gcc/ada/s-tpobop.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --               SYSTEM.TASKING.PROTECTED_OBJECTS.OPERATIONS                --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2008, 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 2,  or (at your option) any later ver- --
  14 -- sion. GNARL 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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package contains all the extended primitives related to protected
  35 --  objects with entries.
  36
  37 --  The handling of protected objects with no entries is done in
  38 --  System.Tasking.Protected_Objects, the simple routines for protected
  39 --  objects with entries in System.Tasking.Protected_Objects.Entries. The
  40 --  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.Exceptions;
  47
  48 with System.Tasking.Protected_Objects.Entries;
  49
  50 package System.Tasking.Protected_Objects.Operations is
  51    pragma Elaborate_Body;
  52
  53    type Communication_Block is private;
  54    --  Objects of this type are passed between GNARL calls to allow RTS
  55    --  information to be preserved.
  56
  57    procedure Protected_Entry_Call
  58      (Object             : Entries.Protection_Entries_Access;
  59       E                  : Protected_Entry_Index;
  60       Uninterpreted_Data : System.Address;
  61       Mode               : Call_Modes;
  62       Block              : out Communication_Block);
  63    --  Make a protected entry call to the specified object.
  64    --  Pend a protected entry call on the protected object represented
  65    --  by Object. A pended call is not queued; it may be executed immediately
  66    --  or queued, depending on the state of the entry barrier.
  67    --
  68    --    E
  69    --      The index representing the entry to be called.
  70    --
  71    --    Uninterpreted_Data
  72    --      This will be returned by Next_Entry_Call when this call is serviced.
  73    --      It can be used by the compiler to pass information between the
  74    --      caller and the server, in particular entry parameters.
  75    --
  76    --    Mode
  77    --      The kind of call to be pended
  78    --
  79    --    Block
  80    --      Information passed between runtime calls by the compiler
  81
  82    procedure Timed_Protected_Entry_Call
  83      (Object                : Entries.Protection_Entries_Access;
  84       E                     : Protected_Entry_Index;
  85       Uninterpreted_Data    : System.Address;
  86       Timeout               : Duration;
  87       Mode                  : Delay_Modes;
  88       Entry_Call_Successful : out Boolean);
  89    --  Same as the Protected_Entry_Call but with time-out specified.
  90    --  This routines is used when we do not use ATC mechanism to implement
  91    --  timed entry calls.
  92
  93    procedure Service_Entries (Object : Entries.Protection_Entries_Access);
  94    pragma Inline (Service_Entries);
  95
  96    procedure PO_Service_Entries
  97      (Self_ID       : Task_Id;
  98       Object        : Entries.Protection_Entries_Access;
  99       Unlock_Object : Boolean := True);
 100    --  Service all entry queues of the specified object, executing the
 101    --  corresponding bodies of any queued entry calls that are waiting
 102    --  on True barriers. This is used when the state of a protected
 103    --  object may have changed, in particular after the execution of
 104    --  the statement sequence of a protected procedure.
 105    --
 106    --  Note that servicing an entry may change the value of one or more
 107    --  barriers, so this routine keeps checking barriers until all of
 108    --  them are closed.
 109    --
 110    --  This must be called with abort deferred and with the corresponding
 111    --  object locked.
 112    --
 113    --  If Unlock_Object is set True, then Object is unlocked on return,
 114    --  otherwise Object remains locked and the caller is responsible for
 115    --  the required unlock.
 116
 117    procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
 118    --  Called from within an entry body procedure, indicates that the
 119    --  corresponding entry call has been serviced.
 120
 121    procedure Exceptional_Complete_Entry_Body
 122      (Object : Entries.Protection_Entries_Access;
 123       Ex     : Ada.Exceptions.Exception_Id);
 124    --  Perform all of the functions of Complete_Entry_Body. In addition,
 125    --  report in Ex the exception whose propagation terminated the entry
 126    --  body to the runtime system.
