gcc/ada/s-interr.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
   4 --                                                                          --
   5 --                     S Y S T E M . I N T E R R U P T S                    --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --         Copyright (C) 1992-2014, 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 --  Invariants:
  33
  34 --  All user-handleable interrupts are masked at all times in all tasks/threads
  35 --  except possibly for the Interrupt_Manager task.
  36
  37 --  When a user task wants to achieve masking/unmasking an interrupt, it must
  38 --  call Block_Interrupt/Unblock_Interrupt, which will have the effect of
  39 --  unmasking/masking the interrupt in the Interrupt_Manager task.
  40
  41 --  Note : Direct calls to sigaction, sigprocmask, pthread_sigsetmask or any
  42 --  other low-level interface that changes the interrupt action or
  43 --  interrupt mask needs a careful thought.
  44
  45 --  One may achieve the effect of system calls first masking RTS blocked
  46 --  (by calling Block_Interrupt) for the interrupt under consideration.
  47 --  This will make all the tasks in RTS blocked for the Interrupt.
  48
  49 --  Once we associate a Server_Task with an interrupt, the task never goes
  50 --  away, and we never remove the association.
  51
  52 --  There is no more than one interrupt per Server_Task and no more than one
  53 --  Server_Task per interrupt.
  54
  55 with Ada.Exceptions;
  56 with Ada.Task_Identification;
  57
  58 with System.Task_Primitives;
  59 with System.Interrupt_Management;
  60
  61 with System.Interrupt_Management.Operations;
  62 pragma Elaborate_All (System.Interrupt_Management.Operations);
  63
  64 with System.IO;
  65
  66 with System.Task_Primitives.Operations;
  67 with System.Task_Primitives.Interrupt_Operations;
  68 with System.Storage_Elements;
  69 with System.Tasking.Utilities;
  70
  71 with System.Tasking.Rendezvous;
  72 pragma Elaborate_All (System.Tasking.Rendezvous);
  73
  74 with System.Tasking.Initialization;
  75 with System.Parameters;
  76
  77 with Ada.Unchecked_Conversion;
  78
  79 package body System.Interrupts is
  80
  81    use Parameters;
  82    use Tasking;
  83
  84    package POP renames System.Task_Primitives.Operations;
  85    package PIO renames System.Task_Primitives.Interrupt_Operations;
  86    package IMNG renames System.Interrupt_Management;
  87    package IMOP renames System.Interrupt_Management.Operations;
  88
  89    function To_System is new Ada.Unchecked_Conversion
  90      (Ada.Task_Identification.Task_Id, Task_Id);
  91
  92    -----------------
  93    -- Local Tasks --
  94    -----------------
  95
  96    --  WARNING: System.Tasking.Stages performs calls to this task with
  97    --  low-level constructs. Do not change this spec without synchronizing it.
  98
  99    task Interrupt_Manager is
 100       entry Detach_Interrupt_Entries (T : Task_Id);
 101
 102       entry Initialize (Mask : IMNG.Interrupt_Mask);
 103
 104       entry Attach_Handler
 105         (New_Handler : Parameterless_Handler;
 106          Interrupt   : Interrupt_ID;
 107          Static      : Boolean;
 108          Restoration : Boolean := False);
 109
 110       entry Exchange_Handler
 111         (Old_Handler : out Parameterless_Handler;
 112          New_Handler : Parameterless_Handler;
 113          Interrupt   : Interrupt_ID;
 114          Static      : Boolean);
 115
 116       entry Detach_Handler
 117         (Interrupt   : Interrupt_ID;
 118          Static      : Boolean);
 119
 120       entry Bind_Interrupt_To_Entry
 121         (T         : Task_Id;
 122          E         : Task_Entry_Index;
 123          Interrupt : Interrupt_ID);
 124
 125       entry Block_Interrupt (Interrupt : Interrupt_ID);
 126
 127       entry Unblock_Interrupt (Interrupt : Interrupt_ID);
 128
 129       entry Ignore_Interrupt (Interrupt : Interrupt_ID);
 130
 131       entry Unignore_Interrupt (Interrupt : Interrupt_ID);
 132
 133       pragma Interrupt_Priority (System.Interrupt_Priority'Last);
 134    end Interrupt_Manager;
 135
 136    task type Server_Task (Interrupt : Interrupt_ID) is
 137       pragma Priority (System.Interrupt_Priority'Last);
 138       --  Note: the above pragma Priority is strictly speaking improper since
 139       --  it is outside the range of allowed priorities, but the compiler
 140       --  treats system units specially and does not apply this range checking
 141       --  rule to system units.
 142
 143    end Server_Task;
 144
 145    type Server_Task_Access is access Server_Task;
 146
 147    -------------------------------
 148    -- Local Types and Variables --
 149    -------------------------------
 150
 151    type Entry_Assoc is record
 152       T : Task_Id;
 153       E : Task_Entry_Index;
 154    end record;
 155
 156    type Handler_Assoc is record
 157       H      : Parameterless_Handler;
 158       Static : Boolean;   --  Indicates static binding;
 159    end record;
 160
 161    User_Handler : array (Interrupt_ID'Range) of Handler_Assoc :=
 162                     (others => (null, Static => False));
 163    pragma Volatile_Components (User_Handler);
 164    --  Holds the protected procedure handler (if any) and its Static
 165    --  information for each interrupt. A handler is a Static one if it is
 166    --  specified through the pragma Attach_Handler. Attach_Handler. Otherwise,
 167    --  not static)
 168
 169    User_Entry : array (Interrupt_ID'Range) of Entry_Assoc :=
 170                   (others => (T => Null_Task, E => Null_Task_Entry));
 171    pragma Volatile_Components (User_Entry);
 172    --  Holds the task and entry index (if any) for each interrupt
 173
 174    Blocked : array (Interrupt_ID'Range) of Boolean := (others => False);
 175    pragma Atomic_Components (Blocked);
 176    --  True iff the corresponding interrupt is blocked in the process level
 177
 178    Ignored : array (Interrupt_ID'Range) of Boolean := (others => False);
 179    pragma Atomic_Components (Ignored);
 180    --  True iff the corresponding interrupt is blocked in the process level
 181
 182    Last_Unblocker :
 183      array (Interrupt_ID'Range) of Task_Id := (others => Null_Task);
 184    pragma Atomic_Components (Last_Unblocker);
 185    --  Holds the ID of the last Task which Unblocked this Interrupt. It
 186    --  contains Null_Task if no tasks have ever requested the Unblocking
 187    --  operation or the Interrupt is currently Blocked.
