1 ------------------------------------------------------------------------------
3 -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . S T A G E S --
9 -- Copyright (C) 1992-2004, Free Software Foundation, Inc. --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNARL; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
35 -- Turn off polling, we do not want ATC polling to take place during
36 -- tasking operations. It causes infinite loops and other problems.
39 -- used for Raise_Exception
41 with System
.Tasking
.Debug
;
42 -- used for enabling tasking facilities with gdb
44 with System
.Address_Image
;
45 -- used for the function itself.
47 with System
.Parameters
;
52 with System
.Task_Info
;
53 -- used for Task_Info_Type
55 with System
.Task_Primitives
.Operations
;
56 -- used for Finalize_Lock
66 with System
.Soft_Links
;
67 -- These are procedure pointers to non-tasking routines that use
68 -- task specific data. In the absence of tasking, these routines
69 -- refer to global data. In the presense of tasking, they must be
70 -- replaced with pointers to task-specific versions.
71 -- Also used for Create_TSD, Destroy_TSD, Get_Current_Excep
73 with System
.Tasking
.Initialization
;
74 -- Used for Remove_From_All_Tasks_List
77 -- Initialization.Poll_Base_Priority_Change
78 -- Finalize_Attributes_Link
79 -- Initialize_Attributes_Link
81 pragma Elaborate_All
(System
.Tasking
.Initialization
);
82 -- This insures that tasking is initialized if any tasks are created.
84 with System
.Tasking
.Utilities
;
85 -- Used for Make_Passive
88 with System
.Tasking
.Queuing
;
89 -- Used for Dequeue_Head
91 with System
.Tasking
.Rendezvous
;
92 -- Used for Call_Simple
94 with System
.OS_Primitives
;
95 -- Used for Delay_Modes
97 with System
.Finalization_Implementation
;
98 -- Used for System.Finalization_Implementation.Finalize_Global_List
100 with System
.Secondary_Stack
;
103 with System
.Storage_Elements
;
104 -- used for Storage_Array
106 with System
.Standard_Library
;
107 -- used for Exception_Trace
109 with System
.Traces
.Tasking
;
110 -- used for Send_Trace_Info
112 package body System
.Tasking
.Stages
is
114 package STPO
renames System
.Task_Primitives
.Operations
;
115 package SSL
renames System
.Soft_Links
;
116 package SSE
renames System
.Storage_Elements
;
117 package SST
renames System
.Secondary_Stack
;
123 use Task_Primitives
.Operations
;
127 use System
.Traces
.Tasking
;
129 -----------------------
130 -- Local Subprograms --
131 -----------------------
133 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
);
134 -- This procedure outputs the task specific message for exception
137 procedure Task_Wrapper
(Self_ID
: Task_Id
);
138 -- This is the procedure that is called by the GNULL from the
139 -- new context when a task is created. It waits for activation
140 -- and then calls the task body procedure. When the task body
141 -- procedure completes, it terminates the task.
143 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
);
144 -- Complete the calling task.
145 -- This procedure must be called with abort deferred.
146 -- It should only be called by Complete_Task and
147 -- Finalizate_Global_Tasks (for the environment task).
149 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
);
150 -- Complete the current master of the calling task.
151 -- This procedure must be called with abort deferred.
152 -- It should only be called by Vulnerable_Complete_Task and
155 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
);
156 -- Signal to Self_ID's activator that Self_ID has
157 -- completed activation.
159 -- Call this procedure with abort deferred.
161 procedure Abort_Dependents
(Self_ID
: Task_Id
);
162 -- Abort all the direct dependents of Self at its current master
163 -- nesting level, plus all of their dependents, transitively.
164 -- RTS_Lock should be locked by the caller.
166 procedure Vulnerable_Free_Task
(T
: Task_Id
);
167 -- Recover all runtime system storage associated with the task T.
168 -- This should only be called after T has terminated and will no
169 -- longer be referenced.
171 -- For tasks created by an allocator that fails, due to an exception,
172 -- it is called from Expunge_Unactivated_Tasks.
174 -- It is also called from Unchecked_Deallocation, for objects that
175 -- are or contain tasks.
177 -- Different code is used at master completion, in Terminate_Dependents,
178 -- due to a need for tighter synchronization with the master.
180 ----------------------
181 -- Abort_Dependents --
182 ----------------------
184 procedure Abort_Dependents
(Self_ID
: Task_Id
) is
192 P
:= C
.Common
.Parent
;
196 -- ??? C is supposed to take care of its own dependents, so
197 -- there should be no need to worry about them. Need to double
200 if C
.Master_of_Task
= Self_ID
.Master_Within
then
201 Utilities
.Abort_One_Task
(Self_ID
, C
);
202 C
.Dependents_Aborted
:= True;
208 P
:= P
.Common
.Parent
;
211 C
:= C
.Common
.All_Tasks_Link
;
214 Self_ID
.Dependents_Aborted
:= True;
215 end Abort_Dependents
;
221 procedure Abort_Tasks
(Tasks
: Task_List
) is
223 Utilities
.Abort_Tasks
(Tasks
);
230 -- Note that locks of activator and activated task are both locked
231 -- here. This is necessary because C.Common.State and
232 -- Self.Common.Wait_Count have to be synchronized. This is safe from
233 -- deadlock because the activator is always created before the activated
234 -- task. That satisfies our in-order-of-creation ATCB locking policy.
236 -- At one point, we may also lock the parent, if the parent is
237 -- different from the activator. That is also consistent with the
238 -- lock ordering policy, since the activator cannot be created
239 -- before the parent.
241 -- Since we are holding both the activator's lock, and Task_Wrapper
242 -- locks that before it does anything more than initialize the
243 -- low-level ATCB components, it should be safe to wait to update
244 -- the counts until we see that the thread creation is successful.
