler
 170      (Object : Protection_Entries_Access) return Boolean;
 171    --  Returns True if an Interrupt_Handler or Attach_Handler pragma applies
 172    --  to the protected object. That is to say this primitive returns False for
 173    --  Protection, but is overridden to return True when interrupt handlers are
 174    --  declared so the check required by C.3.1(11) can be implemented in
 175    --  System.Tasking.Protected_Objects.Initialize_Protection.
 176
 177    procedure Initialize_Protection_Entries
 178      (Object           : Protection_Entries_Access;
 179       Ceiling_Priority : Integer;
 180       Compiler_Info    : System.Address;
 181       Entry_Bodies     : Protected_Entry_Body_Access;
 182       Find_Body_Index  : Find_Body_Index_Access);
 183    --  Initialize the Object parameter so that it can be used by the runtime
 184    --  to keep track of the runtime state of a protected object.
 185
 186    procedure Lock_Entries (Object : Protection_Entries_Access);
 187    --  Lock a protected object for write access. Upon return, the caller owns
 188    --  the lock to this object, and no other call to Lock or Lock_Read_Only
 189    --  with the same argument will return until the corresponding call to
 190    --  Unlock has been made by the caller. Program_Error is raised in case of
 191    --  ceiling violation.
 192
 193    procedure Lock_Entries_With_Status
 194      (Object            : Protection_Entries_Access;
 195       Ceiling_Violation : out Boolean);
 196    --  Same as above, but return the ceiling violation status instead of
 197    --  raising Program_Error.
 198
 199    procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access);
 200    --  Lock a protected object for read access. Upon return, the caller owns
 201    --  the lock for read access, and no other calls to Lock with the same
 202    --  argument will return until the corresponding call to Unlock has been
 203    --  made by the caller. Other calls to Lock_Read_Only may (but need not)
 204    --  return before the call to Unlock, and the corresponding callers will
 205    --  also own the lock for read access.
 206    --
 207    --  Note: we are not currently using this interface, it is provided for
 208    --  possible future use. At the current time, everyone uses Lock for both
 209    --  read and write locks.
 210
 211    function Number_Of_Entries
 212      (Object : Protection_Entries_Access) return Entry_Index;
 213    --  Return the number of entries of a protected object
 214
 215    procedure Set_Ceiling
 216      (Object : Protection_Entries_Access;
 217       Prio   : System.Any_Priority);
 218    --  Sets the new ceiling priority of the protected object
 219
 220    procedure Set_Entry_Names
 221      (Object : Protection_Entries_Access;
 222       Names  : Protected_Entry_Names_Access);
 223    --  Associate an array of string that denote entry [family] names with a
 224    --  protected object.
 225
 226    procedure Unlock_Entries (Object : Protection_Entries_Access);
 227    --  Relinquish ownership of the lock for the object represented by the
 228    --  Object parameter. If this ownership was for write access, or if it was
 229    --  for read access where there are no other read access locks outstanding,
 230    --  one (or more, in the case of Lock_Read_Only) of the tasks waiting on
 231    --  this lock (if any) will be given the lock and allowed to return from
 232    --  the Lock or Lock_Read_Only call.
 233
 234 private
 235
 236    overriding procedure Finalize (Object : in out Protection_Entries);
 237    --  Clean up a Protection object; in particular, finalize the associated
 238    --  Lock object.
 239
 240 end System.Tasking.Protected_Objects.Entries;