1 ------------------------------------------------------------------------------
3 -- GNAT 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) 1992-2006, 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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, 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
.Task_Primitives
.Operations
;
48 -- Used for Finalize_Lock
58 with System
.Soft_Links
;
59 -- These are procedure pointers to non-tasking routines that use task
60 -- specific data. In the absence of tasking, these routines refer to global
61 -- data. In the presense of tasking, they must be replaced with pointers to
62 -- task-specific versions. Also used for Create_TSD, Destroy_TSD,
63 -- Get_Current_Excep, Finalize_Global_List, Task_Termination, Handler.
65 with System
.Tasking
.Initialization
;
66 -- Used for Remove_From_All_Tasks_List
69 -- Initialization.Poll_Base_Priority_Change
70 -- Finalize_Attributes_Link
71 -- Initialize_Attributes_Link
73 pragma Elaborate_All
(System
.Tasking
.Initialization
);
74 -- This insures that tasking is initialized if any tasks are created
76 with System
.Tasking
.Utilities
;
77 -- Used for Make_Passive
81 with System
.Tasking
.Queuing
;
82 -- Used for Dequeue_Head
84 with System
.Tasking
.Rendezvous
;
85 -- Used for Call_Simple
87 with System
.OS_Primitives
;
88 -- Used for Delay_Modes
90 with System
.Secondary_Stack
;
93 with System
.Storage_Elements
;
94 -- Used for Storage_Array
96 with System
.Restrictions
;
97 -- Used for Abort_Allowed
99 with System
.Standard_Library
;
100 -- Used for Exception_Trace
102 with System
.Traces
.Tasking
;
103 -- Used for Send_Trace_Info
105 with Unchecked_Deallocation
;
106 -- To recover from failure of ATCB initialization
108 with System
.Stack_Usage
;
110 package body System
.Tasking
.Stages
is
112 package STPO
renames System
.Task_Primitives
.Operations
;
113 package SSL
renames System
.Soft_Links
;
114 package SSE
renames System
.Storage_Elements
;
115 package SST
renames System
.Secondary_Stack
;
121 use Task_Primitives
.Operations
;
125 use System
.Traces
.Tasking
;
127 -----------------------
128 -- Local Subprograms --
129 -----------------------
131 procedure Free
is new
132 Unchecked_Deallocation
(Ada_Task_Control_Block
, Task_Id
);
134 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
);
135 -- This procedure outputs the task specific message for exception
138 procedure Task_Wrapper
(Self_ID
: Task_Id
);
139 pragma Convention
(C
, Task_Wrapper
);
140 -- This is the procedure that is called by the GNULL from the new context
141 -- when a task is created. It waits for activation and then calls the task
142 -- body procedure. When the task body procedure completes, it terminates
145 -- The Task_Wrapper's address will be provided to the underlying threads
146 -- library as the task entry point. Convention C is what makes most sense
147 -- for that purpose (Export C would make the function globally visible,
148 -- and affect the link name on which GDB depends). This will in addition
149 -- trigger an automatic stack alignment suitable for GCC's assumptions if
152 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
);
153 -- Complete the calling task. This procedure must be called with
154 -- abort deferred. It should only be called by Complete_Task and
155 -- Finalizate_Global_Tasks (for the environment task).
157 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
);
158 -- Complete the current master of the calling task. This procedure
159 -- must be called with abort deferred. It should only be called by
160 -- Vulnerable_Complete_Task and Complete_Master.
162 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
);
163 -- Signal to Self_ID's activator that Self_ID has completed activation.
164 -- This procedure must be called with abort deferred.
166 procedure Abort_Dependents
(Self_ID
: Task_Id
);
167 -- Abort all the direct dependents of Self at its current master
168 -- nesting level, plus all of their dependents, transitively.
169 -- RTS_Lock should be locked by the caller.
171 procedure Vulnerable_Free_Task
(T
: Task_Id
);
172 -- Recover all runtime system storage associated with the task T.
173 -- This should only be called after T has terminated and will no
174 -- longer be referenced.
176 -- For tasks created by an allocator that fails, due to an exception,
177 -- it is called from Expunge_Unactivated_Tasks.
179 -- It is also called from Unchecked_Deallocation, for objects that
180 -- are or contain tasks.
182 -- Different code is used at master completion, in Terminate_Dependents,
183 -- due to a need for tighter synchronization with the master.
185 ----------------------
186 -- Abort_Dependents --
187 ----------------------
189 procedure Abort_Dependents
(Self_ID
: Task_Id
) is
196 P
:= C
.Common
.Parent
;
200 -- ??? C is supposed to take care of its own dependents, so
201 -- there should be no need to worry about them. Need to double
204 if C
.Master_of_Task
= Self_ID
.Master_Within
then
205 Utilities
.Abort_One_Task
(Self_ID
, C
);
206 C
.Dependents_Aborted
:= True;
212 P
:= P
.Common
.Parent
;
215 C
:= C
.Common
.All_Tasks_Link
;
218 Self_ID
.Dependents_Aborted
:= True;
219 end Abort_Dependents
;
225 procedure Abort_Tasks
(Tasks
: Task_List
) is
227 Utilities
.Abort_Tasks
(Tasks
);
234 -- Note that locks of activator and activated task are both locked
235 -- here. This is necessary because C.Common.State and
236 -- Self.Common.Wait_Count have to be synchronized. This is safe from
237 -- deadlock because the activator is always created before the activated
238 -- task. That satisfies our in-order-of-creation ATCB locking policy.
240 -- At one point, we may also lock the parent, if the parent is
241 -- different from the activator. That is also consistent with the
242 -- lock ordering policy, since the activator cannot be created
243 -- before the parent.
245 -- Since we are holding both the activator's lock, and Task_Wrapper
246 -- locks that before it does anything more than initialize the
247 -- low-level ATCB components, it should be safe to wait to update
248 -- the counts until we see that the thread creation is successful.
250 -- If the thread creation fails, we do need to close the entries
251 -- of the task. The first phase, of dequeuing calls, only requires
252 -- locking the acceptor's ATCB, but the waking up of the callers
253 -- requires locking the caller's ATCB. We cannot safely do this
254 -- while we are holding other locks. Therefore, the queue-clearing
255 -- operation is done in a separate pass over the activation chain.
257 procedure Activate_Tasks
(Chain_Access
: Activation_Chain_Access
) is
258 Self_ID
: constant Task_Id
:= STPO
.Self
;
261 Next_C
, Last_C
: Task_Id
;
262 Activate_Prio
: System
.Any_Priority
;
264 All_Elaborated
: Boolean := True;
267 -- If pragma Detect_Blocking is active, then we must check whether this
268 -- potentially blocking operation is called from a protected action.