 188
 189    Server_ID : array (Interrupt_ID'Range) of Task_Id :=
 190                  (others => Null_Task);
 191    pragma Atomic_Components (Server_ID);
 192    --  Holds the Task_Id of the Server_Task for each interrupt. Task_Id is
 193    --  needed to accomplish locking per Interrupt base. Also is needed to
 194    --  decide whether to create a new Server_Task.
 195
 196    --  Type and Head, Tail of the list containing Registered Interrupt
 197    --  Handlers. These definitions are used to register the handlers
 198    --  specified by the pragma Interrupt_Handler.
 199
 200    type Registered_Handler;
 201    type R_Link is access all Registered_Handler;
 202
 203    type Registered_Handler is record
 204       H    : System.Address := System.Null_Address;
 205       Next : R_Link := null;
 206    end record;
 207
 208    Registered_Handler_Head : R_Link := null;
 209    Registered_Handler_Tail : R_Link := null;
 210
 211    Access_Hold : Server_Task_Access;
 212    --  Variable used to allocate Server_Task using "new"
 213
 214    -----------------------
 215    -- Local Subprograms --
 216    -----------------------
 217
 218    function Is_Registered (Handler : Parameterless_Handler) return Boolean;
 219    --  See if the Handler has been "pragma"ed using Interrupt_Handler. Always
 220    --  consider a null handler as registered.
 221
 222    --------------------
 223    -- Attach_Handler --
 224    --------------------
 225
 226    --  Calling this procedure with New_Handler = null and Static = True means
 227    --  we want to detach the current handler regardless of the previous
 228    --  handler's binding status (i.e. do not care if it is a dynamic or static
 229    --  handler).
 230
 231    --  This option is needed so that during the finalization of a PO, we can
 232    --  detach handlers attached through pragma Attach_Handler.
 233
 234    procedure Attach_Handler
 235      (New_Handler : Parameterless_Handler;
 236       Interrupt   : Interrupt_ID;
 237       Static      : Boolean := False)
 238    is
 239    begin
 240       if Is_Reserved (Interrupt) then
 241          raise Program_Error with
 242            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 243       end if;
 244
 245       Interrupt_Manager.Attach_Handler (New_Handler, Interrupt, Static);
 246
 247    end Attach_Handler;
 248
 249    -----------------------------
 250    -- Bind_Interrupt_To_Entry --
 251    -----------------------------
 252
 253    --  This procedure raises a Program_Error if it tries to bind an interrupt
 254    --  to which an Entry or a Procedure is already bound.
 255
 256    procedure Bind_Interrupt_To_Entry
 257      (T       : Task_Id;
 258       E       : Task_Entry_Index;
 259       Int_Ref : System.Address)
 260    is
 261       Interrupt : constant Interrupt_ID :=
 262                     Interrupt_ID (Storage_Elements.To_Integer (Int_Ref));
 263
 264    begin
 265       if Is_Reserved (Interrupt) then
 266          raise Program_Error with
 267            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 268       end if;
 269
 270       Interrupt_Manager.Bind_Interrupt_To_Entry (T, E, Interrupt);
 271    end Bind_Interrupt_To_Entry;
 272
 273    ---------------------
 274    -- Block_Interrupt --
 275    ---------------------
 276
 277    procedure Block_Interrupt (Interrupt : Interrupt_ID) is
 278    begin
 279       if Is_Reserved (Interrupt) then
 280          raise Program_Error with
 281            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 282       end if;
 283
 284       Interrupt_Manager.Block_Interrupt (Interrupt);
 285    end Block_Interrupt;
 286
 287    ---------------------
 288    -- Current_Handler --
 289    ---------------------
 290
 291    function Current_Handler
 292      (Interrupt : Interrupt_ID) return Parameterless_Handler
 293    is
 294    begin
 295       if Is_Reserved (Interrupt) then
 296          raise Program_Error with
 297            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 298       end if;
 299
 300       --  ??? Since Parameterless_Handler is not Atomic, the current
 301       --  implementation is wrong. We need a new service in Interrupt_Manager
 302       --  to ensure atomicity.
 303
 304       return User_Handler (Interrupt).H;
 305    end Current_Handler;
 306
 307    --------------------
 308    -- Detach_Handler --
 309    --------------------
 310
 311    --  Calling this procedure with Static = True means we want to Detach the
 312    --  current handler regardless of the previous handler's binding status
 313    --  (i.e. do not care if it is a dynamic or static handler).
 314
 315    --  This option is needed so that during the finalization of a PO, we can
 316    --  detach handlers attached through pragma Attach_Handler.
 317
 318    procedure Detach_Handler
 319      (Interrupt : Interrupt_ID;
 320       Static    : Boolean := False)
 321    is
 322    begin
 323       if Is_Reserved (Interrupt) then
 324          raise Program_Error with
 325            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 326       end if;
 327
 328       Interrupt_Manager.Detach_Handler (Interrupt, Static);
 329    end Detach_Handler;
 330
 331    ------------------------------
 332    -- Detach_Interrupt_Entries --
 333    ------------------------------
 334
 335    procedure Detach_Interrupt_Entries (T : Task_Id) is
 336    begin
 337       Interrupt_Manager.Detach_Interrupt_Entries (T);
 338    end Detach_Interrupt_Entries;
 339
 340    ----------------------
 341    -- Exchange_Handler --
 342    ----------------------
 343
 344    --  Calling this procedure with New_Handler = null and Static = True means
 345    --  we want to detach the current handler regardless of the previous
 346    --  handler's binding status (i.e. do not care if it is a dynamic or static
 347    --  handler).
 348
 349    --  This option is needed so that during the finalization of a PO, we can
 350    --  detach handlers attached through pragma Attach_Handler.
 351
 352    procedure Exchange_Handler
 353      (Old_Handler : out Parameterless_Handler;
 354       New_Handler : Parameterless_Handler;
 355       Interrupt   : Interrupt_ID;
 356       Static      : Boolean := False)
 357    is
 358    begin
 359       if Is_Reserved (Interrupt) then
 360          raise Program_Error with
 361            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 362       end if;
 363
 364       Interrupt_Manager.Exchange_Handler
 365         (Old_Handler, New_Handler, Interrupt, Static);
 366    end Exchange_Handler;
 367
 368    --------------
 369    -- Finalize --
 370    --------------
 371
 372    procedure Finalize (Object : in out Static_Interrupt_Protection) is
 373       function State
 374         (Int : System.Interrupt_Management.Interrupt_ID) return Character;
 375       pragma Import (C, State, "__gnat_get_interrupt_state");
 376       --  Get interrupt state for interrupt number Int. Defined in init.c
 377
 378       Default : constant Character := 's';
 379       --    's'   Interrupt_State pragma set state to System (use "default"
 380       --           system handler)
 381
 382    begin
 383       --  ??? loop to be executed only when we're not doing library level
 384       --  finalization, since in this case all interrupt tasks are gone.
