gcc/ada/libgnarl/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) 1992-2024, 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    --  Index of the entry (and in some cases of the queue)
  54
  55    type Find_Body_Index_Access is access
  56      function
  57        (O : System.Address;
  58         E : Protected_Entry_Index)
  59         return Protected_Entry_Index;
  60    --  Convert a queue index to an entry index (an entry family has one entry
  61    --  index for several queue indexes).
  62
  63    type Protected_Entry_Body_Array is
  64      array (Positive_Protected_Entry_Index range <>) of Entry_Body;
  65    --  Contains executable code for all entry bodies of a protected type
  66
  67    type Protected_Entry_Body_Access is
  68      access constant Protected_Entry_Body_Array;
  69
  70    type Protected_Entry_Queue_Array is
  71      array (Protected_Entry_Index range <>) of Entry_Queue;
  72
  73    type Protected_Entry_Queue_Max_Array is
  74      array (Positive_Protected_Entry_Index range <>) of Natural;
  75
  76    type Protected_Entry_Queue_Max_Access is
  77      access constant Protected_Entry_Queue_Max_Array;
  78
  79    --  The following type contains the GNARL state of a protected object.
  80    --  The application-defined portion of the state (i.e. private objects)
  81    --  is maintained by the compiler-generated code. Note that there is a
  82    --  simplified version of this type declared in System.Tasking.PO_Simple
  83    --  that handle the simple case (no entries).
  84
  85    type Protection_Entries (Num_Entries : Protected_Entry_Index) is new
  86      Ada.Finalization.Limited_Controlled
  87    with record
  88       L : aliased Task_Primitives.Lock;
  89       --  The underlying lock associated with a Protection_Entries. Note
  90       --  that you should never (un)lock Object.L directly, but instead
  91       --  use Lock_Entries/Unlock_Entries.
  92
  93       Compiler_Info : System.Address;
  94       --  Pointer to compiler-generated record representing protected object
  95
  96       Call_In_Progress : Entry_Call_Link;
  97       --  Pointer to the entry call being executed (if any)
  98
  99       Ceiling : System.Any_Priority;
 100       --  Ceiling priority associated with the protected object
 101
 102       New_Ceiling : System.Any_Priority;
 103       --  New ceiling priority associated to the protected object. In case
 104       --  of assignment of a new ceiling priority to the protected object the
 105       --  frontend generates a call to set_ceiling to save the new value in
 106       --  this field. After such assignment this value can be read by means
 107       --  of the 'Priority attribute, which generates a call to get_ceiling.
 108       --  However, the ceiling of the protected object will not be changed
 109       --  until completion of the protected action in which the assignment
 110       --  has been executed (AARM D.5.2 (10/2)).
 111
 112       Owner : Task_Id;
 113       --  This field contains the protected object's owner. Null_Task
 114       --  indicates that the protected object is not currently being used.
 115       --  This information is used for detecting the type of potentially
 116       --  blocking operations described in the ARM 9.5.1, par. 15 (external
 117       --  calls on a protected subprogram with the same target object as that
 118       --  of the protected action).
 119
 120       Old_Base_Priority : System.Any_Priority;
 121       --  Task's base priority when the protected operation was called
 122
 123       Pending_Action : Boolean;
 124       --  Flag indicating that priority has been dipped temporarily in order
 125       --  to avoid violating the priority ceiling of the lock associated with
 126       --  this protected object, in Lock_Server. The flag tells Unlock_Server
 127       --  or Unlock_And_Update_Server to restore the old priority to
 128       --  Old_Base_Priority. This is needed because of situations (bad
 129       --  language design?) where one needs to lock a PO but to do so would
 130       --  violate the priority ceiling. For example, this can happen when an
 131       --  entry call has been requeued to a lower-priority object, and the
 132       --  caller then tries to cancel the call while its own priority is
 133       --  higher than the ceiling of the new PO.
 134
 135       Finalized : Boolean := False;
 136       --  Set to True by Finalize to make this routine idempotent
 137
 138       Entry_Bodies : Protected_Entry_Body_Access;
 139       --  Pointer to an array containing the executable code for all entry
 140       --  bodies of a protected type.
 141
 142       Find_Body_Index : Find_Body_Index_Access;
 143       --  A function which maps the entry index in a call (which denotes the
 144       --  queue of the proper entry) into the body of the entry.
 145
 146       Entry_Queue_Maxes : Protected_Entry_Queue_Max_Access;
 147       --  Access to an array of naturals representing the max value for each
 148       --  entry's queue length. A value of 0 signifies no max.
