1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
------------------------------------------------------------------------------
-- --
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . T A S K I N G . D E B U G --
-- --
-- S p e c --
-- --
-- $Revision: 1.16 $
-- --
-- Copyright (C) 1997-1998, Free Software Foundation, Inc. --
-- --
-- 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 package encapsulates all direct interfaces to task debugging services
-- that are needed by gdb with gnat mode (1.17 and higher)
with Interfaces.C;
with System.Tasking;
with System.OS_Interface;
package System.Tasking.Debug is
subtype int is Interfaces.C.int;
subtype unsigned_long is Interfaces.C.unsigned_long;
package ST renames System.Tasking;
Known_Tasks : array (0 .. 999) of Task_ID;
-- Global array of tasks read by gdb, and updated by
-- Create_Task and Finalize_TCB
procedure Task_Creation_Hook (Thread : OS_Interface.Thread_Id);
-- This procedure is used to notify VxGdb of task's creation.
-- It must be called by the task's creator.
procedure Task_Termination_Hook;
-- This procedure is used to notify VxGdb of task's termination.
function Self return Task_ID;
-- return system ID of current task
procedure List_Tasks;
-- Print a list of all the known Ada tasks with abbreviated state
-- information, one-per-line, to the standard output file
procedure Print_Current_Task;
procedure Print_Task_Info_Header;
procedure Print_Task_Info (T : Task_ID);
-- Write TASK_ID of current task, in hexadecimal, as one line, to
-- the standard output file
--
-- Beware that Print_Current_Task may print garbage during an early
-- stage of activation. There is a small window where a task is just
-- initializing itself and has not yet recorded its own task Id.
--
-- Beware that Print_Current_Task will either not work at all or print
-- garbage if it has interrupted a thread of control that does not
-- correspond to any Ada task. For example, this is could happen if
-- the debugger interrupts a signal handler that is using an alternate
-- stack, or interrupts the dispatcher in the underlying thread
-- implementation.
procedure Set_User_State (Value : Integer);
procedure Print_Accept_Info (T : Task_ID);
procedure Trace
(Self_ID : Task_ID;
Msg : String;
Other_ID : Task_ID;
Flag : Character);
procedure Trace
(Self_ID : Task_ID;
Msg : String;
Flag : Character);
procedure Trace
(Msg : String;
Flag : Character);
procedure Trace
(Msg : String;
Other_ID : Task_ID;
Flag : Character);
procedure Set_Trace
(Flag : Character;
Value : Boolean := True);
function Image (T : Task_ID) return String;
procedure Suspend_All_Tasks (Thread_Self : OS_Interface.Thread_Id);
-- Suspend all the tasks except the one whose associated thread is
-- Thread_Self by traversing All_Tasks_Lists and calling
-- System.Task_Primitives.Operations.Suspend_Task
-- Such functionnality is needed by gdb on some targets (e.g VxWorks)
-- Warning: for efficiency purposes, there is no locking.
procedure Resume_All_Tasks (Thread_Self : OS_Interface.Thread_Id);
-- Resume all the tasks except the one whose associated thread is
-- Thread_Self by traversing All_Tasks_Lists and calling
-- System.Task_Primitives.Operations.Continue_Task
-- Such functionnality is needed by gdb on some targets (e.g VxWorks)
-- Warning: for efficiency purposes, there is no locking.
end System.Tasking.Debug;
-----------------------------
-- Use of These Functions --
-----------------------------
-- Calling complicated functions from the debugger is generally pretty
-- risky, especially in a multithreaded program.
-- The debugger may interrupt something that is not an Ada task,
-- within the thread implementation, and which is not async-safe.
-- For example, under Solaris, it can interrupt code in "_dynamiclwps",
-- which seems to serve as dispatcher when all the user threads are
-- suspended. By experience, we have found that one cannot safely
-- do certain things, apparently including calls to thread primitives
-- from the debugger if the debugger has interrupted at one of these
-- unsafe points. In general, if you interrupt a running program
-- asynchronously (e.g. via control-C), it will not be safe to
-- call the subprograms in this package.
-----------------
-- Future work --
-----------------
-- It would be nice to be able to tell whether execution has been
-- interrupted in an Ada task. A heuristic way of checking this would
-- be if we added to the Ada TCB a component that always contains a
-- constant value that is unlikely to occur accidentally in code or
-- data. We could then check this in the debugger-callable subprograms,
-- and simply return an error code if it looks unsafe to proceed.
-- ???
-- Recently we have added such a marker as a local variable of the
-- task-wrapper routine. This allows Self to generate a fake ATCB for
-- non-Ada threads of control. Given this capability, it is probably
-- time to revisit the issue above.
-- DEADLOCK
-- We follow a simple rule here to avoid deadlock:
-- We do not use any locks in functions called by gdb, and we do not
-- traverse linked lists.
--
-- The use of an array (Known_Tasks) has many advantages:
-- - Easy and fast to examine;
-- - No risk of dangling references (to the next element) when traversing
-- the array.
|
