gcc/ada/s-tpoben.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 --                               E N T R I E S                              --
   7 --                                                                          --
   8 --                                  S p e c                                 --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2006, Free Software Foundation, Inc.         --
  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- --
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  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
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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.                                              --
  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 --  This package contains all the simple primitives related to
  36 --  Protected_Objects with entries (i.e init, lock, unlock).
  37 --  The handling of protected objects with no entries is done in
  38 --  System.Tasking.Protected_Objects, the complex routines for protected
  39 --  objects with entries in System.Tasking.Protected_Objects.Operations.
  40 --  The split between Entries and Operations is needed to break circular
  41 --  dependencies inside the run time.
  42
  43 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  44 --  Any changes to this interface may require corresponding compiler changes.
  45
  46 with Ada.Finalization;
  47 --  used for Limited_Controlled
  48
  49 with Unchecked_Conversion;
  50
  51 package System.Tasking.Protected_Objects.Entries is
  52    pragma Elaborate_Body;
  53
  54    subtype Positive_Protected_Entry_Index is
  55      Protected_Entry_Index range  1 .. Protected_Entry_Index'Last;
  56
  57    type Find_Body_Index_Access is access
  58      function
  59        (O : System.Address;
  60         E : Protected_Entry_Index)
  61         return Protected_Entry_Index;
  62
  63    type Protected_Entry_Body_Array is
  64      array (Positive_Protected_Entry_Index range <>) of Entry_Body;
  65    --  This is an array of the executable code for all entry bodies of
  66    --  a protected type.
  67
  68    type Protected_Entry_Body_Access is access all Protected_Entry_Body_Array;
  69
  70    type Protected_Entry_Queue_Array is
  71      array (Protected_Entry_Index range <>) of Entry_Queue;
  72
  73    --  This type contains the GNARL state of a protected object. The
  74    --  application-defined portion of the state (i.e. private objects)
  75    --  is maintained by the compiler-generated code.
  76    --  note that there is a simplified version of this type declared in
  77    --  System.Tasking.PO_Simple that handle the simple case (no entries).
  78
  79    type Protection_Entries (Num_Entries : Protected_Entry_Index) is new
  80      Ada.Finalization.Limited_Controlled
  81    with record
  82       L                 : aliased Task_Primitives.Lock;
  83       --  The underlying lock associated with a Protection_Entries.
  84       --  Note that you should never (un)lock Object.L directly, but instead
  85       --  use Lock_Entries/Unlock_Entries.
  86
  87       Compiler_Info : System.Address;
  88       --  Pointer to compiler-generated record representing protected object
  89
  90       Call_In_Progress : Entry_Call_Link;
  91       --  Pointer to the entry call being executed (if any)
  92
  93       Ceiling : System.Any_Priority;
  94       --  Ceiling priority associated with the protected object
  95
  96       New_Ceiling : System.Any_Priority;
  97       --  New ceiling priority associated to the protected object. In case
  98       --  of assignment of a new ceiling priority to the protected object the
  99       --  frontend generates a call to set_ceiling to save the new value in
 100       --  this field. After such assignment this value can be read by means
 101       --  of the 'Priority attribute, which generates a call to get_ceiling.
 102       --  However, the ceiling of the protected object will not be changed
 103       --  until completion of the protected action in which the assignment
 104       --  has been executed (AARM D.5.2 (10/2)).
 105
 106       Owner : Task_Id;
 107       --  This field contains the protected object's owner. Null_Task
 108       --  indicates that the protected object is not currently being used.
 109       --  This information is used for detecting the type of potentially
 110       --  blocking operations described in the ARM 9.5.1, par. 15 (external
 111       --  calls on a protected subprogram with the same target object as that
 112       --  of the protected action).
 113
 114       Old_Base_Priority : System.Any_Priority;
 115       --  Task's base priority when the protected operation was called
 116
 117       Pending_Action  : Boolean;
 118       --  Flag indicating that priority has been dipped temporarily in order
 119       --  to avoid violating the priority ceiling of the lock associated with
 120       --  this protected object, in Lock_Server. The flag tells Unlock_Server
 121       --  or Unlock_And_Update_Server to restore the old priority to
 122       --  Old_Base_Priority. This is needed because of situations (bad
 123       --  language design?) where one needs to lock a PO but to do so would
 124       --  violate the priority ceiling. For example, this can happen when an
 125       --  entry call has been requeued to a lower-priority object, and the
 126       --  caller then tries to cancel the call while its own priority is
 127       --  higher than the ceiling of the new PO.
