--- /dev/null
+------------------------------------------------------------------------------
+-- --
+-- 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: 1.7 $
+-- --
+-- Copyright (C) 1991-2003, 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;
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