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+------------------------------------------------------------------------------
+-- --
+-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
+-- --
+-- SYSTEM.TASKING.PROTECTED_OBJECTS.OPERATIONS --
+-- --
+-- S p e c --
+-- --
+-- Copyright (C) 1992-2009, Free Software Foundation, Inc. --
+-- --
+-- GNARL is free software; you can redistribute it and/or modify it under --
+-- terms of the GNU General Public License as published by the Free Soft- --
+-- ware Foundation; either version 3, or (at your option) any later ver- --
+-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE. --
+-- --
+-- As a special exception under Section 7 of GPL version 3, you are granted --
+-- additional permissions described in the GCC Runtime Library Exception, --
+-- version 3.1, as published by the Free Software Foundation. --
+-- --
+-- You should have received a copy of the GNU General Public License and --
+-- a copy of the GCC Runtime Library Exception along with this program; --
+-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
+-- <http://www.gnu.org/licenses/>. --
+-- --
+-- GNARL was developed by the GNARL team at Florida State University. --
+-- Extensive contributions were provided by Ada Core Technologies, Inc. --
+-- --
+------------------------------------------------------------------------------
+
+-- This package contains all the extended primitives related to protected
+-- objects with entries.
+
+-- The handling of protected objects with no entries is done in
+-- System.Tasking.Protected_Objects, the simple routines for protected
+-- objects with entries in System.Tasking.Protected_Objects.Entries. The
+-- split between Entries and Operations is needed to break circular
+-- dependencies inside the run time.
+
+-- Note: the compiler generates direct calls to this interface, via Rtsfind.
+-- Any changes to this interface may require corresponding compiler changes.
+
+with Ada.Exceptions;
+
+with System.Tasking.Protected_Objects.Entries;
+
+package System.Tasking.Protected_Objects.Operations is
+ pragma Elaborate_Body;
+
+ type Communication_Block is private;
+ -- Objects of this type are passed between GNARL calls to allow RTS
+ -- information to be preserved.
+
+ procedure Protected_Entry_Call
+ (Object : Entries.Protection_Entries_Access;
+ E : Protected_Entry_Index;
+ Uninterpreted_Data : System.Address;
+ Mode : Call_Modes;
+ Block : out Communication_Block);
+ -- Make a protected entry call to the specified object.
+ -- Pend a protected entry call on the protected object represented
+ -- by Object. A pended call is not queued; it may be executed immediately
+ -- or queued, depending on the state of the entry barrier.
+ --
+ -- E
+ -- The index representing the entry to be called.
+ --
+ -- Uninterpreted_Data
+ -- This will be returned by Next_Entry_Call when this call is serviced.
+ -- It can be used by the compiler to pass information between the
+ -- caller and the server, in particular entry parameters.
+ --
+ -- Mode
+ -- The kind of call to be pended
+ --
+ -- Block
+ -- Information passed between runtime calls by the compiler
+
+ procedure Timed_Protected_Entry_Call
+ (Object : Entries.Protection_Entries_Access;
+ E : Protected_Entry_Index;
+ Uninterpreted_Data : System.Address;
+ Timeout : Duration;
+ Mode : Delay_Modes;
+ Entry_Call_Successful : out Boolean);
+ -- Same as the Protected_Entry_Call but with time-out specified.
+ -- This routines is used when we do not use ATC mechanism to implement
+ -- timed entry calls.
+
+ procedure Service_Entries (Object : Entries.Protection_Entries_Access);
+ pragma Inline (Service_Entries);
+
+ procedure PO_Service_Entries
+ (Self_ID : Task_Id;
+ Object : Entries.Protection_Entries_Access;
+ Unlock_Object : Boolean := True);
+ -- Service all entry queues of the specified object, executing the
+ -- corresponding bodies of any queued entry calls that are waiting
+ -- on True barriers. This is used when the state of a protected
+ -- object may have changed, in particular after the execution of
+ -- the statement sequence of a protected procedure.
+ --
+ -- Note that servicing an entry may change the value of one or more
+ -- barriers, so this routine keeps checking barriers until all of
+ -- them are closed.
+ --
+ -- This must be called with abort deferred and with the corresponding
+ -- object locked.
