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) 1992-2008, 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 tasking
36 -- operations. It causes infinite loops and other problems.
39 with Ada
.Unchecked_Deallocation
;
41 with System
.Tasking
.Debug
;
42 with System
.Address_Image
;
43 with System
.Task_Primitives
;
44 with System
.Task_Primitives
.Operations
;
45 with System
.Tasking
.Utilities
;
46 with System
.Tasking
.Queuing
;
47 with System
.Tasking
.Rendezvous
;
48 with System
.OS_Primitives
;
49 with System
.Secondary_Stack
;
50 with System
.Storage_Elements
;
51 with System
.Restrictions
;
52 with System
.Standard_Library
;
53 with System
.Traces
.Tasking
;
54 with System
.Stack_Usage
;
56 with System
.Soft_Links
;
57 -- These are procedure pointers to non-tasking routines that use task
58 -- specific data. In the absence of tasking, these routines refer to global
59 -- data. In the presence of tasking, they must be replaced with pointers to
60 -- task-specific versions. Also used for Create_TSD, Destroy_TSD,
61 -- Get_Current_Excep, Finalize_Global_List, Task_Termination, Handler.
63 with System
.Tasking
.Initialization
;
64 pragma Elaborate_All
(System
.Tasking
.Initialization
);
65 -- This insures that tasking is initialized if any tasks are created
67 package body System
.Tasking
.Stages
is
69 package STPO
renames System
.Task_Primitives
.Operations
;
70 package SSL
renames System
.Soft_Links
;
71 package SSE
renames System
.Storage_Elements
;
72 package SST
renames System
.Secondary_Stack
;
78 use Task_Primitives
.Operations
;
82 use System
.Traces
.Tasking
;
84 -----------------------
85 -- Local Subprograms --
86 -----------------------
89 Ada
.Unchecked_Deallocation
(Ada_Task_Control_Block
, Task_Id
);
91 procedure Free_Entry_Names
(T
: Task_Id
);
92 -- Deallocate all string names associated with task entries
94 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
);
95 -- This procedure outputs the task specific message for exception
98 procedure Task_Wrapper
(Self_ID
: Task_Id
);
99 pragma Convention
(C
, Task_Wrapper
);
100 -- This is the procedure that is called by the GNULL from the new context
101 -- when a task is created. It waits for activation and then calls the task
102 -- body procedure. When the task body procedure completes, it terminates
105 -- The Task_Wrapper's address will be provided to the underlying threads
106 -- library as the task entry point. Convention C is what makes most sense
107 -- for that purpose (Export C would make the function globally visible,
108 -- and affect the link name on which GDB depends). This will in addition
109 -- trigger an automatic stack alignment suitable for GCC's assumptions if
112 -- "Vulnerable_..." in the procedure names below means they must be called
113 -- with abort deferred.
115 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
);
116 -- Complete the calling task. This procedure must be called with
117 -- abort deferred. It should only be called by Complete_Task and
118 -- Finalize_Global_Tasks (for the environment task).
120 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
);
121 -- Complete the current master of the calling task. This procedure
122 -- must be called with abort deferred. It should only be called by
123 -- Vulnerable_Complete_Task and Complete_Master.
125 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
);
126 -- Signal to Self_ID's activator that Self_ID has completed activation.
127 -- This procedure must be called with abort deferred.
129 procedure Abort_Dependents
(Self_ID
: Task_Id
);
130 -- Abort all the direct dependents of Self at its current master nesting
131 -- level, plus all of their dependents, transitively. RTS_Lock should be
132 -- locked by the caller.
134 procedure Vulnerable_Free_Task
(T
: Task_Id
);
135 -- Recover all runtime system storage associated with the task T. This
136 -- should only be called after T has terminated and will no longer be
139 -- For tasks created by an allocator that fails, due to an exception, it is
140 -- called from Expunge_Unactivated_Tasks.
142 -- Different code is used at master completion, in Terminate_Dependents,
143 -- due to a need for tighter synchronization with the master.
145 ----------------------
146 -- Abort_Dependents --
147 ----------------------
149 procedure Abort_Dependents
(Self_ID
: Task_Id
) is
156 P
:= C
.Common
.Parent
;
160 -- ??? C is supposed to take care of its own dependents, so
161 -- there should be no need to worry about them. Need to double
164 if C
.Master_of_Task
= Self_ID
.Master_Within
then
165 Utilities
.Abort_One_Task
(Self_ID
, C
);
166 C
.Dependents_Aborted
:= True;
172 P
:= P
.Common
.Parent
;
175 C
:= C
.Common
.All_Tasks_Link
;
178 Self_ID
.Dependents_Aborted
:= True;
179 end Abort_Dependents
;
185 procedure Abort_Tasks
(Tasks
: Task_List
) is
187 Utilities
.Abort_Tasks
(Tasks
);
194 -- Note that locks of activator and activated task are both locked here.
195 -- This is necessary because C.Common.State and Self.Common.Wait_Count have
196 -- to be synchronized. This is safe from deadlock because the activator is
197 -- always created before the activated task. That satisfies our
198 -- in-order-of-creation ATCB locking policy.
200 -- At one point, we may also lock the parent, if the parent is different
201 -- from the activator. That is also consistent with the lock ordering
202 -- policy, since the activator cannot be created before the parent.
204 -- Since we are holding both the activator's lock, and Task_Wrapper locks
205 -- that before it does anything more than initialize the low-level ATCB
206 -- components, it should be safe to wait to update the counts until we see
207 -- that the thread creation is successful.
209 -- If the thread creation fails, we do need to close the entries of the
210 -- task. The first phase, of dequeuing calls, only requires locking the
211 -- acceptor's ATCB, but the waking up of the callers requires locking the
212 -- caller's ATCB. We cannot safely do this while we are holding other
213 -- locks. Therefore, the queue-clearing operation is done in a separate
214 -- pass over the activation chain.
216 procedure Activate_Tasks
(Chain_Access
: Activation_Chain_Access
) is
217 Self_ID
: constant Task_Id
:= STPO
.Self
;
220 Next_C
, Last_C
: Task_Id
;
221 Activate_Prio
: System
.Any_Priority
;
223 All_Elaborated
: Boolean := True;
226 -- If pragma Detect_Blocking is active, then we must check whether this
227 -- potentially blocking operation is called from a protected action.
229 if System
.Tasking
.Detect_Blocking
230 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
232 raise Program_Error
with "potentially blocking operation";
236 (Debug
.Trace
(Self_ID
, "Activate_Tasks", 'C'));
238 Initialization
.Defer_Abort_Nestable
(Self_ID
);
240 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
242 -- Lock RTS_Lock, to prevent activated tasks from racing ahead before
243 -- we finish activating the chain.
247 -- Check that all task bodies have been elaborated
249 C
:= Chain_Access
.T_ID
;
252 if C
.Common
.Elaborated
/= null
253 and then not C
.Common
.Elaborated
.all
255 All_Elaborated
:= False;
258 -- Reverse the activation chain so that tasks are activated in the
259 -- same order they're declared.
