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) 1992-2009, 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 the extended primitives related to protected
  33 --  objects with entries.
  34
  35 --  The handling of protected objects with no entries is done in
  36 --  System.Tasking.Protected_Objects, the simple routines for protected
  37 --  objects with entries in System.Tasking.Protected_Objects.Entries. The
  38 --  split between Entries and Operations is needed to break circular
  39 --  dependencies inside the run time.
  40
  41 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  42 --  Any changes to this interface may require corresponding compiler changes.
  43
  44 with Ada.Exceptions;
  45
  46 with System.Tasking.Protected_Objects.Entries;
  47
  48 package System.Tasking.Protected_Objects.Operations is
  49    pragma Elaborate_Body;
  50
  51    type Communication_Block is private;
  52    --  Objects of this type are passed between GNARL calls to allow RTS
  53    --  information to be preserved.
  54
  55    procedure Protected_Entry_Call
  56      (Object             : Entries.Protection_Entries_Access;
  57       E                  : Protected_Entry_Index;
  58       Uninterpreted_Data : System.Address;
  59       Mode               : Call_Modes;
  60       Block              : out Communication_Block);
  61    --  Make a protected entry call to the specified object.
  62    --  Pend a protected entry call on the protected object represented
  63    --  by Object. A pended call is not queued; it may be executed immediately
  64    --  or queued, depending on the state of the entry barrier.
  65    --
  66    --    E
  67    --      The index representing the entry to be called.
  68    --
  69    --    Uninterpreted_Data
  70    --      This will be returned by Next_Entry_Call when this call is serviced.
  71    --      It can be used by the compiler to pass information between the
  72    --      caller and the server, in particular entry parameters.
  73    --
  74    --    Mode
  75    --      The kind of call to be pended
  76    --
  77    --    Block
  78    --      Information passed between runtime calls by the compiler
  79
  80    procedure Timed_Protected_Entry_Call
  81      (Object                : Entries.Protection_Entries_Access;
  82       E                     : Protected_Entry_Index;
  83       Uninterpreted_Data    : System.Address;
  84       Timeout               : Duration;
  85       Mode                  : Delay_Modes;
  86       Entry_Call_Successful : out Boolean);
  87    --  Same as the Protected_Entry_Call but with time-out specified.
  88    --  This routines is used when we do not use ATC mechanism to implement
  89    --  timed entry calls.
  90
  91    procedure Service_Entries (Object : Entries.Protection_Entries_Access);
  92    pragma Inline (Service_Entries);
  93
  94    procedure PO_Service_Entries
  95      (Self_ID       : Task_Id;
  96       Object        : Entries.Protection_Entries_Access;
  97       Unlock_Object : Boolean := True);
  98    --  Service all entry queues of the specified object, executing the
  99    --  corresponding bodies of any queued entry calls that are waiting
 100    --  on True barriers. This is used when the state of a protected
 101    --  object may have changed, in particular after the execution of
 102    --  the statement sequence of a protected procedure.
 103    --
 104    --  Note that servicing an entry may change the value of one or more
 105    --  barriers, so this routine keeps checking barriers until all of
 106    --  them are closed.
 107    --
 108    --  This must be called with abort deferred and with the corresponding
 109    --  object locked.
 110    --
 111    --  If Unlock_Object is set True, then Object is unlocked on return,
 112    --  otherwise Object remains locked and the caller is responsible for
 113    --  the required unlock.
 114
 115    procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
 116    --  Called from within an entry body procedure, indicates that the
 117    --  corresponding entry call has been serviced.
 118
 119    procedure Exceptional_Complete_Entry_Body
 120      (Object : Entries.Protection_Entries_Access;
 121       Ex     : Ada.Exceptions.Exception_Id);
 122    --  Perform all of the functions of Complete_Entry_Body. In addition,
 123    --  report in Ex the exception whose propagation terminated the entry
 124    --  body to the runtime system.
