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) 1992-2009, 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 3, or (at your option) any later ver- --
14 -- sion. GNAT 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
30 ------------------------------------------------------------------------------
33 -- Turn off polling, we do not want ATC polling to take place during tasking
34 -- operations. It causes infinite loops and other problems.
37 with Ada.Unchecked_Deallocation;
39 with System.Tasking.Debug;
40 with System.Address_Image;
41 with System.Task_Primitives;
42 with System.Task_Primitives.Operations;
43 with System.Tasking.Utilities;
44 with System.Tasking.Queuing;
45 with System.Tasking.Rendezvous;
46 with System.OS_Primitives;
47 with System.Secondary_Stack;
48 with System.Storage_Elements;
49 with System.Restrictions;
50 with System.Standard_Library;
51 with System.Traces.Tasking;
52 with System.Stack_Usage;
54 with System.Soft_Links;
55 -- These are procedure pointers to non-tasking routines that use task
56 -- specific data. In the absence of tasking, these routines refer to global
57 -- data. In the presence of tasking, they must be replaced with pointers to
58 -- task-specific versions. Also used for Create_TSD, Destroy_TSD,
59 -- Get_Current_Excep, Finalize_Global_List, Task_Termination, Handler.
61 with System.Tasking.Initialization;
62 pragma Elaborate_All (System.Tasking.Initialization);
63 -- This insures that tasking is initialized if any tasks are created
65 package body System.Tasking.Stages is
67 package STPO renames System.Task_Primitives.Operations;
68 package SSL renames System.Soft_Links;
69 package SSE renames System.Storage_Elements;
70 package SST renames System.Secondary_Stack;
76 use Task_Primitives.Operations;
80 use System.Traces.Tasking;
82 -----------------------
83 -- Local Subprograms --
84 -----------------------
87 Ada.Unchecked_Deallocation (Ada_Task_Control_Block, Task_Id);
89 procedure Free_Entry_Names (T : Task_Id);
90 -- Deallocate all string names associated with task entries
92 procedure Trace_Unhandled_Exception_In_Task (Self_Id : Task_Id);
93 -- This procedure outputs the task specific message for exception
96 procedure Task_Wrapper (Self_ID : Task_Id);
97 pragma Convention (C, Task_Wrapper);
98 -- This is the procedure that is called by the GNULL from the new context
99 -- when a task is created. It waits for activation and then calls the task
100 -- body procedure. When the task body procedure completes, it terminates
103 -- The Task_Wrapper's address will be provided to the underlying threads
104 -- library as the task entry point. Convention C is what makes most sense
105 -- for that purpose (Export C would make the function globally visible,
106 -- and affect the link name on which GDB depends). This will in addition
107 -- trigger an automatic stack alignment suitable for GCC's assumptions if
110 -- "Vulnerable_..." in the procedure names below means they must be called
111 -- with abort deferred.
113 procedure Vulnerable_Complete_Task (Self_ID : Task_Id);
114 -- Complete the calling task. This procedure must be called with
115 -- abort deferred. It should only be called by Complete_Task and
116 -- Finalize_Global_Tasks (for the environment task).
118 procedure Vulnerable_Complete_Master (Self_ID : Task_Id);
119 -- Complete the current master of the calling task. This procedure
120 -- must be called with abort deferred. It should only be called by
121 -- Vulnerable_Complete_Task and Complete_Master.
123 procedure Vulnerable_Complete_Activation (Self_ID : Task_Id);
124 -- Signal to Self_ID's activator that Self_ID has completed activation.
125 -- This procedure must be called with abort deferred.
127 procedure Abort_Dependents (Self_ID : Task_Id);
128 -- Abort all the direct dependents of Self at its current master nesting
129 -- level, plus all of their dependents, transitively. RTS_Lock should be
130 -- locked by the caller.
132 procedure Vulnerable_Free_Task (T : Task_Id);
133 -- Recover all runtime system storage associated with the task T. This
134 -- should only be called after T has terminated and will no longer be
137 -- For tasks created by an allocator that fails, due to an exception, it is
138 -- called from Expunge_Unactivated_Tasks.
140 -- Different code is used at master completion, in Terminate_Dependents,
141 -- due to a need for tighter synchronization with the master.
143 ----------------------
144 -- Abort_Dependents --
145 ----------------------
147 procedure Abort_Dependents (Self_ID : Task_Id) is
154 P := C.Common.Parent;
158 -- ??? C is supposed to take care of its own dependents, so
159 -- there should be no need to worry about them. Need to double
162 if C.Master_of_Task = Self_ID.Master_Within then
163 Utilities.Abort_One_Task (Self_ID, C);
164 C.Dependents_Aborted := True;
170 P := P.Common.Parent;
173 C := C.Common.All_Tasks_Link;
176 Self_ID.Dependents_Aborted := True;
177 end Abort_Dependents;
183 procedure Abort_Tasks (Tasks : Task_List) is
185 Utilities.Abort_Tasks (Tasks);
192 -- Note that locks of activator and activated task are both locked here.
193 -- This is necessary because C.Common.State and Self.Common.Wait_Count have
194 -- to be synchronized. This is safe from deadlock because the activator is
195 -- always created before the activated task. That satisfies our
196 -- in-order-of-creation ATCB locking policy.
198 -- At one point, we may also lock the parent, if the parent is different
199 -- from the activator. That is also consistent with the lock ordering
200 -- policy, since the activator cannot be created before the parent.
202 -- Since we are holding both the activator's lock, and Task_Wrapper locks
203 -- that before it does anything more than initialize the low-level ATCB
204 -- components, it should be safe to wait to update the counts until we see
205 -- that the thread creation is successful.
207 -- If the thread creation fails, we do need to close the entries of the
208 -- task. The first phase, of dequeuing calls, only requires locking the
209 -- acceptor's ATCB, but the waking up of the callers requires locking the
210 -- caller's ATCB. We cannot safely do this while we are holding other
211 -- locks. Therefore, the queue-clearing operation is done in a separate
212 -- pass over the activation chain.
214 procedure Activate_Tasks (Chain_Access : Activation_Chain_Access) is
215 Self_ID : constant Task_Id := STPO.Self;
218 Next_C, Last_C : Task_Id;
219 Activate_Prio : System.Any_Priority;
221 All_Elaborated : Boolean := True;
224 -- If pragma Detect_Blocking is active, then we must check whether this
225 -- potentially blocking operation is called from a protected action.
227 if System.Tasking.Detect_Blocking
228 and then Self_ID.Common.Protected_Action_Nesting > 0
230 raise Program_Error with "potentially blocking operation";
234 (Debug.Trace (Self_ID, "Activate_Tasks", 'C'));
236 Initialization.Defer_Abort_Nestable (Self_ID);
238 pragma Assert (Self_ID.Common.Wait_Count = 0);
240 -- Lock RTS_Lock, to prevent activated tasks from racing ahead before
241 -- we finish activating the chain.
