gcc/ada/s-interr-vms.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) 1992-2006, 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- --
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  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
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  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This is an OpenVMS/Alpha version of this package
  35
  36 --  Invariants:
  37
  38 --  Once we associate a Server_Task with an interrupt, the task never
  39 --  goes away, and we never remove the association.
  40
  41 --  There is no more than one interrupt per Server_Task and no more than
  42 --  one Server_Task per interrupt.
  43
  44 --  Within this package, the lock L is used to protect the various status
  45 --  tables. If there is a Server_Task associated with an interrupt, we use
  46 --  the per-task lock of the Server_Task instead so that we protect the
  47 --  status between Interrupt_Manager and Server_Task. Protection among
  48 --  service requests are done using User Request to Interrupt_Manager
  49 --  rendezvous.
  50
  51 with Ada.Task_Identification;
  52 --  used for Task_Id type
  53
  54 with Ada.Exceptions;
  55 --  used for Raise_Exception
  56
  57 with System.Task_Primitives;
  58 --  used for RTS_Lock
  59 --           Self
  60
  61 with System.Interrupt_Management;
  62 --  used for Reserve
  63 --           Interrupt_ID
  64 --           Interrupt_Mask
  65 --           Abort_Task_Interrupt
  66
  67 with System.Interrupt_Management.Operations;
  68 --  used for Thread_Block_Interrupt
  69 --           Thread_Unblock_Interrupt
  70 --           Install_Default_Action
  71 --           Install_Ignore_Action
  72 --           Copy_Interrupt_Mask
  73 --           Set_Interrupt_Mask
  74 --           Empty_Interrupt_Mask
  75 --           Fill_Interrupt_Mask
  76 --           Add_To_Interrupt_Mask
  77 --           Delete_From_Interrupt_Mask
  78 --           Interrupt_Wait
  79 --           Interrupt_Self_Process
  80 --           Get_Interrupt_Mask
  81 --           Set_Interrupt_Mask
  82 --           IS_Member
  83 --           Environment_Mask
  84 pragma Elaborate_All (System.Interrupt_Management.Operations);
  85
  86 with System.Task_Primitives.Operations;
  87 --  used for Write_Lock
  88 --           Unlock
  89 --           Abort
  90 --           Wakeup_Task
  91 --           Sleep
  92 --           Initialize_Lock
  93
  94 with System.Task_Primitives.Interrupt_Operations;
  95 --  used for Set_Interrupt_ID
  96
  97 with System.Storage_Elements;
  98 --  used for To_Address
  99 --           To_Integer
 100 --           Integer_Address
 101
 102 with System.Tasking.Utilities;
 103 --  used for Make_Independent
 104
 105 with System.Tasking.Rendezvous;
 106 --  used for Call_Simple
 107 pragma Elaborate_All (System.Tasking.Rendezvous);
 108
 109 with System.Tasking.Initialization;
 110 --  used for Defer_Abort
 111 --           Undefer_Abort
 112
 113 with System.Parameters;
 114 --  used for Single_Lock
 115
 116 with Unchecked_Conversion;
 117
 118 package body System.Interrupts is
 119
 120    use Tasking;
 121    use System.Parameters;
 122    use Ada.Exceptions;
 123
 124    package POP renames System.Task_Primitives.Operations;
 125    package PIO renames System.Task_Primitives.Interrupt_Operations;
 126    package IMNG renames System.Interrupt_Management;
 127    package IMOP renames System.Interrupt_Management.Operations;
 128
 129    function To_System is new Unchecked_Conversion
 130      (Ada.Task_Identification.Task_Id, Task_Id);
 131
 132    -----------------
 133    -- Local Tasks --
 134    -----------------
 135
 136    --  WARNING: System.Tasking.Stages performs calls to this task with
 137    --  low-level constructs. Do not change this spec without synchronizing it.
 138
 139    task Interrupt_Manager is
 140       entry Detach_Interrupt_Entries (T : Task_Id);
 141
 142       entry Initialize (Mask : IMNG.Interrupt_Mask);
 143
 144       entry Attach_Handler
 145         (New_Handler : Parameterless_Handler;
 146          Interrupt   : Interrupt_ID;
 147          Static      : Boolean;
 148          Restoration : Boolean := False);
 149
 150       entry Exchange_Handler
 151         (Old_Handler : out Parameterless_Handler;
 152          New_Handler : Parameterless_Handler;
 153          Interrupt   : Interrupt_ID;
 154          Static      : Boolean);
 155
 156       entry Detach_Handler
 157         (Interrupt   : Interrupt_ID;
 158          Static      : Boolean);
 159
 160       entry Bind_Interrupt_To_Entry
 161         (T         : Task_Id;
 162          E         : Task_Entry_Index;
 163          Interrupt : Interrupt_ID);
 164
 165       entry Block_Interrupt (Interrupt : Interrupt_ID);
 166
 167       entry Unblock_Interrupt (Interrupt : Interrupt_ID);
 168
 169       entry Ignore_Interrupt (Interrupt : Interrupt_ID);
 170
 171       entry Unignore_Interrupt (Interrupt : Interrupt_ID);
 172
 173       pragma Interrupt_Priority (System.Interrupt_Priority'Last);
 174    end Interrupt_Manager;
 175
 176    task type Server_Task (Interrupt : Interrupt_ID) is
 177       pragma Priority (System.Interrupt_Priority'Last);
 178       --  Note: the above pragma Priority is strictly speaking improper since
 179       --  it is outside the range of allowed priorities, but the compiler
 180       --  treats system units specially and does not apply this range checking
 181       --  rule to system units.
