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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- 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 . --
-- S I N G L E _ E N T R Y --
-- --
-- B o d y --
-- --
-- Copyright (C) 1998-2005, 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 2, or (at your option) any later ver- --
-- sion. GNARL 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNARL; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNARL was developed by the GNARL team at Florida State University. --
-- Extensive contributions were provided by Ada Core Technologies, Inc. --
-- --
------------------------------------------------------------------------------
pragma Style_Checks (All_Checks);
-- Turn off subprogram ordering check, since restricted GNARLI
-- subprograms are gathered together at end.
-- This package provides an optimized version of Protected_Objects.Operations
-- and Protected_Objects.Entries making the following assumptions:
-- PO has only one entry
-- There is only one caller at a time (No_Entry_Queue)
-- There is no dynamic priority support (No_Dynamic_Priorities)
-- No Abort Statements
-- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
-- PO are at library level
-- No Requeue
-- None of the tasks will terminate (no need for finalization)
-- This interface is intended to be used in the ravenscar and restricted
-- profiles, the compiler is responsible for ensuring that the conditions
-- mentioned above are respected, except for the No_Entry_Queue restriction
-- that is checked dynamically in this package, since the check cannot be
-- performed at compile time, and is relatively cheap (see PO_Do_Or_Queue,
-- Service_Entry).
pragma Polling (Off);
-- Turn off polling, we do not want polling to take place during tasking
-- operations. It can cause infinite loops and other problems.
pragma Suppress (All_Checks);
with System.Task_Primitives.Operations;
-- used for Self
-- Finalize_Lock
-- Write_Lock
-- Unlock
with Ada.Exceptions;
-- used for Exception_Id
-- Raise_Exception
with System.Parameters;
-- used for Single_Lock
package body System.Tasking.Protected_Objects.Single_Entry is
package STPO renames System.Task_Primitives.Operations;
use Parameters;
-----------------------
-- Local Subprograms --
-----------------------
procedure Send_Program_Error
(Self_Id : Task_Id;
Entry_Call : Entry_Call_Link);
pragma Inline (Send_Program_Error);
-- Raise Program_Error in the caller of the specified entry call
--------------------------
-- Entry Calls Handling --
--------------------------
procedure Wakeup_Entry_Caller
(Self_ID : Task_Id;
Entry_Call : Entry_Call_Link;
New_State : Entry_Call_State);
pragma Inline (Wakeup_Entry_Caller);
-- This is called at the end of service of an entry call,
-- to abort the caller if he is in an abortable part, and
-- to wake up the caller if he is on Entry_Caller_Sleep.
-- Call it holding the lock of Entry_Call.Self.
--
-- Timed_Call or Simple_Call:
-- The caller is waiting on Entry_Caller_Sleep, in
-- Wait_For_Completion, or Wait_For_Completion_With_Timeout.
procedure Wait_For_Completion (Entry_Call : Entry_Call_Link);
pragma Inline (Wait_For_Completion);
-- This procedure suspends the calling task until the specified entry call
-- has either been completed or cancelled. On exit, the call will not be
-- queued. This waits for calls on protected entries.
-- Call this only when holding Self_ID locked.
procedure Wait_For_Completion_With_Timeout
(Entry_Call : Entry_Call_Link;
Wakeup_Time : Duration;
Mode : Delay_Modes);
-- Same as Wait_For_Completion but it waits for a timeout with the value
-- specified in Wakeup_Time as well.
procedure Check_Exception
(Self_ID : Task_Id;
Entry_Call : Entry_Call_Link);
pragma Inline (Check_Exception);
-- Raise any pending exception from the Entry_Call.
-- This should be called at the end of every compiler interface procedure
-- that implements an entry call.
-- The caller should not be holding any locks, or there will be deadlock.
procedure PO_Do_Or_Queue
(Self_Id : Task_Id;
Object : Protection_Entry_Access;
Entry_Call : Entry_Call_Link);
-- This procedure executes or queues an entry call, depending
-- on the status of the corresponding barrier. It assumes that the
-- specified object is locked.