270 if System
.Tasking
.Detect_Blocking
271 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
273 Ada
.Exceptions
.Raise_Exception
274 (Program_Error
'Identity, "potentially blocking operation");
278 (Debug
.Trace
(Self_ID
, "Activate_Tasks", 'C'));
280 Initialization
.Defer_Abort_Nestable
(Self_ID
);
282 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
284 -- Lock RTS_Lock, to prevent activated tasks from racing ahead before
285 -- we finish activating the chain.
289 -- Check that all task bodies have been elaborated
291 C
:= Chain_Access
.T_ID
;
294 if C
.Common
.Elaborated
/= null
295 and then not C
.Common
.Elaborated
.all
297 All_Elaborated
:= False;
300 -- Reverse the activation chain so that tasks are
301 -- activated in the same order they're declared.
303 Next_C
:= C
.Common
.Activation_Link
;
304 C
.Common
.Activation_Link
:= Last_C
;
309 Chain_Access
.T_ID
:= Last_C
;
311 if not All_Elaborated
then
313 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
315 (Program_Error
'Identity, "Some tasks have not been elaborated");
318 -- Activate all the tasks in the chain. Creation of the thread of
319 -- control was deferred until activation. So create it now.
321 C
:= Chain_Access
.T_ID
;
323 if C
.Common
.State
/= Terminated
then
324 pragma Assert
(C
.Common
.State
= Unactivated
);
326 P
:= C
.Common
.Parent
;
330 if C
.Common
.Base_Priority
< Get_Priority
(Self_ID
) then
331 Activate_Prio
:= Get_Priority
(Self_ID
);
333 Activate_Prio
:= C
.Common
.Base_Priority
;
336 System
.Task_Primitives
.Operations
.Create_Task
337 (C
, Task_Wrapper
'Address,
339 (C
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
340 Activate_Prio
, Success
);
342 -- There would be a race between the created task and the
343 -- creator to do the following initialization, if we did not
344 -- have a Lock/Unlock_RTS pair in the task wrapper to prevent
345 -- it from racing ahead.
348 C
.Common
.State
:= Runnable
;
351 P
.Awake_Count
:= P
.Awake_Count
+ 1;
352 P
.Alive_Count
:= P
.Alive_Count
+ 1;
354 if P
.Common
.State
= Master_Completion_Sleep
and then
355 C
.Master_of_Task
= P
.Master_Within
357 pragma Assert
(Self_ID
/= P
);
358 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
+ 1;
365 -- No need to set Awake_Count, State, etc. here since the loop
366 -- below will do that for any Unactivated tasks.
370 Self_ID
.Common
.Activation_Failed
:= True;
374 C
:= C
.Common
.Activation_Link
;
377 if not Single_Lock
then
381 -- Close the entries of any tasks that failed thread creation,
382 -- and count those that have not finished activation.
384 Write_Lock
(Self_ID
);
385 Self_ID
.Common
.State
:= Activator_Sleep
;
387 C
:= Chain_Access
.T_ID
;
391 if C
.Common
.State
= Unactivated
then
392 C
.Common
.Activator
:= null;
393 C
.Common
.State
:= Terminated
;
395 Utilities
.Cancel_Queued_Entry_Calls
(C
);
397 elsif C
.Common
.Activator
/= null then
398 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
402 P
:= C
.Common
.Activation_Link
;
403 C
.Common
.Activation_Link
:= null;
407 -- Wait for the activated tasks to complete activation. It is
408 -- unsafe to abort any of these tasks until the count goes to zero.
411 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
412 exit when Self_ID
.Common
.Wait_Count
= 0;
413 Sleep
(Self_ID
, Activator_Sleep
);
416 Self_ID
.Common
.State
:= Runnable
;
423 -- Remove the tasks from the chain
425 Chain_Access
.T_ID
:= null;
426 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
428 if Self_ID
.Common
.Activation_Failed
then
429 Self_ID
.Common
.Activation_Failed
:= False;
430 Raise_Exception
(Tasking_Error
'Identity,
431 "Failure during activation");
435 -------------------------
436 -- Complete_Activation --
437 -------------------------
439 procedure Complete_Activation
is
440 Self_ID
: constant Task_Id
:= STPO
.Self
;
443 Initialization
.Defer_Abort_Nestable
(Self_ID
);
449 Vulnerable_Complete_Activation
(Self_ID
);
455 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
458 -- Why do we need to allow for nested deferral here?
460 if Runtime_Traces
then
461 Send_Trace_Info
(T_Activate
);
463 end Complete_Activation
;
465 ---------------------
466 -- Complete_Master --
467 ---------------------
469 procedure Complete_Master
is
470 Self_ID
: constant Task_Id
:= STPO
.Self
;
472 pragma Assert
(Self_ID
.Deferral_Level
> 0);
473 Vulnerable_Complete_Master
(Self_ID
);
480 -- See comments on Vulnerable_Complete_Task for details
482 procedure Complete_Task
is
483 Self_ID
: constant Task_Id
:= STPO
.Self
;
486 pragma Assert
(Self_ID
.Deferral_Level
> 0);
488 Vulnerable_Complete_Task
(Self_ID
);
490 -- All of our dependents have terminated. Never undefer abort again!
498 -- Compiler interface only. Do not call from within the RTS.
499 -- This must be called to create a new task.
501 procedure Create_Task
503 Size
: System
.Parameters
.Size_Type
;
504 Task_Info
: System
.Task_Info
.Task_Info_Type
;
505 Num_Entries
: Task_Entry_Index
;
506 Master
: Master_Level
;
507 State
: Task_Procedure_Access
;
508 Discriminants
: System
.Address
;
509 Elaborated
: Access_Boolean
;
510 Chain
: in out Activation_Chain
;
512 Created_Task
: out Task_Id
)
515 Self_ID
: constant Task_Id
:= STPO
.Self
;
517 Base_Priority
: System
.Any_Priority
;
521 -- If Master is greater than the current master, it means that Master
522 -- has already awaited its dependent tasks. This raises Program_Error,
523 -- by 4.8(10.3/2). See AI-280.