245 -- Check that all task bodies have been elaborated
247 C := Chain_Access.T_ID;
250 if C.Common.Elaborated /= null
251 and then not C.Common.Elaborated.all
253 All_Elaborated := False;
256 -- Reverse the activation chain so that tasks are activated in the
257 -- same order they're declared.
259 Next_C := C.Common.Activation_Link;
260 C.Common.Activation_Link := Last_C;
265 Chain_Access.T_ID := Last_C;
267 if not All_Elaborated then
269 Initialization.Undefer_Abort_Nestable (Self_ID);
270 raise Program_Error with "Some tasks have not been elaborated";
273 -- Activate all the tasks in the chain. Creation of the thread of
274 -- control was deferred until activation. So create it now.
276 C := Chain_Access.T_ID;
278 if C.Common.State /= Terminated then
279 pragma Assert (C.Common.State = Unactivated);
281 P := C.Common.Parent;
285 if C.Common.Base_Priority < Get_Priority (Self_ID) then
286 Activate_Prio := Get_Priority (Self_ID);
288 Activate_Prio := C.Common.Base_Priority;
291 System.Task_Primitives.Operations.Create_Task
292 (C, Task_Wrapper'Address,
294 (C.Common.Compiler_Data.Pri_Stack_Info.Size),
295 Activate_Prio, Success);
297 -- There would be a race between the created task and the creator
298 -- to do the following initialization, if we did not have a
299 -- Lock/Unlock_RTS pair in the task wrapper to prevent it from
303 C.Common.State := Runnable;
306 P.Awake_Count := P.Awake_Count + 1;
307 P.Alive_Count := P.Alive_Count + 1;
309 if P.Common.State = Master_Completion_Sleep and then
310 C.Master_of_Task = P.Master_Within
312 pragma Assert (Self_ID /= P);
313 P.Common.Wait_Count := P.Common.Wait_Count + 1;
320 -- No need to set Awake_Count, State, etc. here since the loop
321 -- below will do that for any Unactivated tasks.
325 Self_ID.Common.Activation_Failed := True;
329 C := C.Common.Activation_Link;
332 if not Single_Lock then
336 -- Close the entries of any tasks that failed thread creation, and count
337 -- those that have not finished activation.
339 Write_Lock (Self_ID);
340 Self_ID.Common.State := Activator_Sleep;
342 C := Chain_Access.T_ID;
346 if C.Common.State = Unactivated then
347 C.Common.Activator := null;
348 C.Common.State := Terminated;
350 Utilities.Cancel_Queued_Entry_Calls (C);
352 elsif C.Common.Activator /= null then
353 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
357 P := C.Common.Activation_Link;
358 C.Common.Activation_Link := null;
362 -- Wait for the activated tasks to complete activation. It is
363 -- unsafe to abort any of these tasks until the count goes to zero.
366 exit when Self_ID.Common.Wait_Count = 0;
367 Sleep (Self_ID, Activator_Sleep);
370 Self_ID.Common.State := Runnable;
377 -- Remove the tasks from the chain
379 Chain_Access.T_ID := null;
380 Initialization.Undefer_Abort_Nestable (Self_ID);
382 if Self_ID.Common.Activation_Failed then
383 Self_ID.Common.Activation_Failed := False;
384 raise Tasking_Error with "Failure during activation";
388 -------------------------
389 -- Complete_Activation --
390 -------------------------
392 procedure Complete_Activation is
393 Self_ID : constant Task_Id := STPO.Self;
396 Initialization.Defer_Abort_Nestable (Self_ID);
402 Vulnerable_Complete_Activation (Self_ID);
408 Initialization.Undefer_Abort_Nestable (Self_ID);
410 -- ??? Why do we need to allow for nested deferral here?
412 if Runtime_Traces then
413 Send_Trace_Info (T_Activate);
415 end Complete_Activation;
417 ---------------------
418 -- Complete_Master --
419 ---------------------
421 procedure Complete_Master is
422 Self_ID : constant Task_Id := STPO.Self;
425 (Self_ID.Deferral_Level > 0
426 or else not System.Restrictions.Abort_Allowed);
427 Vulnerable_Complete_Master (Self_ID);
434 -- See comments on Vulnerable_Complete_Task for details
436 procedure Complete_Task is
437 Self_ID : constant Task_Id := STPO.Self;
441 (Self_ID.Deferral_Level > 0
442 or else not System.Restrictions.Abort_Allowed);
444 Vulnerable_Complete_Task (Self_ID);
446 -- All of our dependents have terminated. Never undefer abort again!
454 -- Compiler interface only. Do not call from within the RTS. This must be
455 -- called to create a new task.
457 procedure Create_Task
459 Size : System.Parameters.Size_Type;
460 Task_Info : System.Task_Info.Task_Info_Type;
461 Relative_Deadline : Ada.Real_Time.Time_Span;
462 Num_Entries : Task_Entry_Index;
463 Master : Master_Level;
464 State : Task_Procedure_Access;
465 Discriminants : System.Address;
466 Elaborated : Access_Boolean;
467 Chain : in out Activation_Chain;
469 Created_Task : out Task_Id;
470 Build_Entry_Names : Boolean)
473 Self_ID : constant Task_Id := STPO.Self;
475 Base_Priority : System.Any_Priority;
478 pragma Unreferenced (Relative_Deadline);
479 -- EDF scheduling is not supported by any of the target platforms so
480 -- this parameter is not passed any further.
483 -- If Master is greater than the current master, it means that Master
484 -- has already awaited its dependent tasks. This raises Program_Error,
485 -- by 4.8(10.3/2). See AI-280. Ignore this check for foreign threads.
487 if Self_ID.Master_of_Task /= Foreign_Task_Level
488 and then Master > Self_ID.Master_Within
490 raise Program_Error with
491 "create task after awaiting termination";
494 -- If pragma Detect_Blocking is active must be checked whether this
495 -- potentially blocking operation is called from a protected action.
497 if System.Tasking.Detect_Blocking
498 and then Self_ID.Common.Protected_Action_Nesting > 0
500 raise Program_Error with "potentially blocking operation";
504 (Debug.Trace (Self_ID, "Create_Task", 'C'));
506 if Priority = Unspecified_Priority then
507 Base_Priority := Self_ID.Common.Base_Priority;
509 Base_Priority := System.Any_Priority (Priority);
512 -- Find parent P of new Task, via master level number
517 while P.Master_of_Task >= Master loop
518 P := P.Common.Parent;
523 Initialization.Defer_Abort_Nestable (Self_ID);
526 T := New_ATCB (Num_Entries);
529 Initialization.Undefer_Abort_Nestable (Self_ID);
530 raise Storage_Error with "Cannot allocate task";
533 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks. Up to this
534 -- point, it is possible that we may be part of a family of tasks that
538 Write_Lock (Self_ID);
540 -- Now, we must check that we have not been aborted. If so, we should
541 -- give up on creating this task, and simply return.