261 Next_C
:= C
.Common
.Activation_Link
;
262 C
.Common
.Activation_Link
:= Last_C
;
267 Chain_Access
.T_ID
:= Last_C
;
269 if not All_Elaborated
then
271 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
272 raise Program_Error
with "Some tasks have not been elaborated";
275 -- Activate all the tasks in the chain. Creation of the thread of
276 -- control was deferred until activation. So create it now.
278 C
:= Chain_Access
.T_ID
;
280 if C
.Common
.State
/= Terminated
then
281 pragma Assert
(C
.Common
.State
= Unactivated
);
283 P
:= C
.Common
.Parent
;
287 if C
.Common
.Base_Priority
< Get_Priority
(Self_ID
) then
288 Activate_Prio
:= Get_Priority
(Self_ID
);
290 Activate_Prio
:= C
.Common
.Base_Priority
;
293 System
.Task_Primitives
.Operations
.Create_Task
294 (C
, Task_Wrapper
'Address,
296 (C
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
297 Activate_Prio
, Success
);
299 -- There would be a race between the created task and the creator
300 -- to do the following initialization, if we did not have a
301 -- Lock/Unlock_RTS pair in the task wrapper to prevent it from
305 C
.Common
.State
:= Runnable
;
308 P
.Awake_Count
:= P
.Awake_Count
+ 1;
309 P
.Alive_Count
:= P
.Alive_Count
+ 1;
311 if P
.Common
.State
= Master_Completion_Sleep
and then
312 C
.Master_of_Task
= P
.Master_Within
314 pragma Assert
(Self_ID
/= P
);
315 P
.Common
.Wait_Count
:= P
.Common
.Wait_Count
+ 1;
322 -- No need to set Awake_Count, State, etc. here since the loop
323 -- below will do that for any Unactivated tasks.
327 Self_ID
.Common
.Activation_Failed
:= True;
331 C
:= C
.Common
.Activation_Link
;
334 if not Single_Lock
then
338 -- Close the entries of any tasks that failed thread creation, and count
339 -- those that have not finished activation.
341 Write_Lock
(Self_ID
);
342 Self_ID
.Common
.State
:= Activator_Sleep
;
344 C
:= Chain_Access
.T_ID
;
348 if C
.Common
.State
= Unactivated
then
349 C
.Common
.Activator
:= null;
350 C
.Common
.State
:= Terminated
;
352 Utilities
.Cancel_Queued_Entry_Calls
(C
);
354 elsif C
.Common
.Activator
/= null then
355 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
359 P
:= C
.Common
.Activation_Link
;
360 C
.Common
.Activation_Link
:= null;
364 -- Wait for the activated tasks to complete activation. It is
365 -- unsafe to abort any of these tasks until the count goes to zero.
368 exit when Self_ID
.Common
.Wait_Count
= 0;
369 Sleep
(Self_ID
, Activator_Sleep
);
372 Self_ID
.Common
.State
:= Runnable
;
379 -- Remove the tasks from the chain
381 Chain_Access
.T_ID
:= null;
382 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
384 if Self_ID
.Common
.Activation_Failed
then
385 Self_ID
.Common
.Activation_Failed
:= False;
386 raise Tasking_Error
with "Failure during activation";
390 -------------------------
391 -- Complete_Activation --
392 -------------------------
394 procedure Complete_Activation
is
395 Self_ID
: constant Task_Id
:= STPO
.Self
;
398 Initialization
.Defer_Abort_Nestable
(Self_ID
);
404 Vulnerable_Complete_Activation
(Self_ID
);
410 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
412 -- ??? Why do we need to allow for nested deferral here?
414 if Runtime_Traces
then
415 Send_Trace_Info
(T_Activate
);
417 end Complete_Activation
;
419 ---------------------
420 -- Complete_Master --
421 ---------------------
423 procedure Complete_Master
is
424 Self_ID
: constant Task_Id
:= STPO
.Self
;
427 (Self_ID
.Deferral_Level
> 0
428 or else not System
.Restrictions
.Abort_Allowed
);
429 Vulnerable_Complete_Master
(Self_ID
);
436 -- See comments on Vulnerable_Complete_Task for details
438 procedure Complete_Task
is
439 Self_ID
: constant Task_Id
:= STPO
.Self
;
443 (Self_ID
.Deferral_Level
> 0
444 or else not System
.Restrictions
.Abort_Allowed
);
446 Vulnerable_Complete_Task
(Self_ID
);
448 -- All of our dependents have terminated. Never undefer abort again!
456 -- Compiler interface only. Do not call from within the RTS. This must be
457 -- called to create a new task.
459 procedure Create_Task
461 Size
: System
.Parameters
.Size_Type
;
462 Task_Info
: System
.Task_Info
.Task_Info_Type
;
463 Relative_Deadline
: Ada
.Real_Time
.Time_Span
;
464 Num_Entries
: Task_Entry_Index
;
465 Master
: Master_Level
;
466 State
: Task_Procedure_Access
;
467 Discriminants
: System
.Address
;
468 Elaborated
: Access_Boolean
;
469 Chain
: in out Activation_Chain
;
471 Created_Task
: out Task_Id
;
472 Build_Entry_Names
: Boolean)
475 Self_ID
: constant Task_Id
:= STPO
.Self
;
477 Base_Priority
: System
.Any_Priority
;
480 pragma Unreferenced
(Relative_Deadline
);
481 -- EDF scheduling is not supported by any of the target platforms so
482 -- this parameter is not passed any further.
485 -- If Master is greater than the current master, it means that Master
486 -- has already awaited its dependent tasks. This raises Program_Error,
487 -- by 4.8(10.3/2). See AI-280. Ignore this check for foreign threads.
489 if Self_ID
.Master_of_Task
/= Foreign_Task_Level
490 and then Master
> Self_ID
.Master_Within
492 raise Program_Error
with
493 "create task after awaiting termination";
496 -- If pragma Detect_Blocking is active must be checked whether this
497 -- potentially blocking operation is called from a protected action.
499 if System
.Tasking
.Detect_Blocking
500 and then Self_ID
.Common
.Protected_Action_Nesting
> 0
502 raise Program_Error
with "potentially blocking operation";
506 (Debug
.Trace
(Self_ID
, "Create_Task", 'C'));
508 if Priority
= Unspecified_Priority
then
509 Base_Priority
:= Self_ID
.Common
.Base_Priority
;
511 Base_Priority
:= System
.Any_Priority
(Priority
);
514 -- Find parent P of new Task, via master level number
519 while P
.Master_of_Task
>= Master
loop
520 P
:= P
.Common
.Parent
;
525 Initialization
.Defer_Abort_Nestable
(Self_ID
);
528 T
:= New_ATCB
(Num_Entries
);
531 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
532 raise Storage_Error
with "Cannot allocate task";
535 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks. Up to this
536 -- point, it is possible that we may be part of a family of tasks that
540 Write_Lock
(Self_ID
);
542 -- Now, we must check that we have not been aborted. If so, we should
543 -- give up on creating this task, and simply return.
