------------------------------------------------------------------------------ -- -- -- 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 -- -- -- -- $Revision$ -- -- -- Copyright (C) 1997-2001, 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 functionality 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 functionality 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.