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) 1992-2011, 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.Interrupt_Management;
40 with System.Tasking.Debug;
41 with System.Address_Image;
42 with System.Task_Primitives;
43 with System.Task_Primitives.Operations;
44 with System.Tasking.Utilities;
45 with System.Tasking.Queuing;
46 with System.Tasking.Rendezvous;
47 with System.OS_Primitives;
48 with System.Secondary_Stack;
49 with System.Storage_Elements;
50 with System.Restrictions;
51 with System.Standard_Library;
52 with System.Traces.Tasking;
53 with System.Stack_Usage;
55 with System.Soft_Links;
56 -- These are procedure pointers to non-tasking routines that use task
57 -- specific data. In the absence of tasking, these routines refer to global
58 -- data. In the presence of tasking, they must be replaced with pointers to
59 -- task-specific versions. Also used for Create_TSD, Destroy_TSD, Get_Current
60 -- _Excep, Finalize_Library_Objects, Task_Termination, Handler.
62 with System.Tasking.Initialization;
63 pragma Elaborate_All (System.Tasking.Initialization);
64 -- This insures that tasking is initialized if any tasks are created
66 package body System.Tasking.Stages is
68 package STPO renames System.Task_Primitives.Operations;
69 package SSL renames System.Soft_Links;
70 package SSE renames System.Storage_Elements;
71 package SST renames System.Secondary_Stack;
77 use Task_Primitives.Operations;
81 use System.Traces.Tasking;
83 -----------------------
84 -- Local Subprograms --
85 -----------------------
88 Ada.Unchecked_Deallocation (Ada_Task_Control_Block, Task_Id);
90 procedure Free_Entry_Names (T : Task_Id);
91 -- Deallocate all string names associated with task entries
93 procedure Trace_Unhandled_Exception_In_Task (Self_Id : Task_Id);
94 -- This procedure outputs the task specific message for exception
97 procedure Task_Wrapper (Self_ID : Task_Id);
98 pragma Convention (C, Task_Wrapper);
99 -- This is the procedure that is called by the GNULL from the new context
100 -- when a task is created. It waits for activation and then calls the task
101 -- body procedure. When the task body procedure completes, it terminates
104 -- The Task_Wrapper's address will be provided to the underlying threads
105 -- library as the task entry point. Convention C is what makes most sense
106 -- for that purpose (Export C would make the function globally visible,
107 -- and affect the link name on which GDB depends). This will in addition
108 -- trigger an automatic stack alignment suitable for GCC's assumptions if
111 -- "Vulnerable_..." in the procedure names below means they must be called
112 -- with abort deferred.
114 procedure Vulnerable_Complete_Task (Self_ID : Task_Id);
115 -- Complete the calling task. This procedure must be called with
116 -- abort deferred. It should only be called by Complete_Task and
117 -- Finalize_Global_Tasks (for the environment task).
119 procedure Vulnerable_Complete_Master (Self_ID : Task_Id);
120 -- Complete the current master of the calling task. This procedure
121 -- must be called with abort deferred. It should only be called by
122 -- Vulnerable_Complete_Task and Complete_Master.
124 procedure Vulnerable_Complete_Activation (Self_ID : Task_Id);
125 -- Signal to Self_ID's activator that Self_ID has completed activation.
126 -- This procedure must be called with abort deferred.
128 procedure Abort_Dependents (Self_ID : Task_Id);
129 -- Abort all the direct dependents of Self at its current master nesting
130 -- level, plus all of their dependents, transitively. RTS_Lock should be
131 -- locked by the caller.
133 procedure Vulnerable_Free_Task (T : Task_Id);
134 -- Recover all runtime system storage associated with the task T. This
135 -- should only be called after T has terminated and will no longer be
138 -- For tasks created by an allocator that fails, due to an exception, it is
139 -- called from Expunge_Unactivated_Tasks.
141 -- Different code is used at master completion, in Terminate_Dependents,
142 -- due to a need for tighter synchronization with the master.
144 ----------------------
145 -- Abort_Dependents --
146 ----------------------
148 procedure Abort_Dependents (Self_ID : Task_Id) is
155 P := C.Common.Parent;
159 -- ??? C is supposed to take care of its own dependents, so
160 -- there should be no need to worry about them. Need to double
163 if C.Master_of_Task = Self_ID.Master_Within then
164 Utilities.Abort_One_Task (Self_ID, C);
165 C.Dependents_Aborted := True;
171 P := P.Common.Parent;
174 C := C.Common.All_Tasks_Link;
177 Self_ID.Dependents_Aborted := True;
178 end Abort_Dependents;
184 procedure Abort_Tasks (Tasks : Task_List) is
186 Utilities.Abort_Tasks (Tasks);
193 -- Note that locks of activator and activated task are both locked here.
194 -- This is necessary because C.Common.State and Self.Common.Wait_Count have
195 -- to be synchronized. This is safe from deadlock because the activator is
196 -- always created before the activated task. That satisfies our
197 -- in-order-of-creation ATCB locking policy.
199 -- At one point, we may also lock the parent, if the parent is different
200 -- from the activator. That is also consistent with the lock ordering
201 -- policy, since the activator cannot be created before the parent.
203 -- Since we are holding both the activator's lock, and Task_Wrapper locks
204 -- that before it does anything more than initialize the low-level ATCB
205 -- components, it should be safe to wait to update the counts until we see
206 -- that the thread creation is successful.
208 -- If the thread creation fails, we do need to close the entries of the
209 -- task. The first phase, of dequeuing calls, only requires locking the
210 -- acceptor's ATCB, but the waking up of the callers requires locking the
211 -- caller's ATCB. We cannot safely do this while we are holding other
212 -- locks. Therefore, the queue-clearing operation is done in a separate
213 -- pass over the activation chain.
215 procedure Activate_Tasks (Chain_Access : Activation_Chain_Access) is
216 Self_ID : constant Task_Id := STPO.Self;
219 Next_C, Last_C : Task_Id;
220 Activate_Prio : System.Any_Priority;
222 All_Elaborated : Boolean := True;
225 -- If pragma Detect_Blocking is active, then we must check whether this
226 -- potentially blocking operation is called from a protected action.
228 if System.Tasking.Detect_Blocking
229 and then Self_ID.Common.Protected_Action_Nesting > 0
231 raise Program_Error with "potentially blocking operation";
235 (Debug.Trace (Self_ID, "Activate_Tasks", 'C'));
237 Initialization.Defer_Abort_Nestable (Self_ID);
239 pragma Assert (Self_ID.Common.Wait_Count = 0);
241 -- Lock RTS_Lock, to prevent activated tasks from racing ahead before
242 -- we finish activating the chain.
246 -- Check that all task bodies have been elaborated
248 C := Chain_Access.T_ID;
251 if C.Common.Elaborated /= null
252 and then not C.Common.Elaborated.all
254 All_Elaborated := False;
257 -- Reverse the activation chain so that tasks are activated in the
258 -- same order they're declared.
260 Next_C := C.Common.Activation_Link;
261 C.Common.Activation_Link := Last_C;
266 Chain_Access.T_ID := Last_C;
268 if not All_Elaborated then
270 Initialization.Undefer_Abort_Nestable (Self_ID);
271 raise Program_Error with "Some tasks have not been elaborated";
274 -- Activate all the tasks in the chain. Creation of the thread of
275 -- control was deferred until activation. So create it now.
