+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
--- --
--- SYSTEM.TASK_PRIMITIVES.OPERATIONS.SELF --
--- --
--- B o d y --
--- --
--- $Revision: 1.1.16.1 $
--- --
--- Copyright (C) 1991-1998, 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 Solaris Sparc (native) version of this package.
-
-with System.Machine_Code;
--- used for Asm
-
-separate (System.Task_Primitives.Operations)
-
-----------
--- Self --
-----------
-
--- For Solaris version of RTS, we use a short cut to get the self
--- information faster:
-
--- We have noticed that on Sparc Solaris, the register g7 always
--- contains the address near the frame pointer (fp) of the active
--- thread (fixed offset). This means, if we declare a variable near
--- the top of the stack for each threads (in our case in the task wrapper)
--- and let the variable hold the Task_ID information, we can get the
--- value without going through the thr_getspecific kernel call.
---
--- There are two things to take care in this trick.
---
--- 1) We need to calculate the offset between the g7 value and the
--- local variable address.
--- Possible Solutions :
--- a) Use gdb to figure out the offset.
--- b) Figure it out during the elaboration of RTS by, say,
--- creating a dummy task.
--- We used solution a) mainly because it is more efficient and keeps
--- the RTS from being cluttered with stuff that we won't be used
--- for all environments (i.e., we would have to at least introduce
--- new interfaces).
---
--- On Sparc Solaris the offset was #10#108# (= #16#6b#) with gcc 2.7.2.
--- With gcc 2.8.0, the offset is #10#116# (= #16#74#).
---
--- 2) We can not use the same offset business for the main thread
--- because we do not use a wrapper for the main thread.
--- Previousely, we used the difference between g7 and fp to determine
--- wether a task was the main task or not. But this was obviousely
--- wrong since it worked only for tasks that use small amount of
--- stack.
--- So, we now take advantage of the code that recognizes foreign
--- threads (see below) for the main task.
---
--- NOTE: What we are doing here is ABSOLUTELY for Solaris 2.4, 2.5 and 2.6
--- on Sun.
-
--- We need to make sure this is OK when we move to other versions
--- of the same OS.
-
--- We always can go back to the old way of doing this and we include
--- the code which use thr_getspecifics. Also, look for %%%%%
--- in comments for other necessary modifications.
-
--- This code happens to work with Solaris 2.5.1 too, but with gcc
--- 2.8.0, this offset is different.
-
--- ??? Try to rethink the approach here to get a more flexible
--- solution at run time ?
-
--- One other solution (close to 1-b) would be to add some scanning
--- routine in Enter_Task to compute the offset since now we have
--- a magic number at the beginning of the task code.
-
--- function Self return Task_ID is
--- Temp : aliased System.Address;
--- Result : Interfaces.C.int;
---
--- begin
--- Result := thr_getspecific (ATCB_Key, Temp'Unchecked_Access);
--- pragma Assert (Result = 0);
--- return To_Task_ID (Temp);
--- end 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 run-time 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
- X : Ptr;
- Result : Interfaces.C.int;
-
- function Get_G7 return Interfaces.C.unsigned;
- pragma Inline (Get_G7);
-
- use System.Machine_Code;
-
- ------------
- -- Get_G7 --
- ------------
-
- function Get_G7 return Interfaces.C.unsigned is
- Result : Interfaces.C.unsigned;
-
- begin
- Asm ("mov %%g7,%0", Interfaces.C.unsigned'Asm_Output ("=r", Result));
- return Result;
- end Get_G7;
-
--- Start of processing for Self
-
-begin
- if To_Iptr (Get_G7 - 120).all /=
- Interfaces.C.unsigned (ATCB_Magic_Code)
- then
- -- Check whether this is a thread we have seen before (e.g the
- -- main task).
- -- 120 = 116 + Magic_Type'Size/System.Storage_Unit
-
- declare
- Unknown_Task : aliased System.Address;
-
- begin
- Result :=
- thr_getspecific (ATCB_Key, Unknown_Task'Unchecked_Access);
-
- pragma Assert (Result = 0);
-
- if Unknown_Task = System.Null_Address then
-
- -- We are seeing this thread for the first time.
-
- return New_Fake_ATCB (Get_G7);
-
- else
- return To_Task_ID (Unknown_Task);
- end if;
- end;
- end if;
-
- X := To_Ptr (Get_G7 - 116);
- return X.all;
-
-end Self;
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