---------------------
-- Check_Exception --
---------------------
procedure Check_Exception
(Self_ID : Task_Id;
Entry_Call : Entry_Call_Link)
is
pragma Warnings (Off, Self_ID);
procedure Internal_Raise (X : Ada.Exceptions.Exception_Id);
pragma Import (C, Internal_Raise, "__gnat_raise_with_msg");
use type Ada.Exceptions.Exception_Id;
E : constant Ada.Exceptions.Exception_Id :=
Entry_Call.Exception_To_Raise;
begin
if E /= Ada.Exceptions.Null_Id then
Internal_Raise (E);
end if;
end Check_Exception;
------------------------
-- Send_Program_Error --
------------------------
procedure Send_Program_Error
(Self_Id : Task_Id;
Entry_Call : Entry_Call_Link)
is
Caller : constant Task_Id := Entry_Call.Self;
begin
Entry_Call.Exception_To_Raise := Program_Error'Identity;
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Caller);
Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
STPO.Unlock (Caller);
if Single_Lock then
STPO.Unlock_RTS;
end if;
end Send_Program_Error;
-------------------------
-- Wait_For_Completion --
-------------------------
procedure Wait_For_Completion (Entry_Call : Entry_Call_Link) is
Self_Id : constant Task_Id := Entry_Call.Self;
begin
Self_Id.Common.State := Entry_Caller_Sleep;
STPO.Sleep (Self_Id, Entry_Caller_Sleep);
Self_Id.Common.State := Runnable;
end Wait_For_Completion;
--------------------------------------
-- Wait_For_Completion_With_Timeout --
--------------------------------------
procedure Wait_For_Completion_With_Timeout
(Entry_Call : Entry_Call_Link;
Wakeup_Time : Duration;
Mode : Delay_Modes)
is
Self_Id : constant Task_Id := Entry_Call.Self;
Timedout : Boolean;
Yielded : Boolean;
use type Ada.Exceptions.Exception_Id;
begin
-- This procedure waits for the entry call to be served, with a timeout.
-- It tries to cancel the call if the timeout expires before the call is
-- served.
-- If we wake up from the timed sleep operation here, it may be for the
-- following possible reasons:
-- 1) The entry call is done being served.
-- 2) The timeout has expired (Timedout = True)
-- Once the timeout has expired we may need to continue to wait if the
-- call is already being serviced. In that case, we want to go back to
-- sleep, but without any timeout. The variable Timedout is used to
-- control this. If the Timedout flag is set, we do not need to Sleep
-- with a timeout. We just sleep until we get a wakeup for some status
-- change.
pragma Assert (Entry_Call.Mode = Timed_Call);
Self_Id.Common.State := Entry_Caller_Sleep;
STPO.Timed_Sleep
(Self_Id, Wakeup_Time, Mode, Entry_Caller_Sleep, Timedout, Yielded);
if Timedout then
Entry_Call.State := Cancelled;
else
Entry_Call.State := Done;
end if;
Self_Id.Common.State := Runnable;
end Wait_For_Completion_With_Timeout;
-------------------------
-- Wakeup_Entry_Caller --
-------------------------
-- This is called at the end of service of an entry call, to abort the
-- caller if he is in an abortable part, and to wake up the caller if it
-- is on Entry_Caller_Sleep. It assumes that the call is already off-queue.
-- (This enforces the rule that a task must be off-queue if its state is
-- Done or Cancelled.) Call it holding the lock of Entry_Call.Self.
-- Timed_Call or Simple_Call:
-- The caller is waiting on Entry_Caller_Sleep, in
-- Wait_For_Completion, or Wait_For_Completion_With_Timeout.