 149
 150       Entry_Queues : Protected_Entry_Queue_Array (1 .. Num_Entries);
 151       --  Action and barrier subprograms for the protected type.
 152    end record;
 153
 154    --  No default initial values for this type, since call records will need to
 155    --  be re-initialized before every use.
 156
 157    type Protection_Entries_Access is access all Protection_Entries'Class;
 158    --  See comments in s-tassta.adb about the implicit call to Current_Master
 159    --  generated by this declaration.
 160
 161    function To_Address is
 162      new Ada.Unchecked_Conversion (Protection_Entries_Access, System.Address);
 163    function To_Protection is
 164      new Ada.Unchecked_Conversion (System.Address, Protection_Entries_Access);
 165
 166    function Get_Ceiling
 167      (Object : Protection_Entries_Access) return System.Any_Priority;
 168    --  Returns the new ceiling priority of the protected object
 169
 170    function Has_Interrupt_Or_Attach_Handler
 171      (Object : Protection_Entries_Access) return Boolean;
 172    --  Returns True if an Interrupt_Handler or Attach_Handler pragma applies
 173    --  to the protected object. That is to say this primitive returns False for
 174    --  Protection, but is overridden to return True when interrupt handlers are
 175    --  declared so the check required by C.3.1(11) can be implemented in
 176    --  System.Tasking.Protected_Objects.Initialize_Protection.
 177
 178    procedure Initialize_Protection_Entries
 179      (Object            : Protection_Entries_Access;
 180       Ceiling_Priority  : Integer;
 181       Compiler_Info     : System.Address;
 182       Entry_Queue_Maxes : Protected_Entry_Queue_Max_Access;
 183       Entry_Bodies      : Protected_Entry_Body_Access;
 184       Find_Body_Index   : Find_Body_Index_Access);
 185    --  Initialize the Object parameter so that it can be used by the runtime
 186    --  to keep track of the runtime state of a protected object.
 187
 188    procedure Lock_Entries (Object : Protection_Entries_Access);
 189    --  Lock a protected object for write access. Upon return, the caller owns
 190    --  the lock to this object, and no other call to Lock or Lock_Read_Only
 191    --  with the same argument will return until the corresponding call to
 192    --  Unlock has been made by the caller. Program_Error is raised in case
 193    --  of ceiling violation, or if the protected object has already been
 194    --  finalized, or if Detect_Blocking is true and the protected object
 195    --  is already locked by the current task. In the Program_Error cases,
 196    --  the object is not locked.
 197
 198    procedure Lock_Entries_With_Status
 199      (Object            : Protection_Entries_Access;
 200       Ceiling_Violation : out Boolean);
 201    --  Same as above, but return the ceiling violation status instead of
 202    --  raising Program_Error. This raises Program_Error in the other
 203    --  cases mentioned for Lock_Entries. In the Program_Error cases,
 204    --  the object is not locked.
 205
 206    procedure Lock_Read_Only_Entries (Object : Protection_Entries_Access);
 207    --  Lock a protected object for read access. Upon return, the caller owns
 208    --  the lock for read access, and no other calls to Lock with the same
 209    --  argument will return until the corresponding call to Unlock has been
 210    --  made by the caller. Other calls to Lock_Read_Only may (but need not)
 211    --  return before the call to Unlock, and the corresponding callers will
 212    --  also own the lock for read access.
 213    --
 214    --  Note: we are not currently using this interface, it is provided for
 215    --  possible future use. At the current time, everyone uses Lock for both
 216    --  read and write locks.
 217
 218    function Number_Of_Entries
 219      (Object : Protection_Entries_Access) return Entry_Index;
 220    --  Return the number of entries of a protected object
 221
 222    procedure Set_Ceiling
 223      (Object : Protection_Entries_Access;
 224       Prio   : System.Any_Priority);
 225    --  Sets the new ceiling priority of the protected object
 226
 227    procedure Unlock_Entries (Object : Protection_Entries_Access);
 228    --  Relinquish ownership of the lock for the object represented by the
 229    --  Object parameter. If this ownership was for write access, or if it was
 230    --  for read access where there are no other read access locks outstanding,
 231    --  one (or more, in the case of Lock_Read_Only) of the tasks waiting on
 232    --  this lock (if any) will be given the lock and allowed to return from
 233    --  the Lock or Lock_Read_Only call.
 234
 235 private
 236
 237    overriding procedure Finalize (Object : in out Protection_Entries);
 238    --  Clean up a Protection object; in particular, finalize the associated
 239    --  Lock object.
 240
 241 end System.Tasking.Protected_Objects.Entries;