246 -- If the thread creation fails, we do need to close the entries
247 -- of the task. The first phase, of dequeuing calls, only requires
248 -- locking the acceptor's ATCB, but the waking up of the callers
249 -- requires locking the caller's ATCB. We cannot safely do this
250 -- while we are holding other locks. Therefore, the queue-clearing
251 -- operation is done in a separate pass over the activation chain.
253 procedure Activate_Tasks
(Chain_Access
: Activation_Chain_Access
) is
254 Self_ID
: constant Task_Id
:= STPO
.Self
;
257 Next_C
, Last_C
: Task_Id
;
258 Activate_Prio
: System
.Any_Priority
;
260 All_Elaborated
: Boolean := True;
264 (Debug
.Trace
(Self_ID
, "Activate_Tasks", 'C'));
266 Initialization
.Defer_Abort_Nestable
(Self_ID
);
268 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
270 -- Lock RTS_Lock, to prevent activated tasks
271 -- from racing ahead before we finish activating the chain.
275 -- Check that all task bodies have been elaborated.
277 C
:= Chain_Access
.T_ID
;
281 if C
.Common
.Elaborated
/= null
282 and then not C
.Common
.Elaborated
.all
284 All_Elaborated
:= False;
287 -- Reverse the activation chain so that tasks are
288 -- activated in the same order they're declared.
290 Next_C
:= C
.Common
.Activation_Link
;
291 C
.Common
.Activation_Link
:= Last_C
;
296 Chain_Access
.T_ID
:= Last_C
;
298 if not All_Elaborated
then
300 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
302 (Program_Error
'Identity, "Some tasks have not been elaborated");
305 -- Activate all the tasks in the chain.
306 -- Creation of the thread of control was deferred until
307 -- activation. So create it now.
309 C
:= Chain_Access
.T_ID
;
312 if C
.Common
.State
/= Terminated
then
313 pragma Assert
(C
.Common
.State
= Unactivated
);
315 P
:= C
.Common
.Parent
;
319 if C
.Common
.Base_Priority
< Get_Priority
(Self_ID
) then
320 Activate_Prio
:= Get_Priority
(Self_ID
);
322 Activate_Prio
:= C
.Common
.Base_Priority
;
325 System
.Task_Primitives
.Operations
.Create_Task
326 (C
, Task_Wrapper
'Address,
328 (C
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
329 Activate_Prio
, Success
);
331 -- There would be a race between the created task and the
332 -- creator to do the following initialization, if we did not
333 -- have a Lock/Unlock_RTS pair in the task wrapper to prevent
334 -- it from racing ahead.
337 C
.Common
.State
:= Runnable
;
340 P
.Awake_Count
:= P
.Awake_Count
+ 1;
341 P
.Alive_Count
:= P
.Alive_Count
+ 1;
343 if P
.Common
.State
= Master_Completion_Sleep
and then
344 C
.Master_of_Task
= P
.Master_Within
346 pragma Assert
(Self_ID
/= P
);
347 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
+ 1;
354 -- No need to set Awake_Count, State, etc. here since the loop
355 -- below will do that for any Unactivated tasks.
359 Self_ID
.Common
.Activation_Failed
:= True;
363 C
:= C
.Common
.Activation_Link
;
366 if not Single_Lock
then
370 -- Close the entries of any tasks that failed thread creation,
371 -- and count those that have not finished activation.
373 Write_Lock
(Self_ID
);
374 Self_ID
.Common
.State
:= Activator_Sleep
;
376 C
:= Chain_Access
.T_ID
;
380 if C
.Common
.State
= Unactivated
then
381 C
.Common
.Activator
:= null;
382 C
.Common
.State
:= Terminated
;
384 Utilities
.Cancel_Queued_Entry_Calls
(C
);
386 elsif C
.Common
.Activator
/= null then
387 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
391 P
:= C
.Common
.Activation_Link
;
392 C
.Common
.Activation_Link
:= null;
396 -- Wait for the activated tasks to complete activation. It is
397 -- unsafe to abort any of these tasks until the count goes to zero.
400 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
401 exit when Self_ID
.Common
.Wait_Count
= 0;
402 Sleep
(Self_ID
, Activator_Sleep
);
405 Self_ID
.Common
.State
:= Runnable
;
412 -- Remove the tasks from the chain
414 Chain_Access
.T_ID
:= null;
415 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
417 if Self_ID
.Common
.Activation_Failed
then
418 Self_ID
.Common
.Activation_Failed
:= False;
419 Raise_Exception
(Tasking_Error
'Identity,
420 "Failure during activation");
424 -------------------------
425 -- Complete_Activation --
426 -------------------------
428 procedure Complete_Activation
is
429 Self_ID
: constant Task_Id
:= STPO
.Self
;
431 Initialization
.Defer_Abort_Nestable
(Self_ID
);
437 Vulnerable_Complete_Activation
(Self_ID
);
443 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
446 -- Why do we need to allow for nested deferral here?
448 if Runtime_Traces
then
449 Send_Trace_Info
(T_Activate
);
451 end Complete_Activation
;
453 ---------------------
454 -- Complete_Master --
455 ---------------------
457 procedure Complete_Master
is
458 Self_ID
: constant Task_Id
:= STPO
.Self
;
461 pragma Assert
(Self_ID
.Deferral_Level
> 0);
463 Vulnerable_Complete_Master
(Self_ID
);
470 -- See comments on Vulnerable_Complete_Task for details
472 procedure Complete_Task
is
473 Self_ID
: constant Task_Id
:= STPO
.Self
;
475 pragma Assert
(Self_ID
.Deferral_Level
> 0);
477 Vulnerable_Complete_Task
(Self_ID
);
479 -- All of our dependents have terminated. Never undefer abort again!