525 if Master
> Self_ID
.Master_Within
then
526 raise Program_Error
with
527 "create task after awaiting termination";
530 -- If pragma Detect_Blocking is active must be checked whether
531 -- this potentially blocking operation is called from a
534 if System
.Tasking
.Detect_Blocking
535 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
537 Ada
.Exceptions
.Raise_Exception
538 (Program_Error
'Identity, "potentially blocking operation");
542 (Debug
.Trace
(Self_ID
, "Create_Task", 'C'));
544 if Priority
= Unspecified_Priority
then
545 Base_Priority
:= Self_ID
.Common
.Base_Priority
;
547 Base_Priority
:= System
.Any_Priority
(Priority
);
550 -- Find parent P of new Task, via master level number
555 while P
.Master_of_Task
>= Master
loop
556 P
:= P
.Common
.Parent
;
561 Initialization
.Defer_Abort_Nestable
(Self_ID
);
564 T
:= New_ATCB
(Num_Entries
);
567 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
568 Raise_Exception
(Storage_Error
'Identity, "Cannot allocate task");
571 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks.
572 -- Up to this point, it is possible that we may be part of
573 -- a family of tasks that is being aborted.
576 Write_Lock
(Self_ID
);
578 -- Now, we must check that we have not been aborted.
579 -- If so, we should give up on creating this task,
580 -- and simply return.
582 if not Self_ID
.Callable
then
583 pragma Assert
(Self_ID
.Pending_ATC_Level
= 0);
584 pragma Assert
(Self_ID
.Pending_Action
);
586 (Chain
.T_ID
= null or else Chain
.T_ID
.Common
.State
= Unactivated
);
590 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
592 -- ??? Should never get here
594 pragma Assert
(False);
595 raise Standard
'Abort_Signal;
598 Initialize_ATCB
(Self_ID
, State
, Discriminants
, P
, Elaborated
,
599 Base_Priority
, Task_Info
, Size
, T
, Success
);
605 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
607 (Storage_Error
'Identity, "Failed to initialize task");
610 T
.Master_of_Task
:= Master
;
611 T
.Master_Within
:= T
.Master_of_Task
+ 1;
613 for L
in T
.Entry_Calls
'Range loop
614 T
.Entry_Calls
(L
).Self
:= T
;
615 T
.Entry_Calls
(L
).Level
:= L
;
618 if Task_Image
'Length = 0 then
619 T
.Common
.Task_Image_Len
:= 0;
622 T
.Common
.Task_Image
(1) := Task_Image
(Task_Image
'First);
624 -- Remove unwanted blank space generated by 'Image
626 for J
in Task_Image
'First + 1 .. Task_Image
'Last loop
627 if Task_Image
(J
) /= ' '
628 or else Task_Image
(J
- 1) /= '('
631 T
.Common
.Task_Image
(Len
) := Task_Image
(J
);
632 exit when Len
= T
.Common
.Task_Image
'Last;
636 T
.Common
.Task_Image_Len
:= Len
;
642 -- Create TSD as early as possible in the creation of a task, since it
643 -- may be used by the operation of Ada code within the task.
645 SSL
.Create_TSD
(T
.Common
.Compiler_Data
);
646 T
.Common
.Activation_Link
:= Chain
.T_ID
;
648 Initialization
.Initialize_Attributes_Link
.all (T
);
650 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
652 if Runtime_Traces
then
653 Send_Trace_Info
(T_Create
, T
);
661 function Current_Master
return Master_Level
is
663 return STPO
.Self
.Master_Within
;
670 procedure Enter_Master
is
671 Self_ID
: constant Task_Id
:= STPO
.Self
;
673 Self_ID
.Master_Within
:= Self_ID
.Master_Within
+ 1;
676 -------------------------------
677 -- Expunge_Unactivated_Tasks --
678 -------------------------------
680 -- See procedure Close_Entries for the general case
682 procedure Expunge_Unactivated_Tasks
(Chain
: in out Activation_Chain
) is
683 Self_ID
: constant Task_Id
:= STPO
.Self
;
685 Call
: Entry_Call_Link
;
690 (Debug
.Trace
(Self_ID
, "Expunge_Unactivated_Tasks", 'C'));
692 Initialization
.Defer_Abort_Nestable
(Self_ID
);
695 -- Experimentation has shown that abort is sometimes (but not
696 -- always) already deferred when this is called.
698 -- That may indicate an error. Find out what is going on
702 pragma Assert
(C
.Common
.State
= Unactivated
);
704 Temp
:= C
.Common
.Activation_Link
;
706 if C
.Common
.State
= Unactivated
then
710 for J
in 1 .. C
.Entry_Num
loop
711 Queuing
.Dequeue_Head
(C
.Entry_Queues
(J
), Call
);
712 pragma Assert
(Call
= null);
717 Initialization
.Remove_From_All_Tasks_List
(C
);
720 Vulnerable_Free_Task
(C
);
726 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
727 end Expunge_Unactivated_Tasks
;
729 ---------------------------
730 -- Finalize_Global_Tasks --
731 ---------------------------
734 -- We have a potential problem here if finalization of global
735 -- objects does anything with signals or the timer server, since
736 -- by that time those servers have terminated.
738 -- It is hard to see how that would occur
740 -- However, a better solution might be to do all this finalization
741 -- using the global finalization chain.
743 procedure Finalize_Global_Tasks
is
744 Self_ID
: constant Task_Id
:= STPO
.Self
;
748 if Self_ID
.Deferral_Level
= 0 then
750 -- In principle, we should be able to predict whether
751 -- abort is already deferred here (and it should not be deferred
752 -- yet but in practice it seems Finalize_Global_Tasks is being
753 -- called sometimes, from RTS code for exceptions, with abort already
756 Initialization
.Defer_Abort_Nestable
(Self_ID
);
758 -- Never undefer again!!!
761 -- This code is only executed by the environment task
763 pragma Assert
(Self_ID
= Environment_Task
);
765 -- Set Environment_Task'Callable to false to notify library-level tasks
766 -- that it is waiting for them (cf 5619-003).
768 Self_ID
.Callable
:= False;
770 -- Exit level 2 master, for normal tasks in library-level packages
774 -- Force termination of "independent" library-level server tasks
778 Abort_Dependents
(Self_ID
);
780 if not Single_Lock
then
784 -- We need to explicitely wait for the task to be terminated here
785 -- because on true concurrent system, we may end this procedure
786 -- before the tasks are really terminated.
788 Write_Lock
(Self_ID
);
791 exit when Utilities
.Independent_Task_Count
= 0;
793 -- We used to yield here, but this did not take into account
794 -- low priority tasks that would cause dead lock in some cases.
798 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
799 Self_ID
.Common
.State
, Ignore
, Ignore
);
802 -- ??? On multi-processor environments, it seems that the above loop
803 -- isn't sufficient, so we need to add an additional delay.
