1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- 4-- -- 5-- S Y S T E M . T A S K I N G -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2015, Free Software Foundation, Inc. -- 10-- -- 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. -- 17-- -- 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. -- 21-- -- 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/>. -- 26-- -- 27-- GNARL was developed by the GNARL team at Florida State University. -- 28-- Extensive contributions were provided by Ada Core Technologies, Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This package provides necessary type definitions for compiler interface 33 34-- Note: the compiler generates direct calls to this interface, via Rtsfind. 35-- Any changes to this interface may require corresponding compiler changes. 36 37with Ada.Exceptions; 38with Ada.Unchecked_Conversion; 39 40with System.Parameters; 41with System.Task_Info; 42with System.Soft_Links; 43with System.Task_Primitives; 44with System.Stack_Usage; 45with System.Multiprocessors; 46 47package System.Tasking is 48 pragma Preelaborate; 49 50 ------------------- 51 -- Locking Rules -- 52 ------------------- 53 54 -- The following rules must be followed at all times, to prevent 55 -- deadlock and generally ensure correct operation of locking. 56 57 -- Never lock a lock unless abort is deferred 58 59 -- Never undefer abort while holding a lock 60 61 -- Overlapping critical sections must be properly nested, and locks must 62 -- be released in LIFO order. E.g., the following is not allowed: 63 64 -- Lock (X); 65 -- ... 66 -- Lock (Y); 67 -- ... 68 -- Unlock (X); 69 -- ... 70 -- Unlock (Y); 71 72 -- Locks with lower (smaller) level number cannot be locked 73 -- while holding a lock with a higher level number. (The level 74 75 -- 1. System.Tasking.PO_Simple.Protection.L (any PO lock) 76 -- 2. System.Tasking.Initialization.Global_Task_Lock (in body) 77 -- 3. System.Task_Primitives.Operations.Single_RTS_Lock 78 -- 4. System.Tasking.Ada_Task_Control_Block.LL.L (any TCB lock) 79 80 -- Clearly, there can be no circular chain of hold-and-wait 81 -- relationships involving locks in different ordering levels. 82 83 -- We used to have Global_Task_Lock before Protection.L but this was 84 -- clearly wrong since there can be calls to "new" inside protected 85 -- operations. The new ordering prevents these failures. 86 87 -- Sometimes we need to hold two ATCB locks at the same time. To allow us 88 -- to order the locking, each ATCB is given a unique serial number. If one 89 -- needs to hold locks on two ATCBs at once, the lock with lower serial 90 -- number must be locked first. We avoid holding three or more ATCB locks, 91 -- because that can easily lead to complications that cause race conditions 92 -- and deadlocks. 93 94 -- We don't always need to check the serial numbers, since the serial 95 -- numbers are assigned sequentially, and so: 96 97 -- . The parent of a task always has a lower serial number. 98 -- . The activator of a task always has a lower serial number. 99 -- . The environment task has a lower serial number than any other task. 100 -- . If the activator of a task is different from the task's parent, 101 -- the parent always has a lower serial number than the activator. 102 103 --------------------------------- 104 -- Task_Id related definitions -- 105 --------------------------------- 106 107 type Ada_Task_Control_Block; 108 109 type Task_Id is access all Ada_Task_Control_Block; 110 for Task_Id'Size use System.Task_Primitives.Task_Address_Size; 111 112 Null_Task : constant Task_Id; 113 114 type Task_List is array (Positive range <>) of Task_Id; 115 116 function Self return Task_Id; 117 pragma Inline (Self); 118 -- This is the compiler interface version of this function. Do not call 119 -- from the run-time system. 120 121 function To_Task_Id is 122 new Ada.Unchecked_Conversion 123 (System.Task_Primitives.Task_Address, Task_Id); 124 function To_Address is 125 new Ada.Unchecked_Conversion 126 (Task_Id, System.Task_Primitives.Task_Address); 127 128 ----------------------- 129 -- Enumeration types -- 130 ----------------------- 131 132 type Task_States is 133 (Unactivated, 134 -- TCB initialized but not task has not been created. 135 -- It cannot be executing. 136 137-- Activating, 138-- -- ??? Temporarily at end of list for GDB compatibility 139-- -- Task has been created and is being made Runnable. 140 141 -- Active states 142 -- For all states from here down, the task has been activated. 143 -- For all states from here down, except for Terminated, the task 144 -- may be executing. 145 -- Activator = null iff it has not yet completed activating. 146 147 Runnable, 148 -- Task is not blocked for any reason known to Ada. 149 -- (It may be waiting for a mutex, though.) 150 -- It is conceptually "executing" in normal mode. 151 152 Terminated, 153 -- The task is terminated, in the sense of ARM 9.3 (5). 154 -- Any dependents that were waiting on terminate 155 -- alternatives have been awakened and have terminated themselves. 156 157 Activator_Sleep, 158 -- Task is waiting for created tasks to complete activation 159 160 Acceptor_Sleep, 161 -- Task is waiting on an accept or select with terminate 162 163-- Acceptor_Delay_Sleep, 164-- -- ??? Temporarily at end of list for GDB compatibility 165-- -- Task is waiting on an selective wait statement 166 167 Entry_Caller_Sleep, 168 -- Task is waiting on an entry call 169 170 Async_Select_Sleep, 171 -- Task is waiting to start the abortable part of an 172 -- asynchronous select statement. 173 174 Delay_Sleep, 175 -- Task is waiting on a select statement with only a delay 176 -- alternative open. 177 178 Master_Completion_Sleep, 179 -- Master completion has two phases. 180 -- In Phase 1 the task is sleeping in Complete_Master 181 -- having completed a master within itself, 182 -- and is waiting for the tasks dependent on that master to become 183 -- terminated or waiting on a terminate Phase. 