277 C := Chain_Access.T_ID;
279 if C.Common.State /= Terminated then
280 pragma Assert (C.Common.State = Unactivated);
282 P := C.Common.Parent;
287 (if C.Common.Base_Priority < Get_Priority (Self_ID)
288 then Get_Priority (Self_ID)
289 else 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 := Activating;
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;
316 for J in System.Tasking.Debug.Known_Tasks'Range loop
317 if System.Tasking.Debug.Known_Tasks (J) = null then
318 System.Tasking.Debug.Known_Tasks (J) := C;
319 C.Known_Tasks_Index := J;
324 if Global_Task_Debug_Event_Set then
325 Debug.Signal_Debug_Event
326 (Debug.Debug_Event_Activating, C);
329 C.Common.State := Runnable;
335 -- No need to set Awake_Count, State, etc. here since the loop
336 -- below will do that for any Unactivated tasks.
340 Self_ID.Common.Activation_Failed := True;
344 C := C.Common.Activation_Link;
347 if not Single_Lock then
351 -- Close the entries of any tasks that failed thread creation, and count
352 -- those that have not finished activation.
354 Write_Lock (Self_ID);
355 Self_ID.Common.State := Activator_Sleep;
357 C := Chain_Access.T_ID;
361 if C.Common.State = Unactivated then
362 C.Common.Activator := null;
363 C.Common.State := Terminated;
365 Utilities.Cancel_Queued_Entry_Calls (C);
367 elsif C.Common.Activator /= null then
368 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
372 P := C.Common.Activation_Link;
373 C.Common.Activation_Link := null;
377 -- Wait for the activated tasks to complete activation. It is
378 -- unsafe to abort any of these tasks until the count goes to zero.
381 exit when Self_ID.Common.Wait_Count = 0;
382 Sleep (Self_ID, Activator_Sleep);
385 Self_ID.Common.State := Runnable;
392 -- Remove the tasks from the chain
394 Chain_Access.T_ID := null;
395 Initialization.Undefer_Abort_Nestable (Self_ID);
397 if Self_ID.Common.Activation_Failed then
398 Self_ID.Common.Activation_Failed := False;
399 raise Tasking_Error with "Failure during activation";
403 -------------------------
404 -- Complete_Activation --
405 -------------------------
407 procedure Complete_Activation is
408 Self_ID : constant Task_Id := STPO.Self;
411 Initialization.Defer_Abort_Nestable (Self_ID);
417 Vulnerable_Complete_Activation (Self_ID);
423 Initialization.Undefer_Abort_Nestable (Self_ID);
425 -- ??? Why do we need to allow for nested deferral here?
427 if Runtime_Traces then
428 Send_Trace_Info (T_Activate);
430 end Complete_Activation;
432 ---------------------
433 -- Complete_Master --
434 ---------------------
436 procedure Complete_Master is
437 Self_ID : constant Task_Id := STPO.Self;
440 (Self_ID.Deferral_Level > 0
441 or else not System.Restrictions.Abort_Allowed);
442 Vulnerable_Complete_Master (Self_ID);
449 -- See comments on Vulnerable_Complete_Task for details
451 procedure Complete_Task is
452 Self_ID : constant Task_Id := STPO.Self;
456 (Self_ID.Deferral_Level > 0
457 or else not System.Restrictions.Abort_Allowed);
459 Vulnerable_Complete_Task (Self_ID);
461 -- All of our dependents have terminated. Never undefer abort again!
469 -- Compiler interface only. Do not call from within the RTS. This must be
470 -- called to create a new task.
472 procedure Create_Task
474 Size : System.Parameters.Size_Type;
475 Task_Info : System.Task_Info.Task_Info_Type;
477 Relative_Deadline : Ada.Real_Time.Time_Span;
478 Num_Entries : Task_Entry_Index;
479 Master : Master_Level;
480 State : Task_Procedure_Access;
481 Discriminants : System.Address;
482 Elaborated : Access_Boolean;
483 Chain : in out Activation_Chain;
485 Created_Task : out Task_Id;
486 Build_Entry_Names : Boolean)
489 Self_ID : constant Task_Id := STPO.Self;
491 Base_Priority : System.Any_Priority;
493 Base_CPU : System.Multiprocessors.CPU_Range;
495 pragma Unreferenced (Relative_Deadline);
496 -- EDF scheduling is not supported by any of the target platforms so
497 -- this parameter is not passed any further.
500 -- If Master is greater than the current master, it means that Master
501 -- has already awaited its dependent tasks. This raises Program_Error,
502 -- by 4.8(10.3/2). See AI-280. Ignore this check for foreign threads.
504 if Self_ID.Master_of_Task /= Foreign_Task_Level
505 and then Master > Self_ID.Master_Within
507 raise Program_Error with
508 "create task after awaiting termination";
511 -- If pragma Detect_Blocking is active must be checked whether this
512 -- potentially blocking operation is called from a protected action.
514 if System.Tasking.Detect_Blocking
515 and then Self_ID.Common.Protected_Action_Nesting > 0
517 raise Program_Error with "potentially blocking operation";
520 pragma Debug (Debug.Trace (Self_ID, "Create_Task", 'C'));
523 (if Priority = Unspecified_Priority
524 then Self_ID.Common.Base_Priority
525 else System.Any_Priority (Priority));
527 if CPU /= Unspecified_CPU
528 and then (CPU < Integer (System.Multiprocessors.CPU_Range'First)
529 or else CPU > Integer (System.Multiprocessors.CPU_Range'Last)
530 or else CPU > Integer (System.Multiprocessors.Number_Of_CPUs))
532 raise Tasking_Error with "CPU not in range";
534 -- Normal CPU affinity
537 (if CPU = Unspecified_CPU
538 then Self_ID.Common.Base_CPU
539 else System.Multiprocessors.CPU_Range (CPU));
542 -- Find parent P of new Task, via master level number
547 while P.Master_of_Task >= Master loop
548 P := P.Common.Parent;
553 Initialization.Defer_Abort_Nestable (Self_ID);
556 T := New_ATCB (Num_Entries);
559 Initialization.Undefer_Abort_Nestable (Self_ID);
560 raise Storage_Error with "Cannot allocate task";
563 -- RTS_Lock is used by Abort_Dependents and Abort_Tasks. Up to this
564 -- point, it is possible that we may be part of a family of tasks that
568 Write_Lock (Self_ID);
570 -- Now, we must check that we have not been aborted. If so, we should
571 -- give up on creating this task, and simply return.
573 if not Self_ID.Callable then
574 pragma Assert (Self_ID.Pending_ATC_Level = 0);
575 pragma Assert (Self_ID.Pending_Action);
577 (Chain.T_ID = null or else Chain.T_ID.Common.State = Unactivated);
581 Initialization.Undefer_Abort_Nestable (Self_ID);
583 -- ??? Should never get here
585 pragma Assert (False);
586 raise Standard'Abort_Signal;
589 Initialize_ATCB (Self_ID, State, Discriminants, P, Elaborated,
590 Base_Priority, Base_CPU, Task_Info, Size, T, Success);
596 Initialization.Undefer_Abort_Nestable (Self_ID);
597 raise Storage_Error with "Failed to initialize task";
600 if Master = Foreign_Task_Level + 2 then
602 -- This should not happen, except when a foreign task creates non
603 -- library-level Ada tasks. In this case, we pretend the master is
604 -- a regular library level task, otherwise the run-time will get
605 -- confused when waiting for these tasks to terminate.
