gcc/ada/s-tpobop.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 --                             O P E R A T I O N S                          --
   7 --                                                                          --
   8 --                                  S p e c                                 --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2005, 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- --
  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,  51  Franklin  Street,  Fifth  Floor, --
  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 extended primitives related to protected
  36 --  objects with entries.
  37
  38 --  The handling of protected objects with no entries is done in
  39 --  System.Tasking.Protected_Objects, the simple routines for protected
  40 --  objects with entries in System.Tasking.Protected_Objects.Entries. The
  41 --  split between Entries and Operations is needed to break circular
  42 --  dependencies inside the run time.
  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
  47 with Ada.Exceptions;
  48 --  Used for Exception_Id
  49
  50 with System.Tasking.Protected_Objects.Entries;
  51
  52 package System.Tasking.Protected_Objects.Operations is
  53    pragma Elaborate_Body;
  54
  55    type Communication_Block is private;
  56    --  Objects of this type are passed between GNARL calls to allow RTS
  57    --  information to be preserved.
  58
  59    procedure Protected_Entry_Call
  60      (Object             : Entries.Protection_Entries_Access;
  61       E                  : Protected_Entry_Index;
  62       Uninterpreted_Data : System.Address;
  63       Mode               : Call_Modes;
  64       Block              : out Communication_Block);
  65    --  Make a protected entry call to the specified object.
  66    --  Pend a protected entry call on the protected object represented
  67    --  by Object. A pended call is not queued; it may be executed immediately
  68    --  or queued, depending on the state of the entry barrier.
  69    --
  70    --    E
  71    --      The index representing the entry to be called.
  72    --
  73    --    Uninterpreted_Data
  74    --      This will be returned by Next_Entry_Call when this call is serviced.
  75    --      It can be used by the compiler to pass information between the
  76    --      caller and the server, in particular entry parameters.
  77    --
  78    --    Mode
  79    --      The kind of call to be pended
  80    --
  81    --    Block
  82    --      Information passed between runtime calls by the compiler
  83
  84    procedure Timed_Protected_Entry_Call
  85      (Object                : Entries.Protection_Entries_Access;
  86       E                     : Protected_Entry_Index;
  87       Uninterpreted_Data    : System.Address;
  88       Timeout               : Duration;
  89       Mode                  : Delay_Modes;
  90       Entry_Call_Successful : out Boolean);
  91       --  Same as the Protected_Entry_Call but with time-out specified.
  92       --  This routines is used when we do not use ATC mechanism to implement
  93       --  timed entry calls.
  94
  95    procedure Service_Entries (Object : Entries.Protection_Entries_Access);
  96    pragma Inline (Service_Entries);
  97
  98    procedure PO_Service_Entries
  99      (Self_ID       : Task_Id;
 100       Object        : Entries.Protection_Entries_Access;
 101       Unlock_Object : Boolean := True);
 102    --  Service all entry queues of the specified object, executing the
 103    --  corresponding bodies of any queued entry calls that are waiting
 104    --  on True barriers. This is used when the state of a protected
 105    --  object may have changed, in particular after the execution of
 106    --  the statement sequence of a protected procedure.
 107    --
 108    --  Note that servicing an entry may change the value of one or more
 109    --  barriers, so this routine keeps checking barriers until all of
 110    --  them are closed.
 111    --
 112    --  This must be called with abort deferred and with the corresponding
 113    --  object locked.
 114    --
 115    --  If Unlock_Object is set True, then Object is unlocked on return,
 116    --  otherwise Object remains locked and the caller is responsible for
 117    --  the required unlock.
 118
 119    procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
 120    --  Called from within an entry body procedure, indicates that the
 121    --  corresponding entry call has been serviced.
 122
 123    procedure Exceptional_Complete_Entry_Body
 124      (Object : Entries.Protection_Entries_Access;
 125       Ex     : Ada.Exceptions.Exception_Id);
 126    --  Perform all of the functions of Complete_Entry_Body. In addition,
 127    --  report in Ex the exception whose propagation terminated the entry
 128    --  body to the runtime system.
 129
 130    procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
 131    --  Attempt to cancel the most recent protected entry call. If the call is
 132    --  not queued abortably, wait until it is or until it has completed.
 133    --  If the call is actually cancelled, the called object will be
 134    --  locked on return from this call. Get_Cancelled (Block) can be
 135    --  used to determine if the cancellation took place; there
 136    --  may be entries needing service in this case.
 137    --
 138    --  Block passes information between this and other runtime calls.
 139
 140    function Enqueued (Block : Communication_Block) return Boolean;
 141    --  Returns True if the Protected_Entry_Call which returned the
 142    --  specified Block object was queued; False otherwise.
 143
 144    function Cancelled (Block : Communication_Block) return Boolean;
 145    --  Returns True if the Protected_Entry_Call which returned the
 146    --  specified Block object was cancelled, False otherwise.
 147
 148    procedure Requeue_Protected_Entry
 149      (Object     : Entries.Protection_Entries_Access;
 150       New_Object : Entries.Protection_Entries_Access;
 151       E          : Protected_Entry_Index;
 152       With_Abort : Boolean);
 153    --  If Object = New_Object, queue the protected entry call on Object
 154    --   currently being serviced on the queue corresponding to the entry
 155    --   represented by E.
 156    --
 157    --  If Object /= New_Object, transfer the call to New_Object.E,
 158    --   executing or queuing it as appropriate.
 159    --
 160    --  With_Abort---True if the call is to be queued abortably, false
 161    --   otherwise.
 162
 163    procedure Requeue_Task_To_Protected_Entry
 164      (New_Object : Entries.Protection_Entries_Access;
 165       E          : Protected_Entry_Index;
 166       With_Abort : Boolean);
 167    --  Transfer task entry call currently being serviced to entry E
 168    --   on New_Object.
 169    --
 170    --  With_Abort---True if the call is to be queued abortably, false
 171    --   otherwise.
 172
 173    function Protected_Count
 174      (Object : Entries.Protection_Entries'Class;
 175       E      : Protected_Entry_Index)
 176       return   Natural;
 177    --  Return the number of entry calls to E on Object
 178
 179    function Protected_Entry_Caller
 180      (Object : Entries.Protection_Entries'Class) return Task_Id;
 181    --  Return value of E'Caller, where E is the protected entry currently
 182    --  being handled. This will only work if called from within an entry
 183    --  body, as required by the LRM (C.7.1(14)).
 184
 185    --  For internal use only
 186
 187    procedure PO_Do_Or_Queue
 188      (Self_ID    : Task_Id;
 189       Object     : Entries.Protection_Entries_Access;
 190       Entry_Call : Entry_Call_Link;
 191       With_Abort : Boolean);
 192    --  This procedure either executes or queues an entry call, depending
 193    --  on the status of the corresponding barrier. It assumes that abort
 194    --  is deferred and that the specified object is locked.
 195
 196 private
 197    type Communication_Block is record
 198       Self      : Task_Id;
 199       Enqueued  : Boolean := True;
 200       Cancelled : Boolean := False;
 201    end record;
 202    pragma Volatile (Communication_Block);
 203
 204    --  ?????
 205    --  The Communication_Block seems to be a relic. At the moment, the
 206    --  compiler seems to be generating unnecessary conditional code based on
 207    --  this block. See the code generated for async. select with task entry
 208    --  call for another way of solving this.
 209
 210 end System.Tasking.Protected_Objects.Operations;