806 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
807 Self_ID
.Common
.State
, Ignore
, Ignore
);
815 -- Complete the environment task
817 Vulnerable_Complete_Task
(Self_ID
);
819 -- Handle normal task termination by the environment task, but only
820 -- for the normal task termination. In the case of Abnormal and
821 -- Unhandled_Exception they must have been handled before, and the
822 -- task termination soft link must have been changed so the task
823 -- termination routine is not executed twice.
825 SSL
.Task_Termination_Handler
.all (Ada
.Exceptions
.Null_Occurrence
);
827 -- Finalize the global list for controlled objects if needed
829 SSL
.Finalize_Global_List
.all;
831 -- Reset the soft links to non-tasking
833 SSL
.Abort_Defer
:= SSL
.Abort_Defer_NT
'Access;
834 SSL
.Abort_Undefer
:= SSL
.Abort_Undefer_NT
'Access;
835 SSL
.Lock_Task
:= SSL
.Task_Lock_NT
'Access;
836 SSL
.Unlock_Task
:= SSL
.Task_Unlock_NT
'Access;
837 SSL
.Get_Jmpbuf_Address
:= SSL
.Get_Jmpbuf_Address_NT
'Access;
838 SSL
.Set_Jmpbuf_Address
:= SSL
.Set_Jmpbuf_Address_NT
'Access;
839 SSL
.Get_Sec_Stack_Addr
:= SSL
.Get_Sec_Stack_Addr_NT
'Access;
840 SSL
.Set_Sec_Stack_Addr
:= SSL
.Set_Sec_Stack_Addr_NT
'Access;
841 SSL
.Check_Abort_Status
:= SSL
.Check_Abort_Status_NT
'Access;
842 SSL
.Get_Stack_Info
:= SSL
.Get_Stack_Info_NT
'Access;
844 -- Don't bother trying to finalize Initialization.Global_Task_Lock
845 -- and System.Task_Primitives.RTS_Lock.
847 end Finalize_Global_Tasks
;
853 procedure Free_Task
(T
: Task_Id
) is
854 Self_Id
: constant Task_Id
:= Self
;
857 if T
.Common
.State
= Terminated
then
859 -- It is not safe to call Abort_Defer or Write_Lock at this stage
861 Initialization
.Task_Lock
(Self_Id
);
864 Initialization
.Remove_From_All_Tasks_List
(T
);
867 Initialization
.Task_Unlock
(Self_Id
);
869 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
871 -- If the task is not terminated, then we simply ignore the call. This
872 -- happens when a user program attempts an unchecked deallocation on
873 -- a non-terminated task.
884 -- The task wrapper is a procedure that is called first for each task
885 -- task body, and which in turn calls the compiler-generated task body
886 -- procedure. The wrapper's main job is to do initialization for the task.
887 -- It also has some locally declared objects that server as per-task local
888 -- data. Task finalization is done by Complete_Task, which is called from
889 -- an at-end handler that the compiler generates.
891 procedure Task_Wrapper
(Self_ID
: Task_Id
) is
892 use type System
.Parameters
.Size_Type
;
893 use type SSE
.Storage_Offset
;
894 use System
.Standard_Library
;
895 use System
.Stack_Usage
;
897 Bottom_Of_Stack
: aliased Integer;
899 Secondary_Stack_Size
:
900 constant SSE
.Storage_Offset
:=
901 Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
*
902 SSE
.Storage_Offset
(Parameters
.Sec_Stack_Ratio
) / 100;
905 aliased SSE
.Storage_Array
906 (1 .. Secondary_Stack_Size
);
908 pragma Warnings
(Off
);
909 Secondary_Stack_Address
: System
.Address
:= Secondary_Stack
'Address;
911 Small_Overflow_Guard
: constant := 4 * 1024;
912 Big_Overflow_Guard
: constant := 16 * 1024;
913 Small_Stack_Limit
: constant := 64 * 1024;
914 -- ??? These three values are experimental, and seems to work on most
915 -- platforms. They still need to be analyzed further.
918 Natural := Natural (Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
);
920 pragma Warnings
(On
);
921 -- Address of secondary stack. In the fixed secondary stack case, this
922 -- value is not modified, causing a warning, hence the bracketing with
923 -- Warnings (Off/On).
925 SEH_Table
: aliased SSE
.Storage_Array
(1 .. 8);
926 -- Structured Exception Registration table (2 words)
928 procedure Install_SEH_Handler
(Addr
: System
.Address
);
929 pragma Import
(C
, Install_SEH_Handler
, "__gnat_install_SEH_handler");
930 -- Install the SEH (Structured Exception Handling) handler
932 Cause
: Cause_Of_Termination
:= Normal
;
933 -- Indicates the reason why this task terminates. Normal corresponds to
934 -- a task terminating due to completing the last statement of its body,
935 -- or as a result of waiting on a terminate alternative. If the task
936 -- terminates because it is being aborted then Cause will be set to
937 -- Abnormal. If the task terminates because of an exception raised by
938 -- the execution of its task body, then Cause is set to
939 -- Unhandled_Exception.