487 -- Compiler interface only. Do not call from within the RTS.
488 -- This must be called to create a new task.
490 procedure Create_Task
492 Size
: System
.Parameters
.Size_Type
;
493 Task_Info
: System
.Task_Info
.Task_Info_Type
;
494 Num_Entries
: Task_Entry_Index
;
495 Master
: Master_Level
;
496 State
: Task_Procedure_Access
;
497 Discriminants
: System
.Address
;
498 Elaborated
: Access_Boolean
;
499 Chain
: in out Activation_Chain
;
501 Created_Task
: out Task_Id
)
504 Self_ID
: constant Task_Id
:= STPO
.Self
;
506 Base_Priority
: System
.Any_Priority
;
511 (Debug
.Trace
(Self_ID
, "Create_Task", 'C'));
513 if Priority
= Unspecified_Priority
then
514 Base_Priority
:= Self_ID
.Common
.Base_Priority
;
516 Base_Priority
:= System
.Any_Priority
(Priority
);
519 -- Find parent P of new Task, via master level number
524 while P
.Master_of_Task
>= Master
loop
525 P
:= P
.Common
.Parent
;
530 Initialization
.Defer_Abort_Nestable
(Self_ID
);
533 T
:= New_ATCB
(Num_Entries
);
537 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
538 Raise_Exception
(Storage_Error
'Identity, "Cannot allocate task");
541 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks.
542 -- Up to this point, it is possible that we may be part of
543 -- a family of tasks that is being aborted.
546 Write_Lock
(Self_ID
);
548 -- Now, we must check that we have not been aborted.
549 -- If so, we should give up on creating this task,
550 -- and simply return.
552 if not Self_ID
.Callable
then
553 pragma Assert
(Self_ID
.Pending_ATC_Level
= 0);
554 pragma Assert
(Self_ID
.Pending_Action
);
555 pragma Assert
(Chain
.T_ID
= null
556 or else Chain
.T_ID
.Common
.State
= Unactivated
);
560 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
562 -- ??? Should never get here
564 pragma Assert
(False);
565 raise Standard
'Abort_Signal;
568 Initialize_ATCB
(Self_ID
, State
, Discriminants
, P
, Elaborated
,
569 Base_Priority
, Task_Info
, Size
, T
, Success
);
574 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
576 (Storage_Error
'Identity, "Failed to initialize task");
579 T
.Master_of_Task
:= Master
;
580 T
.Master_Within
:= T
.Master_of_Task
+ 1;
582 for L
in T
.Entry_Calls
'Range loop
583 T
.Entry_Calls
(L
).Self
:= T
;
584 T
.Entry_Calls
(L
).Level
:= L
;
587 if Task_Image
'Length = 0 then
588 T
.Common
.Task_Image_Len
:= 0;
591 T
.Common
.Task_Image
(1) := Task_Image
(Task_Image
'First);
593 for J
in Task_Image
'First + 1 .. Task_Image
'Last loop
595 -- Remove unwanted blank space generated by 'Image
597 if Task_Image
(J
) /= ' '
598 or else Task_Image
(J
- 1) /= '('
601 T
.Common
.Task_Image
(Len
) := Task_Image
(J
);
603 exit when Len
= T
.Common
.Task_Image
'Last;
607 T
.Common
.Task_Image_Len
:= Len
;
613 -- Create TSD as early as possible in the creation of a task, since it
614 -- may be used by the operation of Ada code within the task.
616 SSL
.Create_TSD
(T
.Common
.Compiler_Data
);
617 T
.Common
.Activation_Link
:= Chain
.T_ID
;
619 Initialization
.Initialize_Attributes_Link
.all (T
);
621 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
623 if Runtime_Traces
then
624 Send_Trace_Info
(T_Create
, T
);
632 function Current_Master
return Master_Level
is
634 return STPO
.Self
.Master_Within
;
641 procedure Enter_Master
is
642 Self_ID
: constant Task_Id
:= STPO
.Self
;
645 Self_ID
.Master_Within
:= Self_ID
.Master_Within
+ 1;
648 -------------------------------
649 -- Expunge_Unactivated_Tasks --
650 -------------------------------
652 -- See procedure Close_Entries for the general case.
654 procedure Expunge_Unactivated_Tasks
(Chain
: in out Activation_Chain
) is
655 Self_ID
: constant Task_Id
:= STPO
.Self
;
657 Call
: Entry_Call_Link
;
662 (Debug
.Trace
(Self_ID
, "Expunge_Unactivated_Tasks", 'C'));
664 Initialization
.Defer_Abort_Nestable
(Self_ID
);
667 -- Experimentation has shown that abort is sometimes (but not
668 -- always) already deferred when this is called.
670 -- That may indicate an error. Find out what is going on.
675 pragma Assert
(C
.Common
.State
= Unactivated
);
677 Temp
:= C
.Common
.Activation_Link
;
679 if C
.Common
.State
= Unactivated
then
683 for J
in 1 .. C
.Entry_Num
loop
684 Queuing
.Dequeue_Head
(C
.Entry_Queues
(J
), Call
);
685 pragma Assert
(Call
= null);
690 Initialization
.Remove_From_All_Tasks_List
(C
);
693 Vulnerable_Free_Task
(C
);
699 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
700 end Expunge_Unactivated_Tasks
;
702 ---------------------------
703 -- Finalize_Global_Tasks --
704 ---------------------------
707 -- We have a potential problem here if finalization of global
708 -- objects does anything with signals or the timer server, since
709 -- by that time those servers have terminated.
711 -- It is hard to see how that would occur.
713 -- However, a better solution might be to do all this finalization
714 -- using the global finalization chain.