543 if not Self_ID.Callable then
544 pragma Assert (Self_ID.Pending_ATC_Level = 0);
545 pragma Assert (Self_ID.Pending_Action);
547 (Chain.T_ID = null or else Chain.T_ID.Common.State = Unactivated);
551 Initialization.Undefer_Abort_Nestable (Self_ID);
553 -- ??? Should never get here
555 pragma Assert (False);
556 raise Standard'Abort_Signal;
559 Initialize_ATCB (Self_ID, State, Discriminants, P, Elaborated,
560 Base_Priority, Task_Info, Size, T, Success);
566 Initialization.Undefer_Abort_Nestable (Self_ID);
567 raise Storage_Error with "Failed to initialize task";
570 if Master = Foreign_Task_Level + 2 then
572 -- This should not happen, except when a foreign task creates non
573 -- library-level Ada tasks. In this case, we pretend the master is
574 -- a regular library level task, otherwise the run-time will get
575 -- confused when waiting for these tasks to terminate.
577 T.Master_of_Task := Library_Task_Level;
579 T.Master_of_Task := Master;
582 T.Master_Within := T.Master_of_Task + 1;
584 for L in T.Entry_Calls'Range loop
585 T.Entry_Calls (L).Self := T;
586 T.Entry_Calls (L).Level := L;
589 if Task_Image'Length = 0 then
590 T.Common.Task_Image_Len := 0;
593 T.Common.Task_Image (1) := Task_Image (Task_Image'First);
595 -- Remove unwanted blank space generated by 'Image
597 for J in Task_Image'First + 1 .. Task_Image'Last loop
598 if Task_Image (J) /= ' '
599 or else Task_Image (J - 1) /= '('
602 T.Common.Task_Image (Len) := Task_Image (J);
603 exit when Len = T.Common.Task_Image'Last;
607 T.Common.Task_Image_Len := Len;
610 if Build_Entry_Names then
612 new Entry_Names_Array (1 .. Entry_Index (Num_Entries));
618 -- Create TSD as early as possible in the creation of a task, since it
619 -- may be used by the operation of Ada code within the task.
621 SSL.Create_TSD (T.Common.Compiler_Data);
622 T.Common.Activation_Link := Chain.T_ID;
624 Initialization.Initialize_Attributes_Link.all (T);
626 Initialization.Undefer_Abort_Nestable (Self_ID);
628 if Runtime_Traces then
629 Send_Trace_Info (T_Create, T);
637 function Current_Master return Master_Level is
639 return STPO.Self.Master_Within;
646 procedure Enter_Master is
647 Self_ID : constant Task_Id := STPO.Self;
649 Self_ID.Master_Within := Self_ID.Master_Within + 1;
652 -------------------------------
653 -- Expunge_Unactivated_Tasks --
654 -------------------------------
656 -- See procedure Close_Entries for the general case
658 procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain) is
659 Self_ID : constant Task_Id := STPO.Self;
661 Call : Entry_Call_Link;
666 (Debug.Trace (Self_ID, "Expunge_Unactivated_Tasks", 'C'));
668 Initialization.Defer_Abort_Nestable (Self_ID);
671 -- Experimentation has shown that abort is sometimes (but not always)
672 -- already deferred when this is called.
674 -- That may indicate an error. Find out what is going on
678 pragma Assert (C.Common.State = Unactivated);
680 Temp := C.Common.Activation_Link;
682 if C.Common.State = Unactivated then
686 for J in 1 .. C.Entry_Num loop
687 Queuing.Dequeue_Head (C.Entry_Queues (J), Call);
688 pragma Assert (Call = null);
693 Initialization.Remove_From_All_Tasks_List (C);
696 Vulnerable_Free_Task (C);
702 Initialization.Undefer_Abort_Nestable (Self_ID);
703 end Expunge_Unactivated_Tasks;
705 ---------------------------
706 -- Finalize_Global_Tasks --
707 ---------------------------
710 -- We have a potential problem here if finalization of global objects does
711 -- anything with signals or the timer server, since by that time those
712 -- servers have terminated.
714 -- It is hard to see how that would occur
716 -- However, a better solution might be to do all this finalization
717 -- using the global finalization chain.
719 procedure Finalize_Global_Tasks is
720 Self_ID : constant Task_Id := STPO.Self;
723 pragma Unreferenced (Ignore);
726 if Self_ID.Deferral_Level = 0 then
728 -- In principle, we should be able to predict whether abort is
729 -- already deferred here (and it should not be deferred yet but in
730 -- practice it seems Finalize_Global_Tasks is being called sometimes,
731 -- from RTS code for exceptions, with abort already deferred.
733 Initialization.Defer_Abort_Nestable (Self_ID);
735 -- Never undefer again!!!
738 -- This code is only executed by the environment task
740 pragma Assert (Self_ID = Environment_Task);
742 -- Set Environment_Task'Callable to false to notify library-level tasks
743 -- that it is waiting for them.
745 Self_ID.Callable := False;
747 -- Exit level 2 master, for normal tasks in library-level packages
751 -- Force termination of "independent" library-level server tasks
755 Abort_Dependents (Self_ID);
757 if not Single_Lock then
761 -- We need to explicitly wait for the task to be terminated here
762 -- because on true concurrent system, we may end this procedure before
763 -- the tasks are really terminated.
765 Write_Lock (Self_ID);
768 exit when Utilities.Independent_Task_Count = 0;
770 -- We used to yield here, but this did not take into account low
771 -- priority tasks that would cause dead lock in some cases (true
775 (Self_ID, 0.01, System.OS_Primitives.Relative,
776 Self_ID.Common.State, Ignore, Ignore);
779 -- ??? On multi-processor environments, it seems that the above loop
780 -- isn't sufficient, so we need to add an additional delay.
783 (Self_ID, 0.01, System.OS_Primitives.Relative,
784 Self_ID.Common.State, Ignore, Ignore);
792 -- Complete the environment task
794 Vulnerable_Complete_Task (Self_ID);
796 -- Handle normal task termination by the environment task, but only
797 -- for the normal task termination. In the case of Abnormal and
798 -- Unhandled_Exception they must have been handled before, and the
799 -- task termination soft link must have been changed so the task
800 -- termination routine is not executed twice.