 182
 183    end Server_Task;
 184
 185    type Server_Task_Access is access Server_Task;
 186
 187    -------------------------------
 188    -- Local Types and Variables --
 189    -------------------------------
 190
 191    type Entry_Assoc is record
 192       T : Task_Id;
 193       E : Task_Entry_Index;
 194    end record;
 195
 196    type Handler_Assoc is record
 197       H      : Parameterless_Handler;
 198       Static : Boolean;   --  Indicates static binding;
 199    end record;
 200
 201    User_Handler : array (Interrupt_ID'Range) of Handler_Assoc :=
 202                     (others => (null, Static => False));
 203    pragma Volatile_Components (User_Handler);
 204    --  Holds the protected procedure handler (if any) and its Static
 205    --  information for each interrupt. A handler is a Static one if it is
 206    --  specified through the pragma Attach_Handler. Attach_Handler. Otherwise,
 207    --  not static)
 208
 209    User_Entry : array (Interrupt_ID'Range) of Entry_Assoc :=
 210                   (others => (T => Null_Task, E => Null_Task_Entry));
 211    pragma Volatile_Components (User_Entry);
 212    --  Holds the task and entry index (if any) for each interrupt
 213
 214    Blocked : constant array (Interrupt_ID'Range) of Boolean :=
 215      (others => False);
 216    --  ??? pragma Volatile_Components (Blocked);
 217    --  True iff the corresponding interrupt is blocked in the process level
 218
 219    Ignored : array (Interrupt_ID'Range) of Boolean := (others => False);
 220    pragma Volatile_Components (Ignored);
 221    --  True iff the corresponding interrupt is blocked in the process level
 222
 223    Last_Unblocker : constant array (Interrupt_ID'Range) of Task_Id :=
 224      (others => Null_Task);
 225 --  ??? pragma Volatile_Components (Last_Unblocker);
 226    --  Holds the ID of the last Task which Unblocked this Interrupt.
 227    --  It contains Null_Task if no tasks have ever requested the
 228    --  Unblocking operation or the Interrupt is currently Blocked.
 229
 230    Server_ID : array (Interrupt_ID'Range) of Task_Id :=
 231                  (others => Null_Task);
 232    pragma Atomic_Components (Server_ID);
 233    --  Holds the Task_Id of the Server_Task for each interrupt. Task_Id is
 234    --  needed to accomplish locking per Interrupt base. Also is needed to
 235    --  decide whether to create a new Server_Task.
 236
 237    --  Type and Head, Tail of the list containing Registered Interrupt
 238    --  Handlers. These definitions are used to register the handlers specified
 239    --  by the pragma Interrupt_Handler.
 240
 241    type Registered_Handler;
 242    type R_Link is access all Registered_Handler;
 243
 244    type Registered_Handler is record
 245       H :    System.Address := System.Null_Address;
 246       Next : R_Link := null;
 247    end record;
 248
 249    Registered_Handler_Head : R_Link := null;
 250    Registered_Handler_Tail : R_Link := null;
 251
 252    Access_Hold : Server_Task_Access;
 253    --  variable used to allocate Server_Task using "new".
 254
 255    -----------------------
 256    -- Local Subprograms --
 257    -----------------------
 258
 259    function Is_Registered (Handler : Parameterless_Handler) return Boolean;
 260    --  See if the Handler has been "pragma"ed using Interrupt_Handler.
 261    --  Always consider a null handler as registered.
 262
 263    --------------------------------
 264    -- Register_Interrupt_Handler --
 265    --------------------------------
 266
 267    procedure Register_Interrupt_Handler (Handler_Addr : System.Address) is
 268       New_Node_Ptr : R_Link;
 269    begin
 270       --  This routine registers the Handler as usable for Dynamic
 271       --  Interrupt Handler. Routines attaching and detaching Handler
 272       --  dynamically should first consult if the Handler is rgistered.
 273       --  A Program Error should be raised if it is not registered.
 274
 275       --  The pragma Interrupt_Handler can only appear in the library
 276       --  level PO definition and instantiation. Therefore, we do not need
 277       --  to implement Unregistering operation. Neither we need to
 278       --  protect the queue structure using a Lock.