 385
 386       --  If the Abort_Task signal is set to system, it means that we cannot
 387       --  reset interrupt handlers since this would require sending the abort
 388       --  signal to the Server_Task
 389
 390       if not Interrupt_Manager'Terminated
 391         and then
 392           State (System.Interrupt_Management.Abort_Task_Interrupt) /= Default
 393       then
 394          for N in reverse Object.Previous_Handlers'Range loop
 395             Interrupt_Manager.Attach_Handler
 396               (New_Handler => Object.Previous_Handlers (N).Handler,
 397                Interrupt   => Object.Previous_Handlers (N).Interrupt,
 398                Static      => Object.Previous_Handlers (N).Static,
 399                Restoration => True);
 400          end loop;
 401       end if;
 402
 403       Tasking.Protected_Objects.Entries.Finalize
 404         (Tasking.Protected_Objects.Entries.Protection_Entries (Object));
 405    end Finalize;
 406
 407    -------------------------------------
 408    -- Has_Interrupt_Or_Attach_Handler --
 409    -------------------------------------
 410
 411    --  Need comments as to why these always return True ???
 412
 413    function Has_Interrupt_Or_Attach_Handler
 414      (Object : access Dynamic_Interrupt_Protection) return Boolean
 415    is
 416       pragma Unreferenced (Object);
 417    begin
 418       return True;
 419    end Has_Interrupt_Or_Attach_Handler;
 420
 421    function Has_Interrupt_Or_Attach_Handler
 422      (Object : access Static_Interrupt_Protection) return Boolean
 423    is
 424       pragma Unreferenced (Object);
 425    begin
 426       return True;
 427    end Has_Interrupt_Or_Attach_Handler;
 428
 429    ----------------------
 430    -- Ignore_Interrupt --
 431    ----------------------
 432
 433    procedure Ignore_Interrupt (Interrupt : Interrupt_ID) is
 434    begin
 435       if Is_Reserved (Interrupt) then
 436          raise Program_Error with
 437            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 438       end if;
 439
 440       Interrupt_Manager.Ignore_Interrupt (Interrupt);
 441    end Ignore_Interrupt;
 442
 443    ----------------------
 444    -- Install_Handlers --
 445    ----------------------
 446
 447    procedure Install_Handlers
 448      (Object       : access Static_Interrupt_Protection;
 449       New_Handlers : New_Handler_Array)
 450    is
 451    begin
 452       for N in New_Handlers'Range loop
 453
 454          --  We need a lock around this ???
 455
 456          Object.Previous_Handlers (N).Interrupt := New_Handlers (N).Interrupt;
 457          Object.Previous_Handlers (N).Static    := User_Handler
 458            (New_Handlers (N).Interrupt).Static;
 459
 460          --  We call Exchange_Handler and not directly Interrupt_Manager.
 461          --  Exchange_Handler so we get the Is_Reserved check.
 462
 463          Exchange_Handler
 464            (Old_Handler => Object.Previous_Handlers (N).Handler,
 465             New_Handler => New_Handlers (N).Handler,
 466             Interrupt   => New_Handlers (N).Interrupt,
 467             Static      => True);
 468       end loop;
 469    end Install_Handlers;
 470
 471    ---------------------------------
 472    -- Install_Restricted_Handlers --
 473    ---------------------------------
 474
 475    procedure Install_Restricted_Handlers
 476      (Prio     : Any_Priority;
 477       Handlers : New_Handler_Array)
 478    is
 479       pragma Unreferenced (Prio);
 480    begin
 481       for N in Handlers'Range loop
 482          Attach_Handler (Handlers (N).Handler, Handlers (N).Interrupt, True);
 483       end loop;
 484    end Install_Restricted_Handlers;
 485
 486    ----------------
 487    -- Is_Blocked --
 488    ----------------
 489
 490    function Is_Blocked (Interrupt : Interrupt_ID) return Boolean is
 491    begin
 492       if Is_Reserved (Interrupt) then
 493          raise Program_Error with
 494            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 495       end if;
 496
 497       return Blocked (Interrupt);
 498    end Is_Blocked;
 499
 500    -----------------------
 501    -- Is_Entry_Attached --
 502    -----------------------
 503
 504    function Is_Entry_Attached (Interrupt : Interrupt_ID) return Boolean is
 505    begin
 506       if Is_Reserved (Interrupt) then
 507          raise Program_Error with
 508            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 509       end if;
 510
 511       return User_Entry (Interrupt).T /= Null_Task;
 512    end Is_Entry_Attached;
 513
 514    -------------------------
 515    -- Is_Handler_Attached --
 516    -------------------------
 517
 518    function Is_Handler_Attached (Interrupt : Interrupt_ID) return Boolean is
 519    begin
 520       if Is_Reserved (Interrupt) then
 521          raise Program_Error with
 522            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 523       end if;
 524
 525       return User_Handler (Interrupt).H /= null;
 526    end Is_Handler_Attached;
 527
 528    ----------------
 529    -- Is_Ignored --
 530    ----------------
 531
 532    function Is_Ignored (Interrupt : Interrupt_ID) return Boolean is
 533    begin
 534       if Is_Reserved (Interrupt) then
 535          raise Program_Error with
 536            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 537       end if;
 538
 539       return Ignored (Interrupt);
 540    end Is_Ignored;
 541
 542    -------------------
 543    -- Is_Registered --
 544    -------------------
 545
 546    function Is_Registered (Handler : Parameterless_Handler) return Boolean is
 547
 548       type Fat_Ptr is record
 549          Object_Addr  : System.Address;
 550          Handler_Addr : System.Address;
 551       end record;
 552
 553       function To_Fat_Ptr is new Ada.Unchecked_Conversion
 554         (Parameterless_Handler, Fat_Ptr);
 555
 556       Ptr : R_Link;
 557       Fat : Fat_Ptr;
 558
 559    begin
 560       if Handler = null then
 561          return True;
 562       end if;
 563
 564       Fat := To_Fat_Ptr (Handler);
 565
 566       Ptr := Registered_Handler_Head;
 567       while Ptr /= null loop
 568          if Ptr.H = Fat.Handler_Addr then
 569             return True;
 570          end if;
 571
 572          Ptr := Ptr.Next;
 573       end loop;
 574
 575       return False;
 576    end Is_Registered;
 577
 578    -----------------
 579    -- Is_Reserved --
 580    -----------------
 581
 582    function Is_Reserved (Interrupt : Interrupt_ID) return Boolean is
 583    begin
 584       return IMNG.Reserve (IMNG.Interrupt_ID (Interrupt));
 585    end Is_Reserved;
 586
 587    ---------------
 588    -- Reference --
 589    ---------------
 590
 591    function Reference (Interrupt : Interrupt_ID) return System.Address is
 592    begin
 593       if Is_Reserved (Interrupt) then
 594          raise Program_Error with
 595            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 596       end if;
 597
 598       return Storage_Elements.To_Address
 599                (Storage_Elements.Integer_Address (Interrupt));
 600    end Reference;
 601
 602    ---------------------------------
 603    -- Register_Interrupt_Handler  --
 604    ---------------------------------
 605
 606    procedure Register_Interrupt_Handler (Handler_Addr : System.Address) is
 607       New_Node_Ptr : R_Link;
 608
 609    begin
 610       --  This routine registers the Handler as usable for Dynamic Interrupt
 611       --  Handler. Routines attaching and detaching Handler dynamically should
 612       --  first consult if the Handler is registered. A Program Error should
 613       --  be raised if it is not registered.