184 185 Master_Phase_2_Sleep, 186 -- In Phase 2 the task is sleeping in Complete_Master 187 -- waiting for tasks on terminate alternatives to finish 188 -- terminating. 189 190 -- The following are special uses of sleep, for server tasks 191 -- within the run-time system. 192 193 Interrupt_Server_Idle_Sleep, 194 Interrupt_Server_Blocked_Interrupt_Sleep, 195 Timer_Server_Sleep, 196 AST_Server_Sleep, 197 198 Asynchronous_Hold, 199 -- The task has been held by Asynchronous_Task_Control.Hold_Task 200 201 Interrupt_Server_Blocked_On_Event_Flag, 202 -- The task has been blocked on a system call waiting for a 203 -- completion event/signal to occur. 204 205 Activating, 206 -- Task has been created and is being made Runnable 207 208 Acceptor_Delay_Sleep 209 -- Task is waiting on an selective wait statement 210 ); 211 212 type Call_Modes is 213 (Simple_Call, Conditional_Call, Asynchronous_Call, Timed_Call); 214 215 type Select_Modes is (Simple_Mode, Else_Mode, Terminate_Mode, Delay_Mode); 216 217 subtype Delay_Modes is Integer; 218 219 ------------------------------- 220 -- Entry related definitions -- 221 ------------------------------- 222 223 Null_Entry : constant := 0; 224 225 Max_Entry : constant := Integer'Last; 226 227 Interrupt_Entry : constant := -2; 228 229 Cancelled_Entry : constant := -1; 230 231 type Entry_Index is range Interrupt_Entry .. Max_Entry; 232 233 Null_Task_Entry : constant := Null_Entry; 234 235 Max_Task_Entry : constant := Max_Entry; 236 237 type Task_Entry_Index is new Entry_Index 238 range Null_Task_Entry .. Max_Task_Entry; 239 240 type Entry_Call_Record; 241 242 type Entry_Call_Link is access all Entry_Call_Record; 243 244 type Entry_Queue is record 245 Head : Entry_Call_Link; 246 Tail : Entry_Call_Link; 247 end record; 248 249 type Task_Entry_Queue_Array is 250 array (Task_Entry_Index range <>) of Entry_Queue; 251 252 -- A data structure which contains the string names of entries and entry 253 -- family members. 254 255 type String_Access is access all String; 256 257 type Task_Entry_Names_Array is 258 array (Entry_Index range <>) of String_Access; 259 260 type Task_Entry_Names_Access is access all Task_Entry_Names_Array; 261 262 ---------------------------------- 263 -- Entry_Call_Record definition -- 264 ---------------------------------- 265 266 type Entry_Call_State is 267 (Never_Abortable, 268 -- the call is not abortable, and never can be 269 270 Not_Yet_Abortable, 271 -- the call is not abortable, but may become so 272 273 Was_Abortable, 274 -- the call is not abortable, but once was 275 276 Now_Abortable, 277 -- the call is abortable 278 279 Done, 280 -- the call has been completed 281 282 Cancelled 283 -- the call was asynchronous, and was cancelled 284 ); 285 pragma Ordered (Entry_Call_State); 286 287 -- Never_Abortable is used for calls that are made in a abort deferred 288 -- region (see ARM 9.8(5-11), 9.8 (20)). Such a call is never abortable. 289 290 -- The Was_ vs. Not_Yet_ distinction is needed to decide whether it is OK 291 -- to advance into the abortable part of an async. select stmt. That is 292 -- allowed iff the mode is Now_ or Was_. 293 294 -- Done indicates the call has been completed, without cancellation, or no 295 -- call has been made yet at this ATC nesting level, and so aborting the 296 -- call is no longer an issue. Completion of the call does not necessarily 297 -- indicate "success"; the call may be returning an exception if 298 -- Exception_To_Raise is non-null. 299 300 -- Cancelled indicates the call was cancelled, and so aborting the call is 301 -- no longer an issue. 302 303 -- The call is on an entry queue unless State >= Done, in which case it may 304 -- or may not be still Onqueue. 305 306 -- Please do not modify the order of the values, without checking all uses 307 -- of this type. We rely on partial "monotonicity" of 308 -- Entry_Call_Record.State to avoid locking when we access this value for 309 -- certain tests. In particular: 310 311 -- 1) Once State >= Done, we can rely that the call has been 312 -- completed. If State >= Done, it will not 313 -- change until the task does another entry call at this level. 314 315 -- 2) Once State >= Was_Abortable, we can rely that the call has 316 -- been queued abortably at least once, and so the check for 317 -- whether it is OK to advance to the abortable part of an 318 -- async. select statement does not need to lock anything. 319 320 type Restricted_Entry_Call_Record is record 321 Self : Task_Id; 322 -- ID of the caller 323 324 Mode : Call_Modes; 325 326 State : Entry_Call_State; 327 pragma Atomic (State); 328 -- Indicates part of the state of the call. 329 -- 330 -- Protection: If the call is not on a queue, it should only be 331 -- accessed by Self, and Self does not need any lock to modify this 332 -- field. 333 -- 334 -- Once the call is on a queue, the value should be something other 335 -- than Done unless it is cancelled, and access is controller by the 336 -- "server" of the queue -- i.e., the lock of Checked_To_Protection 337 -- (Call_Target) if the call record is on the queue of a PO, or the 338 -- lock of Called_Target if the call is on the queue of a task. See 339 -- comments on type declaration for more details. 340 341 Uninterpreted_Data : System.Address; 342 -- Data passed by the compiler 343 344 Exception_To_Raise : Ada.Exceptions.Exception_Id; 345 -- The exception to raise once this call has been completed without 346 -- being aborted. 347 end record; 348 pragma Suppress_Initialization (Restricted_Entry_Call_Record); 349 350 ------------------------------------------- 351 -- Task termination procedure definition -- 352 ------------------------------------------- 353 354 -- We need to redefine here these types (already defined in 355 -- Ada.Task_Termination) for avoiding circular dependencies. 