 279
 280       pragma Assert (Handler_Addr /= System.Null_Address);
 281
 282       New_Node_Ptr := new Registered_Handler;
 283       New_Node_Ptr.H := Handler_Addr;
 284
 285       if Registered_Handler_Head = null then
 286          Registered_Handler_Head := New_Node_Ptr;
 287          Registered_Handler_Tail := New_Node_Ptr;
 288
 289       else
 290          Registered_Handler_Tail.Next := New_Node_Ptr;
 291          Registered_Handler_Tail := New_Node_Ptr;
 292       end if;
 293    end Register_Interrupt_Handler;
 294
 295    -------------------
 296    -- Is_Registered --
 297    -------------------
 298
 299    function Is_Registered (Handler : Parameterless_Handler) return Boolean is
 300       type Fat_Ptr is record
 301          Object_Addr  : System.Address;
 302          Handler_Addr : System.Address;
 303       end record;
 304
 305       function To_Fat_Ptr is new Unchecked_Conversion
 306         (Parameterless_Handler, Fat_Ptr);
 307
 308       Ptr : R_Link;
 309       Fat : Fat_Ptr;
 310
 311    begin
 312       if Handler = null then
 313          return True;
 314       end if;
 315
 316       Fat := To_Fat_Ptr (Handler);
 317
 318       Ptr := Registered_Handler_Head;
 319
 320       while Ptr /= null loop
 321          if Ptr.H = Fat.Handler_Addr then
 322             return True;
 323          end if;
 324
 325          Ptr := Ptr.Next;
 326       end loop;
 327
 328       return False;
 329    end Is_Registered;
 330
 331    -----------------
 332    -- Is_Reserved --
 333    -----------------
 334
 335    function Is_Reserved (Interrupt : Interrupt_ID) return Boolean is
 336    begin
 337       return IMNG.Reserve (IMNG.Interrupt_ID (Interrupt));
 338    end Is_Reserved;
 339
 340    -----------------------
 341    -- Is_Entry_Attached --
 342    -----------------------
 343
 344    function Is_Entry_Attached (Interrupt : Interrupt_ID) return Boolean is
 345    begin
 346       if Is_Reserved (Interrupt) then
 347          Raise_Exception (Program_Error'Identity, "Interrupt" &
 348            Interrupt_ID'Image (Interrupt) & " is reserved");
 349       end if;
 350
 351       return User_Entry (Interrupt).T /= Null_Task;
 352    end Is_Entry_Attached;
 353
 354    -------------------------
 355    -- Is_Handler_Attached --
 356    -------------------------
 357
 358    function Is_Handler_Attached (Interrupt : Interrupt_ID) return Boolean is
 359    begin
 360       if Is_Reserved (Interrupt) then
 361          Raise_Exception (Program_Error'Identity, "Interrupt" &
 362            Interrupt_ID'Image (Interrupt) & " is reserved");
 363       end if;
 364
 365       return User_Handler (Interrupt).H /= null;
 366    end Is_Handler_Attached;
 367
 368    ----------------
 369    -- Is_Blocked --
 370    ----------------
 371
 372    function Is_Blocked (Interrupt : Interrupt_ID) return Boolean is
 373    begin
 374       if Is_Reserved (Interrupt) then
 375          Raise_Exception (Program_Error'Identity, "Interrupt" &
 376            Interrupt_ID'Image (Interrupt) & " is reserved");
 377       end if;
 378
 379       return Blocked (Interrupt);
 380    end Is_Blocked;
 381
 382    ----------------
 383    -- Is_Ignored --
 384    ----------------
 385
 386    function Is_Ignored (Interrupt : Interrupt_ID) return Boolean is
 387    begin
 388       if Is_Reserved (Interrupt) then
 389          Raise_Exception (Program_Error'Identity, "Interrupt" &
 390            Interrupt_ID'Image (Interrupt) & " is reserved");
 391       end if;
 392
 393       return Ignored (Interrupt);
 394    end Is_Ignored;
 395
 396    ---------------------
 397    -- Current_Handler --
 398    ---------------------
 399
 400    function Current_Handler
 401      (Interrupt : Interrupt_ID) return Parameterless_Handler
 402    is
 403    begin
 404       if Is_Reserved (Interrupt) then
 405          Raise_Exception (Program_Error'Identity, "Interrupt" &
 406            Interrupt_ID'Image (Interrupt) & " is reserved");
 407       end if;
 408
 409       --  ??? Since Parameterless_Handler is not Atomic, the current
 410       --  implementation is wrong. We need a new service in Interrupt_Manager
 411       --  to ensure atomicity.
 412
 413       return User_Handler (Interrupt).H;
 414    end Current_Handler;
 415
 416    --------------------
 417    -- Attach_Handler --
 418    --------------------
 419
 420    --  Calling this procedure with New_Handler = null and Static = True
 421    --  means we want to detach the current handler regardless of the
 422    --  previous handler's binding status (ie. do not care if it is a
 423    --  dynamic or static handler).
 424
 425    --  This option is needed so that during the finalization of a PO, we
 426    --  can detach handlers attached through pragma Attach_Handler.
 427
 428    procedure Attach_Handler
 429      (New_Handler : Parameterless_Handler;
 430       Interrupt   : Interrupt_ID;
 431       Static      : Boolean := False) is
 432    begin
 433       if Is_Reserved (Interrupt) then
 434          Raise_Exception (Program_Error'Identity, "Interrupt" &
 435            Interrupt_ID'Image (Interrupt) & " is reserved");
 436       end if;
 437
 438       Interrupt_Manager.Attach_Handler (New_Handler, Interrupt, Static);
 439
 440    end Attach_Handler;
 441
 442    ----------------------
 443    -- Exchange_Handler --
 444    ----------------------
 445
 446    --  Calling this procedure with New_Handler = null and Static = True means
 447    --  we want to detach the current handler regardless of the previous
 448    --  handler's binding status (ie. do not care if it is dynamic or static
 449    --  handler).
