330 lines
13 KiB
Ada
330 lines
13 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
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-- --
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-- S Y S T E M . T A S K I N G . R E N D E Z V O U S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1992-2020, Free Software Foundation, Inc. --
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-- --
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-- GNARL is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNARL was developed by the GNARL team at Florida State University. --
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-- Extensive contributions were provided by Ada Core Technologies, Inc. --
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-- --
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------------------------------------------------------------------------------
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-- Note: the compiler generates direct calls to this interface, via Rtsfind.
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-- Any changes to this interface may require corresponding compiler changes.
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with Ada.Exceptions;
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with System.Tasking.Protected_Objects.Entries;
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package System.Tasking.Rendezvous is
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package STPE renames System.Tasking.Protected_Objects.Entries;
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procedure Task_Entry_Call
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(Acceptor : Task_Id;
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E : Task_Entry_Index;
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Uninterpreted_Data : System.Address;
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Mode : Call_Modes;
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Rendezvous_Successful : out Boolean);
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-- General entry call used to implement ATC or conditional entry calls.
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-- Compiler interface only. Do not call from within the RTS.
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-- Acceptor is the ID of the acceptor task.
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-- E is the entry index requested.
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-- Uninterpreted_Data represents the parameters of the entry. It is
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-- constructed by the compiler for the caller and the callee; therefore,
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-- the run time never needs to decode this data.
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-- Mode can be either Asynchronous_Call (ATC) or Conditional_Call.
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-- Rendezvous_Successful is set to True on return if the call was serviced.
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procedure Timed_Task_Entry_Call
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(Acceptor : Task_Id;
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E : Task_Entry_Index;
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Uninterpreted_Data : System.Address;
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Timeout : Duration;
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Mode : Delay_Modes;
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Rendezvous_Successful : out Boolean);
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-- Timed entry call without using ATC.
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-- Compiler interface only. Do not call from within the RTS.
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-- See Task_Entry_Call for details on Acceptor, E and Uninterpreted_Data.
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-- Timeout is the value of the time out.
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-- Mode determines whether the delay is relative or absolute.
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procedure Call_Simple
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(Acceptor : Task_Id;
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E : Task_Entry_Index;
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Uninterpreted_Data : System.Address);
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-- Simple entry call.
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-- Compiler interface only. Do not call from within the RTS.
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--
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-- source:
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-- T.E1 (Params);
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--
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-- expansion:
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-- declare
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-- P : parms := (parm1, parm2, parm3);
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-- X : Task_Entry_Index := 1;
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-- begin
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-- Call_Simple (t._task_id, X, P'Address);
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-- parm1 := P.param1;
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-- parm2 := P.param2;
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-- ...
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-- end;
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procedure Cancel_Task_Entry_Call (Cancelled : out Boolean);
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-- Cancel pending asynchronous task entry call.
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-- Compiler interface only. Do not call from within the RTS.
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-- See Exp_Ch9.Expand_N_Asynchronous_Select for code expansion.
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procedure Requeue_Task_Entry
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(Acceptor : Task_Id;
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E : Task_Entry_Index;
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With_Abort : Boolean);
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-- Requeue from a task entry to a task entry.
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-- Compiler interface only. Do not call from within the RTS.
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-- The code generation for task entry requeues is different from that for
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-- protected entry requeues. There is a "goto" that skips around the call
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-- to Complete_Rendezvous, so that Requeue_Task_Entry must also do the work
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-- of Complete_Rendezvous. The difference is that it does not report that
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-- the call's State = Done.
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--
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-- source:
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-- accept e1 do
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-- ...A...
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-- requeue e2;
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-- ...B...
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-- end e1;
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--
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-- expansion:
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-- A62b : address;
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-- L61b : label
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-- begin
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-- accept_call (1, A62b);
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-- ...A...
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-- requeue_task_entry (tTV!(t)._task_id, 2, false);
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-- goto L61b;
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-- ...B...
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-- complete_rendezvous;
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-- <<L61b>>
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-- exception
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-- when others =>
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-- exceptional_complete_rendezvous (current_exception);
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-- end;
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procedure Requeue_Protected_To_Task_Entry
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(Object : STPE.Protection_Entries_Access;
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Acceptor : Task_Id;
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E : Task_Entry_Index;
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With_Abort : Boolean);
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-- Requeue from a protected entry to a task entry.
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-- Compiler interface only. Do not call from within the RTS.
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--
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-- source:
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-- entry e2 when b is
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-- begin
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-- b := false;
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-- ...A...
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-- requeue t.e2;
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-- end e2;
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--
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-- expansion:
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-- procedure rPT__E14b (O : address; P : address; E :
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-- protected_entry_index) is
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-- type rTVP is access rTV;
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-- freeze rTVP []
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-- _object : rTVP := rTVP!(O);
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-- begin
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-- declare
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-- rR : protection renames _object._object;
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-- vP : integer renames _object.v;
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-- bP : boolean renames _object.b;
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-- begin
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-- b := false;
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-- ...A...
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-- requeue_protected_to_task_entry (rR'unchecked_access, tTV!(t).