607 T.Master_of_Task := Library_Task_Level;
610 T.Master_of_Task := Master;
613 T.Master_Within := T.Master_of_Task + 1;
615 for L in T.Entry_Calls'Range loop
616 T.Entry_Calls (L).Self := T;
617 T.Entry_Calls (L).Level := L;
620 if Task_Image'Length = 0 then
621 T.Common.Task_Image_Len := 0;
624 T.Common.Task_Image (1) := Task_Image (Task_Image'First);
626 -- Remove unwanted blank space generated by 'Image
628 for J in Task_Image'First + 1 .. Task_Image'Last loop
629 if Task_Image (J) /= ' '
630 or else Task_Image (J - 1) /= '('
633 T.Common.Task_Image (Len) := Task_Image (J);
634 exit when Len = T.Common.Task_Image'Last;
638 T.Common.Task_Image_Len := Len;
644 -- Note: we should not call 'new' while holding locks since new
645 -- may use locks (e.g. RTS_Lock under Windows) itself and cause a
648 if Build_Entry_Names then
650 new Entry_Names_Array (1 .. Entry_Index (Num_Entries));
653 -- Create TSD as early as possible in the creation of a task, since it
654 -- may be used by the operation of Ada code within the task.
656 SSL.Create_TSD (T.Common.Compiler_Data);
657 T.Common.Activation_Link := Chain.T_ID;
659 Initialization.Initialize_Attributes_Link.all (T);
661 Initialization.Undefer_Abort_Nestable (Self_ID);
663 if Runtime_Traces then
664 Send_Trace_Info (T_Create, T);
672 function Current_Master return Master_Level is
674 return STPO.Self.Master_Within;
681 procedure Enter_Master is
682 Self_ID : constant Task_Id := STPO.Self;
684 Self_ID.Master_Within := Self_ID.Master_Within + 1;
687 -------------------------------
688 -- Expunge_Unactivated_Tasks --
689 -------------------------------
691 -- See procedure Close_Entries for the general case
693 procedure Expunge_Unactivated_Tasks (Chain : in out Activation_Chain) is
694 Self_ID : constant Task_Id := STPO.Self;
696 Call : Entry_Call_Link;
701 (Debug.Trace (Self_ID, "Expunge_Unactivated_Tasks", 'C'));
703 Initialization.Defer_Abort_Nestable (Self_ID);
706 -- Experimentation has shown that abort is sometimes (but not always)
707 -- already deferred when this is called.
709 -- That may indicate an error. Find out what is going on
713 pragma Assert (C.Common.State = Unactivated);
715 Temp := C.Common.Activation_Link;
717 if C.Common.State = Unactivated then
721 for J in 1 .. C.Entry_Num loop
722 Queuing.Dequeue_Head (C.Entry_Queues (J), Call);
723 pragma Assert (Call = null);
728 Initialization.Remove_From_All_Tasks_List (C);
731 Vulnerable_Free_Task (C);
737 Initialization.Undefer_Abort_Nestable (Self_ID);
738 end Expunge_Unactivated_Tasks;
740 ---------------------------
741 -- Finalize_Global_Tasks --
742 ---------------------------
745 -- We have a potential problem here if finalization of global objects does
746 -- anything with signals or the timer server, since by that time those
747 -- servers have terminated.
749 -- It is hard to see how that would occur
751 -- However, a better solution might be to do all this finalization
752 -- using the global finalization chain.
754 procedure Finalize_Global_Tasks is
755 Self_ID : constant Task_Id := STPO.Self;
758 pragma Unreferenced (Ignore);
761 (Int : System.Interrupt_Management.Interrupt_ID) return Character;
762 pragma Import (C, State, "__gnat_get_interrupt_state");
763 -- Get interrupt state for interrupt number Int. Defined in init.c
765 Default : constant Character := 's';
766 -- 's' Interrupt_State pragma set state to System (use "default"
770 if Self_ID.Deferral_Level = 0 then
772 -- In principle, we should be able to predict whether abort is
773 -- already deferred here (and it should not be deferred yet but in
774 -- practice it seems Finalize_Global_Tasks is being called sometimes,
775 -- from RTS code for exceptions, with abort already deferred.
777 Initialization.Defer_Abort_Nestable (Self_ID);
779 -- Never undefer again!!!
782 -- This code is only executed by the environment task
784 pragma Assert (Self_ID = Environment_Task);
786 -- Set Environment_Task'Callable to false to notify library-level tasks
787 -- that it is waiting for them.
789 Self_ID.Callable := False;
791 -- Exit level 2 master, for normal tasks in library-level packages
795 -- Force termination of "independent" library-level server tasks
799 Abort_Dependents (Self_ID);
801 if not Single_Lock then
805 -- We need to explicitly wait for the task to be terminated here
806 -- because on true concurrent system, we may end this procedure before
807 -- the tasks are really terminated.
809 Write_Lock (Self_ID);
811 -- If the Abort_Task signal is set to system, it means that we may not
812 -- have been able to abort all independent tasks (in particular
813 -- Server_Task may be blocked, waiting for a signal), in which case,
814 -- do not wait for Independent_Task_Count to go down to 0.
817 (System.Interrupt_Management.Abort_Task_Interrupt) /= Default
820 exit when Utilities.Independent_Task_Count = 0;
822 -- We used to yield here, but this did not take into account low
823 -- priority tasks that would cause dead lock in some cases (true
827 (Self_ID, 0.01, System.OS_Primitives.Relative,
828 Self_ID.Common.State, Ignore, Ignore);
832 -- ??? On multi-processor environments, it seems that the above loop
833 -- isn't sufficient, so we need to add an additional delay.
836 (Self_ID, 0.01, System.OS_Primitives.Relative,
837 Self_ID.Common.State, Ignore, Ignore);
845 -- Complete the environment task
847 Vulnerable_Complete_Task (Self_ID);
849 -- Handle normal task termination by the environment task, but only
850 -- for the normal task termination. In the case of Abnormal and
851 -- Unhandled_Exception they must have been handled before, and the
852 -- task termination soft link must have been changed so the task
853 -- termination routine is not executed twice.
855 SSL.Task_Termination_Handler.all (Ada.Exceptions.Null_Occurrence);
857 -- Finalize all library-level controlled objects
859 if not SSL."=" (SSL.Finalize_Library_Objects, null) then
860 SSL.Finalize_Library_Objects.all;
863 -- Reset the soft links to non-tasking
865 SSL.Abort_Defer := SSL.Abort_Defer_NT'Access;
866 SSL.Abort_Undefer := SSL.Abort_Undefer_NT'Access;
867 SSL.Lock_Task := SSL.Task_Lock_NT'Access;
868 SSL.Unlock_Task := SSL.Task_Unlock_NT'Access;
869 SSL.Get_Jmpbuf_Address := SSL.Get_Jmpbuf_Address_NT'Access;
870 SSL.Set_Jmpbuf_Address := SSL.Set_Jmpbuf_Address_NT'Access;
871 SSL.Get_Sec_Stack_Addr := SSL.Get_Sec_Stack_Addr_NT'Access;
872 SSL.Set_Sec_Stack_Addr := SSL.Set_Sec_Stack_Addr_NT'Access;
873 SSL.Check_Abort_Status := SSL.Check_Abort_Status_NT'Access;
874 SSL.Get_Stack_Info := SSL.Get_Stack_Info_NT'Access;
876 -- Don't bother trying to finalize Initialization.Global_Task_Lock
877 -- and System.Task_Primitives.RTS_Lock.