 450
 451    --  This option is needed so that during the finalization of a PO, we can
 452    --  detach handlers attached through pragma Attach_Handler.
 453
 454    procedure Exchange_Handler
 455      (Old_Handler : out Parameterless_Handler;
 456       New_Handler : Parameterless_Handler;
 457       Interrupt   : Interrupt_ID;
 458       Static      : Boolean := False)
 459    is
 460    begin
 461       if Is_Reserved (Interrupt) then
 462          Raise_Exception (Program_Error'Identity, "Interrupt" &
 463            Interrupt_ID'Image (Interrupt) & " is reserved");
 464       end if;
 465
 466       Interrupt_Manager.Exchange_Handler
 467         (Old_Handler, New_Handler, Interrupt, Static);
 468
 469    end Exchange_Handler;
 470
 471    --------------------
 472    -- Detach_Handler --
 473    --------------------
 474
 475    --  Calling this procedure with Static = True means we want to Detach the
 476    --  current handler regardless of the previous handler's binding status
 477    --  (i.e. do not care if it is a dynamic or static handler).
 478
 479    --  This option is needed so that during the finalization of a PO, we can
 480    --  detach handlers attached through pragma Attach_Handler.
 481
 482    procedure Detach_Handler
 483      (Interrupt : Interrupt_ID;
 484       Static    : Boolean := False)
 485    is
 486    begin
 487       if Is_Reserved (Interrupt) then
 488          Raise_Exception (Program_Error'Identity, "Interrupt" &
 489            Interrupt_ID'Image (Interrupt) & " is reserved");
 490       end if;
 491
 492       Interrupt_Manager.Detach_Handler (Interrupt, Static);
 493    end Detach_Handler;
 494
 495    ---------------
 496    -- Reference --
 497    ---------------
 498
 499    function Reference (Interrupt : Interrupt_ID) return System.Address is
 500    begin
 501       if Is_Reserved (Interrupt) then
 502          Raise_Exception (Program_Error'Identity, "Interrupt" &
 503            Interrupt_ID'Image (Interrupt) & " is reserved");
 504       end if;
 505
 506       return Storage_Elements.To_Address
 507         (Storage_Elements.Integer_Address (Interrupt));
 508    end Reference;
 509
 510    -----------------------------
 511    -- Bind_Interrupt_To_Entry --
 512    -----------------------------
 513
 514    --  This procedure raises a Program_Error if it tries to
 515    --  bind an interrupt to which an Entry or a Procedure is
 516    --  already bound.
 517
 518    procedure Bind_Interrupt_To_Entry
 519      (T       : Task_Id;
 520       E       : Task_Entry_Index;
 521       Int_Ref : System.Address)
 522    is
 523       Interrupt : constant Interrupt_ID :=
 524         Interrupt_ID (Storage_Elements.To_Integer (Int_Ref));
 525
 526    begin
 527       if Is_Reserved (Interrupt) then
 528          Raise_Exception (Program_Error'Identity, "Interrupt" &
 529            Interrupt_ID'Image (Interrupt) & " is reserved");
 530       end if;
 531
 532       Interrupt_Manager.Bind_Interrupt_To_Entry (T, E, Interrupt);
 533
 534    end Bind_Interrupt_To_Entry;
 535
 536    ------------------------------
 537    -- Detach_Interrupt_Entries --
 538    ------------------------------
 539
 540    procedure Detach_Interrupt_Entries (T : Task_Id) is
 541    begin
 542       Interrupt_Manager.Detach_Interrupt_Entries (T);
 543    end Detach_Interrupt_Entries;
 544
 545    ---------------------
 546    -- Block_Interrupt --
 547    ---------------------
 548
 549    procedure Block_Interrupt (Interrupt : Interrupt_ID) is
 550    begin
 551       if Is_Reserved (Interrupt) then
 552          Raise_Exception (Program_Error'Identity, "Interrupt" &
 553            Interrupt_ID'Image (Interrupt) & " is reserved");
 554       end if;
 555
 556       Interrupt_Manager.Block_Interrupt (Interrupt);
 557    end Block_Interrupt;
 558
 559    -----------------------
 560    -- Unblock_Interrupt --
 561    -----------------------
 562
 563    procedure Unblock_Interrupt (Interrupt : Interrupt_ID) is
 564    begin
 565       if Is_Reserved (Interrupt) then
 566          Raise_Exception (Program_Error'Identity, "Interrupt" &
 567            Interrupt_ID'Image (Interrupt) & " is reserved");
 568       end if;
 569
 570       Interrupt_Manager.Unblock_Interrupt (Interrupt);
 571    end Unblock_Interrupt;
 572
 573    ------------------
 574    -- Unblocked_By --
 575    ------------------
 576
 577    function Unblocked_By
 578      (Interrupt : Interrupt_ID) return System.Tasking.Task_Id is
 579    begin
 580       if Is_Reserved (Interrupt) then
 581          Raise_Exception (Program_Error'Identity, "Interrupt" &
 582            Interrupt_ID'Image (Interrupt) & " is reserved");
 583       end if;
 584
 585       return Last_Unblocker (Interrupt);
 586    end Unblocked_By;
 587
 588    ----------------------
 589    -- Ignore_Interrupt --
 590    ----------------------
 591
 592    procedure Ignore_Interrupt (Interrupt : Interrupt_ID) is
 593    begin
 594       if Is_Reserved (Interrupt) then
 595          Raise_Exception (Program_Error'Identity, "Interrupt" &
 596            Interrupt_ID'Image (Interrupt) & " is reserved");
 597       end if;
 598
 599       Interrupt_Manager.Ignore_Interrupt (Interrupt);
