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------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . T A S K I N G . U T I L I T I E S -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2009, Free Software Foundation, Inc. -- -- -- -- GNARL is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- <http://www.gnu.org/licenses/>. -- -- -- -- GNARL was developed by the GNARL team at Florida State University. -- -- Extensive contributions were provided by Ada Core Technologies, Inc. -- -- -- ------------------------------------------------------------------------------ -- This package provides RTS Internal Declarations -- These declarations are not part of the GNARLI pragma Polling (Off); -- Turn off polling, we do not want ATC polling to take place during tasking -- operations. It causes infinite loops and other problems. with System.Tasking.Debug; with System.Task_Primitives.Operations; with System.Tasking.Initialization; with System.Tasking.Queuing; with System.Parameters; with System.Traces.Tasking; package body System.Tasking.Utilities is package STPO renames System.Task_Primitives.Operations; use Parameters; use Tasking.Debug; use Task_Primitives; use Task_Primitives.Operations; use System.Traces; use System.Traces.Tasking; -------------------- -- Abort_One_Task -- -------------------- -- Similar to Locked_Abort_To_Level (Self_ID, T, 0), but: -- (1) caller should be holding no locks except RTS_Lock when Single_Lock -- (2) may be called for tasks that have not yet been activated -- (3) always aborts whole task procedure Abort_One_Task (Self_ID : Task_Id; T : Task_Id) is begin if Parameters.Runtime_Traces then Send_Trace_Info (T_Abort, Self_ID, T); end if; Write_Lock (T); if T.Common.State = Unactivated then T.Common.Activator := null; T.Common.State := Terminated; T.Callable := False; Cancel_Queued_Entry_Calls (T); elsif T.Common.State /= Terminated then Initialization.Locked_Abort_To_Level (Self_ID, T, 0); end if; Unlock (T); end Abort_One_Task; ----------------- -- Abort_Tasks -- ----------------- -- This must be called to implement the abort statement. -- Much of the actual work of the abort is done by the abortee, -- via the Abort_Handler signal handler, and propagation of the -- Abort_Signal special exception. procedure Abort_Tasks (Tasks : Task_List) is Self_Id : constant Task_Id := STPO.Self; C : Task_Id; P : Task_Id; begin -- If pragma Detect_Blocking is active then Program_Error must be -- raised if this potentially blocking operation is called from a -- protected action. if System.Tasking.Detect_Blocking and then Self_Id.Common.Protected_Action_Nesting > 0 then raise Program_Error with "potentially blocking operation"; end if; Initialization.Defer_Abort_Nestable (Self_Id); -- ????? -- Really should not be nested deferral here. -- Patch for code generation error that defers abort before -- evaluating parameters of an entry call (at least, timed entry -- calls), and so may propagate an exception that causes abort -- to remain undeferred indefinitely. See C97404B. When all -- such bugs are fixed, this patch can be removed. Lock_RTS; for J in Tasks'Range loop C := Tasks (J); Abort_One_Task (Self_Id, C); end loop; C := All_Tasks_List; while C /= null loop if C.Pending_ATC_Level > 0 then P := C.Common.Parent; while P /= null loop if P.Pending_ATC_Level = 0 then Abort_One_Task (Self_Id, C); exit; end if; P := P.Common.Parent; end loop; end if; C := C.Common.All_Tasks_Link; end loop; Unlock_RTS; Initialization.Undefer_Abort_Nestable (Self_Id); end Abort_Tasks; ------------------------------- -- Cancel_Queued_Entry_Calls -- ------------------------------- -- This should only be called by T, unless T is a terminated previously -- unactivated task. procedure Cancel_Queued_Entry_Calls (T : Task_Id) is Next_Entry_Call : Entry_Call_Link; Entry_Call : Entry_Call_Link; Self_Id : constant Task_Id := STPO.Self; Caller : Task_Id; pragma Unreferenced (Caller); -- Should this be removed ??? Level : Integer; pragma Unreferenced (Level); -- Should this be removed ??? begin pragma Assert (T = Self or else T.Common.State = Terminated); for