879 end Finalize_Global_Tasks;
881 ----------------------
882 -- Free_Entry_Names --
883 ----------------------
885 procedure Free_Entry_Names (T : Task_Id) is
886 Names : Entry_Names_Array_Access := T.Entry_Names;
888 procedure Free_Entry_Names_Array_Access is new
889 Ada.Unchecked_Deallocation
890 (Entry_Names_Array, Entry_Names_Array_Access);
897 Free_Entry_Names_Array (Names.all);
898 Free_Entry_Names_Array_Access (Names);
899 end Free_Entry_Names;
905 procedure Free_Task (T : Task_Id) is
906 Self_Id : constant Task_Id := Self;
909 if T.Common.State = Terminated then
911 -- It is not safe to call Abort_Defer or Write_Lock at this stage
913 Initialization.Task_Lock (Self_Id);
916 Initialization.Finalize_Attributes_Link.all (T);
917 Initialization.Remove_From_All_Tasks_List (T);
920 Initialization.Task_Unlock (Self_Id);
922 Free_Entry_Names (T);
923 System.Task_Primitives.Operations.Finalize_TCB (T);
925 -- If the task is not terminated, then we simply ignore the call. This
926 -- happens when a user program attempts an unchecked deallocation on
927 -- a non-terminated task.
934 ---------------------------
935 -- Move_Activation_Chain --
936 ---------------------------
938 procedure Move_Activation_Chain
939 (From, To : Activation_Chain_Access;
940 New_Master : Master_ID)
942 Self_ID : constant Task_Id := STPO.Self;
947 (Debug.Trace (Self_ID, "Move_Activation_Chain", 'C'));
949 -- Nothing to do if From is empty, and we can check that without
958 Initialization.Defer_Abort (Self_ID);
960 -- Loop through the From chain, changing their Master_of_Task
961 -- fields, and to find the end of the chain.
964 C.Master_of_Task := New_Master;
965 exit when C.Common.Activation_Link = null;
966 C := C.Common.Activation_Link;
969 -- Hook From in at the start of To
971 C.Common.Activation_Link := To.all.T_ID;
972 To.all.T_ID := From.all.T_ID;
976 From.all.T_ID := null;
978 Initialization.Undefer_Abort (Self_ID);
979 end Move_Activation_Chain;
981 -- Compiler interface only. Do not call from within the RTS
987 procedure Set_Entry_Name
989 Pos : Task_Entry_Index;
993 pragma Assert (T.Entry_Names /= null);
995 T.Entry_Names (Entry_Index (Pos)) := Val;
1002 -- The task wrapper is a procedure that is called first for each task body
1003 -- and which in turn calls the compiler-generated task body procedure.
1004 -- The wrapper's main job is to do initialization for the task. It also
1005 -- has some locally declared objects that serve as per-task local data.
1006 -- Task finalization is done by Complete_Task, which is called from an
1007 -- at-end handler that the compiler generates.
1009 procedure Task_Wrapper (Self_ID : Task_Id) is
1010 use type SSE.Storage_Offset;
1011 use System.Standard_Library;
1012 use System.Stack_Usage;
1014 Bottom_Of_Stack : aliased Integer;
1016 Task_Alternate_Stack :
1017 aliased SSE.Storage_Array (1 .. Alternate_Stack_Size);
1018 -- The alternate signal stack for this task, if any
1020 Use_Alternate_Stack : constant Boolean := Alternate_Stack_Size /= 0;
1021 -- Whether to use above alternate signal stack for stack overflows
1023 Secondary_Stack_Size :
1024 constant SSE.Storage_Offset :=
1025 Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size *
1026 SSE.Storage_Offset (Parameters.Sec_Stack_Percentage) / 100;
1028 Secondary_Stack : aliased SSE.Storage_Array (1 .. Secondary_Stack_Size);
1030 Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
1031 -- Address of secondary stack. In the fixed secondary stack case, this
1032 -- value is not modified, causing a warning, hence the bracketing with
1033 -- Warnings (Off/On). But why is so much *more* bracketed???
1035 SEH_Table : aliased SSE.Storage_Array (1 .. 8);
1036 -- Structured Exception Registration table (2 words)
1038 procedure Install_SEH_Handler (Addr : System.Address);
1039 pragma Import (C, Install_SEH_Handler, "__gnat_install_SEH_handler");
1040 -- Install the SEH (Structured Exception Handling) handler
1042 Cause : Cause_Of_Termination := Normal;
1043 -- Indicates the reason why this task terminates. Normal corresponds to
1044 -- a task terminating due to completing the last statement of its body,
1045 -- or as a result of waiting on a terminate alternative. If the task
1046 -- terminates because it is being aborted then Cause will be set to
1047 -- Abnormal. If the task terminates because of an exception raised by
1048 -- the execution of its task body, then Cause is set to
1049 -- Unhandled_Exception.
1051 EO : Exception_Occurrence;
1052 -- If the task terminates because of an exception raised by the
1053 -- execution of its task body, then EO will contain the associated
1054 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
1056 TH : Termination_Handler := null;
1057 -- Pointer to the protected procedure to be executed upon task
1060 procedure Search_Fall_Back_Handler (ID : Task_Id);
1061 -- Procedure that searches recursively a fall-back handler through the
1062 -- master relationship. If the handler is found, its pointer is stored
1065 ------------------------------
1066 -- Search_Fall_Back_Handler --
1067 ------------------------------
1069 procedure Search_Fall_Back_Handler (ID : Task_Id) is
1071 -- If there is a fall back handler, store its pointer for later
1074 if ID.Common.Fall_Back_Handler /= null then
1075 TH := ID.Common.Fall_Back_Handler;
1077 -- Otherwise look for a fall back handler in the parent
1079 elsif ID.Common.Parent /= null then
1080 Search_Fall_Back_Handler (ID.Common.Parent);
1082 -- Otherwise, do nothing
1087 end Search_Fall_Back_Handler;
1090 pragma Assert (Self_ID.Deferral_Level = 1);
1092 -- Assume a size of the stack taken at this stage
1094 if not Parameters.Sec_Stack_Dynamic then
1095 Self_ID.Common.Compiler_Data.Sec_Stack_Addr :=
1096 Secondary_Stack'Address;
1097 SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
1100 if Use_Alternate_Stack then
1101 Self_ID.Common.Task_Alternate_Stack := Task_Alternate_Stack'Address;
1104 -- Set the guard page at the bottom of the stack. The call to unprotect
1105 -- the page is done in Terminate_Task
1107 Stack_Guard (Self_ID, True);
1109 -- Initialize low-level TCB components, that cannot be initialized by
1110 -- the creator. Enter_Task sets Self_ID.LL.Thread
1112 Enter_Task (Self_ID);
1114 -- Initialize dynamic stack usage
1116 if System.Stack_Usage.Is_Enabled then
1118 Guard_Page_Size : constant := 12 * 1024;
1119 -- Part of the stack used as a guard page. This is an OS dependent
1120 -- value, so we need to use the maximum. This value is only used
1121 -- when the stack address is known, that is currently Windows.