545 if not Self_ID
.Callable
then
546 pragma Assert
(Self_ID
.Pending_ATC_Level
= 0);
547 pragma Assert
(Self_ID
.Pending_Action
);
549 (Chain
.T_ID
= null or else Chain
.T_ID
.Common
.State
= Unactivated
);
553 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
555 -- ??? Should never get here
557 pragma Assert
(False);
558 raise Standard
'Abort_Signal;
561 Initialize_ATCB
(Self_ID
, State
, Discriminants
, P
, Elaborated
,
562 Base_Priority
, Task_Info
, Size
, T
, Success
);
568 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
569 raise Storage_Error
with "Failed to initialize task";
572 if Master
= Foreign_Task_Level
+ 2 then
574 -- This should not happen, except when a foreign task creates non
575 -- library-level Ada tasks. In this case, we pretend the master is
576 -- a regular library level task, otherwise the run-time will get
577 -- confused when waiting for these tasks to terminate.
579 T
.Master_of_Task
:= Library_Task_Level
;
581 T
.Master_of_Task
:= Master
;
584 T
.Master_Within
:= T
.Master_of_Task
+ 1;
586 for L
in T
.Entry_Calls
'Range loop
587 T
.Entry_Calls
(L
).Self
:= T
;
588 T
.Entry_Calls
(L
).Level
:= L
;
591 if Task_Image
'Length = 0 then
592 T
.Common
.Task_Image_Len
:= 0;
595 T
.Common
.Task_Image
(1) := Task_Image
(Task_Image
'First);
597 -- Remove unwanted blank space generated by 'Image
599 for J
in Task_Image
'First + 1 .. Task_Image
'Last loop
600 if Task_Image
(J
) /= ' '
601 or else Task_Image
(J
- 1) /= '('
604 T
.Common
.Task_Image
(Len
) := Task_Image
(J
);
605 exit when Len
= T
.Common
.Task_Image
'Last;
609 T
.Common
.Task_Image_Len
:= Len
;
612 if Build_Entry_Names
then
614 new Entry_Names_Array
(1 .. Entry_Index
(Num_Entries
));
620 -- Create TSD as early as possible in the creation of a task, since it
621 -- may be used by the operation of Ada code within the task.
623 SSL
.Create_TSD
(T
.Common
.Compiler_Data
);
624 T
.Common
.Activation_Link
:= Chain
.T_ID
;
626 Initialization
.Initialize_Attributes_Link
.all (T
);
628 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
630 if Runtime_Traces
then
631 Send_Trace_Info
(T_Create
, T
);
639 function Current_Master
return Master_Level
is
641 return STPO
.Self
.Master_Within
;
648 procedure Enter_Master
is
649 Self_ID
: constant Task_Id
:= STPO
.Self
;
651 Self_ID
.Master_Within
:= Self_ID
.Master_Within
+ 1;
654 -------------------------------
655 -- Expunge_Unactivated_Tasks --
656 -------------------------------
658 -- See procedure Close_Entries for the general case
660 procedure Expunge_Unactivated_Tasks
(Chain
: in out Activation_Chain
) is
661 Self_ID
: constant Task_Id
:= STPO
.Self
;
663 Call
: Entry_Call_Link
;
668 (Debug
.Trace
(Self_ID
, "Expunge_Unactivated_Tasks", 'C'));
670 Initialization
.Defer_Abort_Nestable
(Self_ID
);
673 -- Experimentation has shown that abort is sometimes (but not always)
674 -- already deferred when this is called.
676 -- That may indicate an error. Find out what is going on
680 pragma Assert
(C
.Common
.State
= Unactivated
);
682 Temp
:= C
.Common
.Activation_Link
;
684 if C
.Common
.State
= Unactivated
then
688 for J
in 1 .. C
.Entry_Num
loop
689 Queuing
.Dequeue_Head
(C
.Entry_Queues
(J
), Call
);
690 pragma Assert
(Call
= null);
695 Initialization
.Remove_From_All_Tasks_List
(C
);
698 Vulnerable_Free_Task
(C
);
704 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
705 end Expunge_Unactivated_Tasks
;
707 ---------------------------
708 -- Finalize_Global_Tasks --
709 ---------------------------
712 -- We have a potential problem here if finalization of global objects does
713 -- anything with signals or the timer server, since by that time those
714 -- servers have terminated.
716 -- It is hard to see how that would occur
718 -- However, a better solution might be to do all this finalization
719 -- using the global finalization chain.
721 procedure Finalize_Global_Tasks
is
722 Self_ID
: constant Task_Id
:= STPO
.Self
;
725 pragma Unreferenced
(Ignore
);
728 if Self_ID
.Deferral_Level
= 0 then
730 -- In principle, we should be able to predict whether abort is
731 -- already deferred here (and it should not be deferred yet but in
732 -- practice it seems Finalize_Global_Tasks is being called sometimes,
733 -- from RTS code for exceptions, with abort already deferred.
735 Initialization
.Defer_Abort_Nestable
(Self_ID
);
737 -- Never undefer again!!!
740 -- This code is only executed by the environment task
742 pragma Assert
(Self_ID
= Environment_Task
);
744 -- Set Environment_Task'Callable to false to notify library-level tasks
745 -- that it is waiting for them.
747 Self_ID
.Callable
:= False;
749 -- Exit level 2 master, for normal tasks in library-level packages
753 -- Force termination of "independent" library-level server tasks
757 Abort_Dependents
(Self_ID
);
759 if not Single_Lock
then
763 -- We need to explicitly wait for the task to be terminated here
764 -- because on true concurrent system, we may end this procedure before
765 -- the tasks are really terminated.
767 Write_Lock
(Self_ID
);
770 exit when Utilities
.Independent_Task_Count
= 0;
772 -- We used to yield here, but this did not take into account low
773 -- priority tasks that would cause dead lock in some cases (true
777 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
778 Self_ID
.Common
.State
, Ignore
, Ignore
);
781 -- ??? On multi-processor environments, it seems that the above loop
782 -- isn't sufficient, so we need to add an additional delay.
785 (Self_ID
, 0.01, System
.OS_Primitives
.Relative
,
786 Self_ID
.Common
.State
, Ignore
, Ignore
);
794 -- Complete the environment task
796 Vulnerable_Complete_Task
(Self_ID
);
798 -- Handle normal task termination by the environment task, but only
799 -- for the normal task termination. In the case of Abnormal and
800 -- Unhandled_Exception they must have been handled before, and the
801 -- task termination soft link must have been changed so the task
802 -- termination routine is not executed twice.
804 SSL
.Task_Termination_Handler
.all (Ada
.Exceptions
.Null_Occurrence
);
806 -- Finalize the global list for controlled objects if needed
808 SSL
.Finalize_Global_List
.all;
810 -- Reset the soft links to non-tasking
812 SSL
.Abort_Defer
:= SSL
.Abort_Defer_NT
'Access;
813 SSL
.Abort_Undefer
:= SSL
.Abort_Undefer_NT
'Access;
814 SSL
.Lock_Task
:= SSL
.Task_Lock_NT
'Access;
815 SSL
.Unlock_Task
:= SSL
.Task_Unlock_NT
'Access;
816 SSL
.Get_Jmpbuf_Address
:= SSL
.Get_Jmpbuf_Address_NT
'Access;
817 SSL
.Set_Jmpbuf_Address
:= SSL
.Set_Jmpbuf_Address_NT
'Access;
818 SSL
.Get_Sec_Stack_Addr
:= SSL
.Get_Sec_Stack_Addr_NT
'Access;
819 SSL
.Set_Sec_Stack_Addr
:= SSL
.Set_Sec_Stack_Addr_NT
'Access;
820 SSL
.Check_Abort_Status
:= SSL
.Check_Abort_Status_NT
'Access;
821 SSL
.Get_Stack_Info
:= SSL
.Get_Stack_Info_NT
'Access;
823 -- Don't bother trying to finalize Initialization.Global_Task_Lock
824 -- and System.Task_Primitives.RTS_Lock.