941 EO
: Exception_Occurrence
;
942 -- If the task terminates because of an exception raised by the
943 -- execution of its task body, then EO will contain the associated
944 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
946 TH
: Termination_Handler
:= null;
947 -- Pointer to the protected procedure to be executed upon task
950 procedure Search_Fall_Back_Handler
(ID
: Task_Id
);
951 -- Procedure that searches recursively a fall-back handler through the
952 -- master relationship. If the handler is found, its pointer is stored
955 procedure Search_Fall_Back_Handler
(ID
: Task_Id
) is
957 -- If there is a fall back handler, store its pointer for later
960 if ID
.Common
.Fall_Back_Handler
/= null then
961 TH
:= ID
.Common
.Fall_Back_Handler
;
963 -- Otherwise look for a fall back handler in the parent
965 elsif ID
.Common
.Parent
/= null then
966 Search_Fall_Back_Handler
(ID
.Common
.Parent
);
968 -- Otherwise, do nothing
973 end Search_Fall_Back_Handler
;
976 pragma Assert
(Self_ID
.Deferral_Level
= 1);
978 -- Assume a size of the stack taken at this stage
980 if Size
< Small_Stack_Limit
then
981 Size
:= Size
- Small_Overflow_Guard
;
983 Size
:= Size
- Big_Overflow_Guard
;
986 if not Parameters
.Sec_Stack_Dynamic
then
987 Self_ID
.Common
.Compiler_Data
.Sec_Stack_Addr
:=
988 Secondary_Stack
'Address;
989 SST
.SS_Init
(Secondary_Stack_Address
, Integer (Secondary_Stack
'Last));
990 Size
:= Size
- Natural (Secondary_Stack_Size
);
993 if System
.Stack_Usage
.Is_Enabled
then
995 Initialize_Analyzer
(Self_ID
.Common
.Analyzer
,
996 Self_ID
.Common
.Task_Image
997 (1 .. Self_ID
.Common
.Task_Image_Len
),
999 SSE
.To_Integer
(Bottom_Of_Stack
'Address));
1001 Fill_Stack
(Self_ID
.Common
.Analyzer
);
1004 -- Set the guard page at the bottom of the stack. The call to unprotect
1005 -- the page is done in Terminate_Task
1007 Stack_Guard
(Self_ID
, True);
1009 -- Initialize low-level TCB components, that cannot be initialized
1010 -- by the creator. Enter_Task sets Self_ID.Known_Tasks_Index and
1011 -- also Self_ID.LL.Thread
1013 Enter_Task
(Self_ID
);
1015 -- We setup the SEH (Structured Exception Handling) handler if supported
1018 Install_SEH_Handler
(SEH_Table
'Address);
1020 -- Initialize exception occurrence
1022 Save_Occurrence
(EO
, Ada
.Exceptions
.Null_Occurrence
);
1024 -- We lock RTS_Lock to wait for activator to finish activating the rest
1025 -- of the chain, so that everyone in the chain comes out in priority
1028 -- This also protects the value of
1029 -- Self_ID.Common.Activator.Common.Wait_Count.
1034 if not System
.Restrictions
.Abort_Allowed
then
1036 -- If Abort is not allowed, reset the deferral level since it will
1037 -- not get changed by the generated code. Keeping a default value
1038 -- of one would prevent some operations (e.g. select or delay) to
1039 -- proceed successfully.
1041 Self_ID
.Deferral_Level
:= 0;
1045 -- We are separating the following portion of the code in order to
1046 -- place the exception handlers in a different block. In this way,
1047 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
1048 -- set Self in Enter_Task
1050 -- Call the task body procedure
1052 -- The task body is called with abort still deferred. That
1053 -- eliminates a dangerous window, for which we had to patch-up in
1056 -- During the expansion of the task body, we insert an RTS-call
1057 -- to Abort_Undefer, at the first point where abort should be
1060 Self_ID
.Common
.Task_Entry_Point
(Self_ID
.Common
.Task_Arg
);
1061 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1064 -- We can't call Terminate_Task in the exception handlers below,
1065 -- since there may be (e.g. in the case of GCC exception handling)
1066 -- clean ups associated with the exception handler that need to
1067 -- access task specific data.
1069 -- Defer abort so that this task can't be aborted while exiting
1071 when Standard
'Abort_Signal =>
1072 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1074 -- Update the cause that motivated the task termination so that
1075 -- the appropriate information is passed to the task termination
1076 -- procedure. Task termination as a result of waiting on a
1077 -- terminate alternative is a normal termination, although it is
1078 -- implemented using the abort mechanisms.
1080 if Self_ID
.Terminate_Alternative
then
1086 -- ??? Using an E : others here causes CD2C11A to fail on
1087 -- DEC Unix, see 7925-005.
1089 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1091 -- Perform the task specific exception tracing duty. We handle
1092 -- these outputs here and not in the common notification routine
1093 -- because we need access to tasking related data and we don't
1094 -- want to drag dependencies against tasking related units in the
1095 -- the common notification units. Additionally, no trace is ever
1096 -- triggered from the common routine for the Unhandled_Raise case
1097 -- in tasks, since an exception never appears unhandled in this
1098 -- context because of this handler.
1100 if Exception_Trace
= Unhandled_Raise
then
1101 Trace_Unhandled_Exception_In_Task
(Self_ID
);
1104 -- Update the cause that motivated the task termination so that
1105 -- the appropriate information is passed to the task termination
1106 -- procedure, as well as the associated Exception_Occurrence.
1108 Cause
:= Unhandled_Exception
;
1109 Save_Occurrence
(EO
, SSL
.Get_Current_Excep
.all.all);
1112 -- Look for a task termination handler. This code is for all tasks but
1113 -- the environment task. The task termination code for the environment
1114 -- task is executed by SSL.Task_Termination_Handler.
1120 Write_Lock
(Self_ID
);
1122 if Self_ID
.Common
.Specific_Handler
/= null then
1123 TH
:= Self_ID
.Common
.Specific_Handler
;
1125 -- Look for a fall-back handler following the master relationship
1128 Search_Fall_Back_Handler
(Self_ID
);
1137 -- Execute the task termination handler if we found it
1140 TH
.all (Cause
, Self_ID
, EO
);
1143 if System
.Stack_Usage
.Is_Enabled
then
1144 Compute_Result
(Self_ID
.Common
.Analyzer
);
1145 Report_Result
(Self_ID
.Common
.Analyzer
);
1148 Terminate_Task
(Self_ID
);
1151 --------------------
1152 -- Terminate_Task --
1153 --------------------
1155 -- Before we allow the thread to exit, we must clean up. This is a
1156 -- a delicate job. We must wake up the task's master, who may immediately
1157 -- try to deallocate the ATCB out from under the current task WHILE IT IS
1160 -- To avoid this, the parent task must be blocked up to the latest
1161 -- statement executed. The trouble is that we have another step that we
1162 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
1163 -- We have to postpone that until the end because compiler-generated code
1164 -- is likely to try to access that data at just about any point.
1166 -- We can't call Destroy_TSD while we are holding any other locks, because
1167 -- it locks Global_Task_Lock, and our deadlock prevention rules require
1168 -- that to be the outermost lock. Our first "solution" was to just lock
1169 -- Global_Task_Lock in addition to the other locks, and force the parent to
1170 -- also lock this lock between its wakeup and its freeing of the ATCB. See
1171 -- Complete_Task for the parent-side of the code that has the matching
1172 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1173 -- since the operation Task_Unlock continued to access the ATCB after
1174 -- unlocking, after which the parent was observed to race ahead, deallocate
1175 -- the ATCB, and then reallocate it to another task. The call to
1176 -- Undefer_Abortion in Task_Unlock by the "terminated" task was overwriting
1177 -- the data of the new task that reused the ATCB! To solve this problem, we
1178 -- introduced the new operation Final_Task_Unlock.
