1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- S Y S T E M . T A S K I N G . R E S T R I C T E D . S T A G E S --
9 -- Copyright (C) 1999-2007, Free Software Foundation, Inc. --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNARL; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
34 pragma Style_Checks (All_Checks);
35 -- Turn off subprogram alpha order check, since we group soft link
36 -- bodies and also separate off subprograms for restricted GNARLI.
38 -- This is a simplified version of the System.Tasking.Stages package,
39 -- intended to be used in a restricted run time.
41 -- This package represents the high level tasking interface used by the
42 -- compiler to expand Ada 95 tasking constructs into simpler run time calls.
45 -- Turn off polling, we do not want ATC polling to take place during
46 -- tasking operations. It causes infinite loops and other problems.
49 -- used for Exception_Occurrence
51 with System.Task_Primitives.Operations;
52 -- used for Enter_Task
58 with System.Soft_Links;
59 -- used for the non-tasking routines (*_NT) that refer to global data.
60 -- They are needed here before the tasking run time has been elaborated.
61 -- used for Create_TSD
62 -- This package also provides initialization routines for task specific data.
63 -- The GNARL must call these to be sure that all non-tasking
64 -- Ada constructs will work.
66 with System.Soft_Links.Tasking;
67 -- Used for Init_Tasking_Soft_Links
69 with System.Secondary_Stack;
72 with System.Storage_Elements;
73 -- used for Storage_Array;
75 package body System.Tasking.Restricted.Stages is
77 package STPO renames System.Task_Primitives.Operations;
78 package SSL renames System.Soft_Links;
79 package SSE renames System.Storage_Elements;
80 package SST renames System.Secondary_Stack;
85 use Task_Primitives.Operations;
88 Global_Task_Lock : aliased System.Task_Primitives.RTS_Lock;
89 -- This is a global lock; it is used to execute in mutual exclusion
90 -- from all other tasks. It is only used by Task_Lock and Task_Unlock.
92 -----------------------------------------------------------------
93 -- Tasking versions of services needed by non-tasking programs --
94 -----------------------------------------------------------------
96 function Get_Current_Excep return SSL.EOA;
97 -- Task-safe version of SSL.Get_Current_Excep
100 -- Locks out other tasks. Preceding a section of code by Task_Lock and
101 -- following it by Task_Unlock creates a critical region. This is used
102 -- for ensuring that a region of non-tasking code (such as code used to
103 -- allocate memory) is tasking safe. Note that it is valid for calls to
104 -- Task_Lock/Task_Unlock to be nested, and this must work properly, i.e.
105 -- only the corresponding outer level Task_Unlock will actually unlock.
107 procedure Task_Unlock;
108 -- Releases lock previously set by call to Task_Lock. In the nested case,
109 -- all nested locks must be released before other tasks competing for the
110 -- tasking lock are released.
112 -----------------------
113 -- Local Subprograms --
114 -----------------------
116 procedure Task_Wrapper (Self_ID : Task_Id);
117 -- This is the procedure that is called by the GNULL from the
118 -- new context when a task is created. It waits for activation
119 -- and then calls the task body procedure. When the task body
120 -- procedure completes, it terminates the task.
122 procedure Terminate_Task (Self_ID : Task_Id);
123 -- Terminate the calling task.
124 -- This should only be called by the Task_Wrapper procedure.
127 -- This procedure performs the initialization of the GNARL.
128 -- It consists of initializing the environment task, global locks, and
129 -- installing tasking versions of certain operations used by the compiler.
130 -- Init_RTS is called during elaboration.
132 -----------------------
133 -- Get_Current_Excep --
134 -----------------------
136 function Get_Current_Excep return SSL.EOA is
138 return STPO.Self.Common.Compiler_Data.Current_Excep'Access;
139 end Get_Current_Excep;
145 procedure Task_Lock is
146 Self_ID : constant Task_Id := STPO.Self;
149 Self_ID.Common.Global_Task_Lock_Nesting :=
150 Self_ID.Common.Global_Task_Lock_Nesting + 1;
152 if Self_ID.Common.Global_Task_Lock_Nesting = 1 then
153 STPO.Write_Lock (Global_Task_Lock'Access, Global_Lock => True);
161 procedure Task_Unlock is
162 Self_ID : constant Task_Id := STPO.Self;
165 pragma Assert (Self_ID.Common.Global_Task_Lock_Nesting > 0);
166 Self_ID.Common.Global_Task_Lock_Nesting :=
167 Self_ID.Common.Global_Task_Lock_Nesting - 1;
169 if Self_ID.Common.Global_Task_Lock_Nesting = 0 then
170 STPO.Unlock (Global_Task_Lock'Access, Global_Lock => True);
178 -- The task wrapper is a procedure that is called first for each task
179 -- task body, and which in turn calls the compiler-generated task body
180 -- procedure. The wrapper's main job is to do initialization for the task.