J in 1 .. T.Entry_Num loop Queuing.Dequeue_Head (T.Entry_Queues (J), Entry_Call); while Entry_Call /= null loop -- Leave Entry_Call.Done = False, since this is cancelled Caller := Entry_Call.Self; Entry_Call.Exception_To_Raise := Tasking_Error'Identity; Queuing.Dequeue_Head (T.Entry_Queues (J), Next_Entry_Call); Level := Entry_Call.Level - 1; Unlock (T); Write_Lock (Entry_Call.Self); Initialization.Wakeup_Entry_Caller (Self_Id, Entry_Call, Cancelled); Unlock (Entry_Call.Self); Write_Lock (T); Entry_Call.State := Done; Entry_Call := Next_Entry_Call; end loop; end loop; end Cancel_Queued_Entry_Calls; ------------------------ -- Exit_One_ATC_Level -- ------------------------ -- Call only with abort deferred and holding lock of Self_Id. -- This is a bit of common code for all entry calls. -- The effect is to exit one level of ATC nesting. -- If we have reached the desired ATC nesting level, reset the -- requested level to effective infinity, to allow further calls. -- In any case, reset Self_Id.Aborting, to allow re-raising of -- Abort_Signal. procedure Exit_One_ATC_Level (Self_ID : Task_Id) is begin Self_ID.ATC_Nesting_Level := Self_ID.ATC_Nesting_Level - 1; pragma Debug (Debug.Trace (Self_ID, "EOAL: exited to ATC level: " & ATC_Level'Image (Self_ID.ATC_Nesting_Level), 'A')); pragma Assert (Self_ID.ATC_Nesting_Level >= 1); if Self_ID.Pending_ATC_Level < ATC_Level_Infinity then if Self_ID.Pending_ATC_Level = Self_ID.ATC_Nesting_Level then Self_ID.Pending_ATC_Level := ATC_Level_Infinity; Self_ID.Aborting := False; else -- Force the next Undefer_Abort to re-raise Abort_Signal pragma Assert (Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level); if Self_ID.Aborting then Self_ID.ATC_Hack := True; Self_ID.Pending_Action := True; end if; end if; end if; end Exit_One_ATC_Level; ---------------------- -- Make_Independent -- ---------------------- procedure Make_Independent is Self_Id : constant Task_Id := STPO.Self; Environment_Task : constant Task_Id := STPO.Environment_Task; Parent : constant Task_Id := Self_Id.Common.Parent; Parent_Needs_Updating : Boolean := False; Master_of_Task : Integer; begin if Self_Id.Known_Tasks_Index /= -1 then Known_Tasks (Self_Id.Known_Tasks_Index) := null; end if; Initialization.Defer_Abort (Self_Id); if Single_Lock then Lock_RTS; end if; Write_Lock (Environment_Task); Write_Lock (Self_Id); pragma Assert (Parent = Environment_Task or else Self_Id.Master_of_Task = Library_Task_Level); Master_of_Task := Self_Id.Master_of_Task; Self_Id.Master_of_Task := Independent_Task_Level; -- The run time assumes that the parent of an independent task is the -- environment task. if Parent /= Environment_Task then -- We cannot lock three tasks at the same time, so defer the -- operations on the parent. Parent_Needs_Updating := True; Self_Id.Common.Parent := Environment_Task; end if; -- Update Independent_Task_Count that is needed for the GLADE -- termination rule. See also pending update in -- System.Tasking.Stages.Check_Independent Independent_Task_Count := Independent_Task_Count + 1; Unlock (Self_Id); -- Changing the parent after creation is not trivial. Do not forget -- to update the old parent counts, and the new parent (i.e. the -- Environment_Task) counts. if Parent_Needs_Updating then Write_Lock (Parent); Parent.Awake_Count := Parent.Awake_Count - 1; Parent.Alive_Count := Parent.Alive_Count - 1; Environment_Task.Awake_Count := Environment_Task.Awake_Count + 1; Environment_Task.Alive_Count := Environment_Task.Alive_Count + 1; Unlock (Parent); end if; -- In case the environment task is already waiting for children to -- complete. -- ??? There may be a race condition if the environment task was not in -- master completion sleep when this task was created, but now is if Environment_Task.Common.State = Master_Completion_Sleep and then Master_of_Task = Environment_Task.Master_Within then Environment_Task.Common.Wait_Count := Environment_Task.Common.Wait_Count - 1; end if; Unlock (Environment_Task); if Single_Lock then Unlock_RTS; end if; Initialization.Undefer_Abort (Self_Id); end Make_Independent; ------------------ -- Make_Passive -- ------------------ procedure Make_Passive (Self_ID : Task_Id; Task_Completed : Boolean) is C : Task_Id := Self_ID; P : Task_Id := C.Common.Parent; Master_Completion_Phase : Integer; begin if P /= null then Write_Lock (P); end if; Write_Lock (C); if Task_Completed then Self_ID.Common.State := Terminated; if Self_ID.Awake_Count = 0 then -- We are completing via a terminate alternative. -- Our parent should wait in Phase 2 of Complete_Master. Master_Completion_Phase := 2; pragma Assert (Task_Completed); pragma Assert (Self_ID.Terminate_Alternative); pragma Assert (Self_ID.Alive_Count = 1); else -- We are NOT on a terminate alternative. -- Our parent should wait in Phase 1 of Complete_Master. Master_Completion_Phase := 1; pragma Assert (Self_ID.Awake_Count >= 1); end if; -- We are accepting with a terminate alternative else if Self_ID.Open_Accepts = null then -- Somebody started a rendezvous while we had our lock open. -- Skip the terminate alternative. Unlock (C); if P /= null then Unlock (P); end if; return; end if; Self_ID.Terminate_Alternative := True; Master_Completion_Phase := 0; pragma Assert (Self_ID.Terminate_Alternative); pragma Assert (Self_ID.Awake_Count >= 1); end if; if Master_Completion_Phase = 2 then -- Since our Awake_Count is zero but our Alive_Count -- is nonzero, we have been accepting with a terminate -- alternative, and we now have been told to terminate -- by a completed master (in some ancestor task) that -- is waiting (with zero Awake_Count) in Phase 2 of -- Complete_Master. pragma Debug (Debug.Trace (Self_ID, "Make_Passive: Phase 2", 'M')); pragma Assert (P /= null); C.Alive_Count := C.Alive_Count - 1; if C.Alive_Count > 0 then Unlock (C); Unlock (P); return; end if; -- C's count just went to zero, indicating that -- all of C's dependents are terminated. -- C has a parent, P. loop -- C's count just went to zero, indicating that all of C's -- dependents are terminated. C has a parent, P. Notify P that -- C and its dependents have all terminated. P.Alive_Count := P.Alive_Count - 1; exit when P.Alive_Count > 0; Unlock (C); Unlock (P); C := P; P := C.Common.Parent; -- Environment task cannot have terminated yet pragma Assert (P /= null); Write_Lock (P); Write_Lock (C); end loop; if P.Common.State = Master_Phase_2_Sleep and then C.Master_of_Task = P.Master_Within then pragma Assert (P.Common.Wait_Count > 0); P.Common.Wait_Count := P.Common.Wait_Count - 1; if P.Common.Wait_Count = 0 then Wakeup (P, Master_Phase_2_Sleep); end if; end if; Unlock (C); Unlock (P); return; end if; -- We are terminating in Phase 1 or Complete_Master, -- or are accepting on a terminate alternative. C.Awake_Count := C.Awake_Count - 1; if Task_Completed then C.Alive_Count := C.Alive_Count - 1; end if; if C.Awake_Count > 0 or else P = null then Unlock (C); if P /= null then Unlock (P); end if; return; end if; -- C's count just went to zero, indicating that all of C's -- dependents are terminated or accepting with terminate alt. -- C has a parent, P. loop -- Notify P that C has gone passive if P.Awake_Count > 0 then P.Awake_Count := P.Awake_Count - 1; end if; if Task_Completed and then C.Alive_Count = 0 then P.Alive_Count := P.Alive_Count - 1; end if; exit when P.Awake_Count > 0; Unlock (C); Unlock (P); C := P; P := C.Common.Parent; if P = null then return; end if; Write_Lock (P); Write_Lock (C); end loop; -- P has non-passive dependents if P.Common.State = Master_Completion_Sleep and then C.Master_of_Task = P.Master_Within then pragma Debug (Debug.Trace (Self_ID, "Make_Passive: Phase 1, parent waiting", 'M')); -- If parent is in Master_Completion_Sleep, it -- cannot be on a terminate alternative, hence -- it cannot have Awake_Count of zero. pragma Assert (P.Common.Wait_Count > 0); P.Common.Wait_Count := P.Common.Wait_Count - 1; if P.Common.Wait_Count = 0 then Wakeup (P, Master_Completion_Sleep); end if; else pragma Debug (Debug.Trace (Self_ID, "Make_Passive: Phase 1, parent awake", 'M')); null; end if; Unlock (C); Unlock (P); end Make_Passive; end System.Tasking.Utilities;
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