826 end Finalize_Global_Tasks
;
828 ----------------------
829 -- Free_Entry_Names --
830 ----------------------
832 procedure Free_Entry_Names
(T
: Task_Id
) is
833 Names
: Entry_Names_Array_Access
:= T
.Entry_Names
;
835 procedure Free_Entry_Names_Array_Access
is new
836 Ada
.Unchecked_Deallocation
837 (Entry_Names_Array
, Entry_Names_Array_Access
);
844 Free_Entry_Names_Array
(Names
.all);
845 Free_Entry_Names_Array_Access
(Names
);
846 end Free_Entry_Names
;
852 procedure Free_Task
(T
: Task_Id
) is
853 Self_Id
: constant Task_Id
:= Self
;
856 if T
.Common
.State
= Terminated
then
858 -- It is not safe to call Abort_Defer or Write_Lock at this stage
860 Initialization
.Task_Lock
(Self_Id
);
863 Initialization
.Finalize_Attributes_Link
.all (T
);
864 Initialization
.Remove_From_All_Tasks_List
(T
);
867 Initialization
.Task_Unlock
(Self_Id
);
869 Free_Entry_Names
(T
);
870 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
872 -- If the task is not terminated, then we simply ignore the call. This
873 -- happens when a user program attempts an unchecked deallocation on
874 -- a non-terminated task.
881 ---------------------------
882 -- Move_Activation_Chain --
883 ---------------------------
885 procedure Move_Activation_Chain
886 (From
, To
: Activation_Chain_Access
;
887 New_Master
: Master_ID
)
889 Self_ID
: constant Task_Id
:= STPO
.Self
;
894 (Debug
.Trace
(Self_ID
, "Move_Activation_Chain", 'C'));
896 -- Nothing to do if From is empty, and we can check that without
905 Initialization
.Defer_Abort
(Self_ID
);
907 -- Loop through the From chain, changing their Master_of_Task
908 -- fields, and to find the end of the chain.
911 C
.Master_of_Task
:= New_Master
;
912 exit when C
.Common
.Activation_Link
= null;
913 C
:= C
.Common
.Activation_Link
;
916 -- Hook From in at the start of To
918 C
.Common
.Activation_Link
:= To
.all.T_ID
;
919 To
.all.T_ID
:= From
.all.T_ID
;
923 From
.all.T_ID
:= null;
925 Initialization
.Undefer_Abort
(Self_ID
);
926 end Move_Activation_Chain
;
928 -- Compiler interface only. Do not call from within the RTS.
934 procedure Set_Entry_Name
936 Pos
: Task_Entry_Index
;
940 pragma Assert
(T
.Entry_Names
/= null);
942 T
.Entry_Names
(Entry_Index
(Pos
)) := Val
;
949 -- The task wrapper is a procedure that is called first for each task body
950 -- and which in turn calls the compiler-generated task body procedure.
951 -- The wrapper's main job is to do initialization for the task. It also
952 -- has some locally declared objects that serve as per-task local data.
953 -- Task finalization is done by Complete_Task, which is called from an
954 -- at-end handler that the compiler generates.
956 procedure Task_Wrapper
(Self_ID
: Task_Id
) is
957 use type SSE
.Storage_Offset
;
958 use System
.Standard_Library
;
959 use System
.Stack_Usage
;
961 Bottom_Of_Stack
: aliased Integer;
963 Task_Alternate_Stack
:
964 aliased SSE
.Storage_Array
(1 .. Alternate_Stack_Size
);
965 -- The alternate signal stack for this task, if any
967 Use_Alternate_Stack
: constant Boolean := Alternate_Stack_Size
/= 0;
968 -- Whether to use above alternate signal stack for stack overflows
970 Secondary_Stack_Size
:
971 constant SSE
.Storage_Offset
:=
972 Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
*
973 SSE
.Storage_Offset
(Parameters
.Sec_Stack_Ratio
) / 100;
975 Secondary_Stack
: aliased SSE
.Storage_Array
(1 .. Secondary_Stack_Size
);
977 pragma Warnings
(Off
);
978 -- Why are warnings being turned off here???
980 Secondary_Stack_Address
: System
.Address
:= Secondary_Stack
'Address;
981 -- Address of secondary stack. In the fixed secondary stack case, this
982 -- value is not modified, causing a warning, hence the bracketing with
983 -- Warnings (Off/On). But why is so much *more* bracketed???
985 Small_Overflow_Guard
: constant := 12 * 1024;
986 -- Note: this used to be 4K, but was changed to 12K, since smaller
987 -- values resulted in segmentation faults from dynamic stack analysis.
989 Big_Overflow_Guard
: constant := 16 * 1024;
990 Small_Stack_Limit
: constant := 64 * 1024;
991 -- ??? These three values are experimental, and seems to work on most
992 -- platforms. They still need to be analyzed further. They also need
993 -- documentation, what are they???
996 Natural (Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
);
998 Overflow_Guard
: Natural;
999 -- Size of the overflow guard, used by dynamic stack usage analysis
1001 pragma Warnings
(On
);
1003 SEH_Table
: aliased SSE
.Storage_Array
(1 .. 8);
1004 -- Structured Exception Registration table (2 words)
1006 procedure Install_SEH_Handler
(Addr
: System
.Address
);
1007 pragma Import
(C
, Install_SEH_Handler
, "__gnat_install_SEH_handler");
1008 -- Install the SEH (Structured Exception Handling) handler
1010 Cause
: Cause_Of_Termination
:= Normal
;
1011 -- Indicates the reason why this task terminates. Normal corresponds to
1012 -- a task terminating due to completing the last statement of its body,
1013 -- or as a result of waiting on a terminate alternative. If the task
1014 -- terminates because it is being aborted then Cause will be set to
1015 -- Abnormal. If the task terminates because of an exception raised by
1016 -- the execution of its task body, then Cause is set to
1017 -- Unhandled_Exception.