 600    end Ignore_Interrupt;
 601
 602    ------------------------
 603    -- Unignore_Interrupt --
 604    ------------------------
 605
 606    procedure Unignore_Interrupt (Interrupt : Interrupt_ID) is
 607    begin
 608       if Is_Reserved (Interrupt) then
 609          Raise_Exception (Program_Error'Identity, "Interrupt" &
 610            Interrupt_ID'Image (Interrupt) & " is reserved");
 611       end if;
 612
 613       Interrupt_Manager.Unignore_Interrupt (Interrupt);
 614    end Unignore_Interrupt;
 615
 616    -----------------------
 617    -- Interrupt_Manager --
 618    -----------------------
 619
 620    task body Interrupt_Manager is
 621
 622       --------------------
 623       -- Local Routines --
 624       --------------------
 625
 626       procedure Unprotected_Exchange_Handler
 627         (Old_Handler : out Parameterless_Handler;
 628          New_Handler : Parameterless_Handler;
 629          Interrupt   : Interrupt_ID;
 630          Static      : Boolean;
 631          Restoration : Boolean := False);
 632
 633       procedure Unprotected_Detach_Handler
 634         (Interrupt : Interrupt_ID;
 635          Static    : Boolean);
 636
 637       ----------------------------------
 638       -- Unprotected_Exchange_Handler --
 639       ----------------------------------
 640
 641       procedure Unprotected_Exchange_Handler
 642         (Old_Handler : out Parameterless_Handler;
 643          New_Handler : Parameterless_Handler;
 644          Interrupt   : Interrupt_ID;
 645          Static      : Boolean;
 646          Restoration : Boolean := False)
 647       is
 648       begin
 649          if User_Entry (Interrupt).T /= Null_Task then
 650             --  In case we have an Interrupt Entry already installed.
 651             --  raise a program error. (propagate it to the caller).
 652
 653             Raise_Exception (Program_Error'Identity,
 654               "An interrupt is already installed");
 655          end if;
 656
 657          --  Note : A null handler with Static = True will
 658          --  pass the following check. That is the case when we want to
 659          --  Detach a handler regardless of the Static status
 660          --  of the current_Handler.
 661          --  We don't check anything if Restoration is True, since we
 662          --  may be detaching a static handler to restore a dynamic one.
 663
 664          if not Restoration and then not Static
 665             --  Tries to overwrite a static Interrupt Handler with a
 666             --  dynamic Handler
 667
 668            and then (User_Handler (Interrupt).Static
 669
 670                         --  The new handler is not specified as an
 671                         --  Interrupt Handler by a pragma.
 672
 673                         or else not Is_Registered (New_Handler))
 674          then
 675             Raise_Exception (Program_Error'Identity,
 676               "Trying to overwrite a static Interrupt Handler with a " &
 677               "dynamic Handler");
 678          end if;
 679
 680          --  The interrupt should no longer be ingnored if
 681          --  it was ever ignored.
 682
 683          Ignored (Interrupt) := False;
 684
 685          --  Save the old handler
 686
 687          Old_Handler := User_Handler (Interrupt).H;
 688
 689          --  The new handler
 690
 691          User_Handler (Interrupt).H := New_Handler;
 692
 693          if New_Handler = null then
 694
 695             --  The null handler means we are detaching the handler.
 696
 697             User_Handler (Interrupt).Static := False;
 698
 699          else
 700             User_Handler (Interrupt).Static := Static;
 701          end if;
 702
 703          --  Invoke a corresponding Server_Task if not yet created.
 704          --  Place Task_Id info in Server_ID array.
 705
 706          if Server_ID (Interrupt) = Null_Task then
 707             Access_Hold := new Server_Task (Interrupt);
 708             Server_ID (Interrupt) := To_System (Access_Hold.all'Identity);
 709          else
 710             POP.Wakeup (Server_ID (Interrupt), Interrupt_Server_Idle_Sleep);
 711          end if;
 712
 713       end Unprotected_Exchange_Handler;
 714
 715       --------------------------------
 716       -- Unprotected_Detach_Handler --
 717       --------------------------------
 718
 719       procedure Unprotected_Detach_Handler
 720         (Interrupt   : Interrupt_ID;
 721          Static      : Boolean)
 722       is
 723       begin
 724          if User_Entry (Interrupt).T /= Null_Task then
 725             --  In case we have an Interrupt Entry installed.
 726             --  raise a program error. (propagate it to the caller).
 727
 728             Raise_Exception (Program_Error'Identity,
 729               "An interrupt entry is already installed");
 730          end if;
 731
 732          --  Note : Static = True will pass the following check. That is the
 733          --  case when we want to detach a handler regardless of the static
 734          --  status of the current_Handler.
 735
 736          if not Static and then User_Handler (Interrupt).Static then
 737             --  Tries to detach a static Interrupt Handler.