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-- _task_id, 2, false);
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-- return;
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-- end;
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-- complete_entry_body (_object._object'unchecked_access, objectF =>
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-- 0);
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-- return;
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-- exception
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-- when others =>
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-- abort_undefer.all;
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-- exceptional_complete_entry_body (_object._object'
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-- unchecked_access, current_exception, objectF => 0);
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-- return;
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-- end rPT__E14b;
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procedure Selective_Wait
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(Open_Accepts : Accept_List_Access;
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Select_Mode : Select_Modes;
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Uninterpreted_Data : out System.Address;
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Index : out Select_Index);
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-- Implement select statement.
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-- Compiler interface only. Do not call from within the RTS.
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-- See comments on Accept_Call.
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--
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-- source:
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-- select accept e1 do
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-- ...A...
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-- end e1;
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-- ...B...
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-- or accept e2;
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-- ...C...
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-- end select;
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--
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-- expansion:
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-- A32b : address;
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-- declare
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-- A37b : T36b;
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-- A37b (1) := (null_body => false, s => 1);
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-- A37b (2) := (null_body => true, s => 2);
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-- S0 : aliased T36b := accept_list'A37b;
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-- J1 : select_index := 0;
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-- procedure e1A is
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-- begin
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-- abort_undefer.all;
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-- ...A...
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-- <<L31b>>
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-- complete_rendezvous;
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-- exception
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-- when all others =>
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-- exceptional_complete_rendezvous (get_gnat_exception);
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-- end e1A;
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-- begin
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-- selective_wait (S0'unchecked_access, simple_mode, A32b, J1);
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-- case J1 is
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-- when 0 =>
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-- goto L3;
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-- when 1 =>
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-- e1A;
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-- goto L1;
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-- when 2 =>
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-- goto L2;
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-- when others =>
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-- goto L3;
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-- end case;
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-- <<L1>>
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-- ...B...
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-- goto L3;
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-- <<L2>>
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-- ...C...
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-- goto L3;
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-- <<L3>>
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-- end;
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procedure Timed_Selective_Wait
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(Open_Accepts : Accept_List_Access;
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Select_Mode : Select_Modes;
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Uninterpreted_Data : out System.Address;
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Timeout : Duration;
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Mode : Delay_Modes;
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Index : out Select_Index);
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-- Selective wait with timeout without using ATC.
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-- Compiler interface only. Do not call from within the RTS.
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procedure Accept_Call
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(E : Task_Entry_Index;
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Uninterpreted_Data : out System.Address);
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-- Accept an entry call.
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-- Compiler interface only. Do not call from within the RTS.
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--
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-- source:
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-- accept E do ...A... end E;
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-- expansion:
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-- A27b : address;
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-- L26b : label
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-- begin
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-- accept_call (1, A27b);
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-- ...A...
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-- complete_rendezvous;
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-- <<L26b>>
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-- exception
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-- when all others =>
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-- exceptional_complete_rendezvous (get_gnat_exception);
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-- end;
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--
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-- The handler for Abort_Signal (*all* others) is to handle the case when
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-- the acceptor is aborted between Accept_Call and the corresponding
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-- Complete_Rendezvous call. We need to wake up the caller in this case.
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--
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-- See also Selective_Wait
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procedure Accept_Trivial (E : Task_Entry_Index);
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-- Accept an entry call that has no parameters and no body.
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-- Compiler interface only. Do not call from within the RTS.
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-- This should only be called when there is no accept body, or the accept
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-- body is empty.
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--
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-- source:
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-- accept E;
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-- expansion:
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-- accept_trivial (1);
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--
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-- The compiler is also able to recognize the following and
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-- translate it the same way.
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--
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-- accept E do null; end E;
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function Task_Count (E : Task_Entry_Index) return Natural;
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-- Return number of tasks waiting on the entry E (of current task)
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-- Compiler interface only. Do not call from within the RTS.
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function Callable (T : Task_Id) return Boolean;
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-- Return T'Callable
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-- Compiler interface. Do not call from within the RTS, except for body of
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-- Ada.Task_Identification.
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type Task_Entry_Nesting_Depth is new Task_Entry_Index
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range 0 .. Max_Task_Entry;
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function Task_Entry_Caller (D : Task_Entry_Nesting_Depth) return Task_Id;
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-- Return E'Caller. This will only work if called from within an
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-- accept statement that is handling E, as required by the LRM (C.7.1(14)).
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-- Compiler interface only. Do not call from within the RTS.
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procedure Complete_Rendezvous;
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-- Called by acceptor to wake up caller
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procedure Exceptional_Complete_Rendezvous
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(Ex : Ada.Exceptions.Exception_Id);
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pragma No_Return (Exceptional_Complete_Rendezvous);
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-- Called by acceptor to mark the end of the current rendezvous and
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-- propagate an exception to the caller.
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-- For internal use only:
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function Task_Do_Or_Queue
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(Self_ID : Task_Id;
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Entry_Call : Entry_Call_Link) return Boolean;
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-- Call this only with abort deferred and holding no locks.
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-- Returns False iff the call cannot be served or queued, as is the
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-- case if the caller is not callable; i.e., a False return value
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-- indicates that Tasking_Error should be raised.
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-- Either initiate the entry call, such that the accepting task is
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-- free to execute the rendezvous, queue the call on the acceptor's
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-- queue, or cancel the call. Conditional calls that cannot be
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-- accepted immediately are cancelled.
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end System.Tasking.Rendezvous;
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