802 SSL.Task_Termination_Handler.all (Ada.Exceptions.Null_Occurrence);
804 -- Finalize the global list for controlled objects if needed
806 SSL.Finalize_Global_List.all;
808 -- Reset the soft links to non-tasking
810 SSL.Abort_Defer := SSL.Abort_Defer_NT'Access;
811 SSL.Abort_Undefer := SSL.Abort_Undefer_NT'Access;
812 SSL.Lock_Task := SSL.Task_Lock_NT'Access;
813 SSL.Unlock_Task := SSL.Task_Unlock_NT'Access;
814 SSL.Get_Jmpbuf_Address := SSL.Get_Jmpbuf_Address_NT'Access;
815 SSL.Set_Jmpbuf_Address := SSL.Set_Jmpbuf_Address_NT'Access;
816 SSL.Get_Sec_Stack_Addr := SSL.Get_Sec_Stack_Addr_NT'Access;
817 SSL.Set_Sec_Stack_Addr := SSL.Set_Sec_Stack_Addr_NT'Access;
818 SSL.Check_Abort_Status := SSL.Check_Abort_Status_NT'Access;
819 SSL.Get_Stack_Info := SSL.Get_Stack_Info_NT'Access;
821 -- Don't bother trying to finalize Initialization.Global_Task_Lock
822 -- and System.Task_Primitives.RTS_Lock.
824 end Finalize_Global_Tasks;
826 ----------------------
827 -- Free_Entry_Names --
828 ----------------------
830 procedure Free_Entry_Names (T : Task_Id) is
831 Names : Entry_Names_Array_Access := T.Entry_Names;
833 procedure Free_Entry_Names_Array_Access is new
834 Ada.Unchecked_Deallocation
835 (Entry_Names_Array, Entry_Names_Array_Access);
842 Free_Entry_Names_Array (Names.all);
843 Free_Entry_Names_Array_Access (Names);
844 end Free_Entry_Names;
850 procedure Free_Task (T : Task_Id) is
851 Self_Id : constant Task_Id := Self;
854 if T.Common.State = Terminated then
856 -- It is not safe to call Abort_Defer or Write_Lock at this stage
858 Initialization.Task_Lock (Self_Id);
861 Initialization.Finalize_Attributes_Link.all (T);
862 Initialization.Remove_From_All_Tasks_List (T);
865 Initialization.Task_Unlock (Self_Id);
867 Free_Entry_Names (T);
868 System.Task_Primitives.Operations.Finalize_TCB (T);
870 -- If the task is not terminated, then we simply ignore the call. This
871 -- happens when a user program attempts an unchecked deallocation on
872 -- a non-terminated task.
879 ---------------------------
880 -- Move_Activation_Chain --
881 ---------------------------
883 procedure Move_Activation_Chain
884 (From, To : Activation_Chain_Access;
885 New_Master : Master_ID)
887 Self_ID : constant Task_Id := STPO.Self;
892 (Debug.Trace (Self_ID, "Move_Activation_Chain", 'C'));
894 -- Nothing to do if From is empty, and we can check that without
903 Initialization.Defer_Abort (Self_ID);
905 -- Loop through the From chain, changing their Master_of_Task
906 -- fields, and to find the end of the chain.
909 C.Master_of_Task := New_Master;
910 exit when C.Common.Activation_Link = null;
911 C := C.Common.Activation_Link;
914 -- Hook From in at the start of To
916 C.Common.Activation_Link := To.all.T_ID;
917 To.all.T_ID := From.all.T_ID;
921 From.all.T_ID := null;
923 Initialization.Undefer_Abort (Self_ID);
924 end Move_Activation_Chain;
926 -- Compiler interface only. Do not call from within the RTS.
932 procedure Set_Entry_Name
934 Pos : Task_Entry_Index;
938 pragma Assert (T.Entry_Names /= null);
940 T.Entry_Names (Entry_Index (Pos)) := Val;
947 -- The task wrapper is a procedure that is called first for each task body
948 -- and which in turn calls the compiler-generated task body procedure.
949 -- The wrapper's main job is to do initialization for the task. It also
950 -- has some locally declared objects that serve as per-task local data.
951 -- Task finalization is done by Complete_Task, which is called from an
952 -- at-end handler that the compiler generates.
954 procedure Task_Wrapper (Self_ID : Task_Id) is
955 use type SSE.Storage_Offset;
956 use System.Standard_Library;
957 use System.Stack_Usage;
959 Bottom_Of_Stack : aliased Integer;
961 Task_Alternate_Stack :
962 aliased SSE.Storage_Array (1 .. Alternate_Stack_Size);
963 -- The alternate signal stack for this task, if any
965 Use_Alternate_Stack : constant Boolean := Alternate_Stack_Size /= 0;
966 -- Whether to use above alternate signal stack for stack overflows
968 Secondary_Stack_Size :
969 constant SSE.Storage_Offset :=
970 Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size *
971 SSE.Storage_Offset (Parameters.Sec_Stack_Ratio) / 100;
973 Secondary_Stack : aliased SSE.Storage_Array (1 .. Secondary_Stack_Size);
975 pragma Warnings (Off);
976 -- Why are warnings being turned off here???
978 Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
979 -- Address of secondary stack. In the fixed secondary stack case, this
980 -- value is not modified, causing a warning, hence the bracketing with
981 -- Warnings (Off/On). But why is so much *more* bracketed???
983 Small_Overflow_Guard : constant := 12 * 1024;
984 -- Note: this used to be 4K, but was changed to 12K, since smaller
985 -- values resulted in segmentation faults from dynamic stack analysis.
987 Big_Overflow_Guard : constant := 16 * 1024;
988 Small_Stack_Limit : constant := 64 * 1024;
989 -- ??? These three values are experimental, and seems to work on most
990 -- platforms. They still need to be analyzed further. They also need
991 -- documentation, what are they???
994 Natural (Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size);
996 Overflow_Guard : Natural;
997 -- Size of the overflow guard, used by dynamic stack usage analysis
999 pragma Warnings (On);
1001 SEH_Table : aliased SSE.Storage_Array (1 .. 8);
1002 -- Structured Exception Registration table (2 words)
1004 procedure Install_SEH_Handler (Addr : System.Address);
1005 pragma Import (C, Install_SEH_Handler, "__gnat_install_SEH_handler");
1006 -- Install the SEH (Structured Exception Handling) handler
1008 Cause : Cause_Of_Termination := Normal;
1009 -- Indicates the reason why this task terminates. Normal corresponds to
1010 -- a task terminating due to completing the last statement of its body,
1011 -- or as a result of waiting on a terminate alternative. If the task
1012 -- terminates because it is being aborted then Cause will be set to
1013 -- Abnormal. If the task terminates because of an exception raised by
1014 -- the execution of its task body, then Cause is set to
1015 -- Unhandled_Exception.