-- Conditional_Call:
-- The caller might be in Wait_For_Completion,
-- waiting for a rendezvous (possibly requeued without abort)
-- to complete.
procedure Wakeup_Entry_Caller
(Self_ID : Task_Id;
Entry_Call : Entry_Call_Link;
New_State : Entry_Call_State)
is
pragma Warnings (Off, Self_ID);
Caller : constant Task_Id := Entry_Call.Self;
begin
pragma Assert (New_State = Done or else New_State = Cancelled);
pragma Assert
(Caller.Common.State /= Terminated and then
Caller.Common.State /= Unactivated);
Entry_Call.State := New_State;
STPO.Wakeup (Caller, Entry_Caller_Sleep);
end Wakeup_Entry_Caller;
-----------------------
-- Restricted GNARLI --
-----------------------
--------------------------------
-- Complete_Single_Entry_Body --
--------------------------------
procedure Complete_Single_Entry_Body (Object : Protection_Entry_Access) is
pragma Warnings (Off, Object);
begin
-- Nothing needs to do (Object.Call_In_Progress.Exception_To_Raise
-- has already been set to Null_Id).
null;
end Complete_Single_Entry_Body;
--------------------------------------------
-- Exceptional_Complete_Single_Entry_Body --
--------------------------------------------
procedure Exceptional_Complete_Single_Entry_Body
(Object : Protection_Entry_Access;
Ex : Ada.Exceptions.Exception_Id) is
begin
Object.Call_In_Progress.Exception_To_Raise := Ex;
end Exceptional_Complete_Single_Entry_Body;
---------------------------------
-- Initialize_Protection_Entry --
---------------------------------
procedure Initialize_Protection_Entry
(Object : Protection_Entry_Access;
Ceiling_Priority : Integer;
Compiler_Info : System.Address;
Entry_Body : Entry_Body_Access)
is
Init_Priority : Integer := Ceiling_Priority;
begin
if Init_Priority = Unspecified_Priority then
Init_Priority := System.Priority'Last;
end if;
STPO.Initialize_Lock (Init_Priority, Object.L'Access);
Object.Ceiling := System.Any_Priority (Init_Priority);
Object.Owner := Null_Task;
Object.Compiler_Info := Compiler_Info;
Object.Call_In_Progress := null;
Object.Entry_Body := Entry_Body;
Object.Entry_Queue := null;
end Initialize_Protection_Entry;
----------------
-- Lock_Entry --
----------------
-- Compiler interface only.
-- Do not call this procedure from within the run-time system.
procedure Lock_Entry (Object : Protection_Entry_Access) is
Ceiling_Violation : Boolean;
begin
-- If pragma Detect_Blocking is active then, as described in the ARM
-- 9.5.1, par. 15, we must check whether this is an external call on a
-- protected subprogram with the same target object as that of the
-- protected action that is currently in progress (i.e., if the caller
-- is already the protected object's owner). If this is the case hence
-- Program_Error must be raised.
if Detect_Blocking and then Object.Owner = Self then
raise Program_Error;
end if;
STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error;
end if;
-- We are entering in a protected action, so that we increase the
-- protected object nesting level (if pragma Detect_Blocking is
-- active), and update the protected object's owner.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Update the protected object's owner
Object.Owner := Self_Id;
-- Increase protected object nesting level
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting + 1;
end;
end if;
end Lock_Entry;
--------------------------
-- Lock_Read_Only_Entry --
--------------------------
-- Compiler interface only
-- Do not call this procedure from within the runtime system
procedure Lock_Read_Only_Entry (Object : Protection_Entry_Access) is
Ceiling_Violation : Boolean;
begin
-- If pragma Detect_Blocking is active then, as described in the ARM
-- 9.5.1, par. 15, we must check whether this is an external call on a
-- protected subprogram with the same target object as that of the
-- protected action that is currently in progress (i.e., if the caller
-- is already the protected object's owner). If this is the case hence
-- Program_Error must be raised.
-- Note that in this case (getting read access), several tasks may
-- have read ownership of the protected object, so that this method of
-- storing the (single) protected object's owner does not work
-- reliably for read locks. However, this is the approach taken for two
-- major reasosn: first, this function is not currently being used (it
-- is provided for possible future use), and second, it largely
-- simplifies the implementation.
if Detect_Blocking and then Object.Owner = Self then
raise Program_Error;
end if;
STPO.Read_Lock (Object.L'Access, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error;
end if;
-- We are entering in a protected action, so that we increase the
-- protected object nesting level (if pragma Detect_Blocking is
-- active), and update the protected object's owner.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Update the protected object's owner
Object.Owner := Self_Id;
-- Increase protected object nesting level
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting + 1;
end;
end if;
end Lock_Read_Only_Entry;
--------------------
-- PO_Do_Or_Queue --
--------------------
procedure PO_Do_Or_Queue
(Self_Id : Task_Id;
Object : Protection_Entry_Access;
Entry_Call : Entry_Call_Link)
is
Barrier_Value : Boolean;
begin
-- When the Action procedure for an entry body returns, it must be
-- completed (having called [Exceptional_]Complete_Entry_Body).