716 procedure Finalize_Global_Tasks
is
717 Self_ID
: constant Task_Id
:= STPO
.Self
;
721 if Self_ID
.Deferral_Level
= 0 then
723 -- In principle, we should be able to predict whether
724 -- abort is already deferred here (and it should not be deferred
725 -- yet but in practice it seems Finalize_Global_Tasks is being
726 -- called sometimes, from RTS code for exceptions, with abort already
729 Initialization
.Defer_Abort_Nestable
(Self_ID
);
731 -- Never undefer again!!!
734 -- This code is only executed by the environment task
736 pragma Assert
(Self_ID
= Environment_Task
);
738 -- Set Environment_Task'Callable to false to notify library-level tasks
739 -- that it is waiting for them (cf 5619-003).
741 Self_ID
.Callable
:= False;
743 -- Exit level 2 master, for normal tasks in library-level packages.
747 -- Force termination of "independent" library-level server tasks.
751 Abort_Dependents
(Self_ID
);
753 if not Single_Lock
then
757 -- We need to explicitely wait for the task to be terminated here
758 -- because on true concurrent system, we may end this procedure
759 -- before the tasks are really terminated.
761 Write_Lock
(Self_ID
);
764 exit when Utilities
.Independent_Task_Count
= 0;
766 -- We used to yield here, but this did not take into account
767 -- low priority tasks that would cause dead lock in some cases.
771 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
772 Self_ID
.Common
.State
, Ignore
, Ignore
);
775 -- ??? On multi-processor environments, it seems that the above loop
776 -- isn't sufficient, so we need to add an additional delay.
779 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
780 Self_ID
.Common
.State
, Ignore
, Ignore
);
788 -- Complete the environment task
790 Vulnerable_Complete_Task
(Self_ID
);
792 System
.Finalization_Implementation
.Finalize_Global_List
;
794 SSL
.Abort_Defer
:= SSL
.Abort_Defer_NT
'Access;
795 SSL
.Abort_Undefer
:= SSL
.Abort_Undefer_NT
'Access;
796 SSL
.Lock_Task
:= SSL
.Task_Lock_NT
'Access;
797 SSL
.Unlock_Task
:= SSL
.Task_Unlock_NT
'Access;
798 SSL
.Get_Jmpbuf_Address
:= SSL
.Get_Jmpbuf_Address_NT
'Access;
799 SSL
.Set_Jmpbuf_Address
:= SSL
.Set_Jmpbuf_Address_NT
'Access;
800 SSL
.Get_Sec_Stack_Addr
:= SSL
.Get_Sec_Stack_Addr_NT
'Access;
801 SSL
.Set_Sec_Stack_Addr
:= SSL
.Set_Sec_Stack_Addr_NT
'Access;
802 SSL
.Get_Exc_Stack_Addr
:= SSL
.Get_Exc_Stack_Addr_NT
'Access;
803 SSL
.Set_Exc_Stack_Addr
:= SSL
.Set_Exc_Stack_Addr_NT
'Access;
804 SSL
.Check_Abort_Status
:= SSL
.Check_Abort_Status_NT
'Access;
805 SSL
.Get_Stack_Info
:= SSL
.Get_Stack_Info_NT
'Access;
807 -- Don't bother trying to finalize Initialization.Global_Task_Lock
808 -- and System.Task_Primitives.RTS_Lock.
810 end Finalize_Global_Tasks
;
816 procedure Free_Task
(T
: Task_Id
) is
817 Self_Id
: constant Task_Id
:= Self
;
820 if T
.Common
.State
= Terminated
then
822 -- It is not safe to call Abort_Defer or Write_Lock at this stage
824 Initialization
.Task_Lock
(Self_Id
);
827 Initialization
.Remove_From_All_Tasks_List
(T
);
830 Initialization
.Task_Unlock
(Self_Id
);
832 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
834 -- If the task is not terminated, then we simply ignore the call. This
835 -- happens when a user program attempts an unchecked deallocation on
836 -- a non-terminated task.
847 -- The task wrapper is a procedure that is called first for each task
848 -- task body, and which in turn calls the compiler-generated task body
849 -- procedure. The wrapper's main job is to do initialization for the task.
850 -- It also has some locally declared objects that server as per-task local
851 -- data. Task finalization is done by Complete_Task, which is called from
852 -- an at-end handler that the compiler generates.
854 procedure Task_Wrapper
(Self_ID
: Task_Id
) is
855 use type System
.Parameters
.Size_Type
;
856 use type SSE
.Storage_Offset
;
857 use System
.Standard_Library
;
859 Secondary_Stack
: aliased SSE
.Storage_Array
860 (1 .. Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
*
861 SSE
.Storage_Offset
(Parameters
.Sec_Stack_Ratio
) / 100);
862 Secondary_Stack_Address
: System
.Address
:= Secondary_Stack
'Address;
865 pragma Assert
(Self_ID
.Deferral_Level
= 1);
867 if not Parameters
.Sec_Stack_Dynamic
then
868 Self_ID
.Common
.Compiler_Data
.Sec_Stack_Addr
:=
869 Secondary_Stack
'Address;
870 SST
.SS_Init
(Secondary_Stack_Address
, Integer (Secondary_Stack
'Last));
873 -- Set the guard page at the bottom of the stack. The call to
874 -- unprotect the page is done in Terminate_Task
876 Stack_Guard
(Self_ID
, True);
878 -- Initialize low-level TCB components, that cannot be initialized
879 -- by the creator. Enter_Task sets Self_ID.Known_Tasks_Index and
880 -- also Self_ID.LL.Thread
882 Enter_Task
(Self_ID
);
884 -- We lock RTS_Lock to wait for activator to finish activating
885 -- the rest of the chain, so that everyone in the chain comes out
886 -- in priority order.