1180 procedure Terminate_Task
(Self_ID
: Task_Id
) is
1181 Environment_Task
: constant Task_Id
:= STPO
.Environment_Task
;
1182 Master_of_Task
: Integer;
1185 Debug
.Task_Termination_Hook
;
1187 if Runtime_Traces
then
1188 Send_Trace_Info
(T_Terminate
);
1191 -- Since GCC cannot allocate stack chunks efficiently without reordering
1192 -- some of the allocations, we have to handle this unexpected situation
1193 -- here. We should normally never have to call Vulnerable_Complete_Task
1194 -- here. See 6602-003 for more details.
1196 if Self_ID
.Common
.Activator
/= null then
1197 Vulnerable_Complete_Task
(Self_ID
);
1200 Initialization
.Task_Lock
(Self_ID
);
1206 Master_of_Task
:= Self_ID
.Master_of_Task
;
1208 -- Check if the current task is an independent task If so, decrement
1209 -- the Independent_Task_Count value.
1211 if Master_of_Task
= 2 then
1213 Utilities
.Independent_Task_Count
:=
1214 Utilities
.Independent_Task_Count
- 1;
1216 Write_Lock
(Environment_Task
);
1217 Utilities
.Independent_Task_Count
:=
1218 Utilities
.Independent_Task_Count
- 1;
1219 Unlock
(Environment_Task
);
1223 -- Unprotect the guard page if needed
1225 Stack_Guard
(Self_ID
, False);
1227 Utilities
.Make_Passive
(Self_ID
, Task_Completed
=> True);
1233 pragma Assert
(Check_Exit
(Self_ID
));
1235 SSL
.Destroy_TSD
(Self_ID
.Common
.Compiler_Data
);
1236 Initialization
.Final_Task_Unlock
(Self_ID
);
1238 -- WARNING: past this point, this thread must assume that the ATCB
1239 -- has been deallocated. It should not be accessed again.
1241 if Master_of_Task
> 0 then
1250 function Terminated
(T
: Task_Id
) return Boolean is
1251 Self_ID
: constant Task_Id
:= STPO
.Self
;
1255 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1262 Result
:= T
.Common
.State
= Terminated
;
1269 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
1273 ----------------------------------------
1274 -- Trace_Unhandled_Exception_In_Task --
1275 ----------------------------------------
1277 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
) is
1278 procedure To_Stderr
(S
: String);
1279 pragma Import
(Ada
, To_Stderr
, "__gnat_to_stderr");
1281 use System
.Soft_Links
;
1282 use System
.Standard_Library
;
1284 function To_Address
is new
1285 Unchecked_Conversion
(Task_Id
, System
.Address
);
1287 function Tailored_Exception_Information
1288 (E
: Exception_Occurrence
) return String;
1290 (Ada
, Tailored_Exception_Information
,
1291 "__gnat_tailored_exception_information");
1293 Excep
: constant Exception_Occurrence_Access
:=
1294 SSL
.Get_Current_Excep
.all;
1297 -- This procedure is called by the task outermost handler in
1298 -- Task_Wrapper below, so only once the task stack has been fully
1299 -- unwound. The common notification routine has been called at the
1300 -- raise point already.
1302 To_Stderr
("task ");
1304 if Self_Id
.Common
.Task_Image_Len
/= 0 then
1306 (Self_Id
.Common
.Task_Image
(1 .. Self_Id
.Common
.Task_Image_Len
));
1310 To_Stderr
(System
.Address_Image
(To_Address
(Self_Id
)));
1311 To_Stderr
(" terminated by unhandled exception");
1312 To_Stderr
((1 => ASCII
.LF
));
1313 To_Stderr
(Tailored_Exception_Information
(Excep
.all));
1314 end Trace_Unhandled_Exception_In_Task
;
1316 ------------------------------------
1317 -- Vulnerable_Complete_Activation --
1318 ------------------------------------
1320 -- As in several other places, the locks of the activator and activated
1321 -- task are both locked here. This follows our deadlock prevention lock
1322 -- ordering policy, since the activated task must be created after the
1325 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
) is
1326 Activator
: constant Task_Id
:= Self_ID
.Common
.Activator
;
1329 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Activation", 'C'));
1331 Write_Lock
(Activator
);
1332 Write_Lock
(Self_ID
);
1334 pragma Assert
(Self_ID
.Common
.Activator
/= null);
1336 -- Remove dangling reference to Activator, since a task may
1337 -- outlive its activator.
1339 Self_ID
.Common
.Activator
:= null;
1341 -- Wake up the activator, if it is waiting for a chain of tasks to
1342 -- activate, and we are the last in the chain to complete activation.
1344 if Activator
.Common
.State
= Activator_Sleep
then
1345 Activator
.Common
.Wait_Count
:= Activator
.Common
.Wait_Count
- 1;
1347 if Activator
.Common
.Wait_Count
= 0 then
1348 Wakeup
(Activator
, Activator_Sleep
);
1352 -- The activator raises a Tasking_Error if any task it is activating
1353 -- is completed before the activation is done. However, if the reason
1354 -- for the task completion is an abort, we do not raise an exception.
1357 if not Self_ID
.Callable
and then Self_ID
.Pending_ATC_Level
/= 0 then
1358 Activator
.Common
.Activation_Failed
:= True;
1364 -- After the activation, active priority should be the same
1365 -- as base priority. We must unlock the Activator first,
1366 -- though, since it should not wait if we have lower priority.
1368 if Get_Priority
(Self_ID
) /= Self_ID
.Common
.Base_Priority
then
1369 Write_Lock
(Self_ID
);
1370 Set_Priority
(Self_ID
, Self_ID
.Common
.Base_Priority
);
1373 end Vulnerable_Complete_Activation
;
1375 --------------------------------
1376 -- Vulnerable_Complete_Master --
1377 --------------------------------
1379 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
) is
1382 CM
: constant Master_Level
:= Self_ID
.Master_Within
;
1383 T
: aliased Task_Id
;
1385 To_Be_Freed
: Task_Id
;
1386 -- This is a list of ATCBs to be freed, after we have released
1387 -- all RTS locks. This is necessary because of the locking order
1388 -- rules, since the storage manager uses Global_Task_Lock.
1390 pragma Warnings
(Off
);
1391 function Check_Unactivated_Tasks
return Boolean;
1392 pragma Warnings
(On
);
1393 -- Temporary error-checking code below. This is part of the checks
1394 -- added in the new run time. Call it only inside a pragma Assert.