1017 EO : Exception_Occurrence;
1018 -- If the task terminates because of an exception raised by the
1019 -- execution of its task body, then EO will contain the associated
1020 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
1022 TH : Termination_Handler := null;
1023 -- Pointer to the protected procedure to be executed upon task
1026 procedure Search_Fall_Back_Handler (ID : Task_Id);
1027 -- Procedure that searches recursively a fall-back handler through the
1028 -- master relationship. If the handler is found, its pointer is stored
1031 ------------------------------
1032 -- Search_Fall_Back_Handler --
1033 ------------------------------
1035 procedure Search_Fall_Back_Handler (ID : Task_Id) is
1037 -- If there is a fall back handler, store its pointer for later
1040 if ID.Common.Fall_Back_Handler /= null then
1041 TH := ID.Common.Fall_Back_Handler;
1043 -- Otherwise look for a fall back handler in the parent
1045 elsif ID.Common.Parent /= null then
1046 Search_Fall_Back_Handler (ID.Common.Parent);
1048 -- Otherwise, do nothing
1053 end Search_Fall_Back_Handler;
1056 pragma Assert (Self_ID.Deferral_Level = 1);
1058 -- Assume a size of the stack taken at this stage
1060 if Size < Small_Stack_Limit then
1061 Overflow_Guard := Small_Overflow_Guard;
1063 Overflow_Guard := Big_Overflow_Guard;
1066 if not Parameters.Sec_Stack_Dynamic then
1067 Self_ID.Common.Compiler_Data.Sec_Stack_Addr :=
1068 Secondary_Stack'Address;
1069 SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
1070 Size := Size - Natural (Secondary_Stack_Size);
1073 if Use_Alternate_Stack then
1074 Self_ID.Common.Task_Alternate_Stack := Task_Alternate_Stack'Address;
1077 Size := Size - Overflow_Guard;
1079 if System.Stack_Usage.Is_Enabled then
1082 (Self_ID.Common.Analyzer,
1083 Self_ID.Common.Task_Image
1084 (1 .. Self_ID.Common.Task_Image_Len),
1086 (Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size),
1088 SSE.To_Integer (Bottom_Of_Stack'Address));
1090 Fill_Stack (Self_ID.Common.Analyzer);
1093 -- Set the guard page at the bottom of the stack. The call to unprotect
1094 -- the page is done in Terminate_Task
1096 Stack_Guard (Self_ID, True);
1098 -- Initialize low-level TCB components, that cannot be initialized by
1099 -- the creator. Enter_Task sets Self_ID.Known_Tasks_Index and also
1100 -- Self_ID.LL.Thread
1102 Enter_Task (Self_ID);
1104 -- We setup the SEH (Structured Exception Handling) handler if supported
1107 Install_SEH_Handler (SEH_Table'Address);
1109 -- Initialize exception occurrence
1111 Save_Occurrence (EO, Ada.Exceptions.Null_Occurrence);
1113 -- We lock RTS_Lock to wait for activator to finish activating the rest
1114 -- of the chain, so that everyone in the chain comes out in priority
1117 -- This also protects the value of
1118 -- Self_ID.Common.Activator.Common.Wait_Count.
1123 if not System.Restrictions.Abort_Allowed then
1125 -- If Abort is not allowed, reset the deferral level since it will
1126 -- not get changed by the generated code. Keeping a default value
1127 -- of one would prevent some operations (e.g. select or delay) to
1128 -- proceed successfully.
1130 Self_ID.Deferral_Level := 0;
1134 -- We are separating the following portion of the code in order to
1135 -- place the exception handlers in a different block. In this way,
1136 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
1137 -- set Self in Enter_Task
1139 -- Call the task body procedure
1141 -- The task body is called with abort still deferred. That
1142 -- eliminates a dangerous window, for which we had to patch-up in
1145 -- During the expansion of the task body, we insert an RTS-call
1146 -- to Abort_Undefer, at the first point where abort should be
1149 Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
1150 Initialization.Defer_Abort_Nestable (Self_ID);
1153 -- We can't call Terminate_Task in the exception handlers below,
1154 -- since there may be (e.g. in the case of GCC exception handling)
1155 -- clean ups associated with the exception handler that need to
1156 -- access task specific data.
1158 -- Defer abort so that this task can't be aborted while exiting
1160 when Standard'Abort_Signal =>
1161 Initialization.Defer_Abort_Nestable (Self_ID);
1163 -- Update the cause that motivated the task termination so that
1164 -- the appropriate information is passed to the task termination
1165 -- procedure. Task termination as a result of waiting on a
1166 -- terminate alternative is a normal termination, although it is
1167 -- implemented using the abort mechanisms.
1169 if Self_ID.Terminate_Alternative then
1175 -- ??? Using an E : others here causes CD2C11A to fail on Tru64
1177 Initialization.Defer_Abort_Nestable (Self_ID);
1179 -- Perform the task specific exception tracing duty. We handle
1180 -- these outputs here and not in the common notification routine
1181 -- because we need access to tasking related data and we don't
1182 -- want to drag dependencies against tasking related units in the
1183 -- the common notification units. Additionally, no trace is ever
1184 -- triggered from the common routine for the Unhandled_Raise case
1185 -- in tasks, since an exception never appears unhandled in this
1186 -- context because of this handler.
1188 if Exception_Trace = Unhandled_Raise then
1189 Trace_Unhandled_Exception_In_Task (Self_ID);
1192 -- Update the cause that motivated the task termination so that
1193 -- the appropriate information is passed to the task termination
1194 -- procedure, as well as the associated Exception_Occurrence.
1196 Cause := Unhandled_Exception;
1197 Save_Occurrence (EO, SSL.Get_Current_Excep.all.all);
1200 -- Look for a task termination handler. This code is for all tasks but
1201 -- the environment task. The task termination code for the environment
1202 -- task is executed by SSL.Task_Termination_Handler.
1208 Write_Lock (Self_ID);
1210 if Self_ID.Common.Specific_Handler /= null then
1211 TH := Self_ID.Common.Specific_Handler;
1213 -- Look for a fall-back handler following the master relationship
1216 Search_Fall_Back_Handler (Self_ID);
1225 -- Execute the task termination handler if we found it
1228 TH.all (Cause, Self_ID, EO);
1231 if System.Stack_Usage.Is_Enabled then
1232 Compute_Result (Self_ID.Common.Analyzer);
1233 Report_Result (Self_ID.Common.Analyzer);
1236 Terminate_Task (Self_ID);
1239 --------------------
1240 -- Terminate_Task --
1241 --------------------
1243 -- Before we allow the thread to exit, we must clean up. This is a
1244 -- delicate job. We must wake up the task's master, who may immediately try
1245 -- to deallocate the ATCB out from under the current task WHILE IT IS STILL
1248 -- To avoid this, the parent task must be blocked up to the latest
1249 -- statement executed. The trouble is that we have another step that we
1250 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
1251 -- We have to postpone that until the end because compiler-generated code
1252 -- is likely to try to access that data at just about any point.