356 357 type Cause_Of_Termination is (Normal, Abnormal, Unhandled_Exception); 358 -- Possible causes for task termination: 359 -- 360 -- Normal means that the task terminates due to completing the 361 -- last sentence of its body, or as a result of waiting on a 362 -- terminate alternative. 363 364 -- Abnormal means that the task terminates because it is being aborted 365 366 -- handled_Exception means that the task terminates because of exception 367 -- raised by the execution of its task_body. 368 369 type Termination_Handler is access protected procedure 370 (Cause : Cause_Of_Termination; 371 T : Task_Id; 372 X : Ada.Exceptions.Exception_Occurrence); 373 -- Used to represent protected procedures to be executed when task 374 -- terminates. 375 376 ------------------------------------ 377 -- Dispatching domain definitions -- 378 ------------------------------------ 379 380 -- We need to redefine here these types (already defined in 381 -- System.Multiprocessor.Dispatching_Domains) for avoiding circular 382 -- dependencies. 383 384 type Dispatching_Domain is 385 array (System.Multiprocessors.CPU range <>) of Boolean; 386 -- A dispatching domain needs to contain the set of processors belonging 387 -- to it. This is a processor mask where a True indicates that the 388 -- processor belongs to the dispatching domain. 389 -- Do not use the full range of CPU_Range because it would create a very 390 -- long array. This way we can use the exact range of processors available 391 -- in the system. 392 393 type Dispatching_Domain_Access is access Dispatching_Domain; 394 395 System_Domain : Dispatching_Domain_Access; 396 -- All processors belong to default system dispatching domain at start up. 397 -- We use a pointer which creates the actual variable for the reasons 398 -- explained bellow in Dispatching_Domain_Tasks. 399 400 Dispatching_Domains_Frozen : Boolean := False; 401 -- True when the main procedure has been called. Hence, no new dispatching 402 -- domains can be created when this flag is True. 403 404 type Array_Allocated_Tasks is 405 array (System.Multiprocessors.CPU range <>) of Natural; 406 -- At start-up time, we need to store the number of tasks attached to 407 -- concrete processors within the system domain (we can only create 408 -- dispatching domains with processors belonging to the system domain and 409 -- without tasks allocated). 410 411 type Array_Allocated_Tasks_Access is access Array_Allocated_Tasks; 412 413 Dispatching_Domain_Tasks : Array_Allocated_Tasks_Access; 414 -- We need to store whether there are tasks allocated to concrete 415 -- processors in the default system dispatching domain because we need to 416 -- check it before creating a new dispatching domain. Two comments about 417 -- why we use a pointer here and not in package Dispatching_Domains: 418 -- 419 -- 1) We use an array created dynamically in procedure Initialize which 420 -- is called at the beginning of the initialization of the run-time 421 -- library. Declaring a static array here in the spec would not work 422 -- across different installations because it would get the value of 423 -- Number_Of_CPUs from the machine where the run-time library is built, 424 -- and not from the machine where the application is executed. That is 425 -- the reason why we create the array (CPU'First .. Number_Of_CPUs) at 426 -- execution time in the procedure body, ensuring that the function 427 -- Number_Of_CPUs is executed at execution time (the same trick as we 428 -- use for System_Domain). 429 -- 430 -- 2) We have moved this declaration from package Dispatching_Domains 431 -- because when we use a pragma CPU, the affinity is passed through the 432 -- call to Create_Task. Hence, at this point, we may need to update the 433 -- number of tasks associated to the processor, but we do not want to 434 -- force a dependency from this package on Dispatching_Domains. 435 436 ------------------------------------ 437 -- Task related other definitions -- 438 ------------------------------------ 439 440 type Activation_Chain is limited private; 441 -- Linked list of to-be-activated tasks, linked through 442 -- Activation_Link. The order of tasks on the list is irrelevant, because 443 -- the priority rules will ensure that they actually start activating in 444 -- priority order. 445 446 type Activation_Chain_Access is access all Activation_Chain; 447 448 type Task_Procedure_Access is access procedure (Arg : System.Address); 449 450 type Access_Boolean is access all Boolean; 451 452 function Detect_Blocking return Boolean; 453 pragma Inline (Detect_Blocking); 454 -- Return whether the Detect_Blocking pragma is enabled 455 456 function Storage_Size (T : Task_Id) return System.Parameters.Size_Type; 457 -- Retrieve from the TCB of the task the allocated size of its stack, 458 -- either the system default or the size specified by a pragma. This is in 459 -- general a non-static value that can depend on discriminants of the task. 460 461 type Bit_Array is array (Integer range <>) of Boolean; 462 pragma Pack (Bit_Array); 463 464 subtype Debug_Event_Array is Bit_Array (1 .. 16); 465 466 Global_Task_Debug_Event_Set : Boolean := False; 467 -- Set True when running under debugger control and a task debug event 468 -- signal has been requested. 469 470 ---------------------------------------------- 471 -- Ada_Task_Control_Block (ATCB) definition -- 472 ---------------------------------------------- 473 474 -- Notes on protection (synchronization) of TRTS data structures 475 476 -- Any field of the TCB can be written by the activator of a task when the 477 -- task is created, since no other task can access the new task's 478 -- state until creation is complete. 479 480 -- The protection for each field is described in a comment starting with 481 -- "Protection:". 