182 -- The variable ID in the task wrapper is used to implement the Self
183 -- function on targets where there is a fast way to find the stack base
184 -- of the current thread, since it should be at a fixed offset from the
187 procedure Task_Wrapper (Self_ID : Task_Id) is
188 ID : Task_Id := Self_ID;
189 pragma Volatile (ID);
190 pragma Warnings (Off, ID);
191 -- Variable used on some targets to implement a fast self. We turn off
192 -- warnings because a stand alone volatile constant has to be imported,
193 -- so we don't want warnings about ID not being referenced, and volatile
196 -- DO NOT delete ID. As noted, it is needed on some targets.
198 use type SSE.Storage_Offset;
200 Secondary_Stack : aliased SSE.Storage_Array
201 (1 .. Self_ID.Common.Compiler_Data.Pri_Stack_Info.Size *
202 SSE.Storage_Offset (Parameters.Sec_Stack_Ratio) / 100);
204 pragma Warnings (Off);
205 Secondary_Stack_Address : System.Address := Secondary_Stack'Address;
206 pragma Warnings (On);
207 -- Address of secondary stack. In the fixed secondary stack case, this
208 -- value is not modified, causing a warning, hence the bracketing with
209 -- Warnings (Off/On).
211 Cause : Cause_Of_Termination := Normal;
212 -- Indicates the reason why this task terminates. Normal corresponds to
213 -- a task terminating due to completing the last statement of its body.
214 -- If the task terminates because of an exception raised by the
215 -- execution of its task body, then Cause is set to Unhandled_Exception.
216 -- Aborts are not allowed in the restriced profile to which this file
219 EO : Exception_Occurrence;
220 -- If the task terminates because of an exception raised by the
221 -- execution of its task body, then EO will contain the associated
222 -- exception occurrence. Otherwise, it will contain Null_Occurrence.
225 if not Parameters.Sec_Stack_Dynamic then
226 Self_ID.Common.Compiler_Data.Sec_Stack_Addr :=
227 Secondary_Stack'Address;
228 SST.SS_Init (Secondary_Stack_Address, Integer (Secondary_Stack'Last));
231 -- Initialize low-level TCB components, that
232 -- cannot be initialized by the creator.
234 Enter_Task (Self_ID);
236 -- Call the task body procedure
239 -- We are separating the following portion of the code in order to
240 -- place the exception handlers in a different block. In this way we
241 -- do not call Set_Jmpbuf_Address (which needs Self) before we set
242 -- Self in Enter_Task.
244 -- Note that in the case of Ravenscar HI-E where there are no
245 -- exception handlers, the exception handler is suppressed.
247 -- Call the task body procedure
249 Self_ID.Common.Task_Entry_Point (Self_ID.Common.Task_Arg);
251 -- Normal task termination
254 Save_Occurrence (EO, Ada.Exceptions.Null_Occurrence);
259 -- Task terminating because of an unhandled exception
261 Cause := Unhandled_Exception;
262 Save_Occurrence (EO, E);
265 -- Look for a fall-back handler. It can be either in the task itself
266 -- or in the environment task. Note that this code is always executed
267 -- by a task whose master is the environment task. The task termination
268 -- code for the environment task is executed by
269 -- SSL.Task_Termination_Handler.
271 -- This package is part of the restricted run time which supports
272 -- neither task hierarchies (No_Task_Hierarchy) nor specific task
273 -- termination handlers (No_Specific_Termination_Handlers).