 128
 129       Finalized : Boolean := False;
 130       --  Set to True by Finalize to make this routine idempotent
 131
 132       Entry_Bodies : Protected_Entry_Body_Access;
 133       --  Pointer to an array containing the executable code for all entry
 134       --  bodies of a protected type.
 135
 136       --  The following function maps the entry index in a call (which denotes
 137       --  the queue to the proper entry) into the body of the entry.
 138
 139       Find_Body_Index : Find_Body_Index_Access;
 140       Entry_Queues      : Protected_Entry_Queue_Array (1 .. Num_Entries);
 141    end record;
 142
 143    --  No default initial values for this type, since call records
 144    --  will need to be re-initialized before every use.
 145
 146    type Protection_Entries_Access is access all Protection_Entries'Class;
 147    --  See comments in s-tassta.adb about the implicit call to Current_Master
 148    --  generated by this declaration.
 149
 150    function To_Address is
 151      new Unchecked_Conversion (Protection_Entries_Access, System.Address);
 152    function To_Protection is
 153      new Unchecked_Conversion (System.Address, Protection_Entries_Access);
 154
 155    function Get_Ceiling
 156      (Object : Protection_Entries_Access) return System.Any_Priority;
 157    --  Returns the new ceiling priority of the protected object
 158
 159    function Has_Interrupt_Or_Attach_Handler
 160      (Object : Protection_Entries_Access) return Boolean;
 161    --  Returns True if an Interrupt_Handler or Attach_Handler pragma applies
 162    --  to the protected object. That is to say this primitive returns False for
 163    --  Protection, but is overriden to return True when interrupt handlers are
 164    --  declared so the check required by C.3.1(11) can be implemented in
 165    --  System.Tasking.Protected_Objects.Initialize_Protection.
 166
 167    procedure Initialize_Protection_Entries
 168      (Object           : Protection_Entries_Access;
 169       Ceiling_Priority : Integer;
 170       Compiler_Info    : System.Address;
 171       Entry_Bodies     : Protected_Entry_Body_Access;
 172       Find_Body_Index  : Find_Body_Index_Access);
 173    --  Initialize the Object parameter so that it can be used by the runtime
 174    --  to keep track of the runtime state of a protected object.
 175
 176    procedure Lock_Entries (Object : Protection_Entries_Access);
 177    --  Lock a protected object for write access. Upon return, the caller owns
 178    --  the lock to this object, and no other call to Lock or Lock_Read_Only
 179    --  with the same argument will return until the corresponding call to
 180    --  Unlock has been made by the caller. Program_Error is raised in case of
 181    --  ceiling violation.
 182
 183    procedure Lock_Entries
 184      (Object : Protection_Entries_Access; Ceiling_Violation : out Boolean);
 185    --  Same as above, but return the ceiling violation status instead of
 186    --  raising Program_Error.
 187
 188    procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access);
 189    --  Lock a protected object for read access. Upon return, the caller owns
 190    --  the lock for read access, and no other calls to Lock with the same
 191    --  argument will return until the corresponding call to Unlock has been
 192    --  made by the caller. Other calls to Lock_Read_Only may (but need not)
 193    --  return before the call to Unlock, and the corresponding callers will
 194    --  also own the lock for read access.
 195    --
 196    --  Note: we are not currently using this interface, it is provided for
 197    --  possible future use. At the current time, everyone uses Lock for both
 198    --  read and write locks.
 199
 200    procedure Set_Ceiling
 201      (Object : Protection_Entries_Access;
 202       Prio   : System.Any_Priority);
 203    --  Sets the new ceiling priority of the protected object
 204
 205    procedure Unlock_Entries (Object : Protection_Entries_Access);
 206    --  Relinquish ownership of the lock for the object represented by the
 207    --  Object parameter. If this ownership was for write access, or if it was
 208    --  for read access where there are no other read access locks outstanding,
 209    --  one (or more, in the case of Lock_Read_Only) of the tasks waiting on
 210    --  this lock (if any) will be given the lock and allowed to return from
 211    --  the Lock or Lock_Read_Only call.
 212
 213 private
 214
 215    procedure Finalize (Object : in out Protection_Entries);
 216    --  Clean up a Protection object; in particular, finalize the associated
 217    --  Lock object.
 218
 219 end System.Tasking.Protected_Objects.Entries;