482 483 -- When a lock is used to protect an ATCB field, this lock is simply named 484 485 -- Some protection is described in terms of tasks related to the 486 -- ATCB being protected. These are: 487 488 -- Self: The task which is controlled by this ATCB 489 -- Acceptor: A task accepting a call from Self 490 -- Caller: A task calling an entry of Self 491 -- Parent: The task executing the master on which Self depends 492 -- Dependent: A task dependent on Self 493 -- Activator: The task that created Self and initiated its activation 494 -- Created: A task created and activated by Self 495 496 -- Note: The order of the fields is important to implement efficiently 497 -- tasking support under gdb. 498 -- Currently gdb relies on the order of the State, Parent, Base_Priority, 499 -- Task_Image, Task_Image_Len, Call and LL fields. 500 501 ------------------------- 502 -- Common ATCB section -- 503 ------------------------- 504 505 -- Section used by all GNARL implementations (regular and restricted) 506 507 type Common_ATCB is limited record 508 State : Task_States; 509 pragma Atomic (State); 510 -- Encodes some basic information about the state of a task, 511 -- including whether it has been activated, whether it is sleeping, 512 -- and whether it is terminated. 513 -- 514 -- Protection: Self.L 515 516 Parent : Task_Id; 517 -- The task on which this task depends. 518 -- See also Master_Level and Master_Within. 519 520 Base_Priority : System.Any_Priority; 521 -- Base priority, not changed during entry calls, only changed 522 -- via dynamic priorities package. 523 -- 524 -- Protection: Only written by Self, accessed by anyone 525 526 Base_CPU : System.Multiprocessors.CPU_Range; 527 -- Base CPU, only changed via dispatching domains package. 528 -- 529 -- Protection: Self.L 530 531 Current_Priority : System.Any_Priority; 532 -- Active priority, except that the effects of protected object 533 -- priority ceilings are not reflected. This only reflects explicit 534 -- priority changes and priority inherited through task activation 535 -- and rendezvous. 536 -- 537 -- Ada 95 notes: In Ada 95, this field will be transferred to the 538 -- Priority field of an Entry_Calls component when an entry call is 539 -- initiated. The Priority of the Entry_Calls component will not change 540 -- for the duration of the call. The accepting task can use it to boost 541 -- its own priority without fear of its changing in the meantime. 542 -- 543 -- This can safely be used in the priority ordering of entry queues. 544 -- Once a call is queued, its priority does not change. 545 -- 546 -- Since an entry call cannot be made while executing a protected 547 -- action, the priority of a task will never reflect a priority ceiling 548 -- change at the point of an entry call. 549 -- 550 -- Protection: Only written by Self, and only accessed when Acceptor 551 -- accepts an entry or when Created activates, at which points Self is 552 -- suspended. 553 554 Protected_Action_Nesting : Natural; 555 pragma Atomic (Protected_Action_Nesting); 556 -- The dynamic level of protected action nesting for this task. This 557 -- field is needed for checking whether potentially blocking operations 558 -- are invoked from protected actions. pragma Atomic is used because it 559 -- can be read/written from protected interrupt handlers. 560 561 Task_Image : String (1 .. System.Parameters.Max_Task_Image_Length); 562 -- Hold a string that provides a readable id for task, built from the 563 -- variable of which it is a value or component. 564 565 Task_Image_Len : Natural; 566 -- Actual length of Task_Image 567 568 Call : Entry_Call_Link; 569 -- The entry call that has been accepted by this task. 570 -- 571 -- Protection: Self.L. Self will modify this field when Self.Accepting 572 -- is False, and will not need the mutex to do so. Once a task sets 573 -- Pending_ATC_Level = 0, no other task can access this field. 574 575 LL : aliased Task_Primitives.Private_Data; 576 -- Control block used by the underlying low-level tasking service 577 -- (GNULLI). 578 -- 579 -- Protection: This is used only by the GNULLI implementation, which 580 -- takes care of all of its synchronization. 581 582 Task_Arg : System.Address; 583 -- The argument to task procedure. Provide a handle for discriminant 584 -- information. 585 -- 586 -- Protection: Part of the synchronization between Self and Activator. 587 -- Activator writes it, once, before Self starts executing. Thereafter, 588 -- Self only reads it. 589 590 Task_Alternate_Stack : System.Address; 591 -- The address of the alternate signal stack for this task, if any 592 -- 593 -- Protection: Only accessed by Self 594 595 Task_Entry_Point : Task_Procedure_Access; 596 -- Information needed to call the procedure containing the code for 597 -- the body of this task. 598 -- 599 -- Protection: Part of the synchronization between Self and Activator. 600 -- Activator writes it, once, before Self starts executing. Self reads 601 -- it, once, as part of its execution. 602 603 Compiler_Data : System.Soft_Links.TSD; 604 -- Task-specific data needed by the compiler to store per-task 605 -- structures. 606 -- 607 -- Protection: Only accessed by Self 608 609 All_Tasks_Link : Task_Id; 610 -- Used to link this task to the list of all tasks in the system 611 -- 612 -- Protection: RTS_Lock 613 614 Activation_Link : Task_Id; 615 -- Used to link this task to a list of tasks to be activated 616 -- 617 -- Protection: Only used by Activator 618 619 Activator : Task_Id; 620 pragma Atomic (Activator); 621 -- The task that created this task, either by declaring it as a task 622 -- object or by executing a task allocator. The value is null iff Self 623 -- has completed activation. 624 -- 625 -- Protection: Set by Activator before Self is activated, and 626 -- only modified by Self after that. Can be read by any task via 627 -- Ada.Task_Identification.Activation_Is_Complete; hence Atomic. 