1123 Small_Overflow_Guard : constant := 12 * 1024;
1124 -- Note: this used to be 4K, but was changed to 12K, since
1125 -- smaller values resulted in segmentation faults from dynamic
1128 Big_Overflow_Guard : constant := 16 * 1024;
1129 Small_Stack_Limit : constant := 64 * 1024;
1130 -- ??? These three values are experimental, and seem to work on
1131 -- most platforms. They still need to be analyzed further. They
1132 -- also need documentation, what are they???
1134 Pattern_Size : Natural :=
1135 Natural (Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size);
1136 -- Size of the pattern
1138 Stack_Base : Address;
1139 -- Address of the base of the stack
1142 Stack_Base := Self_ID.Common.Compiler_Data.Pri_Stack_Info.Base;
1143 if Stack_Base = Null_Address then
1145 -- On many platforms, we don't know the real stack base
1146 -- address. Estimate it using an address in the frame.
1148 Stack_Base := Bottom_Of_Stack'Address;
1150 -- Also reduce the size of the stack to take into account the
1151 -- secondary stack array declared in this frame. This is for
1152 -- sure very conservative.
1154 if not Parameters.Sec_Stack_Dynamic then
1156 Pattern_Size - Natural (Secondary_Stack_Size);
1159 -- Adjustments for inner frames
1161 Pattern_Size := Pattern_Size -
1162 (if Pattern_Size < Small_Stack_Limit
1163 then Small_Overflow_Guard
1164 else Big_Overflow_Guard);
1166 -- Reduce by the size of the final guard page
1167 Pattern_Size := Pattern_Size - Guard_Page_Size;
1172 (Self_ID.Common.Analyzer,
1173 Self_ID.Common.Task_Image (1 .. Self_ID.Common.Task_Image_Len),
1174 Natural (Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size),
1175 SSE.To_Integer (Stack_Base),
1178 Fill_Stack (Self_ID.Common.Analyzer);
1182 -- We setup the SEH (Structured Exception Handling) handler if supported
1185 Install_SEH_Handler (SEH_Table'Address);
1187 -- Initialize exception occurrence
1189 Save_Occurrence (EO, Ada.Exceptions.Null_Occurrence);
1191 -- We lock RTS_Lock to wait for activator to finish activating the rest
1192 -- of the chain, so that everyone in the chain comes out in priority
1195 -- This also protects the value of
1196 -- Self_ID.Common.Activator.Common.Wait_Count.
1201 if not System.Restrictions.Abort_Allowed then
1203 -- If Abort is not allowed, reset the deferral level since it will
1204 -- not get changed by the generated code. Keeping a default value
1205 -- of one would prevent some operations (e.g. select or delay) to
1206 -- proceed successfully.
1208 Self_ID.Deferral_Level := 0;
1211 if Global_Task_Debug_Event_Set then
1212 Debug.Signal_Debug_Event
1213 (Debug.Debug_Event_Run, Self_ID);
1217 -- We are separating the following portion of the code in order to
1218 -- place the exception handlers in a different block. In this way,
1219 -- we do not call Set_Jmpbuf_Address (which needs Self) before we
1220 -- set Self in Enter_Task
1222 -- Call the task body procedure
1224 -- The task body is called with abort still deferred. That
1225 -- eliminates a dangerous window, for which we had to patch-up in
1228 -- During the expansion of the task body, we insert an RTS-call
1229 -- to Abort_Undefer, at the first point where abort should be
1232 Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
1233 Initialization.Defer_Abort_Nestable (Self_ID);
1236 -- We can't call Terminate_Task in the exception handlers below,
1237 -- since there may be (e.g. in the case of GCC exception handling)
1238 -- clean ups associated with the exception handler that need to
1239 -- access task specific data.
1241 -- Defer abort so that this task can't be aborted while exiting
1243 when Standard'Abort_Signal =>
1244 Initialization.Defer_Abort_Nestable (Self_ID);
1246 -- Update the cause that motivated the task termination so that
1247 -- the appropriate information is passed to the task termination
1248 -- procedure. Task termination as a result of waiting on a
1249 -- terminate alternative is a normal termination, although it is
1250 -- implemented using the abort mechanisms.
1252 if Self_ID.Terminate_Alternative then
1255 if Global_Task_Debug_Event_Set then
1256 Debug.Signal_Debug_Event
1257 (Debug.Debug_Event_Terminated, Self_ID);
1262 if Global_Task_Debug_Event_Set then
1263 Debug.Signal_Debug_Event
1264 (Debug.Debug_Event_Abort_Terminated, Self_ID);
1268 -- ??? Using an E : others here causes CD2C11A to fail on Tru64
1270 Initialization.Defer_Abort_Nestable (Self_ID);
1272 -- Perform the task specific exception tracing duty. We handle
1273 -- these outputs here and not in the common notification routine
1274 -- because we need access to tasking related data and we don't
1275 -- want to drag dependencies against tasking related units in the
1276 -- the common notification units. Additionally, no trace is ever
1277 -- triggered from the common routine for the Unhandled_Raise case
1278 -- in tasks, since an exception never appears unhandled in this
1279 -- context because of this handler.
1281 if Exception_Trace = Unhandled_Raise then
1282 Trace_Unhandled_Exception_In_Task (Self_ID);
1285 -- Update the cause that motivated the task termination so that
1286 -- the appropriate information is passed to the task termination
1287 -- procedure, as well as the associated Exception_Occurrence.
1289 Cause := Unhandled_Exception;
1291 Save_Occurrence (EO, SSL.Get_Current_Excep.all.all);
1293 if Global_Task_Debug_Event_Set then
1294 Debug.Signal_Debug_Event
1295 (Debug.Debug_Event_Exception_Terminated, Self_ID);
1299 -- Look for a task termination handler. This code is for all tasks but
1300 -- the environment task. The task termination code for the environment
1301 -- task is executed by SSL.Task_Termination_Handler.
1307 Write_Lock (Self_ID);
1309 if Self_ID.Common.Specific_Handler /= null then
1310 TH := Self_ID.Common.Specific_Handler;
1312 -- Look for a fall-back handler following the master relationship
1315 Search_Fall_Back_Handler (Self_ID);
1324 -- Execute the task termination handler if we found it
1328 TH.all (Cause, Self_ID, EO);
1332 -- RM-C.7.3 requires all exceptions raised here to be ignored
1339 if System.Stack_Usage.Is_Enabled then
1340 Compute_Result (Self_ID.Common.Analyzer);
1341 Report_Result (Self_ID.Common.Analyzer);
1344 Terminate_Task (Self_ID);
1347 --------------------
1348 -- Terminate_Task --
1349 --------------------
1351 -- Before we allow the thread to exit, we must clean up. This is a
1352 -- delicate job. We must wake up the task's master, who may immediately try
1353 -- to deallocate the ATCB out from under the current task WHILE IT IS STILL
1356 -- To avoid this, the parent task must be blocked up to the latest
1357 -- statement executed. The trouble is that we have another step that we
1358 -- also want to postpone to the very end, i.e., calling SSL.Destroy_TSD.