Barrier_Value := Object.Entry_Body.Barrier (Object.Compiler_Info, 1);
if Barrier_Value then
if Object.Call_In_Progress /= null then
-- This violates the No_Entry_Queue restriction, send
-- Program_Error to the caller.
Send_Program_Error (Self_Id, Entry_Call);
return;
end if;
Object.Call_In_Progress := Entry_Call;
Object.Entry_Body.Action
(Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
Object.Call_In_Progress := null;
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Entry_Call.Self);
Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
STPO.Unlock (Entry_Call.Self);
if Single_Lock then
STPO.Unlock_RTS;
end if;
elsif Entry_Call.Mode /= Conditional_Call then
if Object.Entry_Queue /= null then
-- This violates the No_Entry_Queue restriction, send
-- Program_Error to the caller.
Send_Program_Error (Self_Id, Entry_Call);
return;
else
Object.Entry_Queue := Entry_Call;
end if;
else
-- Conditional_Call
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Entry_Call.Self);
Wakeup_Entry_Caller (Self_Id, Entry_Call, Cancelled);
STPO.Unlock (Entry_Call.Self);
if Single_Lock then
STPO.Unlock_RTS;
end if;
end if;
exception
when others =>
Send_Program_Error
(Self_Id, Entry_Call);
end PO_Do_Or_Queue;
----------------------------
-- Protected_Single_Count --
----------------------------
function Protected_Count_Entry (Object : Protection_Entry) return Natural is
begin
if Object.Entry_Queue /= null then
return 1;
else
return 0;
end if;
end Protected_Count_Entry;
---------------------------------
-- Protected_Single_Entry_Call --
---------------------------------
procedure Protected_Single_Entry_Call
(Object : Protection_Entry_Access;
Uninterpreted_Data : System.Address;
Mode : Call_Modes)
is
Self_Id : constant Task_Id := STPO.Self;
Entry_Call : Entry_Call_Record renames Self_Id.Entry_Calls (1);
Ceiling_Violation : Boolean;
begin
-- If pragma Detect_Blocking is active then Program_Error must be
-- raised if this potentially blocking operation is called from a
-- protected action.
if Detect_Blocking
and then Self_Id.Common.Protected_Action_Nesting > 0
then
Ada.Exceptions.Raise_Exception
(Program_Error'Identity, "potentially blocking operation");
end if;
STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error;
end if;
Entry_Call.Mode := Mode;
Entry_Call.State := Now_Abortable;
Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
Unlock_Entry (Object);
-- The call is either `Done' or not. It cannot be cancelled since there
-- is no ATC construct.
pragma Assert (Entry_Call.State /= Cancelled);
if Entry_Call.State /= Done then
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Self_Id);
Wait_For_Completion (Entry_Call'Access);
STPO.Unlock (Self_Id);
if Single_Lock then
STPO.Unlock_RTS;
end if;
end if;
Check_Exception (Self_Id, Entry_Call'Access);
end Protected_Single_Entry_Call;
-----------------------------------
-- Protected_Single_Entry_Caller --
-----------------------------------
function Protected_Single_Entry_Caller
(Object : Protection_Entry) return Task_Id is
begin
return Object.Call_In_Progress.Self;
end Protected_Single_Entry_Caller;
-------------------
-- Service_Entry --
-------------------
procedure Service_Entry (Object : Protection_Entry_Access) is
Self_Id : constant Task_Id := STPO.Self;
Entry_Call : constant Entry_Call_Link := Object.Entry_Queue;
Caller : Task_Id;
begin
if Entry_Call /= null
and then Object.Entry_Body.Barrier (Object.Compiler_Info, 1)
then
Object.Entry_Queue := null;
if Object.Call_In_Progress /= null then
-- Violation of No_Entry_Queue restriction, raise exception
Send_Program_Error (Self_Id, Entry_Call);
Unlock_Entry (Object);
return;
end if;
Object.Call_In_Progress := Entry_Call;
Object.Entry_Body.Action
(Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1);
Object.Call_In_Progress := null;
Caller := Entry_Call.Self;
Unlock_Entry (Object);
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Caller);
Wakeup_Entry_Caller (Self_Id, Entry_Call, Done);
STPO.Unlock (Caller);
if Single_Lock then
STPO.Unlock_RTS;
end if;
else
-- Just unlock the entry
Unlock_Entry (Object);
end if;
exception
when others =>
Send_Program_Error (Self_Id, Entry_Call);
Unlock_Entry (Object);
end Service_Entry;
---------------------------------------
-- Timed_Protected_Single_Entry_Call --
---------------------------------------
-- Compiler interface only. Do not call from within the RTS.