628 629 Wait_Count : Natural; 630 -- This count is used by a task that is waiting for other tasks. At all 631 -- other times, the value should be zero. It is used differently in 632 -- several different states. Since a task cannot be in more than one of 633 -- these states at the same time, a single counter suffices. 634 -- 635 -- Protection: Self.L 636 637 -- Activator_Sleep 638 639 -- This is the number of tasks that this task is activating, i.e. the 640 -- children that have started activation but have not completed it. 641 -- 642 -- Protection: Self.L and Created.L. Both mutexes must be locked, since 643 -- Self.Activation_Count and Created.State must be synchronized. 644 645 -- Master_Completion_Sleep (phase 1) 646 647 -- This is the number dependent tasks of a master being completed by 648 -- Self that are activated, but have not yet terminated, and are not 649 -- waiting on a terminate alternative. 650 651 -- Master_Completion_2_Sleep (phase 2) 652 653 -- This is the count of tasks dependent on a master being completed by 654 -- Self which are waiting on a terminate alternative. 655 656 Elaborated : Access_Boolean; 657 -- Pointer to a flag indicating that this task's body has been 658 -- elaborated. The flag is created and managed by the 659 -- compiler-generated code. 660 -- 661 -- Protection: The field itself is only accessed by Activator. The flag 662 -- that it points to is updated by Master and read by Activator; access 663 -- is assumed to be atomic. 664 665 Activation_Failed : Boolean; 666 -- Set to True if activation of a chain of tasks fails, 667 -- so that the activator should raise Tasking_Error. 668 669 Task_Info : System.Task_Info.Task_Info_Type; 670 -- System-specific attributes of the task as specified by the 671 -- Task_Info pragma. 672 673 Analyzer : System.Stack_Usage.Stack_Analyzer; 674 -- For storing information used to measure the stack usage 675 676 Global_Task_Lock_Nesting : Natural; 677 -- This is the current nesting level of calls to 678 -- System.Tasking.Initialization.Lock_Task. This allows a task to call 679 -- Lock_Task multiple times without deadlocking. A task only locks 680 -- Global_Task_Lock when its Global_Task_Lock_Nesting goes from 0 to 1, 681 -- and only unlocked when it goes from 1 to 0. 682 -- 683 -- Protection: Only accessed by Self 684 685 Fall_Back_Handler : Termination_Handler; 686 -- This is the fall-back handler that applies to the dependent tasks of 687 -- the task. 688 -- 689 -- Protection: Self.L 690 691 Specific_Handler : Termination_Handler; 692 -- This is the specific handler that applies only to this task, and not 693 -- any of its dependent tasks. 694 -- 695 -- Protection: Self.L 696 697 Debug_Events : Debug_Event_Array; 698 -- Word length array of per task debug events, of which 11 kinds are 699 -- currently defined in System.Tasking.Debugging package. 700 701 Domain : Dispatching_Domain_Access; 702 -- Domain is the dispatching domain to which the task belongs. It is 703 -- only changed via dispatching domains package. This field is made 704 -- part of the Common_ATCB, even when restricted run-times (namely 705 -- Ravenscar) do not use it, because this way the field is always 706 -- available to the underlying layers to set the affinity and we do not 707 -- need to do different things depending on the situation. 708 -- 709 -- Protection: Self.L 710 end record; 711 712 --------------------------------------- 713 -- Restricted_Ada_Task_Control_Block -- 714 --------------------------------------- 715 716 -- This type should only be used by the restricted GNARLI and by restricted 717 -- GNULL implementations to allocate an ATCB (see System.Task_Primitives. 718 -- Operations.New_ATCB) that will take significantly less memory. 719 720 -- Note that the restricted GNARLI should only access fields that are 721 -- present in the Restricted_Ada_Task_Control_Block structure. 722 723 type Restricted_Ada_Task_Control_Block (Entry_Num : Task_Entry_Index) is 724 limited record 725 Common : Common_ATCB; 726 -- The common part between various tasking implementations 727 728 Entry_Call : aliased Restricted_Entry_Call_Record; 729 -- Protection: This field is used on entry call "queues" associated 730 -- with protected objects, and is protected by the protected object 731 -- lock. 732 end record; 733 pragma Suppress_Initialization (Restricted_Ada_Task_Control_Block); 734 735 Interrupt_Manager_ID : Task_Id; 736 -- This task ID is declared here to break circular dependencies. 737 -- Also declare Interrupt_Manager_ID after Task_Id is known, to avoid 738 -- generating unneeded finalization code. 739 740 ----------------------- 741 -- List of all Tasks -- 742 ----------------------- 743 744 All_Tasks_List : Task_Id; 745 -- Global linked list of all tasks 746 747 ------------------------------------------ 748 -- Regular (non restricted) definitions -- 749 ------------------------------------------ 750 751 -------------------------------- 752 -- Master Related Definitions -- 753 -------------------------------- 754 755 subtype Master_Level is Integer; 756 subtype Master_ID is Master_Level; 757 758 -- Normally, a task starts out with internal master nesting level one 759 -- larger than external master nesting level. It is incremented by one by 760 -- Enter_Master, which is called in the task body only if the compiler 761 -- thinks the task may have dependent tasks. It is set to 1 for the 762 -- environment task, the level 2 is reserved for server tasks of the 763 -- run-time system (the so called "independent tasks"), and the level 3 is 764 -- for the library level tasks. Foreign threads which are detected by 765 -- the run-time have a level of 0, allowing these tasks to be easily 766 -- distinguished if needed. 