1359 -- We have to postpone that until the end because compiler-generated code
1360 -- is likely to try to access that data at just about any point.
1362 -- We can't call Destroy_TSD while we are holding any other locks, because
1363 -- it locks Global_Task_Lock, and our deadlock prevention rules require
1364 -- that to be the outermost lock. Our first "solution" was to just lock
1365 -- Global_Task_Lock in addition to the other locks, and force the parent to
1366 -- also lock this lock between its wakeup and its freeing of the ATCB. See
1367 -- Complete_Task for the parent-side of the code that has the matching
1368 -- calls to Task_Lock and Task_Unlock. That was not really a solution,
1369 -- since the operation Task_Unlock continued to access the ATCB after
1370 -- unlocking, after which the parent was observed to race ahead, deallocate
1371 -- the ATCB, and then reallocate it to another task. The call to
1372 -- Undefer_Abort in Task_Unlock by the "terminated" task was overwriting
1373 -- the data of the new task that reused the ATCB! To solve this problem, we
1374 -- introduced the new operation Final_Task_Unlock.
1376 procedure Terminate_Task (Self_ID : Task_Id) is
1377 Environment_Task : constant Task_Id := STPO.Environment_Task;
1378 Master_of_Task : Integer;
1381 Debug.Task_Termination_Hook;
1383 if Runtime_Traces then
1384 Send_Trace_Info (T_Terminate);
1387 -- Since GCC cannot allocate stack chunks efficiently without reordering
1388 -- some of the allocations, we have to handle this unexpected situation
1389 -- here. We should normally never have to call Vulnerable_Complete_Task
1392 if Self_ID.Common.Activator /= null then
1393 Vulnerable_Complete_Task (Self_ID);
1396 Initialization.Task_Lock (Self_ID);
1402 Master_of_Task := Self_ID.Master_of_Task;
1404 -- Check if the current task is an independent task If so, decrement
1405 -- the Independent_Task_Count value.
1407 if Master_of_Task = Independent_Task_Level then
1409 Utilities.Independent_Task_Count :=
1410 Utilities.Independent_Task_Count - 1;
1412 Write_Lock (Environment_Task);
1413 Utilities.Independent_Task_Count :=
1414 Utilities.Independent_Task_Count - 1;
1415 Unlock (Environment_Task);
1419 -- Unprotect the guard page if needed
1421 Stack_Guard (Self_ID, False);
1423 Utilities.Make_Passive (Self_ID, Task_Completed => True);
1429 pragma Assert (Check_Exit (Self_ID));
1431 SSL.Destroy_TSD (Self_ID.Common.Compiler_Data);
1432 Initialization.Final_Task_Unlock (Self_ID);
1434 -- WARNING: past this point, this thread must assume that the ATCB has
1435 -- been deallocated. It should not be accessed again.
1437 if Master_of_Task > 0 then
1446 function Terminated (T : Task_Id) return Boolean is
1447 Self_ID : constant Task_Id := STPO.Self;
1451 Initialization.Defer_Abort_Nestable (Self_ID);
1458 Result := T.Common.State = Terminated;
1465 Initialization.Undefer_Abort_Nestable (Self_ID);
1469 ----------------------------------------
1470 -- Trace_Unhandled_Exception_In_Task --
1471 ----------------------------------------
1473 procedure Trace_Unhandled_Exception_In_Task (Self_Id : Task_Id) is
1474 procedure To_Stderr (S : String);
1475 pragma Import (Ada, To_Stderr, "__gnat_to_stderr");
1477 use System.Soft_Links;
1478 use System.Standard_Library;
1480 function To_Address is new
1481 Ada.Unchecked_Conversion
1482 (Task_Id, System.Task_Primitives.Task_Address);
1484 function Tailored_Exception_Information
1485 (E : Exception_Occurrence) return String;
1487 (Ada, Tailored_Exception_Information,
1488 "__gnat_tailored_exception_information");
1490 Excep : constant Exception_Occurrence_Access :=
1491 SSL.Get_Current_Excep.all;
1494 -- This procedure is called by the task outermost handler in
1495 -- Task_Wrapper below, so only once the task stack has been fully
1496 -- unwound. The common notification routine has been called at the
1497 -- raise point already.
1499 -- Lock to prevent unsynchronized output
1501 Initialization.Task_Lock (Self_Id);
1502 To_Stderr ("task ");
1504 if Self_Id.Common.Task_Image_Len /= 0 then
1506 (Self_Id.Common.Task_Image (1 .. Self_Id.Common.Task_Image_Len));
1510 To_Stderr (System.Address_Image (To_Address (Self_Id)));
1511 To_Stderr (" terminated by unhandled exception");
1512 To_Stderr ((1 => ASCII.LF));
1513 To_Stderr (Tailored_Exception_Information (Excep.all));
1514 Initialization.Task_Unlock (Self_Id);
1515 end Trace_Unhandled_Exception_In_Task;
1517 ------------------------------------
1518 -- Vulnerable_Complete_Activation --
1519 ------------------------------------
1521 -- As in several other places, the locks of the activator and activated
1522 -- task are both locked here. This follows our deadlock prevention lock
1523 -- ordering policy, since the activated task must be created after the
1526 procedure Vulnerable_Complete_Activation (Self_ID : Task_Id) is
1527 Activator : constant Task_Id := Self_ID.Common.Activator;
1530 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Activation", 'C'));
1532 Write_Lock (Activator);
1533 Write_Lock (Self_ID);
1535 pragma Assert (Self_ID.Common.Activator /= null);
1537 -- Remove dangling reference to Activator, since a task may
1538 -- outlive its activator.
1540 Self_ID.Common.Activator := null;
1542 -- Wake up the activator, if it is waiting for a chain of tasks to
1543 -- activate, and we are the last in the chain to complete activation.
1545 if Activator.Common.State = Activator_Sleep then
1546 Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
1548 if Activator.Common.Wait_Count = 0 then
1549 Wakeup (Activator, Activator_Sleep);
1553 -- The activator raises a Tasking_Error if any task it is activating
1554 -- is completed before the activation is done. However, if the reason
1555 -- for the task completion is an abort, we do not raise an exception.
1558 if not Self_ID.Callable and then Self_ID.Pending_ATC_Level /= 0 then
1559 Activator.Common.Activation_Failed := True;
1565 -- After the activation, active priority should be the same as base
1566 -- priority. We must unlock the Activator first, though, since it
1567 -- should not wait if we have lower priority.
1569 if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
1570 Write_Lock (Self_ID);
1571 Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
1574 end Vulnerable_Complete_Activation;
1576 --------------------------------
1577 -- Vulnerable_Complete_Master --
1578 --------------------------------
1580 procedure Vulnerable_Complete_Master (Self_ID : Task_Id) is
1583 CM : constant Master_Level := Self_ID.Master_Within;
1584 T : aliased Task_Id;
1586 To_Be_Freed : Task_Id;
1587 -- This is a list of ATCBs to be freed, after we have released all RTS
1588 -- locks. This is necessary because of the locking order rules, since
1589 -- the storage manager uses Global_Task_Lock.