+ --
+ -- If Unlock_Object is set True, then Object is unlocked on return,
+ -- otherwise Object remains locked and the caller is responsible for
+ -- the required unlock.
+
+ procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
+ -- Called from within an entry body procedure, indicates that the
+ -- corresponding entry call has been serviced.
+
+ procedure Exceptional_Complete_Entry_Body
+ (Object : Entries.Protection_Entries_Access;
+ Ex : Ada.Exceptions.Exception_Id);
+ -- Perform all of the functions of Complete_Entry_Body. In addition,
+ -- report in Ex the exception whose propagation terminated the entry
+ -- body to the runtime system.
+
+ procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
+ -- Attempt to cancel the most recent protected entry call. If the call is
+ -- not queued abortably, wait until it is or until it has completed.
+ -- If the call is actually cancelled, the called object will be
+ -- locked on return from this call. Get_Cancelled (Block) can be
+ -- used to determine if the cancellation took place; there
+ -- may be entries needing service in this case.
+ --
+ -- Block passes information between this and other runtime calls.
+
+ function Enqueued (Block : Communication_Block) return Boolean;
+ -- Returns True if the Protected_Entry_Call which returned the
+ -- specified Block object was queued; False otherwise.
+
+ function Cancelled (Block : Communication_Block) return Boolean;
+ -- Returns True if the Protected_Entry_Call which returned the
+ -- specified Block object was cancelled, False otherwise.
+
+ procedure Requeue_Protected_Entry
+ (Object : Entries.Protection_Entries_Access;
+ New_Object : Entries.Protection_Entries_Access;
+ E : Protected_Entry_Index;
+ With_Abort : Boolean);
+ -- If Object = New_Object, queue the protected entry call on Object
+ -- currently being serviced on the queue corresponding to the entry
+ -- represented by E.
+ --
+ -- If Object /= New_Object, transfer the call to New_Object.E,
+ -- executing or queuing it as appropriate.
+ --
+ -- With_Abort---True if the call is to be queued abortably, false
+ -- otherwise.
+
+ procedure Requeue_Task_To_Protected_Entry
+ (New_Object : Entries.Protection_Entries_Access;
+ E : Protected_Entry_Index;
+ With_Abort : Boolean);
+ -- Transfer task entry call currently being serviced to entry E
+ -- on New_Object.
+ --
+ -- With_Abort---True if the call is to be queued abortably, false
+ -- otherwise.
+
+ function Protected_Count
+ (Object : Entries.Protection_Entries'Class;
+ E : Protected_Entry_Index)
+ return Natural;
+ -- Return the number of entry calls to E on Object
+
+ function Protected_Entry_Caller
+ (Object : Entries.Protection_Entries'Class) return Task_Id;
+ -- Return value of E'Caller, where E is the protected entry currently
+ -- being handled. This will only work if called from within an entry
+ -- body, as required by the LRM (C.7.1(14)).
+
+ -- For internal use only
+
+ procedure PO_Do_Or_Queue
+ (Self_ID : Task_Id;
+ Object : Entries.Protection_Entries_Access;
+ Entry_Call : Entry_Call_Link);
+ -- This procedure either executes or queues an entry call, depending
+ -- on the status of the corresponding barrier. It assumes that abort
+ -- is deferred and that the specified object is locked.
+
+private
+ type Communication_Block is record
+ Self : Task_Id;
+ Enqueued : Boolean := True;
+ Cancelled : Boolean := False;
+ end record;
+ pragma Volatile (Communication_Block);
+
+ -- When a program contains limited interfaces, the compiler generates the
+ -- predefined primitives associated with dispatching selects. One of the
+ -- parameters of these routines is of type Communication_Block. Even if
+ -- the program lacks implementing concurrent types, the tasking runtime is
+ -- dragged in unconditionally because of Communication_Block. To avoid this
+ -- case, the compiler uses type Dummy_Communication_Block which defined in
+ -- System.Soft_Links. If the structure of Communication_Block is changed,
+ -- the corresponding dummy type must be changed as well.
+
+ -- The Communication_Block seems to be a relic. At the moment, the
+ -- compiler seems to be generating unnecessary conditional code based on
+ -- this block. See the code generated for async. select with task entry
+ -- call for another way of solving this ???
+
+end System.Tasking.Protected_Objects.Operations;