767 768 Foreign_Task_Level : constant Master_Level := 0; 769 Environment_Task_Level : constant Master_Level := 1; 770 Independent_Task_Level : constant Master_Level := 2; 771 Library_Task_Level : constant Master_Level := 3; 772 773 ------------------- 774 -- Priority info -- 775 ------------------- 776 777 Unspecified_Priority : constant Integer := System.Priority'First - 1; 778 779 Priority_Not_Boosted : constant Integer := System.Priority'First - 1; 780 -- Definition of Priority actually has to come from the RTS configuration 781 782 subtype Rendezvous_Priority is Integer 783 range Priority_Not_Boosted .. System.Any_Priority'Last; 784 785 ------------------- 786 -- Affinity info -- 787 ------------------- 788 789 Unspecified_CPU : constant := -1; 790 -- No affinity specified 791 792 ------------------------------------ 793 -- Rendezvous related definitions -- 794 ------------------------------------ 795 796 No_Rendezvous : constant := 0; 797 798 Max_Select : constant Integer := Integer'Last; 799 -- RTS-defined 800 801 subtype Select_Index is Integer range No_Rendezvous .. Max_Select; 802 -- type Select_Index is range No_Rendezvous .. Max_Select; 803 804 subtype Positive_Select_Index is 805 Select_Index range 1 .. Select_Index'Last; 806 807 type Accept_Alternative is record 808 Null_Body : Boolean; 809 S : Task_Entry_Index; 810 end record; 811 812 type Accept_List is 813 array (Positive_Select_Index range <>) of Accept_Alternative; 814 815 type Accept_List_Access is access constant Accept_List; 816 817 ----------------------------------- 818 -- ATC_Level related definitions -- 819 ----------------------------------- 820 821 Max_ATC_Nesting : constant Natural := 20; 822 823 subtype ATC_Level_Base is Integer range 0 .. Max_ATC_Nesting; 824 825 ATC_Level_Infinity : constant ATC_Level_Base := ATC_Level_Base'Last; 826 827 subtype ATC_Level is ATC_Level_Base range 0 .. ATC_Level_Base'Last - 1; 828 829 subtype ATC_Level_Index is ATC_Level range 1 .. ATC_Level'Last; 830 831 ---------------------------------- 832 -- Entry_Call_Record definition -- 833 ---------------------------------- 834 835 type Entry_Call_Record is record 836 Self : Task_Id; 837 -- ID of the caller 838 839 Mode : Call_Modes; 840 841 State : Entry_Call_State; 842 pragma Atomic (State); 843 -- Indicates part of the state of the call 844 -- 845 -- Protection: If the call is not on a queue, it should only be 846 -- accessed by Self, and Self does not need any lock to modify this 847 -- field. Once the call is on a queue, the value should be something 848 -- other than Done unless it is cancelled, and access is controller by 849 -- the "server" of the queue -- i.e., the lock of Checked_To_Protection 850 -- (Call_Target) if the call record is on the queue of a PO, or the 851 -- lock of Called_Target if the call is on the queue of a task. See 852 -- comments on type declaration for more details. 853 854 Uninterpreted_Data : System.Address; 855 -- Data passed by the compiler 856 857 Exception_To_Raise : Ada.Exceptions.Exception_Id; 858 -- The exception to raise once this call has been completed without 859 -- being aborted. 860 861 Prev : Entry_Call_Link; 862 863 Next : Entry_Call_Link; 864 865 Level : ATC_Level; 866 -- One of Self and Level are redundant in this implementation, since 867 -- each Entry_Call_Record is at Self.Entry_Calls (Level). Since we must 868 -- have access to the entry call record to be reading this, we could 869 -- get Self from Level, or Level from Self. However, this requires 870 -- non-portable address arithmetic. 871 872 E : Entry_Index; 873 874 Prio : System.Any_Priority; 875 876 -- The above fields are those that there may be some hope of packing. 877 -- They are gathered together to allow for compilers that lay records 878 -- out contiguously, to allow for such packing. 879 880 Called_Task : Task_Id; 881 pragma Atomic (Called_Task); 882 -- Use for task entry calls. The value is null if the call record is 883 -- not in use. Conversely, unless State is Done and Onqueue is false, 884 -- Called_Task points to an ATCB. 885 -- 886 -- Protection: Called_Task.L 887 888 Called_PO : System.Address; 889 pragma Atomic (Called_PO); 890 -- Similar to Called_Task but for protected objects 891 -- 892 -- Note that the previous implementation tried to merge both 893 -- Called_Task and Called_PO but this ended up in many unexpected 894 -- complications (e.g having to add a magic number in the ATCB, which 895 -- caused gdb lots of confusion) with no real gain since the 896 -- Lock_Server implementation still need to loop around chasing for 897 -- pointer changes even with a single pointer. 898 899 Acceptor_Prev_Call : Entry_Call_Link; 900 -- For task entry calls only 901 902 Acceptor_Prev_Priority : Rendezvous_Priority := Priority_Not_Boosted; 903 -- For task entry calls only. The priority of the most recent prior 904 -- call being serviced. For protected entry calls, this function should 905 -- be performed by GNULLI ceiling locking. 906 907 Cancellation_Attempted : Boolean := False; 908 pragma Atomic (Cancellation_Attempted); 909 -- Cancellation of the call has been attempted. 910 -- Consider merging this into State??? 911 912 With_Abort : Boolean := False; 913 -- Tell caller whether the call may be aborted 914 -- ??? consider merging this with Was_Abortable state 915 916 Needs_Requeue : Boolean := False; 917 -- Temporary to tell acceptor of task entry call that 918 -- Exceptional_Complete_Rendezvous needs to do requeue. 919 end record; 920 921 ------------------------------------ 922 -- Task related other definitions -- 923 ------------------------------------ 924 925 type Access_Address is access all System.Address; 926 -- Anonymous pointer used to implement task attributes (see s-tataat.adb 927 -- and a-tasatt.adb) 928 929 pragma No_Strict_Aliasing (Access_Address); 930 -- This type is used in contexts where aliasing may be an issue (see 931 -- for example s-tataat.adb), so we avoid any incorrect aliasing 932 -- assumptions. 