1 ------------------------------------------------------------------------------
3 -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- 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 . --
12 -- Copyright (C) 1991-2003, Florida State University --
14 -- GNARL is free software; you can redistribute it and/or modify it under --
15 -- terms of the GNU General Public License as published by the Free Soft- --
16 -- ware Foundation; either version 2, or (at your option) any later ver- --
17 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
18 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
19 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
20 -- for more details. You should have received a copy of the GNU General --
21 -- Public License distributed with GNARL; see file COPYING. If not, write --
22 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
23 -- MA 02111-1307, USA. --
25 -- As a special exception, if other files instantiate generics from this --
26 -- unit, or you link this unit with other files to produce an executable, --
27 -- this unit does not by itself cause the resulting executable to be --
28 -- covered by the GNU General Public License. This exception does not --
29 -- however invalidate any other reasons why the executable file might be --
30 -- covered by the GNU Public License. --
32 -- GNARL was developed by the GNARL team at Florida State University. It is --
33 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
34 -- State University (http://www.gnat.com). --
36 ------------------------------------------------------------------------------
38 -- This is a POSIX version of this package where foreign threads are
40 -- Currently, DEC Unix, SCO UnixWare 7 and RTEMS use this version.
42 with System.Soft_Links;
43 -- used to initialize TSD for a C thread, in function Self
45 separate (System.Task_Primitives.Operations)
46 package body Specific is
52 -- The followings are logically constants, but need to be initialized
55 -- The following gives the Ada run-time direct access to a variable
56 -- context switched by RTEMS at the lowest level.
58 RTEMS_Ada_Self : System.Address;
59 pragma Import (C, RTEMS_Ada_Self, "rtems_ada_self");
61 -- The following are used to allow the Self function to
62 -- automatically generate ATCB's for C threads that happen to call
63 -- Ada procedure, which in turn happen to call the Ada runtime system.
66 type Fake_ATCB_Ptr is access Fake_ATCB;
67 type Fake_ATCB is record
68 Stack_Base : Interfaces.C.unsigned := 0;
69 -- A value of zero indicates the node is not in use.
71 Real_ATCB : aliased Ada_Task_Control_Block (0);
74 Fake_ATCB_List : Fake_ATCB_Ptr;
75 -- A linear linked list.
76 -- The list is protected by All_Tasks_L;
77 -- Nodes are added to this list from the front.
78 -- Once a node is added to this list, it is never removed.
80 Fake_Task_Elaborated : aliased Boolean := True;
81 -- Used to identified fake tasks (i.e., non-Ada Threads).
83 Next_Fake_ATCB : Fake_ATCB_Ptr;
84 -- Used to allocate one Fake_ATCB in advance. See comment in New_Fake_ATCB
86 -----------------------
87 -- Local Subprograms --
88 -----------------------
90 ---------------------------------
91 -- Support for New_Fake_ATCB --
92 ---------------------------------
94 function New_Fake_ATCB return Task_ID;
95 -- Allocate and Initialize a new ATCB. This code can safely be called from
96 -- a foreign thread, as it doesn't access implicitely or explicitely
97 -- "self" before having initialized the new ATCB.
103 function New_Fake_ATCB return Task_ID is
105 P, Q : Fake_ATCB_Ptr;
109 -- This section is ticklish.
110 -- We dare not call anything that might require an ATCB, until
111 -- we have the new ATCB in place.
113 Write_Lock (All_Tasks_L'Access);
118 if P.Stack_Base = 0 then
127 -- Create a new ATCB with zero entries.
129 Self_ID := Next_Fake_ATCB.Real_ATCB'Access;
130 Next_Fake_ATCB.Stack_Base := 1;
131 Next_Fake_ATCB.Next := Fake_ATCB_List;
132 Fake_ATCB_List := Next_Fake_ATCB;
133 Next_Fake_ATCB := null;
136 -- Reuse an existing fake ATCB.
138 Self_ID := Q.Real_ATCB'Access;
142 -- Record this as the Task_ID for the current thread.
144 Self_ID.Common.LL.Thread := pthread_self;
146 RTEMS_Ada_Self := To_Address (Self_ID);
148 -- Do the standard initializations
150 System.Tasking.Initialize_ATCB
151 (Self_ID, null, Null_Address, Null_Task, Fake_Task_Elaborated'Access,
152 System.Priority'First, Task_Info.Unspecified_Task_Info, 0, Self_ID,
154 pragma Assert (Succeeded);
156 -- Finally, it is safe to use an allocator in this thread.
158 if Next_Fake_ATCB = null then
159 Next_Fake_ATCB := new Fake_ATCB;
162 Self_ID.Common.State := Runnable;
163 Self_ID.Awake_Count := 1;
165 -- Since this is not an ordinary Ada task, we will start out undeferred
167 Self_ID.Deferral_Level := 0;
169 System.Soft_Links.Create_TSD (Self_ID.Common.Compiler_Data);
172 -- The following call is commented out to avoid dependence on
173 -- the System.Tasking.Initialization package.
174 -- It seems that if we want Ada.Task_Attributes to work correctly
175 -- for C threads we will need to raise the visibility of this soft
176 -- link to System.Soft_Links.
177 -- We are putting that off until this new functionality is otherwise
179 -- System.Tasking.Initialization.Initialize_Attributes_Link.all (T);
181 for J in Known_Tasks'Range loop
182 if Known_Tasks (J) = null then
183 Known_Tasks (J) := Self_ID;
184 Self_ID.Known_Tasks_Index := J;
189 -- Must not unlock until Next_ATCB is again allocated.
191 Unlock (All_Tasks_L'Access);
199 procedure Initialize (Environment_Task : Task_ID) is
202 RTEMS_Ada_Self := To_Address (Environment_Task);
204 -- Create a free ATCB for use on the Fake_ATCB_List.
206 Next_Fake_ATCB := new Fake_ATCB;
213 procedure Set (Self_Id : Task_ID) is
216 RTEMS_Ada_Self := To_Address (Self_Id);
223 -- To make Ada tasks and C threads interoperate better, we have
224 -- added some functionality to Self. Suppose a C main program
225 -- (with threads) calls an Ada procedure and the Ada procedure
226 -- calls the tasking runtime system. Eventually, a call will be
227 -- made to self. Since the call is not coming from an Ada task,
228 -- there will be no corresponding ATCB.
230 -- (The entire Ada run-time system may not have been elaborated,
231 -- either, but that is a different problem, that we will need to
232 -- solve another way.)
234 -- What we do in Self is to catch references that do not come
235 -- from recognized Ada tasks, and create an ATCB for the calling
238 -- The new ATCB will be "detached" from the normal Ada task
239 -- master hierarchy, much like the existing implicitly created
240 -- signal-server tasks.
242 -- We will also use such points to poll for disappearance of the
243 -- threads associated with any implicit ATCBs that we created
244 -- earlier, and take the opportunity to recover them.
246 -- A nasty problem here is the limitations of the compilation
247 -- order dependency, and in particular the GNARL/GNULLI layering.
248 -- To initialize an ATCB we need to assume System.Tasking has
251 function Self return Task_ID is
252 Result : System.Address;
255 Result := RTEMS_Ada_Self;
257 -- If the key value is Null, then it is a non-Ada task.
259 if Result = System.Null_Address then
260 return New_Fake_ATCB;
263 return To_Task_ID (Result);