1254 -- We can't call Destroy_TSD while we are holding any other locks, because
1255 -- it locks Global_Task_Lock, and our deadlock prevention rules require
1256 -- that to be the outermost lock. Our first "solution" was to just lock
1257 -- Global_Task_Lock in addition to the other locks, and force the parent to
1258 -- also lock this lock between its wakeup and its freeing of the ATCB. See
1259 -- Complete_Task for the parent-side of the code that has the matching
1260 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1261 -- since the operation Task_Unlock continued to access the ATCB after
1262 -- unlocking, after which the parent was observed to race ahead, deallocate
1263 -- the ATCB, and then reallocate it to another task. The call to
1264 -- Undefer_Abort in Task_Unlock by the "terminated" task was overwriting
1265 -- the data of the new task that reused the ATCB! To solve this problem, we
1266 -- introduced the new operation Final_Task_Unlock.
1268 procedure Terminate_Task (Self_ID : Task_Id) is
1269 Environment_Task : constant Task_Id := STPO.Environment_Task;
1270 Master_of_Task : Integer;
1273 Debug.Task_Termination_Hook;
1275 if Runtime_Traces then
1276 Send_Trace_Info (T_Terminate);
1279 -- Since GCC cannot allocate stack chunks efficiently without reordering
1280 -- some of the allocations, we have to handle this unexpected situation
1281 -- here. We should normally never have to call Vulnerable_Complete_Task
1284 if Self_ID.Common.Activator /= null then
1285 Vulnerable_Complete_Task (Self_ID);
1288 Initialization.Task_Lock (Self_ID);
1294 Master_of_Task := Self_ID.Master_of_Task;
1296 -- Check if the current task is an independent task If so, decrement
1297 -- the Independent_Task_Count value.
1299 if Master_of_Task = Independent_Task_Level then
1301 Utilities.Independent_Task_Count :=
1302 Utilities.Independent_Task_Count - 1;
1304 Write_Lock (Environment_Task);
1305 Utilities.Independent_Task_Count :=
1306 Utilities.Independent_Task_Count - 1;
1307 Unlock (Environment_Task);
1311 -- Unprotect the guard page if needed
1313 Stack_Guard (Self_ID, False);
1315 Utilities.Make_Passive (Self_ID, Task_Completed => True);
1321 pragma Assert (Check_Exit (Self_ID));
1323 SSL.Destroy_TSD (Self_ID.Common.Compiler_Data);
1324 Initialization.Final_Task_Unlock (Self_ID);
1326 -- WARNING: past this point, this thread must assume that the ATCB has
1327 -- been deallocated. It should not be accessed again.
1329 if Master_of_Task > 0 then
1338 function Terminated (T : Task_Id) return Boolean is
1339 Self_ID : constant Task_Id := STPO.Self;
1343 Initialization.Defer_Abort_Nestable (Self_ID);
1350 Result := T.Common.State = Terminated;
1357 Initialization.Undefer_Abort_Nestable (Self_ID);
1361 ----------------------------------------
1362 -- Trace_Unhandled_Exception_In_Task --
1363 ----------------------------------------
1365 procedure Trace_Unhandled_Exception_In_Task (Self_Id : Task_Id) is
1366 procedure To_Stderr (S : String);
1367 pragma Import (Ada, To_Stderr, "__gnat_to_stderr");
1369 use System.Soft_Links;
1370 use System.Standard_Library;
1372 function To_Address is new
1373 Ada.Unchecked_Conversion
1374 (Task_Id, System.Task_Primitives.Task_Address);
1376 function Tailored_Exception_Information
1377 (E : Exception_Occurrence) return String;
1379 (Ada, Tailored_Exception_Information,
1380 "__gnat_tailored_exception_information");
1382 Excep : constant Exception_Occurrence_Access :=
1383 SSL.Get_Current_Excep.all;
1386 -- This procedure is called by the task outermost handler in
1387 -- Task_Wrapper below, so only once the task stack has been fully
1388 -- unwound. The common notification routine has been called at the
1389 -- raise point already.
1391 To_Stderr ("task ");
1393 if Self_Id.Common.Task_Image_Len /= 0 then
1395 (Self_Id.Common.Task_Image (1 .. Self_Id.Common.Task_Image_Len));
1399 To_Stderr (System.Address_Image (To_Address (Self_Id)));
1400 To_Stderr (" terminated by unhandled exception");
1401 To_Stderr ((1 => ASCII.LF));
1402 To_Stderr (Tailored_Exception_Information (Excep.all));
1403 end Trace_Unhandled_Exception_In_Task;
1405 ------------------------------------
1406 -- Vulnerable_Complete_Activation --
1407 ------------------------------------
1409 -- As in several other places, the locks of the activator and activated
1410 -- task are both locked here. This follows our deadlock prevention lock
1411 -- ordering policy, since the activated task must be created after the
1414 procedure Vulnerable_Complete_Activation (Self_ID : Task_Id) is
1415 Activator : constant Task_Id := Self_ID.Common.Activator;
1418 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Activation", 'C'));
1420 Write_Lock (Activator);
1421 Write_Lock (Self_ID);
1423 pragma Assert (Self_ID.Common.Activator /= null);
1425 -- Remove dangling reference to Activator, since a task may
1426 -- outlive its activator.
1428 Self_ID.Common.Activator := null;
1430 -- Wake up the activator, if it is waiting for a chain of tasks to
1431 -- activate, and we are the last in the chain to complete activation.
1433 if Activator.Common.State = Activator_Sleep then
1434 Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
1436 if Activator.Common.Wait_Count = 0 then
1437 Wakeup (Activator, Activator_Sleep);
1441 -- The activator raises a Tasking_Error if any task it is activating
1442 -- is completed before the activation is done. However, if the reason
1443 -- for the task completion is an abort, we do not raise an exception.
1446 if not Self_ID.Callable and then Self_ID.Pending_ATC_Level /= 0 then
1447 Activator.Common.Activation_Failed := True;
1453 -- After the activation, active priority should be the same as base
1454 -- priority. We must unlock the Activator first, though, since it
1455 -- should not wait if we have lower priority.
1457 if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
1458 Write_Lock (Self_ID);
1459 Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
1462 end Vulnerable_Complete_Activation;
1464 --------------------------------
1465 -- Vulnerable_Complete_Master --
1466 --------------------------------
1468 procedure Vulnerable_Complete_Master (Self_ID : Task_Id) is
1471 CM : constant Master_Level := Self_ID.Master_Within;
1472 T : aliased Task_Id;
1474 To_Be_Freed : Task_Id;
1475 -- This is a list of ATCBs to be freed, after we have released all RTS
1476 -- locks. This is necessary because of the locking order rules, since
1477 -- the storage manager uses Global_Task_Lock.