1019 EO
: Exception_Occurrence
;
1020 -- If the task terminates because of an exception raised by the
1021 -- execution of its task body, then EO will contain the associated
1022 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
1024 TH
: Termination_Handler
:= null;
1025 -- Pointer to the protected procedure to be executed upon task
1028 procedure Search_Fall_Back_Handler
(ID
: Task_Id
);
1029 -- Procedure that searches recursively a fall-back handler through the
1030 -- master relationship. If the handler is found, its pointer is stored
1033 ------------------------------
1034 -- Search_Fall_Back_Handler --
1035 ------------------------------
1037 procedure Search_Fall_Back_Handler
(ID
: Task_Id
) is
1039 -- If there is a fall back handler, store its pointer for later
1042 if ID
.Common
.Fall_Back_Handler
/= null then
1043 TH
:= ID
.Common
.Fall_Back_Handler
;
1045 -- Otherwise look for a fall back handler in the parent
1047 elsif ID
.Common
.Parent
/= null then
1048 Search_Fall_Back_Handler
(ID
.Common
.Parent
);
1050 -- Otherwise, do nothing
1055 end Search_Fall_Back_Handler
;
1058 pragma Assert
(Self_ID
.Deferral_Level
= 1);
1060 -- Assume a size of the stack taken at this stage
1062 if Size
< Small_Stack_Limit
then
1063 Overflow_Guard
:= Small_Overflow_Guard
;
1065 Overflow_Guard
:= Big_Overflow_Guard
;
1068 if not Parameters
.Sec_Stack_Dynamic
then
1069 Self_ID
.Common
.Compiler_Data
.Sec_Stack_Addr
:=
1070 Secondary_Stack
'Address;
1071 SST
.SS_Init
(Secondary_Stack_Address
, Integer (Secondary_Stack
'Last));
1072 Size
:= Size
- Natural (Secondary_Stack_Size
);
1075 if Use_Alternate_Stack
then
1076 Self_ID
.Common
.Task_Alternate_Stack
:= Task_Alternate_Stack
'Address;
1079 Size
:= Size
- Overflow_Guard
;
1081 if System
.Stack_Usage
.Is_Enabled
then
1084 (Self_ID
.Common
.Analyzer
,
1085 Self_ID
.Common
.Task_Image
1086 (1 .. Self_ID
.Common
.Task_Image_Len
),
1088 (Self_ID
.Common
.Compiler_Data
.Pri_Stack_Info
.Size
),
1090 SSE
.To_Integer
(Bottom_Of_Stack
'Address));
1092 Fill_Stack
(Self_ID
.Common
.Analyzer
);
1095 -- Set the guard page at the bottom of the stack. The call to unprotect
1096 -- the page is done in Terminate_Task
1098 Stack_Guard
(Self_ID
, True);
1100 -- Initialize low-level TCB components, that cannot be initialized by
1101 -- the creator. Enter_Task sets Self_ID.Known_Tasks_Index and also
1102 -- Self_ID.LL.Thread
1104 Enter_Task
(Self_ID
);
1106 -- We setup the SEH (Structured Exception Handling) handler if supported
1109 Install_SEH_Handler
(SEH_Table
'Address);
1111 -- Initialize exception occurrence
1113 Save_Occurrence
(EO
, Ada
.Exceptions
.Null_Occurrence
);
1115 -- We lock RTS_Lock to wait for activator to finish activating the rest
1116 -- of the chain, so that everyone in the chain comes out in priority
1119 -- This also protects the value of
1120 -- Self_ID.Common.Activator.Common.Wait_Count.
1125 if not System
.Restrictions
.Abort_Allowed
then
1127 -- If Abort is not allowed, reset the deferral level since it will
1128 -- not get changed by the generated code. Keeping a default value
1129 -- of one would prevent some operations (e.g. select or delay) to
1130 -- proceed successfully.
1132 Self_ID
.Deferral_Level
:= 0;
1136 -- We are separating the following portion of the code in order to
1137 -- place the exception handlers in a different block. In this way,
1138 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
1139 -- set Self in Enter_Task
1141 -- Call the task body procedure
1143 -- The task body is called with abort still deferred. That
1144 -- eliminates a dangerous window, for which we had to patch-up in
1147 -- During the expansion of the task body, we insert an RTS-call
1148 -- to Abort_Undefer, at the first point where abort should be
1151 Self_ID
.Common
.Task_Entry_Point
(Self_ID
.Common
.Task_Arg
);
1152 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1155 -- We can't call Terminate_Task in the exception handlers below,
1156 -- since there may be (e.g. in the case of GCC exception handling)
1157 -- clean ups associated with the exception handler that need to
1158 -- access task specific data.
1160 -- Defer abort so that this task can't be aborted while exiting
1162 when Standard
'Abort_Signal =>
1163 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1165 -- Update the cause that motivated the task termination so that
1166 -- the appropriate information is passed to the task termination
1167 -- procedure. Task termination as a result of waiting on a
1168 -- terminate alternative is a normal termination, although it is
1169 -- implemented using the abort mechanisms.
1171 if Self_ID
.Terminate_Alternative
then
1177 -- ??? Using an E : others here causes CD2C11A to fail on Tru64
1179 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1181 -- Perform the task specific exception tracing duty. We handle
1182 -- these outputs here and not in the common notification routine
1183 -- because we need access to tasking related data and we don't
1184 -- want to drag dependencies against tasking related units in the
1185 -- the common notification units. Additionally, no trace is ever
1186 -- triggered from the common routine for the Unhandled_Raise case
1187 -- in tasks, since an exception never appears unhandled in this
1188 -- context because of this handler.
1190 if Exception_Trace
= Unhandled_Raise
then
1191 Trace_Unhandled_Exception_In_Task
(Self_ID
);
1194 -- Update the cause that motivated the task termination so that
1195 -- the appropriate information is passed to the task termination
1196 -- procedure, as well as the associated Exception_Occurrence.
1198 Cause
:= Unhandled_Exception
;
1199 Save_Occurrence
(EO
, SSL
.Get_Current_Excep
.all.all);
1202 -- Look for a task termination handler. This code is for all tasks but
1203 -- the environment task. The task termination code for the environment
1204 -- task is executed by SSL.Task_Termination_Handler.
1210 Write_Lock
(Self_ID
);
1212 if Self_ID
.Common
.Specific_Handler
/= null then
1213 TH
:= Self_ID
.Common
.Specific_Handler
;
1215 -- Look for a fall-back handler following the master relationship
1218 Search_Fall_Back_Handler
(Self_ID
);
1227 -- Execute the task termination handler if we found it
1230 TH
.all (Cause
, Self_ID
, EO
);
1233 if System
.Stack_Usage
.Is_Enabled
then
1234 Compute_Result
(Self_ID
.Common
.Analyzer
);
1235 Report_Result
(Self_ID
.Common
.Analyzer
);
1238 Terminate_Task
(Self_ID
);
1241 --------------------
1242 -- Terminate_Task --
1243 --------------------
1245 -- Before we allow the thread to exit, we must clean up. This is a
1246 -- delicate job. We must wake up the task's master, who may immediately try
1247 -- to deallocate the ATCB out from under the current task WHILE IT IS STILL
1250 -- To avoid this, the parent task must be blocked up to the latest
1251 -- statement executed. The trouble is that we have another step that we
1252 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
1253 -- We have to postpone that until the end because compiler-generated code
1254 -- is likely to try to access that data at just about any point.