 614
 615       --  The pragma Interrupt_Handler can only appear in the library level PO
 616       --  definition and instantiation. Therefore, we do not need to implement
 617       --  Unregistering operation. Neither we need to protect the queue
 618       --  structure using a Lock.
 619
 620       pragma Assert (Handler_Addr /= System.Null_Address);
 621
 622       New_Node_Ptr := new Registered_Handler;
 623       New_Node_Ptr.H := Handler_Addr;
 624
 625       if Registered_Handler_Head = null then
 626          Registered_Handler_Head := New_Node_Ptr;
 627          Registered_Handler_Tail := New_Node_Ptr;
 628
 629       else
 630          Registered_Handler_Tail.Next := New_Node_Ptr;
 631          Registered_Handler_Tail := New_Node_Ptr;
 632       end if;
 633    end Register_Interrupt_Handler;
 634
 635    -----------------------
 636    -- Unblock_Interrupt --
 637    -----------------------
 638
 639    procedure Unblock_Interrupt (Interrupt : Interrupt_ID) is
 640    begin
 641       if Is_Reserved (Interrupt) then
 642          raise Program_Error with
 643            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 644       end if;
 645
 646       Interrupt_Manager.Unblock_Interrupt (Interrupt);
 647    end Unblock_Interrupt;
 648
 649    ------------------
 650    -- Unblocked_By --
 651    ------------------
 652
 653    function Unblocked_By
 654      (Interrupt : Interrupt_ID) return System.Tasking.Task_Id
 655    is
 656    begin
 657       if Is_Reserved (Interrupt) then
 658          raise Program_Error with
 659            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 660       end if;
 661
 662       return Last_Unblocker (Interrupt);
 663    end Unblocked_By;
 664
 665    ------------------------
 666    -- Unignore_Interrupt --
 667    ------------------------
 668
 669    procedure Unignore_Interrupt (Interrupt : Interrupt_ID) is
 670    begin
 671       if Is_Reserved (Interrupt) then
 672          raise Program_Error with
 673            "interrupt" & Interrupt_ID'Image (Interrupt) & " is reserved";
 674       end if;
 675
 676       Interrupt_Manager.Unignore_Interrupt (Interrupt);
 677    end Unignore_Interrupt;
 678
 679    -----------------------
 680    -- Interrupt_Manager --
 681    -----------------------
 682
 683    task body Interrupt_Manager is
 684       --  By making this task independent of master, when the process
 685       --  goes away, the Interrupt_Manager will terminate gracefully.
 686
 687       Ignore : constant Boolean := System.Tasking.Utilities.Make_Independent;
 688
 689       ---------------------
 690       -- Local Variables --
 691       ---------------------
 692
 693       Intwait_Mask  : aliased IMNG.Interrupt_Mask;
 694       Ret_Interrupt : Interrupt_ID;
 695       Old_Mask      : aliased IMNG.Interrupt_Mask;
 696       Old_Handler   : Parameterless_Handler;
 697
 698       --------------------
 699       -- Local Routines --
 700       --------------------
 701
 702       procedure Bind_Handler (Interrupt : Interrupt_ID);
 703       --  This procedure does not do anything if the Interrupt is blocked.
 704       --  Otherwise, we have to interrupt Server_Task for status change through
 705       --  Wakeup interrupt.
 706
 707       procedure Unbind_Handler (Interrupt : Interrupt_ID);
 708       --  This procedure does not do anything if the Interrupt is blocked.
 709       --  Otherwise, we have to interrupt Server_Task for status change
 710       --  through abort interrupt.
 711
 712       procedure Unprotected_Exchange_Handler
 713         (Old_Handler : out Parameterless_Handler;
 714          New_Handler : Parameterless_Handler;
 715          Interrupt   : Interrupt_ID;
 716          Static      : Boolean;
 717          Restoration : Boolean := False);
 718
 719       procedure Unprotected_Detach_Handler
 720         (Interrupt   : Interrupt_ID;
 721          Static      : Boolean);
 722
 723       ------------------
 724       -- Bind_Handler --
 725       ------------------
 726
 727       procedure Bind_Handler (Interrupt : Interrupt_ID) is
 728       begin
 729          if not Blocked (Interrupt) then
 730
 731             --  Mask this task for the given Interrupt so that all tasks
 732             --  are masked for the Interrupt and the actual delivery of the
 733             --  Interrupt will be caught using "sigwait" by the
 734             --  corresponding Server_Task.
 735
 736             IMOP.Thread_Block_Interrupt (IMNG.Interrupt_ID (Interrupt));
 737
 738             --  We have installed a Handler or an Entry before we called
 739             --  this procedure. If the Handler Task is waiting to be awakened,
 740             --  do it here. Otherwise, the interrupt will be discarded.
 741
 742             POP.Wakeup (Server_ID (Interrupt), Interrupt_Server_Idle_Sleep);
 743          end if;
 744       end Bind_Handler;
 745
 746       --------------------
 747       -- Unbind_Handler --
 748       --------------------
 749
 750       procedure Unbind_Handler (Interrupt : Interrupt_ID) is
 751          Server : System.Tasking.Task_Id;
 752
 753       begin
 754          if not Blocked (Interrupt) then
 755
 756             --  Currently, there is a Handler or an Entry attached and
 757             --  corresponding Server_Task is waiting on "sigwait." We have to
 758             --  wake up the Server_Task and make it wait on condition variable
 759             --  by sending an Abort_Task_Interrupt
 760
 761             Server := Server_ID (Interrupt);
 762
 763             case Server.Common.State is
 764                when Interrupt_Server_Idle_Sleep |
 765                     Interrupt_Server_Blocked_Interrupt_Sleep
 766                =>
 767                   POP.Wakeup (Server, Server.Common.State);
 768
 769                when Interrupt_Server_Blocked_On_Event_Flag =>
 770                   POP.Abort_Task (Server);
 771
 772                   --  Make sure corresponding Server_Task is out of its
 773                   --  own sigwait state.