1479 pragma Warnings (Off);
1480 function Check_Unactivated_Tasks return Boolean;
1481 pragma Warnings (On);
1482 -- Temporary error-checking code below. This is part of the checks
1483 -- added in the new run time. Call it only inside a pragma Assert.
1485 -----------------------------
1486 -- Check_Unactivated_Tasks --
1487 -----------------------------
1489 function Check_Unactivated_Tasks return Boolean is
1491 if not Single_Lock then
1495 Write_Lock (Self_ID);
1497 C := All_Tasks_List;
1498 while C /= null loop
1499 if C.Common.Activator = Self_ID and then C.Master_of_Task = CM then
1503 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1506 if C.Common.State = Unactivated then
1513 C := C.Common.All_Tasks_Link;
1518 if not Single_Lock then
1523 end Check_Unactivated_Tasks;
1525 -- Start of processing for Vulnerable_Complete_Master
1529 (Debug.Trace (Self_ID, "V_Complete_Master", 'C'));
1531 pragma Assert (Self_ID.Common.Wait_Count = 0);
1533 (Self_ID.Deferral_Level > 0
1534 or else not System.Restrictions.Abort_Allowed);
1536 -- Count how many active dependent tasks this master currently has, and
1537 -- record this in Wait_Count.
1539 -- This count should start at zero, since it is initialized to zero for
1540 -- new tasks, and the task should not exit the sleep-loops that use this
1541 -- count until the count reaches zero.
1543 -- While we're counting, if we run across any unactivated tasks that
1544 -- belong to this master, we summarily terminate them as required by
1548 Write_Lock (Self_ID);
1550 C := All_Tasks_List;
1551 while C /= null loop
1553 -- Terminate unactivated (never-to-be activated) tasks
1555 if C.Common.Activator = Self_ID and then C.Master_of_Task = CM then
1557 pragma Assert (C.Common.State = Unactivated);
1558 -- Usually, C.Common.Activator = Self_ID implies C.Master_of_Task
1559 -- = CM. The only case where C is pending activation by this
1560 -- task, but the master of C is not CM is in Ada 2005, when C is
1561 -- part of a return object of a build-in-place function.
1564 C.Common.Activator := null;
1565 C.Common.State := Terminated;
1566 C.Callable := False;
1567 Utilities.Cancel_Queued_Entry_Calls (C);
1571 -- Count it if dependent on this master
1573 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1576 if C.Awake_Count /= 0 then
1577 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1583 C := C.Common.All_Tasks_Link;
1586 Self_ID.Common.State := Master_Completion_Sleep;
1589 if not Single_Lock then
1593 -- Wait until dependent tasks are all terminated or ready to terminate.
1594 -- While waiting, the task may be awakened if the task's priority needs
1595 -- changing, or this master is aborted. In the latter case, we abort the
1596 -- dependents, and resume waiting until Wait_Count goes to zero.
1598 Write_Lock (Self_ID);
1601 exit when Self_ID.Common.Wait_Count = 0;
1603 -- Here is a difference as compared to Complete_Master
1605 if Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
1606 and then not Self_ID.Dependents_Aborted
1609 Abort_Dependents (Self_ID);
1613 Abort_Dependents (Self_ID);
1615 Write_Lock (Self_ID);
1618 Sleep (Self_ID, Master_Completion_Sleep);
1622 Self_ID.Common.State := Runnable;
1625 -- Dependents are all terminated or on terminate alternatives. Now,
1626 -- force those on terminate alternatives to terminate, by aborting them.
1628 pragma Assert (Check_Unactivated_Tasks);
1630 if Self_ID.Alive_Count > 1 then
1632 -- Consider finding a way to skip the following extra steps if there
1633 -- are no dependents with terminate alternatives. This could be done
1634 -- by adding another count to the ATCB, similar to Awake_Count, but
1635 -- keeping track of tasks that are on terminate alternatives.
1637 pragma Assert (Self_ID.Common.Wait_Count = 0);
1639 -- Force any remaining dependents to terminate by aborting them
1641 if not Single_Lock then
1645 Abort_Dependents (Self_ID);
1647 -- Above, when we "abort" the dependents we are simply using this
1648 -- operation for convenience. We are not required to support the full
1649 -- abort-statement semantics; in particular, we are not required to
1650 -- immediately cancel any queued or in-service entry calls. That is
1651 -- good, because if we tried to cancel a call we would need to lock
1652 -- the caller, in order to wake the caller up. Our anti-deadlock
1653 -- rules prevent us from doing that without releasing the locks on C
1654 -- and Self_ID. Releasing and retaking those locks would be wasteful
1655 -- at best, and should not be considered further without more
1656 -- detailed analysis of potential concurrent accesses to the ATCBs
1657 -- of C and Self_ID.
1659 -- Count how many "alive" dependent tasks this master currently has,
1660 -- and record this in Wait_Count. This count should start at zero,
1661 -- since it is initialized to zero for new tasks, and the task should
1662 -- not exit the sleep-loops that use this count until the count
1665 pragma Assert (Self_ID.Common.Wait_Count = 0);
1667 Write_Lock (Self_ID);
1669 C := All_Tasks_List;
1670 while C /= null loop
1671 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1674 pragma Assert (C.Awake_Count = 0);
1676 if C.Alive_Count > 0 then
1677 pragma Assert (C.Terminate_Alternative);
1678 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1684 C := C.Common.All_Tasks_Link;
1687 Self_ID.Common.State := Master_Phase_2_Sleep;
1690 if not Single_Lock then
1694 -- Wait for all counted tasks to finish terminating themselves
1696 Write_Lock (Self_ID);
1699 exit when Self_ID.Common.Wait_Count = 0;
1700 Sleep (Self_ID, Master_Phase_2_Sleep);
1703 Self_ID.Common.State := Runnable;
1707 -- We don't wake up for abort here. We are already terminating just as
1708 -- fast as we can, so there is no point.
1710 -- Remove terminated tasks from the list of Self_ID's dependents, but
1711 -- don't free their ATCBs yet, because of lock order restrictions, which
1712 -- don't allow us to call "free" or "malloc" while holding any other
1713 -- locks. Instead, we put those ATCBs to be freed onto a temporary list,
1714 -- called To_Be_Freed.
