------------------------------------------------------------------------------ -- -- -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . T A S K _ P R I M I T I V E S . O P E R A T I O N S . -- -- S P E C I F I C -- -- -- -- B o d y -- -- -- -- $Revision: 1.1.4.1 $ -- -- -- Copyright (C) 1991-1999, Florida State University -- -- -- -- 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, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, 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. It is -- -- now maintained by Ada Core Technologies Inc. in cooperation with Florida -- -- State University (http://www.gnat.com). -- -- -- ------------------------------------------------------------------------------ -- This is a POSIX version of this package where foreign threads are -- recognized. -- Currently, DEC Unix, SCO UnixWare 7 and RTEMS use this version. with System.Soft_Links; -- used to initialize TSD for a C thread, in function Self separate (System.Task_Primitives.Operations) package body Specific is ------------------ -- Local Data -- ------------------ -- The followings are logically constants, but need to be initialized -- at run time. -- The following gives the Ada run-time direct access to a variable -- context switched by RTEMS at the lowest level. RTEMS_Ada_Self : System.Address; pragma Import (C, RTEMS_Ada_Self, "rtems_ada_self"); -- The following are used to allow the Self function to -- automatically generate ATCB's for C threads that happen to call -- Ada procedure, which in turn happen to call the Ada runtime system. type Fake_ATCB; type Fake_ATCB_Ptr is access Fake_ATCB; type Fake_ATCB is record Stack_Base : Interfaces.C.unsigned := 0; -- A value of zero indicates the node is not in use. Next : Fake_ATCB_Ptr; Real_ATCB : aliased Ada_Task_Control_Block (0); end record; Fake_ATCB_List : Fake_ATCB_Ptr; -- A linear linked list. -- The list is protected by All_Tasks_L; -- Nodes are added to this list from the front. -- Once a node is added to this list, it is never removed. Fake_Task_Elaborated : aliased Boolean := True; -- Used to identified fake tasks (i.e., non-Ada Threads). Next_Fake_ATCB : Fake_ATCB_Ptr; -- Used to allocate one Fake_ATCB in advance. See comment in New_Fake_ATCB ----------------------- -- Local Subprograms -- ----------------------- --------------------------------- -- Support for New_Fake_ATCB -- --------------------------------- function New_Fake_ATCB return Task_ID; -- Allocate and Initialize a new ATCB. This code can safely be called from -- a foreign thread, as it doesn't access implicitely or explicitely -- "self" before having initialized the new ATCB. ------------------- -- New_Fake_ATCB -- ------------------- function New_Fake_ATCB return Task_ID is Self_ID : Task_ID; P, Q : Fake_ATCB_Ptr; Succeeded : Boolean; begin -- This section is ticklish. -- We dare not call anything that might require an ATCB, until -- we have the new ATCB in place. Write_Lock (All_Tasks_L'Access); Q := null; P := Fake_ATCB_List; while P /= null loop if P.Stack_Base = 0 then Q := P; end if; P := P.Next; end loop; if Q = null then -- Create a new ATCB with zero entries. Self_ID := Next_Fake_ATCB.Real_ATCB'Access; Next_Fake_ATCB.Stack_Base := 1; Next_Fake_ATCB.Next := Fake_ATCB_List; Fake_ATCB_List := Next_Fake_ATCB; Next_Fake_ATCB := null; else -- Reuse an existing fake ATCB. Self_ID := Q.Real_ATCB'Access; Q.Stack_Base := 1; end if; -- Record this as the Task_ID for the current thread. Self_ID.Common.LL.Thread := pthread_self; RTEMS_Ada_Self := To_Address (Self_ID); -- Do the standard initializations System.Tasking.Initialize_ATCB (Self_ID, null, Null_Address, Null_Task, Fake_Task_Elaborated'Access, System.Priority'First, Task_Info.Unspecified_Task_Info, 0, Self_ID, Succeeded); pragma Assert (Succeeded); -- Finally, it is safe to use an allocator in this thread. if Next_Fake_ATCB = null then Next_Fake_ATCB := new Fake_ATCB; end if; Self_ID.Common.State := Runnable; Self_ID.Awake_Count := 1; -- Since this is not an ordinary Ada task, we will start out undeferred Self_ID.Deferral_Level := 0; System.Soft_Links.Create_TSD (Self_ID.Common.Compiler_Data); -- ???? -- The following call is commented out to avoid dependence on -- the System.Tasking.Initialization package. -- It seems that if we want Ada.Task_Attributes to work correctly -- for C threads we will need to raise the visibility of this soft -- link to System.Soft_Links. -- We are putting that off until this new functionality is otherwise -- stable. -- System.Tasking.Initialization.Initialize_Attributes_Link.all (T); for J in Known_Tasks'Range loop if Known_Tasks (J) = null then Known_Tasks (J) := Self_ID; Self_ID.Known_Tasks_Index := J; exit; end if; end loop; -- Must not unlock until Next_ATCB is again allocated. Unlock (All_Tasks_L'Access); return Self_ID; end New_Fake_ATCB; ---------------- -- Initialize -- ---------------- procedure Initialize (Environment_Task : Task_ID) is begin RTEMS_Ada_Self := To_Address (Environment_Task); -- Create a free ATCB for use on the Fake_ATCB_List. Next_Fake_ATCB := new Fake_ATCB; end Initialize; --------- -- Set -- --------- procedure Set (Self_Id : Task_ID) is begin RTEMS_Ada_Self := To_Address (Self_Id); end Set; ---------- -- Self -- ---------- -- To make Ada tasks and C threads interoperate better, we have -- added some functionality to Self. Suppose a C main program -- (with threads) calls an Ada procedure and the Ada procedure -- calls the tasking runtime system. Eventually, a call will be -- made to self. Since the call is not coming from an Ada task, -- there will be no corresponding ATCB. -- (The entire Ada run-time system may not have been elaborated, -- either, but that is a different problem, that we will need to -- solve another way.) -- What we do in Self is to catch references that do not come -- from recognized Ada tasks, and create an ATCB for the calling -- thread. -- The new ATCB will be "detached" from the normal Ada task -- master hierarchy, much like the existing implicitly created -- signal-server tasks. -- We will also use such points to poll for disappearance of the -- threads associated with any implicit ATCBs that we created -- earlier, and take the opportunity to recover them. -- A nasty problem here is the limitations of the compilation -- order dependency, and in particular the GNARL/GNULLI layering. -- To initialize an ATCB we need to assume System.Tasking has -- been elaborated. function Self return Task_ID is Result : System.Address; begin Result := RTEMS_Ada_Self; -- If the key value is Null, then it is a non-Ada task. if Result = System.Null_Address then return New_Fake_ATCB; end if; return To_Task_ID (Result); end Self; end Specific;