1256 -- We can't call Destroy_TSD while we are holding any other locks, because
1257 -- it locks Global_Task_Lock, and our deadlock prevention rules require
1258 -- that to be the outermost lock. Our first "solution" was to just lock
1259 -- Global_Task_Lock in addition to the other locks, and force the parent to
1260 -- also lock this lock between its wakeup and its freeing of the ATCB. See
1261 -- Complete_Task for the parent-side of the code that has the matching
1262 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1263 -- since the operation Task_Unlock continued to access the ATCB after
1264 -- unlocking, after which the parent was observed to race ahead, deallocate
1265 -- the ATCB, and then reallocate it to another task. The call to
1266 -- Undefer_Abort in Task_Unlock by the "terminated" task was overwriting
1267 -- the data of the new task that reused the ATCB! To solve this problem, we
1268 -- introduced the new operation Final_Task_Unlock.
1270 procedure Terminate_Task
(Self_ID
: Task_Id
) is
1271 Environment_Task
: constant Task_Id
:= STPO
.Environment_Task
;
1272 Master_of_Task
: Integer;
1275 Debug
.Task_Termination_Hook
;
1277 if Runtime_Traces
then
1278 Send_Trace_Info
(T_Terminate
);
1281 -- Since GCC cannot allocate stack chunks efficiently without reordering
1282 -- some of the allocations, we have to handle this unexpected situation
1283 -- here. We should normally never have to call Vulnerable_Complete_Task
1286 if Self_ID
.Common
.Activator
/= null then
1287 Vulnerable_Complete_Task
(Self_ID
);
1290 Initialization
.Task_Lock
(Self_ID
);
1296 Master_of_Task
:= Self_ID
.Master_of_Task
;
1298 -- Check if the current task is an independent task If so, decrement
1299 -- the Independent_Task_Count value.
1301 if Master_of_Task
= Independent_Task_Level
then
1303 Utilities
.Independent_Task_Count
:=
1304 Utilities
.Independent_Task_Count
- 1;
1306 Write_Lock
(Environment_Task
);
1307 Utilities
.Independent_Task_Count
:=
1308 Utilities
.Independent_Task_Count
- 1;
1309 Unlock
(Environment_Task
);
1313 -- Unprotect the guard page if needed
1315 Stack_Guard
(Self_ID
, False);
1317 Utilities
.Make_Passive
(Self_ID
, Task_Completed
=> True);
1323 pragma Assert
(Check_Exit
(Self_ID
));
1325 SSL
.Destroy_TSD
(Self_ID
.Common
.Compiler_Data
);
1326 Initialization
.Final_Task_Unlock
(Self_ID
);
1328 -- WARNING: past this point, this thread must assume that the ATCB has
1329 -- been deallocated. It should not be accessed again.
1331 if Master_of_Task
> 0 then
1340 function Terminated
(T
: Task_Id
) return Boolean is
1341 Self_ID
: constant Task_Id
:= STPO
.Self
;
1345 Initialization
.Defer_Abort_Nestable
(Self_ID
);
1352 Result
:= T
.Common
.State
= Terminated
;
1359 Initialization
.Undefer_Abort_Nestable
(Self_ID
);
1363 ----------------------------------------
1364 -- Trace_Unhandled_Exception_In_Task --
1365 ----------------------------------------
1367 procedure Trace_Unhandled_Exception_In_Task
(Self_Id
: Task_Id
) is
1368 procedure To_Stderr
(S
: String);
1369 pragma Import
(Ada
, To_Stderr
, "__gnat_to_stderr");
1371 use System
.Soft_Links
;
1372 use System
.Standard_Library
;
1374 function To_Address
is new
1375 Ada
.Unchecked_Conversion
1376 (Task_Id
, System
.Task_Primitives
.Task_Address
);
1378 function Tailored_Exception_Information
1379 (E
: Exception_Occurrence
) return String;
1381 (Ada
, Tailored_Exception_Information
,
1382 "__gnat_tailored_exception_information");
1384 Excep
: constant Exception_Occurrence_Access
:=
1385 SSL
.Get_Current_Excep
.all;
1388 -- This procedure is called by the task outermost handler in
1389 -- Task_Wrapper below, so only once the task stack has been fully
1390 -- unwound. The common notification routine has been called at the
1391 -- raise point already.
1393 To_Stderr
("task ");
1395 if Self_Id
.Common
.Task_Image_Len
/= 0 then
1397 (Self_Id
.Common
.Task_Image
(1 .. Self_Id
.Common
.Task_Image_Len
));
1401 To_Stderr
(System
.Address_Image
(To_Address
(Self_Id
)));
1402 To_Stderr
(" terminated by unhandled exception");
1403 To_Stderr
((1 => ASCII
.LF
));
1404 To_Stderr
(Tailored_Exception_Information
(Excep
.all));
1405 end Trace_Unhandled_Exception_In_Task
;
1407 ------------------------------------
1408 -- Vulnerable_Complete_Activation --
1409 ------------------------------------
1411 -- As in several other places, the locks of the activator and activated
1412 -- task are both locked here. This follows our deadlock prevention lock
1413 -- ordering policy, since the activated task must be created after the
1416 procedure Vulnerable_Complete_Activation
(Self_ID
: Task_Id
) is
1417 Activator
: constant Task_Id
:= Self_ID
.Common
.Activator
;
1420 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Activation", 'C'));
1422 Write_Lock
(Activator
);
1423 Write_Lock
(Self_ID
);
1425 pragma Assert
(Self_ID
.Common
.Activator
/= null);
1427 -- Remove dangling reference to Activator, since a task may
1428 -- outlive its activator.
1430 Self_ID
.Common
.Activator
:= null;
1432 -- Wake up the activator, if it is waiting for a chain of tasks to
1433 -- activate, and we are the last in the chain to complete activation.
1435 if Activator
.Common
.State
= Activator_Sleep
then
1436 Activator
.Common
.Wait_Count
:= Activator
.Common
.Wait_Count
- 1;
1438 if Activator
.Common
.Wait_Count
= 0 then
1439 Wakeup
(Activator
, Activator_Sleep
);
1443 -- The activator raises a Tasking_Error if any task it is activating
1444 -- is completed before the activation is done. However, if the reason
1445 -- for the task completion is an abort, we do not raise an exception.
1448 if not Self_ID
.Callable
and then Self_ID
.Pending_ATC_Level
/= 0 then
1449 Activator
.Common
.Activation_Failed
:= True;
1455 -- After the activation, active priority should be the same as base
1456 -- priority. We must unlock the Activator first, though, since it
1457 -- should not wait if we have lower priority.
1459 if Get_Priority
(Self_ID
) /= Self_ID
.Common
.Base_Priority
then
1460 Write_Lock
(Self_ID
);
1461 Set_Priority
(Self_ID
, Self_ID
.Common
.Base_Priority
);
1464 end Vulnerable_Complete_Activation
;
1466 --------------------------------
1467 -- Vulnerable_Complete_Master --
1468 --------------------------------
1470 procedure Vulnerable_Complete_Master
(Self_ID
: Task_Id
) is
1473 CM
: constant Master_Level
:= Self_ID
.Master_Within
;
1474 T
: aliased Task_Id
;
1476 To_Be_Freed
: Task_Id
;
1477 -- This is a list of ATCBs to be freed, after we have released all RTS
1478 -- locks. This is necessary because of the locking order rules, since
1479 -- the storage manager uses Global_Task_Lock.