888 -- This also protects the value of
889 -- Self_ID.Common.Activator.Common.Wait_Count.
895 -- We are separating the following portion of the code in order to
896 -- place the exception handlers in a different block. In this way,
897 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
898 -- set Self in Enter_Task
900 -- Call the task body procedure
902 -- The task body is called with abort still deferred. That
903 -- eliminates a dangerous window, for which we had to patch-up in
906 -- During the expansion of the task body, we insert an RTS-call
907 -- to Abort_Undefer, at the first point where abort should be
910 Self_ID
.Common
.Task_Entry_Point
(Self_ID
.Common
.Task_Arg
);
911 Initialization
.Defer_Abort_Nestable
(Self_ID
);
914 -- We can't call Terminate_Task in the exception handlers below,
915 -- since there may be (e.g. in the case of GCC exception handling)
916 -- clean ups associated with the exception handler that need to
917 -- access task specific data.
919 -- Defer abortion so that this task can't be aborted while exiting
921 when Standard
'Abort_Signal =>
922 Initialization
.Defer_Abort_Nestable
(Self_ID
);
925 -- ??? Using an E : others here causes CD2C11A to fail on
926 -- DEC Unix, see 7925-005.
928 Initialization
.Defer_Abort_Nestable
(Self_ID
);
930 -- Perform the task specific exception tracing duty. We handle
931 -- these outputs here and not in the common notification routine
932 -- because we need access to tasking related data and we don't
933 -- want to drag dependencies against tasking related units in the
934 -- the common notification units. Additionally, no trace is ever
935 -- triggered from the common routine for the Unhandled_Raise case
936 -- in tasks, since an exception never appears unhandled in this
937 -- context because of this handler.
939 if Exception_Trace
= Unhandled_Raise
then
940 Trace_Unhandled_Exception_In_Task
(Self_ID
);
944 Terminate_Task
(Self_ID
);
951 -- Before we allow the thread to exit, we must clean up. This is a
952 -- a delicate job. We must wake up the task's master, who may immediately
953 -- try to deallocate the ATCB out from under the current task WHILE IT IS
956 -- To avoid this, the parent task must be blocked up to the latest
957 -- statement executed. The trouble is that we have another step that we
958 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
959 -- We have to postpone that until the end because compiler-generated code
960 -- is likely to try to access that data at just about any point.
962 -- We can't call Destroy_TSD while we are holding any other locks, because
963 -- it locks Global_Task_Lock, and our deadlock prevention rules require
964 -- that to be the outermost lock. Our first "solution" was to just lock
965 -- Global_Task_Lock in addition to the other locks, and force the parent
966 -- to also lock this lock between its wakeup and its freeing of the ATCB.
967 -- See Complete_Task for the parent-side of the code that has the matching
968 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
969 -- since the operation Task_Unlock continued to access the ATCB after
970 -- unlocking, after which the parent was observed to race ahead,
971 -- deallocate the ATCB, and then reallocate it to another task. The
972 -- call to Undefer_Abortion in Task_Unlock by the "terminated" task was
973 -- overwriting the data of the new task that reused the ATCB! To solve
974 -- this problem, we introduced the new operation Final_Task_Unlock.
976 procedure Terminate_Task
(Self_ID
: Task_Id
) is
977 Environment_Task
: constant Task_Id
:= STPO
.Environment_Task
;
978 Master_of_Task
: Integer;
981 Debug
.Task_Termination_Hook
;
983 if Runtime_Traces
then
984 Send_Trace_Info
(T_Terminate
);
987 -- Since GCC cannot allocate stack chunks efficiently without reordering
988 -- some of the allocations, we have to handle this unexpected situation
989 -- here. We should normally never have to call Vulnerable_Complete_Task
990 -- here. See 6602-003 for more details.
992 if Self_ID
.Common
.Activator
/= null then
993 Vulnerable_Complete_Task
(Self_ID
);
996 Initialization
.Task_Lock
(Self_ID
);
1002 Master_of_Task
:= Self_ID
.Master_of_Task
;
1004 -- Check if the current task is an independent task
1005 -- If so, decrement the Independent_Task_Count value.
1007 if Master_of_Task
= 2 then
1009 Utilities
.Independent_Task_Count
:=
1010 Utilities
.Independent_Task_Count
- 1;
1013 Write_Lock
(Environment_Task
);
1014 Utilities
.Independent_Task_Count
:=
1015 Utilities
.Independent_Task_Count
- 1;
1016 Unlock
(Environment_Task
);
1020 -- Unprotect the guard page if needed
1022 Stack_Guard
(Self_ID
, False);
1024 Utilities
.Make_Passive
(Self_ID
, Task_Completed
=> True);
1030 pragma Assert
(Check_Exit
(Self_ID
));
1032 SSL
.Destroy_TSD
(Self_ID
.Common
.Compiler_Data
);
1033 Initialization
.Final_Task_Unlock
(Self_ID
);
1036 -- past this point, this thread must assume that the ATCB
1037 -- has been deallocated. It should not be accessed again.