 774
 775                   Ret_Interrupt :=
 776                     Interrupt_ID (IMOP.Interrupt_Wait (Intwait_Mask'Access));
 777                   pragma Assert
 778                     (Ret_Interrupt = Interrupt_ID (IMNG.Abort_Task_Interrupt));
 779
 780                when Runnable =>
 781                   null;
 782
 783                when others =>
 784                   pragma Assert (False);
 785                   null;
 786             end case;
 787
 788             IMOP.Install_Default_Action (IMNG.Interrupt_ID (Interrupt));
 789
 790             --  Unmake the Interrupt for this task in order to allow default
 791             --  action again.
 792
 793             IMOP.Thread_Unblock_Interrupt (IMNG.Interrupt_ID (Interrupt));
 794
 795          else
 796             IMOP.Install_Default_Action (IMNG.Interrupt_ID (Interrupt));
 797          end if;
 798       end Unbind_Handler;
 799
 800       --------------------------------
 801       -- Unprotected_Detach_Handler --
 802       --------------------------------
 803
 804       procedure Unprotected_Detach_Handler
 805         (Interrupt   : Interrupt_ID;
 806          Static      : Boolean)
 807       is
 808          Old_Handler : Parameterless_Handler;
 809
 810       begin
 811          if User_Entry (Interrupt).T /= Null_Task then
 812
 813             --  In case we have an Interrupt Entry installed, raise a program
 814             --  error, (propagate it to the caller).
 815
 816             raise Program_Error with
 817               "an interrupt entry is already installed";
 818          end if;
 819
 820          --  Note : Static = True will pass the following check. That is the
 821          --  case when we want to detach a handler regardless of the static
 822          --  status of the current_Handler.
 823
 824          if not Static and then User_Handler (Interrupt).Static then
 825
 826             --  Tries to detach a static Interrupt Handler.
 827             --  raise a program error.
 828
 829             raise Program_Error with
 830               "trying to detach a static interrupt handler";
 831          end if;
 832
 833          --  The interrupt should no longer be ignored if
 834          --  it was ever ignored.
 835
 836          Ignored (Interrupt) := False;
 837
 838          Old_Handler := User_Handler (Interrupt).H;
 839
 840          --  The new handler
 841
 842          User_Handler (Interrupt).H := null;
 843          User_Handler (Interrupt).Static := False;
 844
 845          if Old_Handler /= null then
 846             Unbind_Handler (Interrupt);
 847          end if;
 848       end Unprotected_Detach_Handler;
 849
 850       ----------------------------------
 851       -- Unprotected_Exchange_Handler --
 852       ----------------------------------
 853
 854       procedure Unprotected_Exchange_Handler
 855         (Old_Handler : out Parameterless_Handler;
 856          New_Handler : Parameterless_Handler;
 857          Interrupt   : Interrupt_ID;
 858          Static      : Boolean;
 859          Restoration : Boolean := False)
 860       is
 861       begin
 862          if User_Entry (Interrupt).T /= Null_Task then
 863
 864             --  In case we have an Interrupt Entry already installed, raise a
 865             --  program error, (propagate it to the caller).
 866
 867             raise Program_Error with
 868               "an interrupt is already installed";
 869          end if;
 870
 871          --  Note : A null handler with Static = True will pass the following
 872          --  check. That is the case when we want to Detach a handler
 873          --  regardless of the Static status of the current_Handler.
 874
 875          --  We don't check anything if Restoration is True, since we may be
 876          --  detaching a static handler to restore a dynamic one.
 877
 878          if not Restoration and then not Static
 879
 880             --  Tries to overwrite a static Interrupt Handler with a dynamic
 881             --  Handler
 882
 883            and then (User_Handler (Interrupt).Static
 884
 885                        --  The new handler is not specified as an
 886                        --  Interrupt Handler by a pragma.
 887
 888                        or else not Is_Registered (New_Handler))
 889          then
 890             raise Program_Error with
 891               "trying to overwrite a static Interrupt Handler with a " &
 892               "dynamic handler";
 893          end if;
 894
 895          --  The interrupt should no longer be ignored if
 896          --  it was ever ignored.
 897
 898          Ignored (Interrupt) := False;
 899
 900          --  Save the old handler
 901
 902          Old_Handler := User_Handler (Interrupt).H;
 903
 904          --  The new handler
 905
 906          User_Handler (Interrupt).H := New_Handler;
 907
 908          if New_Handler = null then
 909
 910             --  The null handler means we are detaching the handler
 911
 912             User_Handler (Interrupt).Static := False;
 913
 914          else
 915             User_Handler (Interrupt).Static := Static;
 916          end if;
 917
 918          --  Invoke a corresponding Server_Task if not yet created.
 919          --  Place Task_Id info in Server_ID array.
 920
 921          if Server_ID (Interrupt) = Null_Task then
 922
 923             --  When a new Server_Task is created, it should have its
 924             --  signal mask set to the All_Tasks_Mask.
 925
 926             IMOP.Set_Interrupt_Mask
 927               (IMOP.All_Tasks_Mask'Access, Old_Mask'Access);
 928             Access_Hold := new Server_Task (Interrupt);
 929             IMOP.Set_Interrupt_Mask (Old_Mask'Access);
 930
 931             Server_ID (Interrupt) := To_System (Access_Hold.all'Identity);
 932          end if;
 933
 934          if New_Handler = null then
 935             if Old_Handler /= null then
 936                Unbind_Handler (Interrupt);
 937             end if;
 938
 939             return;
 940          end if;
 941
 942          if Old_Handler = null then
 943             Bind_Handler (Interrupt);
 944          end if;
 945       end Unprotected_Exchange_Handler;
 946
 947    --  Start of processing for Interrupt_Manager
 948
 949    begin
 950       --  Environment task gets its own interrupt mask, saves it, and then
 951       --  masks all interrupts except the Keep_Unmasked set.
 952
 953       --  During rendezvous, the Interrupt_Manager receives the old interrupt
 954       --  mask of the environment task, and sets its own interrupt mask to that
 955       --  value.
 956
 957       --  The environment task will call the entry of Interrupt_Manager some
 958       --  during elaboration of the body of this package.
 959
 960       accept Initialize (Mask : IMNG.Interrupt_Mask) do
 961          declare
 962             The_Mask : aliased IMNG.Interrupt_Mask;
 963          begin
 964             IMOP.Copy_Interrupt_Mask (The_Mask, Mask);
 965             IMOP.Set_Interrupt_Mask (The_Mask'Access);
 966          end;
 967       end Initialize;
 968
 969       --  Note: All tasks in RTS will have all the Reserve Interrupts being
 970       --  masked (except the Interrupt_Manager) and Keep_Unmasked unmasked
 971       --  when created.