275 -- There is no need for explicit protection against race conditions
276 -- for Self_ID.Common.Fall_Back_Handler because this procedure can
277 -- only be executed by Self, and the Fall_Back_Handler can only be
280 if Self_ID.Common.Fall_Back_Handler /= null then
281 Self_ID.Common.Fall_Back_Handler (Cause, Self_ID, EO);
284 TH : Termination_Handler := null;
291 Write_Lock (Self_ID.Common.Parent);
293 TH := Self_ID.Common.Parent.Common.Fall_Back_Handler;
295 Unlock (Self_ID.Common.Parent);
301 -- Execute the task termination handler if we found it
304 TH.all (Cause, Self_ID, EO);
309 Terminate_Task (Self_ID);
312 -----------------------
313 -- Restricted GNARLI --
314 -----------------------
316 -------------------------------
317 -- Activate_Restricted_Tasks --
318 -------------------------------
320 -- Note that locks of activator and activated task are both locked here.
321 -- This is necessary because C.State and Self.Wait_Count have to be
322 -- synchronized. This is safe from deadlock because the activator is always
323 -- created before the activated task. That satisfies our
324 -- in-order-of-creation ATCB locking policy.
326 procedure Activate_Restricted_Tasks
327 (Chain_Access : Activation_Chain_Access)
329 Self_ID : constant Task_Id := STPO.Self;
331 Activate_Prio : System.Any_Priority;
335 pragma Assert (Self_ID = Environment_Task);
336 pragma Assert (Self_ID.Common.Wait_Count = 0);
342 -- Lock self, to prevent activated tasks from racing ahead before we
343 -- finish activating the chain.
345 Write_Lock (Self_ID);
347 -- Activate all the tasks in the chain. Creation of the thread of
348 -- control was deferred until activation. So create it now.
350 C := Chain_Access.T_ID;
353 if C.Common.State /= Terminated then
354 pragma Assert (C.Common.State = Unactivated);
358 if C.Common.Base_Priority < Get_Priority (Self_ID) then
359 Activate_Prio := Get_Priority (Self_ID);
361 Activate_Prio := C.Common.Base_Priority;
365 (C, Task_Wrapper'Address,
367 (C.Common.Compiler_Data.Pri_Stack_Info.Size),
368 Activate_Prio, Success);
370 Self_ID.Common.Wait_Count := Self_ID.Common.Wait_Count + 1;
373 C.Common.State := Runnable;
381 C := C.Common.Activation_Link;
384 Self_ID.Common.State := Activator_Sleep;
386 -- Wait for the activated tasks to complete activation. It is unsafe to
387 -- abort any of these tasks until the count goes to zero.
390 exit when Self_ID.Common.Wait_Count = 0;
391 Sleep (Self_ID, Activator_Sleep);
394 Self_ID.Common.State := Runnable;
401 -- Remove the tasks from the chain
403 Chain_Access.T_ID := null;
404 end Activate_Restricted_Tasks;
406 ------------------------------------
407 -- Complete_Restricted_Activation --
408 ------------------------------------
410 -- As in several other places, the locks of the activator and activated
411 -- task are both locked here. This follows our deadlock prevention lock
412 -- ordering policy, since the activated task must be created after the
415 procedure Complete_Restricted_Activation is
416 Self_ID : constant Task_Id := STPO.Self;
417 Activator : constant Task_Id := Self_ID.Common.Activator;
424 Write_Lock (Activator);
425 Write_Lock (Self_ID);
427 -- Remove dangling reference to Activator, since a task may outlive its
430 Self_ID.Common.Activator := null;
432 -- Wake up the activator, if it is waiting for a chain of tasks to
433 -- activate, and we are the last in the chain to complete activation
435 if Activator.Common.State = Activator_Sleep then
436 Activator.Common.Wait_Count := Activator.Common.Wait_Count - 1;
438 if Activator.Common.Wait_Count = 0 then
439 Wakeup (Activator, Activator_Sleep);
450 -- After the activation, active priority should be the same as base
451 -- priority. We must unlock the Activator first, though, since it should
452 -- not wait if we have lower priority.