1591 pragma Warnings (Off);
1592 function Check_Unactivated_Tasks return Boolean;
1593 pragma Warnings (On);
1594 -- Temporary error-checking code below. This is part of the checks
1595 -- added in the new run time. Call it only inside a pragma Assert.
1597 -----------------------------
1598 -- Check_Unactivated_Tasks --
1599 -----------------------------
1601 function Check_Unactivated_Tasks return Boolean is
1603 if not Single_Lock then
1607 Write_Lock (Self_ID);
1609 C := All_Tasks_List;
1610 while C /= null loop
1611 if C.Common.Activator = Self_ID and then C.Master_of_Task = CM then
1615 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1618 if C.Common.State = Unactivated then
1625 C := C.Common.All_Tasks_Link;
1630 if not Single_Lock then
1635 end Check_Unactivated_Tasks;
1637 -- Start of processing for Vulnerable_Complete_Master
1641 (Debug.Trace (Self_ID, "V_Complete_Master", 'C'));
1643 pragma Assert (Self_ID.Common.Wait_Count = 0);
1645 (Self_ID.Deferral_Level > 0
1646 or else not System.Restrictions.Abort_Allowed);
1648 -- Count how many active dependent tasks this master currently has, and
1649 -- record this in Wait_Count.
1651 -- This count should start at zero, since it is initialized to zero for
1652 -- new tasks, and the task should not exit the sleep-loops that use this
1653 -- count until the count reaches zero.
1655 -- While we're counting, if we run across any unactivated tasks that
1656 -- belong to this master, we summarily terminate them as required by
1660 Write_Lock (Self_ID);
1662 C := All_Tasks_List;
1663 while C /= null loop
1665 -- Terminate unactivated (never-to-be activated) tasks
1667 if C.Common.Activator = Self_ID and then C.Master_of_Task = CM then
1669 pragma Assert (C.Common.State = Unactivated);
1670 -- Usually, C.Common.Activator = Self_ID implies C.Master_of_Task
1671 -- = CM. The only case where C is pending activation by this
1672 -- task, but the master of C is not CM is in Ada 2005, when C is
1673 -- part of a return object of a build-in-place function.
1676 C.Common.Activator := null;
1677 C.Common.State := Terminated;
1678 C.Callable := False;
1679 Utilities.Cancel_Queued_Entry_Calls (C);
1683 -- Count it if dependent on this master
1685 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1688 if C.Awake_Count /= 0 then
1689 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1695 C := C.Common.All_Tasks_Link;
1698 Self_ID.Common.State := Master_Completion_Sleep;
1701 if not Single_Lock then
1705 -- Wait until dependent tasks are all terminated or ready to terminate.
1706 -- While waiting, the task may be awakened if the task's priority needs
1707 -- changing, or this master is aborted. In the latter case, we abort the
1708 -- dependents, and resume waiting until Wait_Count goes to zero.
1710 Write_Lock (Self_ID);
1713 exit when Self_ID.Common.Wait_Count = 0;
1715 -- Here is a difference as compared to Complete_Master
1717 if Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
1718 and then not Self_ID.Dependents_Aborted
1721 Abort_Dependents (Self_ID);
1725 Abort_Dependents (Self_ID);
1727 Write_Lock (Self_ID);
1730 Sleep (Self_ID, Master_Completion_Sleep);
1734 Self_ID.Common.State := Runnable;
1737 -- Dependents are all terminated or on terminate alternatives. Now,
1738 -- force those on terminate alternatives to terminate, by aborting them.
1740 pragma Assert (Check_Unactivated_Tasks);
1742 if Self_ID.Alive_Count > 1 then
1744 -- Consider finding a way to skip the following extra steps if there
1745 -- are no dependents with terminate alternatives. This could be done
1746 -- by adding another count to the ATCB, similar to Awake_Count, but
1747 -- keeping track of tasks that are on terminate alternatives.
1749 pragma Assert (Self_ID.Common.Wait_Count = 0);
1751 -- Force any remaining dependents to terminate by aborting them
1753 if not Single_Lock then
1757 Abort_Dependents (Self_ID);
1759 -- Above, when we "abort" the dependents we are simply using this
1760 -- operation for convenience. We are not required to support the full
1761 -- abort-statement semantics; in particular, we are not required to
1762 -- immediately cancel any queued or in-service entry calls. That is
1763 -- good, because if we tried to cancel a call we would need to lock
1764 -- the caller, in order to wake the caller up. Our anti-deadlock
1765 -- rules prevent us from doing that without releasing the locks on C
1766 -- and Self_ID. Releasing and retaking those locks would be wasteful
1767 -- at best, and should not be considered further without more
1768 -- detailed analysis of potential concurrent accesses to the ATCBs
1769 -- of C and Self_ID.
1771 -- Count how many "alive" dependent tasks this master currently has,
1772 -- and record this in Wait_Count. This count should start at zero,
1773 -- since it is initialized to zero for new tasks, and the task should
1774 -- not exit the sleep-loops that use this count until the count
1777 pragma Assert (Self_ID.Common.Wait_Count = 0);
1779 Write_Lock (Self_ID);
1781 C := All_Tasks_List;
1782 while C /= null loop
1783 if C.Common.Parent = Self_ID and then C.Master_of_Task = CM then
1786 pragma Assert (C.Awake_Count = 0);
1788 if C.Alive_Count > 0 then
1789 pragma Assert (C.Terminate_Alternative);
1790 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
1796 C := C.Common.All_Tasks_Link;
1799 Self_ID.Common.State := Master_Phase_2_Sleep;
1802 if not Single_Lock then
1806 -- Wait for all counted tasks to finish terminating themselves
1808 Write_Lock (Self_ID);
1811 exit when Self_ID.Common.Wait_Count = 0;
1812 Sleep (Self_ID, Master_Phase_2_Sleep);
1815 Self_ID.Common.State := Runnable;
1819 -- We don't wake up for abort here. We are already terminating just as
1820 -- fast as we can, so there is no point.
1822 -- Remove terminated tasks from the list of Self_ID's dependents, but
1823 -- don't free their ATCBs yet, because of lock order restrictions, which
1824 -- don't allow us to call "free" or "malloc" while holding any other
1825 -- locks. Instead, we put those ATCBs to be freed onto a temporary list,
1826 -- called To_Be_Freed.