 972
 973       --  Abort_Task_Interrupt is one of the Interrupt unmasked in all tasks.
 974       --  We mask the Interrupt in this particular task so that "sigwait" is
 975       --  possible to catch an explicitly sent Abort_Task_Interrupt from the
 976       --  Server_Tasks.
 977
 978       --  This sigwaiting is needed so that we make sure a Server_Task is out
 979       --  of its own sigwait state. This extra synchronization is necessary to
 980       --  prevent following scenarios.
 981
 982       --   1) Interrupt_Manager sends an Abort_Task_Interrupt to the
 983       --      Server_Task then changes its own interrupt mask (OS level).
 984       --      If an interrupt (corresponding to the Server_Task) arrives
 985       --      in the mean time we have the Interrupt_Manager unmasked and
 986       --      the Server_Task waiting on sigwait.
 987
 988       --   2) For unbinding handler, we install a default action in the
 989       --      Interrupt_Manager. POSIX.1c states that the result of using
 990       --      "sigwait" and "sigaction" simultaneously on the same interrupt
 991       --      is undefined. Therefore, we need to be informed from the
 992       --      Server_Task of the fact that the Server_Task is out of its
 993       --      sigwait stage.
 994
 995       IMOP.Empty_Interrupt_Mask (Intwait_Mask'Access);
 996       IMOP.Add_To_Interrupt_Mask
 997         (Intwait_Mask'Access, IMNG.Abort_Task_Interrupt);
 998       IMOP.Thread_Block_Interrupt
 999         (IMNG.Abort_Task_Interrupt);
1000
1001       loop
1002          --  A block is needed to absorb Program_Error exception
1003
1004          begin
1005             select
1006                accept Attach_Handler
1007                   (New_Handler : Parameterless_Handler;
1008                    Interrupt   : Interrupt_ID;
1009                    Static      : Boolean;
1010                    Restoration : Boolean := False)
1011                do
1012                   Unprotected_Exchange_Handler
1013                     (Old_Handler, New_Handler, Interrupt, Static, Restoration);
1014                end Attach_Handler;
1015
1016             or
1017                accept Exchange_Handler
1018                   (Old_Handler : out Parameterless_Handler;
1019                    New_Handler : Parameterless_Handler;
1020                    Interrupt   : Interrupt_ID;
1021                    Static      : Boolean)
1022                do
1023                   Unprotected_Exchange_Handler
1024                     (Old_Handler, New_Handler, Interrupt, Static);
1025                end Exchange_Handler;
1026
1027             or
1028                accept Detach_Handler
1029                  (Interrupt   : Interrupt_ID;
1030                   Static      : Boolean)
1031                do
1032                   Unprotected_Detach_Handler (Interrupt, Static);
1033                end Detach_Handler;
1034
1035             or
1036                accept Bind_Interrupt_To_Entry
1037                  (T       : Task_Id;
1038                   E       : Task_Entry_Index;
1039                   Interrupt : Interrupt_ID)
1040                do
1041                   --  If there is a binding already (either a procedure or an
1042                   --  entry), raise Program_Error (propagate it to the caller).
1043
1044                   if User_Handler (Interrupt).H /= null
1045                     or else User_Entry (Interrupt).T /= Null_Task
1046                   then
1047                      raise Program_Error with
1048                        "a binding for this interrupt is already present";
1049                   end if;
1050
1051                   --  The interrupt should no longer be ignored if
1052                   --  it was ever ignored.
1053
1054                   Ignored (Interrupt) := False;
1055                   User_Entry (Interrupt) := Entry_Assoc'(T => T, E => E);
1056
1057                   --  Indicate the attachment of Interrupt Entry in ATCB.
1058                   --  This is need so that when an Interrupt Entry task
1059                   --  terminates the binding can be cleaned. The call to
1060                   --  unbinding must be made by the task before it terminates.
1061
1062                   T.Interrupt_Entry := True;
1063
1064                   --  Invoke a corresponding Server_Task if not yet created.
1065                   --  Place Task_Id info in Server_ID array.
1066
1067                   if Server_ID (Interrupt) = Null_Task then
1068
1069                      --  When a new Server_Task is created, it should have its
1070                      --  signal mask set to the All_Tasks_Mask.
1071
1072                      IMOP.Set_Interrupt_Mask
1073                        (IMOP.All_Tasks_Mask'Access, Old_Mask'Access);
1074                      Access_Hold := new Server_Task (Interrupt);
1075                      IMOP.Set_Interrupt_Mask (Old_Mask'Access);
1076                      Server_ID (Interrupt) :=
1077                        To_System (Access_Hold.all'Identity);
1078                   end if;
1079
1080                   Bind_Handler (Interrupt);
1081                end Bind_Interrupt_To_Entry;
1082
1083             or
1084                accept Detach_Interrupt_Entries (T : Task_Id) do
1085                   for J in Interrupt_ID'Range loop
1086                      if not Is_Reserved (J) then
1087                         if User_Entry (J).T = T then
1088
1089                            --  The interrupt should no longer be ignored if
1090                            --  it was ever ignored.
1091
1092                            Ignored (J) := False;
1093                            User_Entry (J) := Entry_Assoc'
1094                              (T => Null_Task, E => Null_Task_Entry);
1095                            Unbind_Handler (J);
1096                         end if;
1097                      end if;
1098                   end loop;
1099
1100                   --  Indicate in ATCB that no Interrupt Entries are attached
1101
1102                   T.Interrupt_Entry := False;
1103                end Detach_Interrupt_Entries;
1104
1105             or
1106                accept Block_Interrupt (Interrupt : Interrupt_ID) do
1107                   if Blocked (Interrupt) then
1108                      return;
1109                   end if;
1110
1111                   Blocked (Interrupt) := True;
1112                   Last_Unblocker (Interrupt) := Null_Task;
1113
1114                   --  Mask this task for the given Interrupt so that all tasks
1115                   --  are masked for the Interrupt.
1116
1117                   IMOP.Thread_Block_Interrupt (IMNG.Interrupt_ID (Interrupt));
1118
1119                   if User_Handler (Interrupt).H /= null
1120                     or else User_Entry (Interrupt).T /= Null_Task
1121                   then
1122                      --  This is the case where the Server_Task is
1123                      --  waiting on "sigwait." Wake it up by sending an
1124                      --  Abort_Task_Interrupt so that the Server_Task waits
1125                      --  on Cond.
1126
1127                      POP.Abort_Task (Server_ID (Interrupt));
1128
1129                      --  Make sure corresponding Server_Task is out of its own
1130                      --  sigwait state.