1481 pragma Warnings
(Off
);
1482 function Check_Unactivated_Tasks
return Boolean;
1483 pragma Warnings
(On
);
1484 -- Temporary error-checking code below. This is part of the checks
1485 -- added in the new run time. Call it only inside a pragma Assert.
1487 -----------------------------
1488 -- Check_Unactivated_Tasks --
1489 -----------------------------
1491 function Check_Unactivated_Tasks
return Boolean is
1493 if not Single_Lock
then
1497 Write_Lock
(Self_ID
);
1499 C
:= All_Tasks_List
;
1500 while C
/= null loop
1501 if C
.Common
.Activator
= Self_ID
and then C
.Master_of_Task
= CM
then
1505 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1508 if C
.Common
.State
= Unactivated
then
1515 C
:= C
.Common
.All_Tasks_Link
;
1520 if not Single_Lock
then
1525 end Check_Unactivated_Tasks
;
1527 -- Start of processing for Vulnerable_Complete_Master
1531 (Debug
.Trace
(Self_ID
, "V_Complete_Master", 'C'));
1533 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1535 (Self_ID
.Deferral_Level
> 0
1536 or else not System
.Restrictions
.Abort_Allowed
);
1538 -- Count how many active dependent tasks this master currently has, and
1539 -- record this in Wait_Count.
1541 -- This count should start at zero, since it is initialized to zero for
1542 -- new tasks, and the task should not exit the sleep-loops that use this
1543 -- count until the count reaches zero.
1545 -- While we're counting, if we run across any unactivated tasks that
1546 -- belong to this master, we summarily terminate them as required by
1550 Write_Lock
(Self_ID
);
1552 C
:= All_Tasks_List
;
1553 while C
/= null loop
1555 -- Terminate unactivated (never-to-be activated) tasks
1557 if C
.Common
.Activator
= Self_ID
and then C
.Master_of_Task
= CM
then
1559 pragma Assert
(C
.Common
.State
= Unactivated
);
1560 -- Usually, C.Common.Activator = Self_ID implies C.Master_of_Task
1561 -- = CM. The only case where C is pending activation by this
1562 -- task, but the master of C is not CM is in Ada 2005, when C is
1563 -- part of a return object of a build-in-place function.
1566 C
.Common
.Activator
:= null;
1567 C
.Common
.State
:= Terminated
;
1568 C
.Callable
:= False;
1569 Utilities
.Cancel_Queued_Entry_Calls
(C
);
1573 -- Count it if dependent on this master
1575 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1578 if C
.Awake_Count
/= 0 then
1579 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1585 C
:= C
.Common
.All_Tasks_Link
;
1588 Self_ID
.Common
.State
:= Master_Completion_Sleep
;
1591 if not Single_Lock
then
1595 -- Wait until dependent tasks are all terminated or ready to terminate.
1596 -- While waiting, the task may be awakened if the task's priority needs
1597 -- changing, or this master is aborted. In the latter case, we abort the
1598 -- dependents, and resume waiting until Wait_Count goes to zero.
1600 Write_Lock
(Self_ID
);
1603 exit when Self_ID
.Common
.Wait_Count
= 0;
1605 -- Here is a difference as compared to Complete_Master
1607 if Self_ID
.Pending_ATC_Level
< Self_ID
.ATC_Nesting_Level
1608 and then not Self_ID
.Dependents_Aborted
1611 Abort_Dependents
(Self_ID
);
1615 Abort_Dependents
(Self_ID
);
1617 Write_Lock
(Self_ID
);
1620 Sleep
(Self_ID
, Master_Completion_Sleep
);
1624 Self_ID
.Common
.State
:= Runnable
;
1627 -- Dependents are all terminated or on terminate alternatives. Now,
1628 -- force those on terminate alternatives to terminate, by aborting them.
1630 pragma Assert
(Check_Unactivated_Tasks
);
1632 if Self_ID
.Alive_Count
> 1 then
1634 -- Consider finding a way to skip the following extra steps if there
1635 -- are no dependents with terminate alternatives. This could be done
1636 -- by adding another count to the ATCB, similar to Awake_Count, but
1637 -- keeping track of tasks that are on terminate alternatives.
1639 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1641 -- Force any remaining dependents to terminate by aborting them
1643 if not Single_Lock
then
1647 Abort_Dependents
(Self_ID
);
1649 -- Above, when we "abort" the dependents we are simply using this
1650 -- operation for convenience. We are not required to support the full
1651 -- abort-statement semantics; in particular, we are not required to
1652 -- immediately cancel any queued or in-service entry calls. That is
1653 -- good, because if we tried to cancel a call we would need to lock
1654 -- the caller, in order to wake the caller up. Our anti-deadlock
1655 -- rules prevent us from doing that without releasing the locks on C
1656 -- and Self_ID. Releasing and retaking those locks would be wasteful
1657 -- at best, and should not be considered further without more
1658 -- detailed analysis of potential concurrent accesses to the ATCBs
1659 -- of C and Self_ID.
1661 -- Count how many "alive" dependent tasks this master currently has,
1662 -- and record this in Wait_Count. This count should start at zero,
1663 -- since it is initialized to zero for new tasks, and the task should
1664 -- not exit the sleep-loops that use this count until the count
1667 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1669 Write_Lock
(Self_ID
);
1671 C
:= All_Tasks_List
;
1672 while C
/= null loop
1673 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
= CM
then
1676 pragma Assert
(C
.Awake_Count
= 0);
1678 if C
.Alive_Count
> 0 then
1679 pragma Assert
(C
.Terminate_Alternative
);
1680 Self_ID
.Common
.Wait_Count
:= Self_ID
.Common
.Wait_Count
+ 1;
1686 C
:= C
.Common
.All_Tasks_Link
;
1689 Self_ID
.Common
.State
:= Master_Phase_2_Sleep
;
1692 if not Single_Lock
then
1696 -- Wait for all counted tasks to finish terminating themselves
1698 Write_Lock
(Self_ID
);
1701 exit when Self_ID
.Common
.Wait_Count
= 0;
1702 Sleep
(Self_ID
, Master_Phase_2_Sleep
);
1705 Self_ID
.Common
.State
:= Runnable
;
1709 -- We don't wake up for abort here. We are already terminating just as
1710 -- fast as we can, so there is no point.
1712 -- Remove terminated tasks from the list of Self_ID's dependents, but
1713 -- don't free their ATCBs yet, because of lock order restrictions, which
1714 -- don't allow us to call "free" or "malloc" while holding any other
1715 -- locks. Instead, we put those ATCBs to be freed onto a temporary list,
1716 -- called To_Be_Freed.