1039 if Master_of_Task
> 0 then
1048 function Terminated
(T
: Task_Id
) return Boolean is
1049 Self_ID
: constant Task_Id
:= STPO
.Self
;
1053 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1060 Result
:= T
.Common
.State
= Terminated
;
1067 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
1071 ----------------------------------------
1072 -- Trace_Unhandled_Exception_In_Task --
1073 ----------------------------------------
1075 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
) is
1076 procedure To_Stderr
(S
: String);
1077 pragma Import
(Ada
, To_Stderr
, "__gnat_to_stderr");
1079 use System
.Task_Info
;
1080 use System
.Soft_Links
;
1081 use System
.Standard_Library
;
1083 function To_Address
is new
1084 Unchecked_Conversion
(Task_Id
, System
.Address
);
1086 function Tailored_Exception_Information
1087 (E
: Exception_Occurrence
) return String;
1089 (Ada
, Tailored_Exception_Information
,
1090 "__gnat_tailored_exception_information");
1092 Excep
: constant Exception_Occurrence_Access
:=
1093 SSL
.Get_Current_Excep
.all;
1096 -- This procedure is called by the task outermost handler in
1097 -- Task_Wrapper below, so only once the task stack has been fully
1098 -- unwound. The common notification routine has been called at the
1099 -- raise point already.
1101 To_Stderr
("task ");
1103 if Self_Id
.Common
.Task_Image_Len
/= 0 then
1105 (Self_Id
.Common
.Task_Image
(1 .. Self_Id
.Common
.Task_Image_Len
));
1109 To_Stderr
(System
.Address_Image
(To_Address
(Self_Id
)));
1110 To_Stderr
(" terminated by unhandled exception");
1111 To_Stderr
((1 => ASCII
.LF
));
1112 To_Stderr
(Tailored_Exception_Information
(Excep
.all));
1113 end Trace_Unhandled_Exception_In_Task
;
1115 ------------------------------------
1116 -- Vulnerable_Complete_Activation --
1117 ------------------------------------
1119 -- As in several other places, the locks of the activator and activated
1120 -- task are both locked here. This follows our deadlock prevention lock
1121 -- ordering policy, since the activated task must be created after the
1124 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
) is
1125 Activator
: constant Task_Id
:= Self_ID
.Common
.Activator
;
1128 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Activation", 'C'));
1130 Write_Lock
(Activator
);
1131 Write_Lock
(Self_ID
);
1133 pragma Assert
(Self_ID
.Common
.Activator
/= null);
1135 -- Remove dangling reference to Activator, since a task may
1136 -- outlive its activator.
1138 Self_ID
.Common
.Activator
:= null;
1140 -- Wake up the activator, if it is waiting for a chain of tasks to
1141 -- activate, and we are the last in the chain to complete activation.
1143 if Activator
.Common
.State
= Activator_Sleep
then
1144 Activator
.Common
.Wait_Count
:= Activator
.Common
.Wait_Count
- 1;
1146 if Activator
.Common
.Wait_Count
= 0 then
1147 Wakeup
(Activator
, Activator_Sleep
);
1151 -- The activator raises a Tasking_Error if any task it is activating
1152 -- is completed before the activation is done. However, if the reason
1153 -- for the task completion is an abortion, we do not raise an exception.
1156 if not Self_ID
.Callable
and then Self_ID
.Pending_ATC_Level
/= 0 then
1157 Activator
.Common
.Activation_Failed
:= True;
1163 -- After the activation, active priority should be the same
1164 -- as base priority. We must unlock the Activator first,
1165 -- though, since it should not wait if we have lower priority.
1167 if Get_Priority
(Self_ID
) /= Self_ID
.Common
.Base_Priority
then
1168 Write_Lock
(Self_ID
);
1169 Set_Priority
(Self_ID
, Self_ID
.Common
.Base_Priority
);
1172 end Vulnerable_Complete_Activation
;
1174 --------------------------------
1175 -- Vulnerable_Complete_Master --
1176 --------------------------------
1178 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
) is
1181 CM
: constant Master_Level
:= Self_ID
.Master_Within
;
1182 T
: aliased Task_Id
;
1184 To_Be_Freed
: Task_Id
;
1185 -- This is a list of ATCBs to be freed, after we have released
1186 -- all RTS locks. This is necessary because of the locking order
1187 -- rules, since the storage manager uses Global_Task_Lock.
1189 pragma Warnings
(Off
);
1190 function Check_Unactivated_Tasks
return Boolean;
1191 pragma Warnings
(On
);
1192 -- Temporary error-checking code below. This is part of the checks
1193 -- added in the new run time. Call it only inside a pragma Assert.
1195 -----------------------------
1196 -- Check_Unactivated_Tasks --
1197 -----------------------------
1199 function Check_Unactivated_Tasks
return Boolean is
1201 if not Single_Lock
then
1205 Write_Lock
(Self_ID
);
1206 C
:= All_Tasks_List
;
1208 while C
/= null loop
1209 if C
.Common
.Activator
= Self_ID
then
1213 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1216 if C
.Common
.State
= Unactivated
then
1223 C
:= C
.Common
.All_Tasks_Link
;
1228 if not Single_Lock
then
1233 end Check_Unactivated_Tasks
;
1235 -- Start of processing for Vulnerable_Complete_Master
1239 (Debug
.Trace
(Self_ID
, "V_Complete_Master", 'C'));
1241 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1242 pragma Assert
(Self_ID
.Deferral_Level
> 0);
1244 -- Count how many active dependent tasks this master currently
1245 -- has, and record this in Wait_Count.
1247 -- This count should start at zero, since it is initialized to
1248 -- zero for new tasks, and the task should not exit the
1249 -- sleep-loops that use this count until the count reaches zero.
1252 Write_Lock
(Self_ID
);
1253 C
:= All_Tasks_List
;
1255 while C
/= null loop
1256 if C
.Common
.Activator
= Self_ID
then
1257 pragma Assert
(C
.Common
.State
= Unactivated
);
1260 C
.Common
.Activator
:= null;
1261 C
.Common
.State
:= Terminated
;
1262 C
.Callable
:= False;
1263 Utilities
.Cancel_Queued_Entry_Calls
(C
);
1267 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1270 if C
.Awake_Count
/= 0 then
1271 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1277 C
:= C
.Common
.All_Tasks_Link
;
1280 Self_ID
.Common
.State
:= Master_Completion_Sleep
;
1283 if not Single_Lock
then
1287 -- Wait until dependent tasks are all terminated or ready to terminate.