 127
 128    procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
 129    --  Attempt to cancel the most recent protected entry call. If the call is
 130    --  not queued abortably, wait until it is or until it has completed.
 131    --  If the call is actually cancelled, the called object will be
 132    --  locked on return from this call. Get_Cancelled (Block) can be
 133    --  used to determine if the cancellation took place; there
 134    --  may be entries needing service in this case.
 135    --
 136    --  Block passes information between this and other runtime calls.
 137
 138    function Enqueued (Block : Communication_Block) return Boolean;
 139    --  Returns True if the Protected_Entry_Call which returned the
 140    --  specified Block object was queued; False otherwise.
 141
 142    function Cancelled (Block : Communication_Block) return Boolean;
 143    --  Returns True if the Protected_Entry_Call which returned the
 144    --  specified Block object was cancelled, False otherwise.
 145
 146    procedure Requeue_Protected_Entry
 147      (Object     : Entries.Protection_Entries_Access;
 148       New_Object : Entries.Protection_Entries_Access;
 149       E          : Protected_Entry_Index;
 150       With_Abort : Boolean);
 151    --  If Object = New_Object, queue the protected entry call on Object
 152    --   currently being serviced on the queue corresponding to the entry
 153    --   represented by E.
 154    --
 155    --  If Object /= New_Object, transfer the call to New_Object.E,
 156    --   executing or queuing it as appropriate.
 157    --
 158    --  With_Abort---True if the call is to be queued abortably, false
 159    --   otherwise.
 160
 161    procedure Requeue_Task_To_Protected_Entry
 162      (New_Object : Entries.Protection_Entries_Access;
 163       E          : Protected_Entry_Index;
 164       With_Abort : Boolean);
 165    --  Transfer task entry call currently being serviced to entry E
 166    --   on New_Object.
 167    --
 168    --  With_Abort---True if the call is to be queued abortably, false
 169    --   otherwise.
 170
 171    function Protected_Count
 172      (Object : Entries.Protection_Entries'Class;
 173       E      : Protected_Entry_Index)
 174       return   Natural;
 175    --  Return the number of entry calls to E on Object
 176
 177    function Protected_Entry_Caller
 178      (Object : Entries.Protection_Entries'Class) return Task_Id;
 179    --  Return value of E'Caller, where E is the protected entry currently
 180    --  being handled. This will only work if called from within an entry
 181    --  body, as required by the LRM (C.7.1(14)).
 182
 183    --  For internal use only
 184
 185    procedure PO_Do_Or_Queue
 186      (Self_ID    : Task_Id;
 187       Object     : Entries.Protection_Entries_Access;
 188       Entry_Call : Entry_Call_Link);
 189    --  This procedure either executes or queues an entry call, depending
 190    --  on the status of the corresponding barrier. It assumes that abort
 191    --  is deferred and that the specified object is locked.
 192
 193 private
 194    type Communication_Block is record
 195       Self      : Task_Id;
 196       Enqueued  : Boolean := True;
 197       Cancelled : Boolean := False;
 198    end record;
 199    pragma Volatile (Communication_Block);
 200
 201    --  When a program contains limited interfaces, the compiler generates the
 202    --  predefined primitives associated with dispatching selects. One of the
 203    --  parameters of these routines is of type Communication_Block. Even if
 204    --  the program lacks implementing concurrent types, the tasking runtime is
 205    --  dragged in unconditionally because of Communication_Block. To avoid this
 206    --  case, the compiler uses type Dummy_Communication_Block which defined in
 207    --  System.Soft_Links. If the structure of Communication_Block is changed,
 208    --  the corresponding dummy type must be changed as well.
 209
 210    --  The Communication_Block seems to be a relic. At the moment, the
 211    --  compiler seems to be generating unnecessary conditional code based on
 212    --  this block. See the code generated for async. select with task entry
 213    --  call for another way of solving this ???
 214
 215 end System.Tasking.Protected_Objects.Operations;