1131
1132                      Ret_Interrupt := Interrupt_ID
1133                        (IMOP.Interrupt_Wait (Intwait_Mask'Access));
1134                      pragma Assert
1135                        (Ret_Interrupt =
1136                         Interrupt_ID (IMNG.Abort_Task_Interrupt));
1137                   end if;
1138                end Block_Interrupt;
1139
1140             or
1141                accept Unblock_Interrupt (Interrupt : Interrupt_ID) do
1142                   if not Blocked (Interrupt) then
1143                      return;
1144                   end if;
1145
1146                   Blocked (Interrupt) := False;
1147                   Last_Unblocker (Interrupt) :=
1148                     To_System (Unblock_Interrupt'Caller);
1149
1150                   if User_Handler (Interrupt).H = null
1151                     and then User_Entry (Interrupt).T = Null_Task
1152                   then
1153                      --  No handler is attached. Unmask the Interrupt so that
1154                      --  the default action can be carried out.
1155
1156                      IMOP.Thread_Unblock_Interrupt
1157                        (IMNG.Interrupt_ID (Interrupt));
1158
1159                   else
1160                      --  The Server_Task must be waiting on the Cond variable
1161                      --  since it was being blocked and an Interrupt Hander or
1162                      --  an Entry was there. Wake it up and let it change it
1163                      --  place of waiting according to its new state.
1164
1165                      POP.Wakeup (Server_ID (Interrupt),
1166                        Interrupt_Server_Blocked_Interrupt_Sleep);
1167                   end if;
1168                end Unblock_Interrupt;
1169
1170             or
1171                accept Ignore_Interrupt (Interrupt : Interrupt_ID) do
1172                   if Ignored (Interrupt) then
1173                      return;
1174                   end if;
1175
1176                   Ignored (Interrupt) := True;
1177
1178                   --  If there is a handler associated with the Interrupt,
1179                   --  detach it first. In this way we make sure that the
1180                   --  Server_Task is not on sigwait. This is legal since
1181                   --  Unignore_Interrupt is to install the default action.
1182
1183                   if User_Handler (Interrupt).H /= null then
1184                      Unprotected_Detach_Handler
1185                        (Interrupt => Interrupt, Static => True);
1186
1187                   elsif User_Entry (Interrupt).T /= Null_Task then
1188                      User_Entry (Interrupt) := Entry_Assoc'
1189                        (T => Null_Task, E => Null_Task_Entry);
1190                      Unbind_Handler (Interrupt);
1191                   end if;
1192
1193                   IMOP.Install_Ignore_Action (IMNG.Interrupt_ID (Interrupt));
1194                end Ignore_Interrupt;
1195
1196             or
1197                accept Unignore_Interrupt (Interrupt : Interrupt_ID) do
1198                   Ignored (Interrupt) := False;
1199
1200                   --  If there is a handler associated with the Interrupt,
1201                   --  detach it first. In this way we make sure that the
1202                   --  Server_Task is not on sigwait. This is legal since
1203                   --  Unignore_Interrupt is to install the default action.
1204
1205                   if User_Handler (Interrupt).H /= null then
1206                      Unprotected_Detach_Handler
1207                        (Interrupt => Interrupt, Static => True);
1208
1209                   elsif User_Entry (Interrupt).T /= Null_Task then
1210                      User_Entry (Interrupt) := Entry_Assoc'
1211                        (T => Null_Task, E => Null_Task_Entry);
1212                      Unbind_Handler (Interrupt);
1213                   end if;
1214
1215                   IMOP.Install_Default_Action (IMNG.Interrupt_ID (Interrupt));
1216                end Unignore_Interrupt;
1217             end select;
1218
1219          exception
1220             --  If there is a program error we just want to propagate it to
1221             --  the caller and do not want to stop this task.
1222
1223             when Program_Error =>
1224                null;
1225
1226             when X : others =>
1227                System.IO.Put_Line ("Exception in Interrupt_Manager");
1228                System.IO.Put_Line (Ada.Exceptions.Exception_Information (X));
1229                pragma Assert (False);
1230          end;
1231       end loop;
1232    end Interrupt_Manager;
1233
1234    -----------------
1235    -- Server_Task --
1236    -----------------
1237
1238    task body Server_Task is
1239       --  By making this task independent of master, when the process goes
1240       --  away, the Server_Task will terminate gracefully.
1241
1242       Ignore : constant Boolean := System.Tasking.Utilities.Make_Independent;
1243
1244       Intwait_Mask    : aliased IMNG.Interrupt_Mask;
1245       Ret_Interrupt   : Interrupt_ID;
1246       Self_ID         : constant Task_Id := Self;
1247       Tmp_Handler     : Parameterless_Handler;
1248       Tmp_ID          : Task_Id;
1249       Tmp_Entry_Index : Task_Entry_Index;
1250
1251    begin
1252       --  Install default action in system level
1253
1254       IMOP.Install_Default_Action (IMNG.Interrupt_ID (Interrupt));
1255
1256       --  Note: All tasks in RTS will have all the Reserve Interrupts being
1257       --  masked (except the Interrupt_Manager) and Keep_Unmasked unmasked when
1258       --  created.
1259
1260       --  Abort_Task_Interrupt is one of the Interrupt unmasked in all tasks.
1261       --  We mask the Interrupt in this particular task so that "sigwait" is
1262       --  possible to catch an explicitly sent Abort_Task_Interrupt from the
1263       --  Interrupt_Manager.
1264
1265       --  There are two Interrupt interrupts that this task catch through
1266       --  "sigwait." One is the Interrupt this task is designated to catch
1267       --  in order to execute user handler or entry. The other one is
1268       --  the Abort_Task_Interrupt. This interrupt is being sent from the
1269       --  Interrupt_Manager to inform status changes (e.g: become Blocked,
1270       --  Handler or Entry is to be detached).
1271
1272       --  Prepare a mask to used for sigwait
1273
1274       IMOP.Empty_Interrupt_Mask (Intwait_Mask'Access);
1275
1276       IMOP.Add_To_Interrupt_Mask
1277         (Intwait_Mask'Access, IMNG.Interrupt_ID (Interrupt));
1278
1279       IMOP.Add_To_Interrupt_Mask
1280         (Intwait_Mask'Access, IMNG.Abort_Task_Interrupt);
1281
1282       IMOP.Thread_Block_Interrupt
1283         (IMNG.Abort_Task_Interrupt);
1284
1285       PIO.Set_Interrupt_ID (IMNG.Interrupt_ID (Interrupt), Self_ID);
1286
1287       loop
1288          System.Tasking.Initialization.Defer_Abort (Self_ID);
1289
1290          if Single_Lock then
1291             POP.Lock_RTS;
1292          end if;
1293
1294          POP.Write_Lock (Self_ID);
1295
1296          if User_Handler (Interrupt).H = null
1297            and then User_Entry (Interrupt).T = Null_Task
1298          then
1299             --  No Interrupt binding. If there is an interrupt,
1300             --  Interrupt_Manager will take default action.