1396 -----------------------------
1397 -- Check_Unactivated_Tasks --
1398 -----------------------------
1400 function Check_Unactivated_Tasks
return Boolean is
1402 if not Single_Lock
then
1406 Write_Lock
(Self_ID
);
1408 C
:= All_Tasks_List
;
1409 while C
/= null loop
1410 if C
.Common
.Activator
= Self_ID
then
1414 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1417 if C
.Common
.State
= Unactivated
then
1424 C
:= C
.Common
.All_Tasks_Link
;
1429 if not Single_Lock
then
1434 end Check_Unactivated_Tasks
;
1436 -- Start of processing for Vulnerable_Complete_Master
1440 (Debug
.Trace
(Self_ID
, "V_Complete_Master", 'C'));
1442 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1443 pragma Assert
(Self_ID
.Deferral_Level
> 0);
1445 -- Count how many active dependent tasks this master currently
1446 -- has, and record this in Wait_Count.
1448 -- This count should start at zero, since it is initialized to
1449 -- zero for new tasks, and the task should not exit the
1450 -- sleep-loops that use this count until the count reaches zero.
1453 Write_Lock
(Self_ID
);
1455 C
:= All_Tasks_List
;
1456 while C
/= null loop
1457 if C
.Common
.Activator
= Self_ID
then
1458 pragma Assert
(C
.Common
.State
= Unactivated
);
1461 C
.Common
.Activator
:= null;
1462 C
.Common
.State
:= Terminated
;
1463 C
.Callable
:= False;
1464 Utilities
.Cancel_Queued_Entry_Calls
(C
);
1468 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1471 if C
.Awake_Count
/= 0 then
1472 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1478 C
:= C
.Common
.All_Tasks_Link
;
1481 Self_ID
.Common
.State
:= Master_Completion_Sleep
;
1484 if not Single_Lock
then
1488 -- Wait until dependent tasks are all terminated or ready to terminate.
1489 -- While waiting, the task may be awakened if the task's priority needs
1490 -- changing, or this master is aborted. In the latter case, we want
1491 -- to abort the dependents, and resume waiting until Wait_Count goes
1494 Write_Lock
(Self_ID
);
1497 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
1498 exit when Self_ID
.Common
.Wait_Count
= 0;
1500 -- Here is a difference as compared to Complete_Master
1502 if Self_ID
.Pending_ATC_Level
< Self_ID
.ATC_Nesting_Level
1503 and then not Self_ID
.Dependents_Aborted
1506 Abort_Dependents
(Self_ID
);
1510 Abort_Dependents
(Self_ID
);
1512 Write_Lock
(Self_ID
);
1515 Sleep
(Self_ID
, Master_Completion_Sleep
);
1519 Self_ID
.Common
.State
:= Runnable
;
1522 -- Dependents are all terminated or on terminate alternatives.
1523 -- Now, force those on terminate alternatives to terminate, by
1526 pragma Assert
(Check_Unactivated_Tasks
);
1528 if Self_ID
.Alive_Count
> 1 then
1530 -- Consider finding a way to skip the following extra steps if there
1531 -- are no dependents with terminate alternatives. This could be done
1532 -- by adding another count to the ATCB, similar to Awake_Count, but
1533 -- keeping track of tasks that are on terminate alternatives.
1535 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1537 -- Force any remaining dependents to terminate by aborting them
1539 if not Single_Lock
then
1543 Abort_Dependents
(Self_ID
);
1545 -- Above, when we "abort" the dependents we are simply using this
1546 -- operation for convenience. We are not required to support the full
1547 -- abort-statement semantics; in particular, we are not required to
1548 -- immediately cancel any queued or in-service entry calls. That is
1549 -- good, because if we tried to cancel a call we would need to lock
1550 -- the caller, in order to wake the caller up. Our anti-deadlock
1551 -- rules prevent us from doing that without releasing the locks on C
1552 -- and Self_ID. Releasing and retaking those locks would be wasteful
1553 -- at best, and should not be considered further without more
1554 -- detailed analysis of potential concurrent accesses to the
1555 -- ATCBs of C and Self_ID.
1557 -- Count how many "alive" dependent tasks this master currently
1558 -- has, and record this in Wait_Count. This count should start at
1559 -- zero, since it is initialized to zero for new tasks, and the
1560 -- task should not exit the sleep-loops that use this count until
1561 -- the count reaches zero.
1563 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1565 Write_Lock
(Self_ID
);
1567 C
:= All_Tasks_List
;
1568 while C
/= null loop
1569 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1572 pragma Assert
(C
.Awake_Count
= 0);
1574 if C
.Alive_Count
> 0 then
1575 pragma Assert
(C
.Terminate_Alternative
);
1576 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1582 C
:= C
.Common
.All_Tasks_Link
;
1585 Self_ID
.Common
.State
:= Master_Phase_2_Sleep
;
1588 if not Single_Lock
then
1592 -- Wait for all counted tasks to finish terminating themselves
1594 Write_Lock
(Self_ID
);
1597 Initialization
.Poll_Base_Priority_Change
(Self_ID
);
1598 exit when Self_ID
.Common
.Wait_Count
= 0;
1599 Sleep
(Self_ID
, Master_Phase_2_Sleep
);
1602 Self_ID
.Common
.State
:= Runnable
;
1606 -- We don't wake up for abort here. We are already terminating just as
1607 -- fast as we can, so there is no point.
1609 -- Remove terminated tasks from the list of Self_ID's dependents, but
1610 -- don't free their ATCBs yet, because of lock order restrictions,
1611 -- which don't allow us to call "free" or "malloc" while holding any
1612 -- other locks. Instead, we put those ATCBs to be freed onto a
1613 -- temporary list, called To_Be_Freed.
1615 if not Single_Lock
then
1619 C
:= All_Tasks_List
;
1621 while C
/= null loop
1622 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
>= CM
then
1624 P
.Common
.All_Tasks_Link
:= C
.Common
.All_Tasks_Link
;
1626 All_Tasks_List
:= C
.Common
.All_Tasks_Link
;
1629 T
:= C
.Common
.All_Tasks_Link
;
1630 C
.Common
.All_Tasks_Link
:= To_Be_Freed
;
1636 C
:= C
.Common
.All_Tasks_Link
;
1642 -- Free all the ATCBs on the list To_Be_Freed
1644 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1645 -- any interrupt entries are detached from them they should no longer
1648 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1649 -- avoid a race between a terminating task and its parent. The parent
1650 -- might try to deallocate the ACTB out from underneath the exiting
1651 -- task. Note that Free will also lock Global_Task_Lock, but that is
1652 -- OK, since this is the *one* lock for which we have a mechanism to
1653 -- support nested locking. See Task_Wrapper and its finalizer for more
1657 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1658 -- references to terminated library-level tasks, which could
1659 -- otherwise occur during finalization of library-level objects.