1288 -- While waiting, the task may be awakened if the task's priority needs
1289 -- changing, or this master is aborted. In the latter case, we want
1290 -- to abort the dependents, and resume waiting until Wait_Count goes
1293 Write_Lock
(Self_ID
);
1296 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
1297 exit when Self_ID
.Common
.Wait_Count
= 0;
1299 -- Here is a difference as compared to Complete_Master
1301 if Self_ID
.Pending_ATC_Level
< Self_ID
.ATC_Nesting_Level
1302 and then not Self_ID
.Dependents_Aborted
1305 Abort_Dependents
(Self_ID
);
1309 Abort_Dependents
(Self_ID
);
1311 Write_Lock
(Self_ID
);
1314 Sleep
(Self_ID
, Master_Completion_Sleep
);
1318 Self_ID
.Common
.State
:= Runnable
;
1321 -- Dependents are all terminated or on terminate alternatives.
1322 -- Now, force those on terminate alternatives to terminate, by
1325 pragma Assert
(Check_Unactivated_Tasks
);
1327 if Self_ID
.Alive_Count
> 1 then
1329 -- Consider finding a way to skip the following extra steps if there
1330 -- are no dependents with terminate alternatives. This could be done
1331 -- by adding another count to the ATCB, similar to Awake_Count, but
1332 -- keeping track of tasks that are on terminate alternatives.
1334 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1336 -- Force any remaining dependents to terminate, by aborting them.
1338 if not Single_Lock
then
1342 Abort_Dependents
(Self_ID
);
1344 -- Above, when we "abort" the dependents we are simply using this
1345 -- operation for convenience. We are not required to support the full
1346 -- abort-statement semantics; in particular, we are not required to
1347 -- immediately cancel any queued or in-service entry calls. That is
1348 -- good, because if we tried to cancel a call we would need to lock
1349 -- the caller, in order to wake the caller up. Our anti-deadlock
1350 -- rules prevent us from doing that without releasing the locks on C
1351 -- and Self_ID. Releasing and retaking those locks would be wasteful
1352 -- at best, and should not be considered further without more
1353 -- detailed analysis of potential concurrent accesses to the
1354 -- ATCBs of C and Self_ID.
1356 -- Count how many "alive" dependent tasks this master currently
1357 -- has, and record this in Wait_Count. This count should start at
1358 -- zero, since it is initialized to zero for new tasks, and the
1359 -- task should not exit the sleep-loops that use this count until
1360 -- the count reaches zero.
1362 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1364 Write_Lock
(Self_ID
);
1365 C
:= All_Tasks_List
;
1367 while C
/= null loop
1368 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1371 pragma Assert
(C
.Awake_Count
= 0);
1373 if C
.Alive_Count
> 0 then
1374 pragma Assert
(C
.Terminate_Alternative
);
1375 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1381 C
:= C
.Common
.All_Tasks_Link
;
1384 Self_ID
.Common
.State
:= Master_Phase_2_Sleep
;
1387 if not Single_Lock
then
1391 -- Wait for all counted tasks to finish terminating themselves.
1393 Write_Lock
(Self_ID
);
1396 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
1397 exit when Self_ID
.Common
.Wait_Count
= 0;
1398 Sleep
(Self_ID
, Master_Phase_2_Sleep
);
1401 Self_ID
.Common
.State
:= Runnable
;
1405 -- We don't wake up for abortion here. We are already terminating
1406 -- just as fast as we can, so there is no point.
1408 -- Remove terminated tasks from the list of Self_ID's dependents, but
1409 -- don't free their ATCBs yet, because of lock order restrictions,
1410 -- which don't allow us to call "free" or "malloc" while holding any
1411 -- other locks. Instead, we put those ATCBs to be freed onto a
1412 -- temporary list, called To_Be_Freed.
1414 if not Single_Lock
then
1418 C
:= All_Tasks_List
;
1421 while C
/= null loop
1422 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
>= CM
then
1424 P
.Common
.All_Tasks_Link
:= C
.Common
.All_Tasks_Link
;
1426 All_Tasks_List
:= C
.Common
.All_Tasks_Link
;
1429 T
:= C
.Common
.All_Tasks_Link
;
1430 C
.Common
.All_Tasks_Link
:= To_Be_Freed
;
1436 C
:= C
.Common
.All_Tasks_Link
;
1442 -- Free all the ATCBs on the list To_Be_Freed.
1444 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1445 -- any interrupt entries are detached from them they should no longer
1448 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1449 -- avoid a race between a terminating task and its parent. The parent
1450 -- might try to deallocate the ACTB out from underneath the exiting
1451 -- task. Note that Free will also lock Global_Task_Lock, but that is
1452 -- OK, since this is the *one* lock for which we have a mechanism to
1453 -- support nested locking. See Task_Wrapper and its finalizer for more
1457 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1458 -- references to terminated library-level tasks, which could
1459 -- otherwise occur during finalization of library-level objects.
1460 -- A better solution might be to hook task objects into the
1461 -- finalization chain and deallocate the ATCB when the task
1462 -- object is deallocated. However, this change is not likely
1463 -- to gain anything significant, since all this storage should
1464 -- be recovered en-masse when the process exits.
1466 while To_Be_Freed
/= null loop
1468 To_Be_Freed
:= T
.Common
.All_Tasks_Link
;
1470 -- ??? On SGI there is currently no Interrupt_Manager, that's
1471 -- why we need to check if the Interrupt_Manager_ID is null
1473 if T
.Interrupt_Entry
and Interrupt_Manager_ID
/= null then
1475 Detach_Interrupt_Entries_Index
: constant Task_Entry_Index
:= 1;
1476 -- Corresponds to the entry index of System.Interrupts.