procedure Timed_Protected_Single_Entry_Call
(Object : Protection_Entry_Access;
Uninterpreted_Data : System.Address;
Timeout : Duration;
Mode : Delay_Modes;
Entry_Call_Successful : out Boolean)
is
Self_Id : constant Task_Id := STPO.Self;
Entry_Call : Entry_Call_Record renames Self_Id.Entry_Calls (1);
Ceiling_Violation : Boolean;
begin
-- If pragma Detect_Blocking is active then Program_Error must be
-- raised if this potentially blocking operation is called from a
-- protected action.
if Detect_Blocking
and then Self_Id.Common.Protected_Action_Nesting > 0
then
Ada.Exceptions.Raise_Exception
(Program_Error'Identity, "potentially blocking operation");
end if;
STPO.Write_Lock (Object.L'Access, Ceiling_Violation);
if Ceiling_Violation then
raise Program_Error;
end if;
Entry_Call.Mode := Timed_Call;
Entry_Call.State := Now_Abortable;
Entry_Call.Uninterpreted_Data := Uninterpreted_Data;
Entry_Call.Exception_To_Raise := Ada.Exceptions.Null_Id;
PO_Do_Or_Queue (Self_Id, Object, Entry_Call'Access);
Unlock_Entry (Object);
-- Try to avoid waiting for completed calls.
-- The call is either `Done' or not. It cannot be cancelled since there
-- is no ATC construct and the timed wait has not started yet.
pragma Assert (Entry_Call.State /= Cancelled);
if Entry_Call.State = Done then
Check_Exception (Self_Id, Entry_Call'Access);
Entry_Call_Successful := True;
return;
end if;
if Single_Lock then
STPO.Lock_RTS;
else
STPO.Write_Lock (Self_Id);
end if;
Wait_For_Completion_With_Timeout (Entry_Call'Access, Timeout, Mode);
if Single_Lock then
STPO.Unlock_RTS;
else
STPO.Unlock (Self_Id);
end if;
pragma Assert (Entry_Call.State >= Done);
Check_Exception (Self_Id, Entry_Call'Access);
Entry_Call_Successful := Entry_Call.State = Done;
end Timed_Protected_Single_Entry_Call;
------------------
-- Unlock_Entry --
------------------
procedure Unlock_Entry (Object : Protection_Entry_Access) is
begin
-- We are exiting from a protected action, so that we decrease the
-- protected object nesting level (if pragma Detect_Blocking is
-- active), and remove ownership of the protected object.
if Detect_Blocking then
declare
Self_Id : constant Task_Id := Self;
begin
-- Calls to this procedure can only take place when being within
-- a protected action and when the caller is the protected
-- object's owner.
pragma Assert (Self_Id.Common.Protected_Action_Nesting > 0
and then Object.Owner = Self_Id);
-- Remove ownership of the protected object
Object.Owner := Null_Task;
Self_Id.Common.Protected_Action_Nesting :=
Self_Id.Common.Protected_Action_Nesting - 1;
end;
end if;
STPO.Unlock (Object.L'Access);
end Unlock_Entry;
end System.Tasking.Protected_Objects.Single_Entry;