 738             --  raise a program error.
 739
 740             Raise_Exception (Program_Error'Identity,
 741               "Trying to detach a static Interrupt Handler");
 742          end if;
 743
 744          --  The interrupt should no longer be ignored if
 745          --  it was ever ignored.
 746
 747          Ignored (Interrupt) := False;
 748
 749          --  The new handler
 750
 751          User_Handler (Interrupt).H := null;
 752          User_Handler (Interrupt).Static := False;
 753          IMOP.Interrupt_Self_Process (IMNG.Interrupt_ID (Interrupt));
 754
 755       end Unprotected_Detach_Handler;
 756
 757    --  Start of processing for Interrupt_Manager
 758
 759    begin
 760       --  By making this task independent of master, when the process
 761       --  goes away, the Interrupt_Manager will terminate gracefully.
 762
 763       System.Tasking.Utilities.Make_Independent;
 764
 765       --  Environmen task gets its own interrupt mask, saves it,
 766       --  and then masks all interrupts except the Keep_Unmasked set.
 767
 768       --  During rendezvous, the Interrupt_Manager receives the old
 769       --  interrupt mask of the environment task, and sets its own
 770       --  interrupt mask to that value.
 771
 772       --  The environment task will call the entry of Interrupt_Manager some
 773       --  during elaboration of the body of this package.
 774
 775       accept Initialize (Mask : IMNG.Interrupt_Mask) do
 776          pragma Warnings (Off, Mask);
 777          null;
 778       end Initialize;
 779
 780       --  Note: All tasks in RTS will have all the Reserve Interrupts
 781       --  being masked (except the Interrupt_Manager) and Keep_Unmasked
 782       --  unmasked when created.
 783
 784       --  Abort_Task_Interrupt is one of the Interrupt unmasked
 785       --  in all tasks. We mask the Interrupt in this particular task
 786       --  so that "sigwait" is possible to catch an explicitely sent
 787       --  Abort_Task_Interrupt from the Server_Tasks.
 788
 789       --  This sigwaiting is needed so that we make sure a Server_Task is
 790       --  out of its own sigwait state. This extra synchronization is
 791       --  necessary to prevent following senarios.
 792
 793       --   1) Interrupt_Manager sends an Abort_Task_Interrupt to the
 794       --      Server_Task then changes its own interrupt mask (OS level).
 795       --      If an interrupt (corresponding to the Server_Task) arrives
 796       --      in the nean time we have the Interrupt_Manager umnasked and
 797       --      the Server_Task waiting on sigwait.
 798
 799       --   2) For unbinding handler, we install a default action in the
 800       --      Interrupt_Manager. POSIX.1c states that the result of using
 801       --      "sigwait" and "sigaction" simaltaneously on the same interrupt
 802       --      is undefined. Therefore, we need to be informed from the
 803       --      Server_Task of the fact that the Server_Task is out of its
 804       --      sigwait stage.
 805
 806       loop
 807          --  A block is needed to absorb Program_Error exception
 808
 809          declare
 810             Old_Handler : Parameterless_Handler;
 811          begin
 812             select
 813
 814             accept Attach_Handler
 815                (New_Handler : Parameterless_Handler;
 816                 Interrupt   : Interrupt_ID;
 817                 Static      : Boolean;
 818                 Restoration : Boolean := False)
 819             do
 820                Unprotected_Exchange_Handler
 821                  (Old_Handler, New_Handler, Interrupt, Static, Restoration);
 822             end Attach_Handler;
 823
 824             or accept Exchange_Handler
 825                (Old_Handler : out Parameterless_Handler;
 826                 New_Handler : Parameterless_Handler;
 827                 Interrupt   : Interrupt_ID;
 828                 Static      : Boolean)
 829             do
 830                Unprotected_Exchange_Handler
 831                  (Old_Handler, New_Handler, Interrupt, Static);
 832             end Exchange_Handler;
 833
 834             or accept Detach_Handler
 835                (Interrupt   : Interrupt_ID;
 836                 Static      : Boolean)
 837             do
 838                Unprotected_Detach_Handler (Interrupt, Static);
 839             end Detach_Handler;
 840
 841             or accept Bind_Interrupt_To_Entry
 842               (T       : Task_Id;
 843                E       : Task_Entry_Index;
 844                Interrupt : Interrupt_ID)
 845             do
 846                --  if there is a binding already (either a procedure or an
 847                --  entry), raise Program_Error (propagate it to the caller).
 848
 849                if User_Handler (Interrupt).H /= null
 850                  or else User_Entry (Interrupt).T /= Null_Task
 851                then
 852                   Raise_Exception (Program_Error'Identity,
 853                     "A binding for this interrupt is already present");
 854                end if;
 855
 856                --  The interrupt should no longer be ingnored if
 857                --  it was ever ignored.
 858
 859                Ignored (Interrupt) := False;
 860                User_Entry (Interrupt) := Entry_Assoc'(T => T, E => E);
 861
 862                --  Indicate the attachment of Interrupt Entry in ATCB.
 863                --  This is need so that when an Interrupt Entry task
 864                --  terminates the binding can be cleaned.
 865                --  The call to unbinding must be
 866                --  make by the task before it terminates.
 867
 868                T.Interrupt_Entry := True;
 869
 870                --  Invoke a corresponding Server_Task if not yet created.