1716 if not Single_Lock then
1720 C := All_Tasks_List;
1722 while C /= null loop
1723 if C.Common.Parent = Self_ID and then C.Master_of_Task >= CM then
1725 P.Common.All_Tasks_Link := C.Common.All_Tasks_Link;
1727 All_Tasks_List := C.Common.All_Tasks_Link;
1730 T := C.Common.All_Tasks_Link;
1731 C.Common.All_Tasks_Link := To_Be_Freed;
1737 C := C.Common.All_Tasks_Link;
1743 -- Free all the ATCBs on the list To_Be_Freed
1745 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1746 -- any interrupt entries are detached from them they should no longer
1749 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1750 -- avoid a race between a terminating task and its parent. The parent
1751 -- might try to deallocate the ACTB out from underneath the exiting
1752 -- task. Note that Free will also lock Global_Task_Lock, but that is
1753 -- OK, since this is the *one* lock for which we have a mechanism to
1754 -- support nested locking. See Task_Wrapper and its finalizer for more
1758 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1759 -- references to terminated library-level tasks, which could otherwise
1760 -- occur during finalization of library-level objects. A better solution
1761 -- might be to hook task objects into the finalization chain and
1762 -- deallocate the ATCB when the task object is deallocated. However,
1763 -- this change is not likely to gain anything significant, since all
1764 -- this storage should be recovered en-masse when the process exits.
1766 while To_Be_Freed /= null loop
1768 To_Be_Freed := T.Common.All_Tasks_Link;
1770 -- ??? On SGI there is currently no Interrupt_Manager, that's
1771 -- why we need to check if the Interrupt_Manager_ID is null
1773 if T.Interrupt_Entry and Interrupt_Manager_ID /= null then
1775 Detach_Interrupt_Entries_Index : constant Task_Entry_Index := 1;
1776 -- Corresponds to the entry index of System.Interrupts.
1777 -- Interrupt_Manager.Detach_Interrupt_Entries.
1778 -- Be sure to update this value when changing
1779 -- Interrupt_Manager specs.
1781 type Param_Type is access all Task_Id;
1783 Param : aliased Param_Type := T'Access;
1786 System.Tasking.Rendezvous.Call_Simple
1787 (Interrupt_Manager_ID, Detach_Interrupt_Entries_Index,
1792 if (T.Common.Parent /= null
1793 and then T.Common.Parent.Common.Parent /= null)
1794 or else T.Master_of_Task > Library_Task_Level
1796 Initialization.Task_Lock (Self_ID);
1798 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1799 -- has not been called yet (case of an unactivated task).
1801 if T.Common.Compiler_Data.Sec_Stack_Addr /= Null_Address then
1802 SSL.Destroy_TSD (T.Common.Compiler_Data);
1805 Vulnerable_Free_Task (T);
1806 Initialization.Task_Unlock (Self_ID);
1810 -- It might seem nice to let the terminated task deallocate its own
1811 -- ATCB. That would not cover the case of unactivated tasks. It also
1812 -- would force us to keep the underlying thread around past termination,
1813 -- since references to the ATCB are possible past termination.
1815 -- Currently, we get rid of the thread as soon as the task terminates,
1816 -- and let the parent recover the ATCB later.
1818 -- Some day, if we want to recover the ATCB earlier, at task
1819 -- termination, we could consider using "fat task IDs", that include the
1820 -- serial number with the ATCB pointer, to catch references to tasks
1821 -- that no longer have ATCBs. It is not clear how much this would gain,
1822 -- since the user-level task object would still be occupying storage.
1824 -- Make next master level up active. We don't need to lock the ATCB,
1825 -- since the value is only updated by each task for itself.
1827 Self_ID.Master_Within := CM - 1;
1828 end Vulnerable_Complete_Master;
1830 ------------------------------
1831 -- Vulnerable_Complete_Task --
1832 ------------------------------
1834 -- Complete the calling task
1836 -- This procedure must be called with abort deferred. It should only be
1837 -- called by Complete_Task and Finalize_Global_Tasks (for the environment
1840 -- The effect is similar to that of Complete_Master. Differences include
1841 -- the closing of entries here, and computation of the number of active
1842 -- dependent tasks in Complete_Master.
1844 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1845 -- because that does its own locking, and because we do not need the lock
1846 -- to test Self_ID.Common.Activator. That value should only be read and
1847 -- modified by Self.
1849 procedure Vulnerable_Complete_Task (Self_ID : Task_Id) is
1852 (Self_ID.Deferral_Level > 0
1853 or else not System.Restrictions.Abort_Allowed);
1854 pragma Assert (Self_ID = Self);
1855 pragma Assert (Self_ID.Master_Within = Self_ID.Master_of_Task + 1
1857 Self_ID.Master_Within = Self_ID.Master_of_Task + 2);
1858 pragma Assert (Self_ID.Common.Wait_Count = 0);
1859 pragma Assert (Self_ID.Open_Accepts = null);
1860 pragma Assert (Self_ID.ATC_Nesting_Level = 1);
1862 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Task", 'C'));
1868 Write_Lock (Self_ID);
1869 Self_ID.Callable := False;
1871 -- In theory, Self should have no pending entry calls left on its
1872 -- call-stack. Each async. select statement should clean its own call,
1873 -- and blocking entry calls should defer abort until the calls are
1874 -- cancelled, then clean up.
1876 Utilities.Cancel_Queued_Entry_Calls (Self_ID);
1879 if Self_ID.Common.Activator /= null then
1880 Vulnerable_Complete_Activation (Self_ID);
1887 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2 we may have
1888 -- dependent tasks for which we need to wait. Otherwise we just exit.
1890 if Self_ID.Master_Within = Self_ID.Master_of_Task + 2 then
1891 Vulnerable_Complete_Master (Self_ID);
1893 end Vulnerable_Complete_Task;
1895 --------------------------
1896 -- Vulnerable_Free_Task --
1897 --------------------------
1899 -- Recover all runtime system storage associated with the task T. This
1900 -- should only be called after T has terminated and will no longer be
1903 -- For tasks created by an allocator that fails, due to an exception, it
1904 -- is called from Expunge_Unactivated_Tasks.
1906 -- For tasks created by elaboration of task object declarations it is
1907 -- called from the finalization code of the Task_Wrapper procedure. It is
1908 -- also called from Ada.Unchecked_Deallocation, for objects that are or
1911 procedure Vulnerable_Free_Task (T : Task_Id) is
1913 pragma Debug (Debug.Trace (Self, "Vulnerable_Free_Task", 'C', T));
1920 Initialization.Finalize_Attributes_Link.all (T);
1927 Free_Entry_Names (T);
1928 System.Task_Primitives.Operations.Finalize_TCB (T);
1929 end Vulnerable_Free_Task;
1931 -- Package elaboration code
1934 -- Establish the Adafinal oftlink
1936 -- This is not done inside the central RTS initialization routine
1937 -- to avoid with-ing this package from System.Tasking.Initialization.
1939 SSL.Adafinal := Finalize_Global_Tasks'Access;
1941 -- Establish soft links for subprograms that manipulate master_id's.
1942 -- This cannot be done when the RTS is initialized, because of various
1943 -- elaboration constraints.
1945 SSL.Current_Master := Stages.Current_Master'Access;
1946 SSL.Enter_Master := Stages.Enter_Master'Access;
1947 SSL.Complete_Master := Stages.Complete_Master'Access;
1948 end System.Tasking.Stages;