454 if Get_Priority (Self_ID) /= Self_ID.Common.Base_Priority then
455 Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
457 end Complete_Restricted_Activation;
459 ------------------------------
460 -- Complete_Restricted_Task --
461 ------------------------------
463 procedure Complete_Restricted_Task is
465 STPO.Self.Common.State := Terminated;
466 end Complete_Restricted_Task;
468 ----------------------------
469 -- Create_Restricted_Task --
470 ----------------------------
472 procedure Create_Restricted_Task
474 Stack_Address : System.Address;
475 Size : System.Parameters.Size_Type;
476 Task_Info : System.Task_Info.Task_Info_Type;
477 State : Task_Procedure_Access;
478 Discriminants : System.Address;
479 Elaborated : Access_Boolean;
480 Chain : in out Activation_Chain;
482 Created_Task : Task_Id)
484 Self_ID : constant Task_Id := STPO.Self;
485 Base_Priority : System.Any_Priority;
490 -- Stack is not preallocated on this target, so that Stack_Address must
493 pragma Assert (Stack_Address = Null_Address);
495 if Priority = Unspecified_Priority then
496 Base_Priority := Self_ID.Common.Base_Priority;
498 Base_Priority := System.Any_Priority (Priority);
505 Write_Lock (Self_ID);
507 -- With no task hierarchy, the parent of all non-Environment tasks that
508 -- are created must be the Environment task
511 (Self_ID, State, Discriminants, Self_ID, Elaborated, Base_Priority,
512 Task_Info, Size, Created_Task, Success);
514 -- If we do our job right then there should never be any failures, which
515 -- was probably said about the Titanic; so just to be safe, let's retain
528 Created_Task.Entry_Calls (1).Self := Created_Task;
531 Integer'Min (Created_Task.Common.Task_Image'Length, Task_Image'Length);
532 Created_Task.Common.Task_Image_Len := Len;
533 Created_Task.Common.Task_Image (1 .. Len) :=
534 Task_Image (Task_Image'First .. Task_Image'First + Len - 1);
542 -- Create TSD as early as possible in the creation of a task, since it
543 -- may be used by the operation of Ada code within the task.
545 SSL.Create_TSD (Created_Task.Common.Compiler_Data);
546 Created_Task.Common.Activation_Link := Chain.T_ID;
547 Chain.T_ID := Created_Task;
548 end Create_Restricted_Task;
550 ---------------------------
551 -- Finalize_Global_Tasks --
552 ---------------------------
554 -- This is needed to support the compiler interface; it will only be called
555 -- by the Environment task. Instead, it will cause the Environment to block
556 -- forever, since none of the dependent tasks are expected to terminate
558 procedure Finalize_Global_Tasks is
559 Self_ID : constant Task_Id := STPO.Self;
562 pragma Assert (Self_ID = STPO.Environment_Task);
568 -- Handle normal task termination by the environment task, but only for
569 -- the normal task termination. In the case of Abnormal and
570 -- Unhandled_Exception they must have been handled before, and the task
571 -- termination soft link must have been changed so the task termination
572 -- routine is not executed twice.
574 -- Note that in the "normal" implementation in s-tassta.adb the task
575 -- termination procedure for the environment task should be executed
576 -- after termination of library-level tasks. However, this
577 -- implementation is to be used when the Ravenscar restrictions are in
578 -- effect, and AI-394 says that if there is a fall-back handler set for
579 -- the partition it should be called when the first task (including the
580 -- environment task) attempts to terminate.
582 SSL.Task_Termination_Handler.all (Ada.Exceptions.Null_Occurrence);
584 Write_Lock (Self_ID);
585 Sleep (Self_ID, Master_Completion_Sleep);
592 -- Should never return from Master Completion Sleep
595 end Finalize_Global_Tasks;
597 ---------------------------
598 -- Restricted_Terminated --
599 ---------------------------
601 function Restricted_Terminated (T : Task_Id) return Boolean is
603 return T.Common.State = Terminated;
604 end Restricted_Terminated;
610 procedure Terminate_Task (Self_ID : Task_Id) is
612 Self_ID.Common.State := Terminated;
619 procedure Init_RTS is
623 -- Initialize lock used to implement mutual exclusion between all tasks
625 STPO.Initialize_Lock (Global_Task_Lock'Access, STPO.Global_Task_Level);
627 -- Notify that the tasking run time has been elaborated so that
628 -- the tasking version of the soft links can be used.
630 SSL.Lock_Task := Task_Lock'Access;
631 SSL.Unlock_Task := Task_Unlock'Access;
632 SSL.Adafinal := Finalize_Global_Tasks'Access;
633 SSL.Get_Current_Excep := Get_Current_Excep'Access;
635 -- Initialize the tasking soft links (if not done yet) that are common
636 -- to the full and the restricted run times.
638 SSL.Tasking.Init_Tasking_Soft_Links;
643 end System.Tasking.Restricted.Stages;