933 934 ---------------------------------------------- 935 -- Ada_Task_Control_Block (ATCB) definition -- 936 ---------------------------------------------- 937 938 type Entry_Call_Array is array (ATC_Level_Index) of 939 aliased Entry_Call_Record; 940 941 type Atomic_Address is mod Memory_Size; 942 pragma Atomic (Atomic_Address); 943 type Attribute_Array is 944 array (1 .. Parameters.Max_Attribute_Count) of Atomic_Address; 945 -- Array of task attributes. The value (Atomic_Address) will either be 946 -- converted to a task attribute if it fits, or to a pointer to a record 947 -- by Ada.Task_Attributes. 948 949 type Task_Serial_Number is mod 2 ** Long_Long_Integer'Size; 950 -- Used to give each task a unique serial number. We want 64-bits for this 951 -- type to get as much uniqueness as possible (2**64 is operationally 952 -- infinite in this context, but 2**32 perhaps could recycle). We use 953 -- Long_Long_Integer (which in the normal case is always 64-bits) rather 954 -- than 64-bits explicitly to allow codepeer to analyze this unit when 955 -- a target configuration file forces the maximum integer size to 32. 956 957 type Ada_Task_Control_Block (Entry_Num : Task_Entry_Index) is limited record 958 Common : Common_ATCB; 959 -- The common part between various tasking implementations 960 961 Entry_Calls : Entry_Call_Array; 962 -- An array of entry calls 963 -- 964 -- Protection: The elements of this array are on entry call queues 965 -- associated with protected objects or task entries, and are protected 966 -- by the protected object lock or Acceptor.L, respectively. 967 968 Entry_Names : Task_Entry_Names_Access := null; 969 -- An array of string names which denotes entry [family member] names. 970 -- The structure is indexed by task entry index and contains Entry_Num 971 -- components. 972 -- 973 -- Protection: The array is populated during task initialization, before 974 -- the task has been activated. No protection is required in this case. 975 976 New_Base_Priority : System.Any_Priority; 977 -- New value for Base_Priority (for dynamic priorities package) 978 -- 979 -- Protection: Self.L 980 981 Open_Accepts : Accept_List_Access; 982 -- This points to the Open_Accepts array of accept alternatives passed 983 -- to the RTS by the compiler-generated code to Selective_Wait. It is 984 -- non-null iff this task is ready to accept an entry call. 985 -- 986 -- Protection: Self.L 987 988 Chosen_Index : Select_Index; 989 -- The index in Open_Accepts of the entry call accepted by a selective 990 -- wait executed by this task. 991 -- 992 -- Protection: Written by both Self and Caller. Usually protected by 993 -- Self.L. However, once the selection is known to have been written it 994 -- can be accessed without protection. This happens after Self has 995 -- updated it itself using information from a suspended Caller, or 996 -- after Caller has updated it and awakened Self. 997 998 Master_of_Task : Master_Level; 999 -- The task executing the master of this task, and the ID of this task's 1000 -- master (unique only among masters currently active within Parent). 1001 -- 1002 -- Protection: Set by Activator before Self is activated, and read 1003 -- after Self is activated. 1004 1005 Master_Within : Master_Level; 1006 -- The ID of the master currently executing within this task; that is, 1007 -- the most deeply nested currently active master. 1008 -- 1009 -- Protection: Only written by Self, and only read by Self or by 1010 -- dependents when Self is attempting to exit a master. Since Self will 1011 -- not write this field until the master is complete, the 1012 -- synchronization should be adequate to prevent races. 1013 1014 Alive_Count : Natural := 0; 1015 -- Number of tasks directly dependent on this task (including itself) 1016 -- that are still "alive", i.e. not terminated. 1017 -- 1018 -- Protection: Self.L 1019 1020 Awake_Count : Natural := 0; 1021 -- Number of tasks directly dependent on this task (including itself) 1022 -- still "awake", i.e., are not terminated and not waiting on a 1023 -- terminate alternative. 1024 -- 1025 -- Invariant: Awake_Count <= Alive_Count 1026 1027 -- Protection: Self.L 1028 1029 -- Beginning of flags 1030 1031 Aborting : Boolean := False; 1032 pragma Atomic (Aborting); 1033 -- Self is in the process of aborting. While set, prevents multiple 1034 -- abort signals from being sent by different aborter while abort 1035 -- is acted upon. This is essential since an aborter which calls 1036 -- Abort_To_Level could set the Pending_ATC_Level to yet a lower level 1037 -- (than the current level), may be preempted and would send the 1038 -- abort signal when resuming execution. At this point, the abortee 1039 -- may have completed abort to the proper level such that the 1040 -- signal (and resulting abort exception) are not handled any more. 1041 -- In other words, the flag prevents a race between multiple aborters 1042 -- 1043 -- Protection: protected by atomic access. 1044 1045 ATC_Hack : Boolean := False; 1046 pragma Atomic (ATC_Hack); 1047 -- ????? 1048 -- Temporary fix, to allow Undefer_Abort to reset Aborting in the 1049 -- handler for Abort_Signal that encloses an async. entry call. 1050 -- For the longer term, this should be done via code in the 1051 -- handler itself. 1052 1053 Callable : Boolean := True; 1054 -- It is OK to call entries of this task 1055 1056 Dependents_Aborted : Boolean := False; 1057 -- This is set to True by whichever task takes responsibility for 1058 -- aborting the dependents of this task. 1059 -- 1060 -- Protection: Self.L 1061 1062 Interrupt_Entry : Boolean := False; 1063 -- Indicates if one or more Interrupt Entries are attached to the task. 1064 -- This flag is needed for cleaning up the Interrupt Entry bindings. 1065 1066 Pending_Action : Boolean := False; 1067 -- Unified flag indicating some action needs to be take when abort 1068 -- next becomes undeferred. Currently set if: 1069 -- . Pending_Priority_Change is set 1070 -- . Pending_ATC_Level is changed 1071 -- . Requeue involving POs 1072 -- (Abortable field may have changed and the Wait_Until_Abortable 1073 -- has to recheck the abortable status of the call.) 1074 -- . Exception_To_Raise is non-null 1075 -- 1076 -- Protection: Self.L 1077 -- 1078 -- This should never be reset back to False outside of the procedure 1079 -- Do_Pending_Action, which is called by Undefer_Abort. It should only 1080 -- be set to True by Set_Priority and Abort_To_Level. 