 125
 126    procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
 127    --  Attempt to cancel the most recent protected entry call. If the call is
 128    --  not queued abortably, wait until it is or until it has completed.
 129    --  If the call is actually cancelled, the called object will be
 130    --  locked on return from this call. Get_Cancelled (Block) can be
 131    --  used to determine if the cancellation took place; there
 132    --  may be entries needing service in this case.
 133    --
 134    --  Block passes information between this and other runtime calls.
 135
 136    function Enqueued (Block : Communication_Block) return Boolean;
 137    --  Returns True if the Protected_Entry_Call which returned the
 138    --  specified Block object was queued; False otherwise.
 139
 140    function Cancelled (Block : Communication_Block) return Boolean;
 141    --  Returns True if the Protected_Entry_Call which returned the
 142    --  specified Block object was cancelled, False otherwise.
 143
 144    procedure Requeue_Protected_Entry
 145      (Object     : Entries.Protection_Entries_Access;
 146       New_Object : Entries.Protection_Entries_Access;
 147       E          : Protected_Entry_Index;
 148       With_Abort : Boolean);
 149    --  If Object = New_Object, queue the protected entry call on Object
 150    --   currently being serviced on the queue corresponding to the entry
 151    --   represented by E.
 152    --
 153    --  If Object /= New_Object, transfer the call to New_Object.E,
 154    --   executing or queuing it as appropriate.
 155    --
 156    --  With_Abort---True if the call is to be queued abortably, false
 157    --   otherwise.
 158
 159    procedure Requeue_Task_To_Protected_Entry
 160      (New_Object : Entries.Protection_Entries_Access;
 161       E          : Protected_Entry_Index;
 162       With_Abort : Boolean);
 163    --  Transfer task entry call currently being serviced to entry E
 164    --   on New_Object.
 165    --
 166    --  With_Abort---True if the call is to be queued abortably, false
 167    --   otherwise.
 168
 169    function Protected_Count
 170      (Object : Entries.Protection_Entries'Class;
 171       E      : Protected_Entry_Index)
 172       return   Natural;
 173    --  Return the number of entry calls to E on Object
 174
 175    function Protected_Entry_Caller
 176      (Object : Entries.Protection_Entries'Class) return Task_Id;
 177    --  Return value of E'Caller, where E is the protected entry currently
 178    --  being handled. This will only work if called from within an entry
 179    --  body, as required by the LRM (C.7.1(14)).
 180
 181    --  For internal use only
 182
 183    procedure PO_Do_Or_Queue
 184      (Self_ID    : Task_Id;
 185       Object     : Entries.Protection_Entries_Access;
 186       Entry_Call : Entry_Call_Link);
 187    --  This procedure either executes or queues an entry call, depending
 188    --  on the status of the corresponding barrier. It assumes that abort
 189    --  is deferred and that the specified object is locked.
 190
 191 private
 192    type Communication_Block is record
 193       Self      : Task_Id;
 194       Enqueued  : Boolean := True;
 195       Cancelled : Boolean := False;
 196    end record;
 197    pragma Volatile (Communication_Block);
 198
 199    --  When a program contains limited interfaces, the compiler generates the
 200    --  predefined primitives associated with dispatching selects. One of the
 201    --  parameters of these routines is of type Communication_Block. Even if
 202    --  the program lacks implementing concurrent types, the tasking runtime is
 203    --  dragged in unconditionally because of Communication_Block. To avoid this
 204    --  case, the compiler uses type Dummy_Communication_Block which defined in
 205    --  System.Soft_Links. If the structure of Communication_Block is changed,
 206    --  the corresponding dummy type must be changed as well.
 207
 208    --  The Communication_Block seems to be a relic. At the moment, the
 209    --  compiler seems to be generating unnecessary conditional code based on
 210    --  this block. See the code generated for async. select with task entry
 211    --  call for another way of solving this ???
 212
 213 end System.Tasking.Protected_Objects.Operations;