1660 -- A better solution might be to hook task objects into the
1661 -- finalization chain and deallocate the ATCB when the task
1662 -- object is deallocated. However, this change is not likely
1663 -- to gain anything significant, since all this storage should
1664 -- be recovered en-masse when the process exits.
1666 while To_Be_Freed
/= null loop
1668 To_Be_Freed
:= T
.Common
.All_Tasks_Link
;
1670 -- ??? On SGI there is currently no Interrupt_Manager, that's
1671 -- why we need to check if the Interrupt_Manager_ID is null
1673 if T
.Interrupt_Entry
and Interrupt_Manager_ID
/= null then
1675 Detach_Interrupt_Entries_Index
: constant Task_Entry_Index
:= 1;
1676 -- Corresponds to the entry index of System.Interrupts.
1677 -- Interrupt_Manager.Detach_Interrupt_Entries.
1678 -- Be sure to update this value when changing
1679 -- Interrupt_Manager specs.
1681 type Param_Type
is access all Task_Id
;
1683 Param
: aliased Param_Type
:= T
'Access;
1686 System
.Tasking
.Rendezvous
.Call_Simple
1687 (Interrupt_Manager_ID
, Detach_Interrupt_Entries_Index
,
1692 if (T
.Common
.Parent
/= null
1693 and then T
.Common
.Parent
.Common
.Parent
/= null)
1694 or else T
.Master_of_Task
> 3
1696 Initialization
.Task_Lock
(Self_ID
);
1698 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1699 -- has not been called yet (case of an unactivated task).
1701 if T
.Common
.Compiler_Data
.Sec_Stack_Addr
/= Null_Address
then
1702 SSL
.Destroy_TSD
(T
.Common
.Compiler_Data
);
1705 Vulnerable_Free_Task
(T
);
1706 Initialization
.Task_Unlock
(Self_ID
);
1710 -- It might seem nice to let the terminated task deallocate its own
1711 -- ATCB. That would not cover the case of unactivated tasks. It also
1712 -- would force us to keep the underlying thread around past termination,
1713 -- since references to the ATCB are possible past termination.
1714 -- Currently, we get rid of the thread as soon as the task terminates,
1715 -- and let the parent recover the ATCB later.
1717 -- Some day, if we want to recover the ATCB earlier, at task
1718 -- termination, we could consider using "fat task IDs", that include the
1719 -- serial number with the ATCB pointer, to catch references to tasks
1720 -- that no longer have ATCBs. It is not clear how much this would gain,
1721 -- since the user-level task object would still be occupying storage.
1723 -- Make next master level up active.
1724 -- We don't need to lock the ATCB, since the value is only updated by
1725 -- each task for itself.
1727 Self_ID
.Master_Within
:= CM
- 1;
1728 end Vulnerable_Complete_Master
;
1730 ------------------------------
1731 -- Vulnerable_Complete_Task --
1732 ------------------------------
1734 -- Complete the calling task
1736 -- This procedure must be called with abort deferred. (That's why the
1737 -- name has "Vulnerable" in it.) It should only be called by Complete_Task
1738 -- and Finalize_Global_Tasks (for the environment task).
1740 -- The effect is similar to that of Complete_Master. Differences include
1741 -- the closing of entries here, and computation of the number of active
1742 -- dependent tasks in Complete_Master.
1744 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1745 -- because that does its own locking, and because we do not need the lock
1746 -- to test Self_ID.Common.Activator. That value should only be read and
1747 -- modified by Self.
1749 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
) is
1751 pragma Assert
(Self_ID
.Deferral_Level
> 0);
1752 pragma Assert
(Self_ID
= Self
);
1753 pragma Assert
(Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 1
1755 Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2);
1756 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1757 pragma Assert
(Self_ID
.Open_Accepts
= null);
1758 pragma Assert
(Self_ID
.ATC_Nesting_Level
= 1);
1760 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Task", 'C'));
1766 Write_Lock
(Self_ID
);
1767 Self_ID
.Callable
:= False;
1769 -- In theory, Self should have no pending entry calls left on its
1770 -- call-stack. Each async. select statement should clean its own call,
1771 -- and blocking entry calls should defer abort until the calls are
1772 -- cancelled, then clean up.
1774 Utilities
.Cancel_Queued_Entry_Calls
(Self_ID
);
1777 if Self_ID
.Common
.Activator
/= null then
1778 Vulnerable_Complete_Activation
(Self_ID
);
1785 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2
1786 -- we may have dependent tasks for which we need to wait.
1787 -- Otherwise, we can just exit.
1789 if Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2 then
1790 Vulnerable_Complete_Master
(Self_ID
);
1792 end Vulnerable_Complete_Task
;
1794 --------------------------
1795 -- Vulnerable_Free_Task --
1796 --------------------------
1798 -- Recover all runtime system storage associated with the task T.
1799 -- This should only be called after T has terminated and will no
1800 -- longer be referenced.
1802 -- For tasks created by an allocator that fails, due to an exception,
1803 -- it is called from Expunge_Unactivated_Tasks.
1805 -- For tasks created by elaboration of task object declarations it
1806 -- is called from the finalization code of the Task_Wrapper procedure.
1807 -- It is also called from Unchecked_Deallocation, for objects that
1808 -- are or contain tasks.
1810 procedure Vulnerable_Free_Task
(T
: Task_Id
) is
1812 pragma Debug
(Debug
.Trace
(Self
, "Vulnerable_Free_Task", 'C', T
));
1819 Initialization
.Finalize_Attributes_Link
.all (T
);
1826 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
1827 end Vulnerable_Free_Task
;
1829 -- Package elaboration code
1832 -- Establish the Adafinal softlink
1834 -- This is not done inside the central RTS initialization routine
1835 -- to avoid with-ing this package from System.Tasking.Initialization.
1837 SSL
.Adafinal
:= Finalize_Global_Tasks
'Access;
1839 -- Establish soft links for subprograms that manipulate master_id's.
1840 -- This cannot be done when the RTS is initialized, because of various
1841 -- elaboration constraints.
1843 SSL
.Current_Master
:= Stages
.Current_Master
'Access;
1844 SSL
.Enter_Master
:= Stages
.Enter_Master
'Access;
1845 SSL
.Complete_Master
:= Stages
.Complete_Master
'Access;
1846 end System
.Tasking
.Stages
;