1081 1082 Pending_Priority_Change : Boolean := False; 1083 -- Flag to indicate pending priority change (for dynamic priorities 1084 -- package). The base priority is updated on the next abort 1085 -- completion point (aka. synchronization point). 1086 -- 1087 -- Protection: Self.L 1088 1089 Terminate_Alternative : Boolean := False; 1090 -- Task is accepting Select with Terminate Alternative 1091 -- 1092 -- Protection: Self.L 1093 1094 -- End of flags 1095 1096 -- Beginning of counts 1097 1098 ATC_Nesting_Level : ATC_Level := 1; 1099 -- The dynamic level of ATC nesting (currently executing nested 1100 -- asynchronous select statements) in this task. 1101 1102 -- Protection: Self_ID.L. Only Self reads or updates this field. 1103 -- Decrementing it deallocates an Entry_Calls component, and care must 1104 -- be taken that all references to that component are eliminated before 1105 -- doing the decrement. This in turn will require locking a protected 1106 -- object (for a protected entry call) or the Acceptor's lock (for a 1107 -- task entry call). No other task should attempt to read or modify 1108 -- this value. 1109 1110 Deferral_Level : Natural := 1; 1111 -- This is the number of times that Defer_Abort has been called by 1112 -- this task without a matching Undefer_Abort call. Abortion is only 1113 -- allowed when this zero. It is initially 1, to protect the task at 1114 -- startup. 1115 1116 -- Protection: Only updated by Self; access assumed to be atomic 1117 1118 Pending_ATC_Level : ATC_Level_Base := ATC_Level_Infinity; 1119 -- The ATC level to which this task is currently being aborted. If the 1120 -- value is zero, the entire task has "completed". That may be via 1121 -- abort, exception propagation, or normal exit. If the value is 1122 -- ATC_Level_Infinity, the task is not being aborted to any level. If 1123 -- the value is positive, the task has not completed. This should ONLY 1124 -- be modified by Abort_To_Level and Exit_One_ATC_Level. 1125 -- 1126 -- Protection: Self.L 1127 1128 Serial_Number : Task_Serial_Number; 1129 -- Monotonic counter to provide some way to check locking rules/ordering 1130 1131 Known_Tasks_Index : Integer := -1; 1132 -- Index in the System.Tasking.Debug.Known_Tasks array 1133 1134 User_State : Long_Integer := 0; 1135 -- User-writeable location, for use in debugging tasks; also provides a 1136 -- simple task specific data. 1137 1138 Free_On_Termination : Boolean := False; 1139 -- Deallocate the ATCB when the task terminates. This flag is normally 1140 -- False, and is set True when Unchecked_Deallocation is called on a 1141 -- non-terminated task so that the associated storage is automatically 1142 -- reclaimed when the task terminates. 1143 1144 Attributes : Attribute_Array := (others => 0); 1145 -- Task attributes 1146 1147 -- IMPORTANT Note: the Entry_Queues field is last for efficiency of 1148 -- access to other fields, do not put new fields after this one. 1149 1150 Entry_Queues : Task_Entry_Queue_Array (1 .. Entry_Num); 1151 -- An array of task entry queues 1152 -- 1153 -- Protection: Self.L. Once a task has set Self.Stage to Completing, it 1154 -- has exclusive access to this field. 1155 end record; 1156 1157 -------------------- 1158 -- Initialization -- 1159 -------------------- 1160 1161 procedure Initialize; 1162 -- This procedure constitutes the first part of the initialization of the 1163 -- GNARL. This includes creating data structures to make the initial thread 1164 -- into the environment task. The last part of the initialization is done 1165 -- in System.Tasking.Initialization or System.Tasking.Restricted.Stages. 1166 -- All the initializations used to be in Tasking.Initialization, but this 1167 -- is no longer possible with the run time simplification (including 1168 -- optimized PO and the restricted run time) since one cannot rely on 1169 -- System.Tasking.Initialization being present, as was done before. 1170 1171 procedure Initialize_ATCB 1172 (Self_ID : Task_Id; 1173 Task_Entry_Point : Task_Procedure_Access; 1174 Task_Arg : System.Address; 1175 Parent : Task_Id; 1176 Elaborated : Access_Boolean; 1177 Base_Priority : System.Any_Priority; 1178 Base_CPU : System.Multiprocessors.CPU_Range; 1179 Domain : Dispatching_Domain_Access; 1180 Task_Info : System.Task_Info.Task_Info_Type; 1181 Stack_Size : System.Parameters.Size_Type; 1182 T : Task_Id; 1183 Success : out Boolean); 1184 -- Initialize fields of the TCB for task T, and link into global TCB 1185 -- structures. Call this only with abort deferred and holding RTS_Lock. 1186 -- Self_ID is the calling task (normally the activator of T). Success is 1187 -- set to indicate whether the TCB was successfully initialized. 1188 1189private 1190 1191 Null_Task : constant Task_Id := null; 1192 1193 type Activation_Chain is limited record 1194 T_ID : Task_Id; 1195 end record; 1196 1197 -- Activation_Chain is an in-out parameter of initialization procedures and 1198 -- it must be passed by reference because the init proc may terminate 1199 -- abnormally after creating task components, and these must be properly 1200 -- registered for removal (Expunge_Unactivated_Tasks). The "limited" forces 1201 -- Activation_Chain to be a by-reference type; see RM-6.2(4). 1202 1203 function Number_Of_Entries (Self_Id : Task_Id) return Entry_Index; 1204 -- Given a task, return the number of entries it contains 1205 1206 procedure Set_Entry_Names 1207 (Self_Id : Task_Id; 1208 Names : Task_Entry_Names_Access); 1209 -- Associate an array of strings denotinge entry [family] names with a task 1210 1211end System.Tasking; 1212