 871                --  Place Task_Id info in Server_ID array.
 872
 873                if Server_ID (Interrupt) = Null_Task then
 874
 875                   Access_Hold := new Server_Task (Interrupt);
 876                   Server_ID (Interrupt) :=
 877                     To_System (Access_Hold.all'Identity);
 878                else
 879                   POP.Wakeup (Server_ID (Interrupt),
 880                               Interrupt_Server_Idle_Sleep);
 881                end if;
 882             end Bind_Interrupt_To_Entry;
 883
 884             or accept Detach_Interrupt_Entries (T : Task_Id)
 885             do
 886                for J in Interrupt_ID'Range loop
 887                   if not Is_Reserved (J) then
 888                      if User_Entry (J).T = T then
 889
 890                         --  The interrupt should no longer be ignored if
 891                         --  it was ever ignored.
 892
 893                         Ignored (J) := False;
 894                         User_Entry (J) :=
 895                           Entry_Assoc'(T => Null_Task, E => Null_Task_Entry);
 896                         IMOP.Interrupt_Self_Process (IMNG.Interrupt_ID (J));
 897                      end if;
 898                   end if;
 899                end loop;
 900
 901                --  Indicate in ATCB that no Interrupt Entries are attached.
 902
 903                T.Interrupt_Entry := False;
 904             end Detach_Interrupt_Entries;
 905
 906             or accept Block_Interrupt (Interrupt : Interrupt_ID) do
 907                pragma Warnings (Off, Interrupt);
 908                raise Program_Error;
 909             end Block_Interrupt;
 910
 911             or accept Unblock_Interrupt (Interrupt : Interrupt_ID) do
 912                pragma Warnings (Off, Interrupt);
 913                raise Program_Error;
 914             end Unblock_Interrupt;
 915
 916             or accept Ignore_Interrupt (Interrupt : Interrupt_ID) do
 917                pragma Warnings (Off, Interrupt);
 918                raise Program_Error;
 919             end Ignore_Interrupt;
 920
 921             or accept Unignore_Interrupt (Interrupt : Interrupt_ID) do
 922                pragma Warnings (Off, Interrupt);
 923                raise Program_Error;
 924             end Unignore_Interrupt;
 925
 926             end select;
 927
 928          exception
 929             --  If there is a program error we just want to propagate it
 930             --  to the caller and do not want to stop this task.
 931
 932             when Program_Error =>
 933                null;
 934
 935             when others =>
 936                pragma Assert (False);
 937                null;
 938          end;
 939       end loop;
 940    end Interrupt_Manager;
 941
 942    -----------------
 943    -- Server_Task --
 944    -----------------
 945
 946    task body Server_Task is
 947       Self_ID         : constant Task_Id := Self;
 948       Tmp_Handler     : Parameterless_Handler;
 949       Tmp_ID          : Task_Id;
 950       Tmp_Entry_Index : Task_Entry_Index;
 951       Intwait_Mask    : aliased IMNG.Interrupt_Mask;
 952
 953    begin
 954       --  By making this task independent of master, when the process
 955       --  goes away, the Server_Task will terminate gracefully.
 956
 957       System.Tasking.Utilities.Make_Independent;
 958
 959       --  Install default action in system level.
 960
 961       IMOP.Install_Default_Action (IMNG.Interrupt_ID (Interrupt));
 962
 963       --  Set up the mask (also clears the event flag)
 964
 965       IMOP.Empty_Interrupt_Mask (Intwait_Mask'Access);
 966       IMOP.Add_To_Interrupt_Mask
 967         (Intwait_Mask'Access, IMNG.Interrupt_ID (Interrupt));
 968
 969       --  Remember the Interrupt_ID for Abort_Task.
 970
 971       PIO.Set_Interrupt_ID (IMNG.Interrupt_ID (Interrupt), Self_ID);
 972
 973       --  Note: All tasks in RTS will have all the Reserve Interrupts
 974       --  being masked (except the Interrupt_Manager) and Keep_Unmasked
 975       --  unmasked when created.
 976
 977       loop
 978          System.Tasking.Initialization.Defer_Abort (Self_ID);
 979
 980          --  A Handler or an Entry is installed. At this point all tasks
 981          --  mask for the Interrupt is masked. Catch the Interrupt using
 982          --  sigwait.
 983
 984          --  This task may wake up from sigwait by receiving an interrupt
 985          --  (Abort_Task_Interrupt) from the Interrupt_Manager for unbinding
 986          --  a Procedure Handler or an Entry. Or it could be a wake up
 987          --  from status change (Unblocked -> Blocked). If that is not
 988          --  the case, we should exceute the attached Procedure or Entry.
 989
 990          if Single_Lock then
 991             POP.Lock_RTS;
 992          end if;
 993
 994          POP.Write_Lock (Self_ID);
 995
 996          if User_Handler (Interrupt).H = null
 997            and then User_Entry (Interrupt).T = Null_Task
 998          then
 999             --  No Interrupt binding. If there is an interrupt,
1000             --  Interrupt_Manager will take default action.