1477 -- Interrupt_Manager.Detach_Interrupt_Entries.
1478 -- Be sure to update this value when changing
1479 -- Interrupt_Manager specs.
1481 type Param_Type
is access all Task_Id
;
1483 Param
: aliased Param_Type
:= T
'Access;
1486 System
.Tasking
.Rendezvous
.Call_Simple
1487 (Interrupt_Manager_ID
, Detach_Interrupt_Entries_Index
,
1492 if (T
.Common
.Parent
/= null
1493 and then T
.Common
.Parent
.Common
.Parent
/= null)
1494 or else T
.Master_of_Task
> 3
1496 Initialization
.Task_Lock
(Self_ID
);
1498 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1499 -- has not been called yet (case of an unactivated task).
1501 if T
.Common
.Compiler_Data
.Sec_Stack_Addr
/= Null_Address
then
1502 SSL
.Destroy_TSD
(T
.Common
.Compiler_Data
);
1505 Vulnerable_Free_Task
(T
);
1506 Initialization
.Task_Unlock
(Self_ID
);
1510 -- It might seem nice to let the terminated task deallocate its own
1511 -- ATCB. That would not cover the case of unactivated tasks. It also
1512 -- would force us to keep the underlying thread around past termination,
1513 -- since references to the ATCB are possible past termination.
1514 -- Currently, we get rid of the thread as soon as the task terminates,
1515 -- and let the parent recover the ATCB later.
1517 -- Some day, if we want to recover the ATCB earlier, at task
1518 -- termination, we could consider using "fat task IDs", that include the
1519 -- serial number with the ATCB pointer, to catch references to tasks
1520 -- that no longer have ATCBs. It is not clear how much this would gain,
1521 -- since the user-level task object would still be occupying storage.
1523 -- Make next master level up active.
1524 -- We don't need to lock the ATCB, since the value is only updated by
1525 -- each task for itself.
1527 Self_ID
.Master_Within
:= CM
- 1;
1528 end Vulnerable_Complete_Master
;
1530 ------------------------------
1531 -- Vulnerable_Complete_Task --
1532 ------------------------------
1534 -- Complete the calling task
1536 -- This procedure must be called with abort deferred. (That's why the
1537 -- name has "Vulnerable" in it.) It should only be called by Complete_Task
1538 -- and Finalize_Global_Tasks (for the environment task).
1540 -- The effect is similar to that of Complete_Master. Differences include
1541 -- the closing of entries here, and computation of the number of active
1542 -- dependent tasks in Complete_Master.
1544 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1545 -- because that does its own locking, and because we do not need the lock
1546 -- to test Self_ID.Common.Activator. That value should only be read and
1547 -- modified by Self.
1549 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
) is
1551 pragma Assert
(Self_ID
.Deferral_Level
> 0);
1552 pragma Assert
(Self_ID
= Self
);
1553 pragma Assert
(Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 1
1555 Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2);
1556 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1557 pragma Assert
(Self_ID
.Open_Accepts
= null);
1558 pragma Assert
(Self_ID
.ATC_Nesting_Level
= 1);
1560 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Task", 'C'));
1566 Write_Lock
(Self_ID
);
1567 Self_ID
.Callable
:= False;
1569 -- In theory, Self should have no pending entry calls left on its
1570 -- call-stack. Each async. select statement should clean its own call,
1571 -- and blocking entry calls should defer abort until the calls are
1572 -- cancelled, then clean up.
1574 Utilities
.Cancel_Queued_Entry_Calls
(Self_ID
);
1577 if Self_ID
.Common
.Activator
/= null then
1578 Vulnerable_Complete_Activation
(Self_ID
);
1585 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2
1586 -- we may have dependent tasks for which we need to wait.
1587 -- Otherwise, we can just exit.
1589 if Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2 then
1590 Vulnerable_Complete_Master
(Self_ID
);
1592 end Vulnerable_Complete_Task
;
1594 --------------------------
1595 -- Vulnerable_Free_Task --
1596 --------------------------
1598 -- Recover all runtime system storage associated with the task T.
1599 -- This should only be called after T has terminated and will no
1600 -- longer be referenced.
1602 -- For tasks created by an allocator that fails, due to an exception,
1603 -- it is called from Expunge_Unactivated_Tasks.
1605 -- For tasks created by elaboration of task object declarations it
1606 -- is called from the finalization code of the Task_Wrapper procedure.
1607 -- It is also called from Unchecked_Deallocation, for objects that
1608 -- are or contain tasks.
1610 procedure Vulnerable_Free_Task
(T
: Task_Id
) is
1612 pragma Debug
(Debug
.Trace
(Self
, "Vulnerable_Free_Task", 'C', T
));
1619 Initialization
.Finalize_Attributes_Link
.all (T
);
1626 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
1627 end Vulnerable_Free_Task
;
1630 -- Establish the Adafinal softlink.
1632 -- This is not done inside the central RTS initialization routine
1633 -- to avoid with-ing this package from System.Tasking.Initialization.
1635 SSL
.Adafinal
:= Finalize_Global_Tasks
'Access;
1637 -- Establish soft links for subprograms that manipulate master_id's.
1638 -- This cannot be done when the RTS is initialized, because of various
1639 -- elaboration constraints.
1641 SSL
.Current_Master
:= Stages
.Current_Master
'Access;
1642 SSL
.Enter_Master
:= Stages
.Enter_Master
'Access;
1643 SSL
.Complete_Master
:= Stages
.Complete_Master
'Access;
1644 end System
.Tasking
.Stages
;