1718 if not Single_Lock
then
1722 C
:= All_Tasks_List
;
1724 while C
/= null loop
1725 if C
.Common
.Parent
= Self_ID
and then C
.Master_of_Task
>= CM
then
1727 P
.Common
.All_Tasks_Link
:= C
.Common
.All_Tasks_Link
;
1729 All_Tasks_List
:= C
.Common
.All_Tasks_Link
;
1732 T
:= C
.Common
.All_Tasks_Link
;
1733 C
.Common
.All_Tasks_Link
:= To_Be_Freed
;
1739 C
:= C
.Common
.All_Tasks_Link
;
1745 -- Free all the ATCBs on the list To_Be_Freed
1747 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1748 -- any interrupt entries are detached from them they should no longer
1751 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1752 -- avoid a race between a terminating task and its parent. The parent
1753 -- might try to deallocate the ACTB out from underneath the exiting
1754 -- task. Note that Free will also lock Global_Task_Lock, but that is
1755 -- OK, since this is the *one* lock for which we have a mechanism to
1756 -- support nested locking. See Task_Wrapper and its finalizer for more
1760 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1761 -- references to terminated library-level tasks, which could otherwise
1762 -- occur during finalization of library-level objects. A better solution
1763 -- might be to hook task objects into the finalization chain and
1764 -- deallocate the ATCB when the task object is deallocated. However,
1765 -- this change is not likely to gain anything significant, since all
1766 -- this storage should be recovered en-masse when the process exits.
1768 while To_Be_Freed
/= null loop
1770 To_Be_Freed
:= T
.Common
.All_Tasks_Link
;
1772 -- ??? On SGI there is currently no Interrupt_Manager, that's
1773 -- why we need to check if the Interrupt_Manager_ID is null
1775 if T
.Interrupt_Entry
and Interrupt_Manager_ID
/= null then
1777 Detach_Interrupt_Entries_Index
: constant Task_Entry_Index
:= 1;
1778 -- Corresponds to the entry index of System.Interrupts.
1779 -- Interrupt_Manager.Detach_Interrupt_Entries.
1780 -- Be sure to update this value when changing
1781 -- Interrupt_Manager specs.
1783 type Param_Type
is access all Task_Id
;
1785 Param
: aliased Param_Type
:= T
'Access;
1788 System
.Tasking
.Rendezvous
.Call_Simple
1789 (Interrupt_Manager_ID
, Detach_Interrupt_Entries_Index
,
1794 if (T
.Common
.Parent
/= null
1795 and then T
.Common
.Parent
.Common
.Parent
/= null)
1796 or else T
.Master_of_Task
> Library_Task_Level
1798 Initialization
.Task_Lock
(Self_ID
);
1800 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1801 -- has not been called yet (case of an unactivated task).
1803 if T
.Common
.Compiler_Data
.Sec_Stack_Addr
/= Null_Address
then
1804 SSL
.Destroy_TSD
(T
.Common
.Compiler_Data
);
1807 Vulnerable_Free_Task
(T
);
1808 Initialization
.Task_Unlock
(Self_ID
);
1812 -- It might seem nice to let the terminated task deallocate its own
1813 -- ATCB. That would not cover the case of unactivated tasks. It also
1814 -- would force us to keep the underlying thread around past termination,
1815 -- since references to the ATCB are possible past termination.
1817 -- Currently, we get rid of the thread as soon as the task terminates,
1818 -- and let the parent recover the ATCB later.
1820 -- Some day, if we want to recover the ATCB earlier, at task
1821 -- termination, we could consider using "fat task IDs", that include the
1822 -- serial number with the ATCB pointer, to catch references to tasks
1823 -- that no longer have ATCBs. It is not clear how much this would gain,
1824 -- since the user-level task object would still be occupying storage.
1826 -- Make next master level up active. We don't need to lock the ATCB,
1827 -- since the value is only updated by each task for itself.
1829 Self_ID
.Master_Within
:= CM
- 1;
1830 end Vulnerable_Complete_Master
;
1832 ------------------------------
1833 -- Vulnerable_Complete_Task --
1834 ------------------------------
1836 -- Complete the calling task
1838 -- This procedure must be called with abort deferred. It should only be
1839 -- called by Complete_Task and Finalize_Global_Tasks (for the environment
1842 -- The effect is similar to that of Complete_Master. Differences include
1843 -- the closing of entries here, and computation of the number of active
1844 -- dependent tasks in Complete_Master.
1846 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1847 -- because that does its own locking, and because we do not need the lock
1848 -- to test Self_ID.Common.Activator. That value should only be read and
1849 -- modified by Self.
1851 procedure Vulnerable_Complete_Task
(Self_ID
: Task_Id
) is
1854 (Self_ID
.Deferral_Level
> 0
1855 or else not System
.Restrictions
.Abort_Allowed
);
1856 pragma Assert
(Self_ID
= Self
);
1857 pragma Assert
(Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 1
1859 Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2);
1860 pragma Assert
(Self_ID
.Common
.Wait_Count
= 0);
1861 pragma Assert
(Self_ID
.Open_Accepts
= null);
1862 pragma Assert
(Self_ID
.ATC_Nesting_Level
= 1);
1864 pragma Debug
(Debug
.Trace
(Self_ID
, "V_Complete_Task", 'C'));
1870 Write_Lock
(Self_ID
);
1871 Self_ID
.Callable
:= False;
1873 -- In theory, Self should have no pending entry calls left on its
1874 -- call-stack. Each async. select statement should clean its own call,
1875 -- and blocking entry calls should defer abort until the calls are
1876 -- cancelled, then clean up.
1878 Utilities
.Cancel_Queued_Entry_Calls
(Self_ID
);
1881 if Self_ID
.Common
.Activator
/= null then
1882 Vulnerable_Complete_Activation
(Self_ID
);
1889 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2 we may have
1890 -- dependent tasks for which we need to wait. Otherwise we just exit.
1892 if Self_ID
.Master_Within
= Self_ID
.Master_of_Task
+ 2 then
1893 Vulnerable_Complete_Master
(Self_ID
);
1895 end Vulnerable_Complete_Task
;
1897 --------------------------
1898 -- Vulnerable_Free_Task --
1899 --------------------------
1901 -- Recover all runtime system storage associated with the task T. This
1902 -- should only be called after T has terminated and will no longer be
1905 -- For tasks created by an allocator that fails, due to an exception, it
1906 -- is called from Expunge_Unactivated_Tasks.
1908 -- For tasks created by elaboration of task object declarations it is
1909 -- called from the finalization code of the Task_Wrapper procedure. It is
1910 -- also called from Ada.Unchecked_Deallocation, for objects that are or
1913 procedure Vulnerable_Free_Task
(T
: Task_Id
) is
1915 pragma Debug
(Debug
.Trace
(Self
, "Vulnerable_Free_Task", 'C', T
));
1922 Initialization
.Finalize_Attributes_Link
.all (T
);
1929 Free_Entry_Names
(T
);
1930 System
.Task_Primitives
.Operations
.Finalize_TCB
(T
);
1931 end Vulnerable_Free_Task
;
1933 -- Package elaboration code
1936 -- Establish the Adafinal oftlink
1938 -- This is not done inside the central RTS initialization routine
1939 -- to avoid with-ing this package from System.Tasking.Initialization.
1941 SSL
.Adafinal
:= Finalize_Global_Tasks
'Access;
1943 -- Establish soft links for subprograms that manipulate master_id's.
1944 -- This cannot be done when the RTS is initialized, because of various
1945 -- elaboration constraints.
1947 SSL
.Current_Master
:= Stages
.Current_Master
'Access;
1948 SSL
.Enter_Master
:= Stages
.Enter_Master
'Access;
1949 SSL
.Complete_Master
:= Stages
.Complete_Master
'Access;
1950 end System
.Tasking
.Stages
;