1828 if not Single_Lock then
1832 C := All_Tasks_List;
1834 while C /= null loop
1835 if C.Common.Parent = Self_ID and then C.Master_of_Task >= CM then
1837 P.Common.All_Tasks_Link := C.Common.All_Tasks_Link;
1839 All_Tasks_List := C.Common.All_Tasks_Link;
1842 T := C.Common.All_Tasks_Link;
1843 C.Common.All_Tasks_Link := To_Be_Freed;
1849 C := C.Common.All_Tasks_Link;
1855 -- Free all the ATCBs on the list To_Be_Freed
1857 -- The ATCBs in the list are no longer in All_Tasks_List, and after
1858 -- any interrupt entries are detached from them they should no longer
1861 -- Global_Task_Lock (Task_Lock/Unlock) is locked in the loop below to
1862 -- avoid a race between a terminating task and its parent. The parent
1863 -- might try to deallocate the ACTB out from underneath the exiting
1864 -- task. Note that Free will also lock Global_Task_Lock, but that is
1865 -- OK, since this is the *one* lock for which we have a mechanism to
1866 -- support nested locking. See Task_Wrapper and its finalizer for more
1870 -- The check "T.Common.Parent /= null ..." below is to prevent dangling
1871 -- references to terminated library-level tasks, which could otherwise
1872 -- occur during finalization of library-level objects. A better solution
1873 -- might be to hook task objects into the finalization chain and
1874 -- deallocate the ATCB when the task object is deallocated. However,
1875 -- this change is not likely to gain anything significant, since all
1876 -- this storage should be recovered en-masse when the process exits.
1878 while To_Be_Freed /= null loop
1880 To_Be_Freed := T.Common.All_Tasks_Link;
1882 -- ??? On SGI there is currently no Interrupt_Manager, that's why we
1883 -- need to check if the Interrupt_Manager_ID is null.
1885 if T.Interrupt_Entry and then Interrupt_Manager_ID /= null then
1887 Detach_Interrupt_Entries_Index : constant Task_Entry_Index := 1;
1888 -- Corresponds to the entry index of System.Interrupts.
1889 -- Interrupt_Manager.Detach_Interrupt_Entries.
1890 -- Be sure to update this value when changing
1891 -- Interrupt_Manager specs.
1893 type Param_Type is access all Task_Id;
1895 Param : aliased Param_Type := T'Access;
1898 System.Tasking.Rendezvous.Call_Simple
1899 (Interrupt_Manager_ID, Detach_Interrupt_Entries_Index,
1904 if (T.Common.Parent /= null
1905 and then T.Common.Parent.Common.Parent /= null)
1906 or else T.Master_of_Task > Library_Task_Level
1908 Initialization.Task_Lock (Self_ID);
1910 -- If Sec_Stack_Addr is not null, it means that Destroy_TSD
1911 -- has not been called yet (case of an unactivated task).
1913 if T.Common.Compiler_Data.Sec_Stack_Addr /= Null_Address then
1914 SSL.Destroy_TSD (T.Common.Compiler_Data);
1917 Vulnerable_Free_Task (T);
1918 Initialization.Task_Unlock (Self_ID);
1922 -- It might seem nice to let the terminated task deallocate its own
1923 -- ATCB. That would not cover the case of unactivated tasks. It also
1924 -- would force us to keep the underlying thread around past termination,
1925 -- since references to the ATCB are possible past termination.
1927 -- Currently, we get rid of the thread as soon as the task terminates,
1928 -- and let the parent recover the ATCB later.
1930 -- Some day, if we want to recover the ATCB earlier, at task
1931 -- termination, we could consider using "fat task IDs", that include the
1932 -- serial number with the ATCB pointer, to catch references to tasks
1933 -- that no longer have ATCBs. It is not clear how much this would gain,
1934 -- since the user-level task object would still be occupying storage.
1936 -- Make next master level up active. We don't need to lock the ATCB,
1937 -- since the value is only updated by each task for itself.
1939 Self_ID.Master_Within := CM - 1;
1940 end Vulnerable_Complete_Master;
1942 ------------------------------
1943 -- Vulnerable_Complete_Task --
1944 ------------------------------
1946 -- Complete the calling task
1948 -- This procedure must be called with abort deferred. It should only be
1949 -- called by Complete_Task and Finalize_Global_Tasks (for the environment
1952 -- The effect is similar to that of Complete_Master. Differences include
1953 -- the closing of entries here, and computation of the number of active
1954 -- dependent tasks in Complete_Master.
1956 -- We don't lock Self_ID before the call to Vulnerable_Complete_Activation,
1957 -- because that does its own locking, and because we do not need the lock
1958 -- to test Self_ID.Common.Activator. That value should only be read and
1959 -- modified by Self.
1961 procedure Vulnerable_Complete_Task (Self_ID : Task_Id) is
1964 (Self_ID.Deferral_Level > 0
1965 or else not System.Restrictions.Abort_Allowed);
1966 pragma Assert (Self_ID = Self);
1967 pragma Assert (Self_ID.Master_Within = Self_ID.Master_of_Task + 1
1969 Self_ID.Master_Within = Self_ID.Master_of_Task + 2);
1970 pragma Assert (Self_ID.Common.Wait_Count = 0);
1971 pragma Assert (Self_ID.Open_Accepts = null);
1972 pragma Assert (Self_ID.ATC_Nesting_Level = 1);
1974 pragma Debug (Debug.Trace (Self_ID, "V_Complete_Task", 'C'));
1980 Write_Lock (Self_ID);
1981 Self_ID.Callable := False;
1983 -- In theory, Self should have no pending entry calls left on its
1984 -- call-stack. Each async. select statement should clean its own call,
1985 -- and blocking entry calls should defer abort until the calls are
1986 -- cancelled, then clean up.
1988 Utilities.Cancel_Queued_Entry_Calls (Self_ID);
1991 if Self_ID.Common.Activator /= null then
1992 Vulnerable_Complete_Activation (Self_ID);
1999 -- If Self_ID.Master_Within = Self_ID.Master_of_Task + 2 we may have
2000 -- dependent tasks for which we need to wait. Otherwise we just exit.
2002 if Self_ID.Master_Within = Self_ID.Master_of_Task + 2 then
2003 Vulnerable_Complete_Master (Self_ID);
2005 end Vulnerable_Complete_Task;
2007 --------------------------
2008 -- Vulnerable_Free_Task --
2009 --------------------------
2011 -- Recover all runtime system storage associated with the task T. This
2012 -- should only be called after T has terminated and will no longer be
2015 -- For tasks created by an allocator that fails, due to an exception, it
2016 -- is called from Expunge_Unactivated_Tasks.
2018 -- For tasks created by elaboration of task object declarations it is
2019 -- called from the finalization code of the Task_Wrapper procedure. It is
2020 -- also called from Ada.Unchecked_Deallocation, for objects that are or
2023 procedure Vulnerable_Free_Task (T : Task_Id) is
2025 pragma Debug (Debug.Trace (Self, "Vulnerable_Free_Task", 'C', T));
2032 Initialization.Finalize_Attributes_Link.all (T);
2039 Free_Entry_Names (T);
2040 System.Task_Primitives.Operations.Finalize_TCB (T);
2041 end Vulnerable_Free_Task;
2043 -- Package elaboration code
2046 -- Establish the Adafinal softlink
2048 -- This is not done inside the central RTS initialization routine
2049 -- to avoid with'ing this package from System.Tasking.Initialization.
2051 SSL.Adafinal := Finalize_Global_Tasks'Access;
2053 -- Establish soft links for subprograms that manipulate master_id's.
2054 -- This cannot be done when the RTS is initialized, because of various
2055 -- elaboration constraints.
2057 SSL.Current_Master := Stages.Current_Master'Access;
2058 SSL.Enter_Master := Stages.Enter_Master'Access;
2059 SSL.Complete_Master := Stages.Complete_Master'Access;
2060 end System.Tasking.Stages;