1301
1302             Self_ID.Common.State := Interrupt_Server_Blocked_Interrupt_Sleep;
1303             POP.Sleep (Self_ID, Interrupt_Server_Idle_Sleep);
1304             Self_ID.Common.State := Runnable;
1305
1306          elsif Blocked (Interrupt) then
1307
1308             --  Interrupt is blocked, stay here, so we won't catch it
1309
1310             Self_ID.Common.State := Interrupt_Server_Blocked_Interrupt_Sleep;
1311             POP.Sleep (Self_ID, Interrupt_Server_Blocked_Interrupt_Sleep);
1312             Self_ID.Common.State := Runnable;
1313
1314          else
1315             --  A Handler or an Entry is installed. At this point all tasks
1316             --  mask for the Interrupt is masked. Catch the Interrupt using
1317             --  sigwait.
1318
1319             --  This task may wake up from sigwait by receiving an interrupt
1320             --  (Abort_Task_Interrupt) from the Interrupt_Manager for unbinding
1321             --  a Procedure Handler or an Entry. Or it could be a wake up
1322             --  from status change (Unblocked -> Blocked). If that is not
1323             --  the case, we should execute the attached Procedure or Entry.
1324
1325             Self_ID.Common.State := Interrupt_Server_Blocked_On_Event_Flag;
1326             POP.Unlock (Self_ID);
1327
1328             if Single_Lock then
1329                POP.Unlock_RTS;
1330             end if;
1331
1332             --  Avoid race condition when terminating application and
1333             --  System.Parameters.No_Abort is True.
1334
1335             if Parameters.No_Abort and then Self_ID.Pending_Action then
1336                Initialization.Do_Pending_Action (Self_ID);
1337             end if;
1338
1339             Ret_Interrupt :=
1340               Interrupt_ID (IMOP.Interrupt_Wait (Intwait_Mask'Access));
1341             Self_ID.Common.State := Runnable;
1342
1343             if Ret_Interrupt = Interrupt_ID (IMNG.Abort_Task_Interrupt) then
1344
1345                --  Inform the Interrupt_Manager of wakeup from above sigwait
1346
1347                POP.Abort_Task (Interrupt_Manager_ID);
1348
1349                if Single_Lock then
1350                   POP.Lock_RTS;
1351                end if;
1352
1353                POP.Write_Lock (Self_ID);
1354
1355             else
1356                if Single_Lock then
1357                   POP.Lock_RTS;
1358                end if;
1359
1360                POP.Write_Lock (Self_ID);
1361
1362                if Ret_Interrupt /= Interrupt then
1363
1364                   --  On some systems (e.g. recent linux kernels), sigwait
1365                   --  may return unexpectedly (with errno set to EINTR).
1366
1367                   null;
1368
1369                else
1370                   --  Even though we have received an Interrupt the status may
1371                   --  have changed already before we got the Self_ID lock above
1372                   --  Therefore we make sure a Handler or an Entry is still
1373                   --  there and make appropriate call.
1374
1375                   --  If there is no calls to make we need to regenerate the
1376                   --  Interrupt in order not to lose it.
1377
1378                   if User_Handler (Interrupt).H /= null then
1379                      Tmp_Handler := User_Handler (Interrupt).H;
1380
1381                      --  RTS calls should not be made with self being locked
1382
1383                      POP.Unlock (Self_ID);
1384
1385                      if Single_Lock then
1386                         POP.Unlock_RTS;
1387                      end if;
1388
1389                      Tmp_Handler.all;
1390
1391                      if Single_Lock then
1392                         POP.Lock_RTS;
1393                      end if;
1394
1395                      POP.Write_Lock (Self_ID);
1396
1397                   elsif User_Entry (Interrupt).T /= Null_Task then
1398                      Tmp_ID := User_Entry (Interrupt).T;
1399                      Tmp_Entry_Index := User_Entry (Interrupt).E;
1400
1401                      --  RTS calls should not be made with self being locked
1402
1403                      if Single_Lock then
1404                         POP.Unlock_RTS;
1405                      end if;
1406
1407                      POP.Unlock (Self_ID);
1408
1409                      System.Tasking.Rendezvous.Call_Simple
1410                        (Tmp_ID, Tmp_Entry_Index, System.Null_Address);
1411
1412                      POP.Write_Lock (Self_ID);
1413
1414                      if Single_Lock then
1415                         POP.Lock_RTS;
1416                      end if;
1417
1418                   else
1419                      --  This is a situation that this task wakes up receiving
1420                      --  an Interrupt and before it gets the lock the Interrupt
1421                      --  is blocked. We do not want to lose the interrupt in
1422                      --  this case so we regenerate the Interrupt to process
1423                      --  level.
1424
1425                      IMOP.Interrupt_Self_Process
1426                        (IMNG.Interrupt_ID (Interrupt));
1427                   end if;
1428                end if;
1429             end if;
1430          end if;
1431
1432          POP.Unlock (Self_ID);
1433
1434          if Single_Lock then
1435             POP.Unlock_RTS;
1436          end if;
1437
1438          System.Tasking.Initialization.Undefer_Abort (Self_ID);
1439
1440          if Self_ID.Pending_Action then
1441             Initialization.Do_Pending_Action (Self_ID);
1442          end if;
1443
1444          --  Undefer abort here to allow a window for this task to be aborted
1445          --  at the time of system shutdown. We also explicitly test for
1446          --  Pending_Action in case System.Parameters.No_Abort is True.
1447
1448       end loop;
1449    end Server_Task;
1450
1451 --  Elaboration code for package System.Interrupts
1452
1453 begin
1454    --  Get Interrupt_Manager's ID so that Abort_Interrupt can be sent
1455
1456    Interrupt_Manager_ID := To_System (Interrupt_Manager'Identity);
1457
1458    --  During the elaboration of this package body we want the RTS
1459    --  to inherit the interrupt mask from the Environment Task.
1460
1461    IMOP.Setup_Interrupt_Mask;
1462
1463    --  The environment task should have gotten its mask from the enclosing
1464    --  process during the RTS start up. (See processing in s-inmaop.adb). Pass
1465    --  the Interrupt_Mask of the environment task to the Interrupt_Manager.
1466
1467    --  Note: At this point we know that all tasks are masked for non-reserved
1468    --  signals. Only the Interrupt_Manager will have masks set up differently
1469    --  inheriting the original environment task's mask.
1470
1471    Interrupt_Manager.Initialize (IMOP.Environment_Mask);
1472 end System.Interrupts;