1001
1002             Self_ID.Common.State := Interrupt_Server_Idle_Sleep;
1003             POP.Sleep (Self_ID, Interrupt_Server_Idle_Sleep);
1004             Self_ID.Common.State := Runnable;
1005
1006          else
1007             Self_ID.Common.State := Interrupt_Server_Blocked_On_Event_Flag;
1008             Self_ID.Common.State := Runnable;
1009
1010             if not (Self_ID.Deferral_Level = 0
1011                     and then Self_ID.Pending_ATC_Level
1012                              < Self_ID.ATC_Nesting_Level)
1013             then
1014                if User_Handler (Interrupt).H /= null then
1015                   Tmp_Handler := User_Handler (Interrupt).H;
1016
1017                   --  RTS calls should not be made with self being locked.
1018
1019                   POP.Unlock (Self_ID);
1020
1021                   if Single_Lock then
1022                      POP.Unlock_RTS;
1023                   end if;
1024
1025                   Tmp_Handler.all;
1026
1027                   if Single_Lock then
1028                      POP.Lock_RTS;
1029                   end if;
1030
1031                   POP.Write_Lock (Self_ID);
1032
1033                elsif User_Entry (Interrupt).T /= Null_Task then
1034                   Tmp_ID := User_Entry (Interrupt).T;
1035                   Tmp_Entry_Index := User_Entry (Interrupt).E;
1036
1037                   --  RTS calls should not be made with self being locked.
1038
1039                   POP.Unlock (Self_ID);
1040
1041                   if Single_Lock then
1042                      POP.Unlock_RTS;
1043                   end if;
1044
1045                   System.Tasking.Rendezvous.Call_Simple
1046                     (Tmp_ID, Tmp_Entry_Index, System.Null_Address);
1047
1048                   if Single_Lock then
1049                      POP.Lock_RTS;
1050                   end if;
1051
1052                   POP.Write_Lock (Self_ID);
1053                end if;
1054             end if;
1055          end if;
1056
1057          POP.Unlock (Self_ID);
1058
1059          if Single_Lock then
1060             POP.Unlock_RTS;
1061          end if;
1062
1063          System.Tasking.Initialization.Undefer_Abort (Self_ID);
1064
1065          --  Undefer abort here to allow a window for this task
1066          --  to be aborted  at the time of system shutdown.
1067       end loop;
1068    end Server_Task;
1069
1070    -------------------------------------
1071    -- Has_Interrupt_Or_Attach_Handler --
1072    -------------------------------------
1073
1074    function Has_Interrupt_Or_Attach_Handler
1075      (Object : access Dynamic_Interrupt_Protection) return Boolean
1076    is
1077       pragma Warnings (Off, Object);
1078
1079    begin
1080       return True;
1081    end Has_Interrupt_Or_Attach_Handler;
1082
1083    --------------
1084    -- Finalize --
1085    --------------
1086
1087    procedure Finalize (Object : in out Static_Interrupt_Protection) is
1088    begin
1089       --  ??? loop to be executed only when we're not doing library level
1090       --  finalization, since in this case all interrupt tasks are gone.
1091
1092       if not Interrupt_Manager'Terminated then
1093          for N in reverse Object.Previous_Handlers'Range loop
1094             Interrupt_Manager.Attach_Handler
1095               (New_Handler => Object.Previous_Handlers (N).Handler,
1096                Interrupt   => Object.Previous_Handlers (N).Interrupt,
1097                Static      => Object.Previous_Handlers (N).Static,
1098                Restoration => True);
1099          end loop;
1100       end if;
1101
1102       Tasking.Protected_Objects.Entries.Finalize
1103         (Tasking.Protected_Objects.Entries.Protection_Entries (Object));
1104    end Finalize;
1105
1106    -------------------------------------
1107    -- Has_Interrupt_Or_Attach_Handler --
1108    -------------------------------------
1109
1110    function Has_Interrupt_Or_Attach_Handler
1111      (Object : access Static_Interrupt_Protection) return Boolean
1112    is
1113       pragma Warnings (Off, Object);
1114    begin
1115       return True;
1116    end Has_Interrupt_Or_Attach_Handler;
1117
1118    ----------------------
1119    -- Install_Handlers --
1120    ----------------------
1121
1122    procedure Install_Handlers
1123      (Object       : access Static_Interrupt_Protection;
1124       New_Handlers : New_Handler_Array)
1125    is
1126    begin
1127       for N in New_Handlers'Range loop
1128
1129          --  We need a lock around this ???
1130
1131          Object.Previous_Handlers (N).Interrupt := New_Handlers (N).Interrupt;
1132          Object.Previous_Handlers (N).Static    := User_Handler
1133            (New_Handlers (N).Interrupt).Static;
1134
1135          --  We call Exchange_Handler and not directly Interrupt_Manager.
1136          --  Exchange_Handler so we get the Is_Reserved check.
1137
1138          Exchange_Handler
1139            (Old_Handler => Object.Previous_Handlers (N).Handler,
1140             New_Handler => New_Handlers (N).Handler,
1141             Interrupt   => New_Handlers (N).Interrupt,
1142             Static      => True);
1143       end loop;
1144    end Install_Handlers;
1145
1146 --  Elaboration code for package System.Interrupts
1147
1148 begin
1149
1150    --  Get Interrupt_Manager's ID so that Abort_Interrupt can be sent.
1151
1152    Interrupt_Manager_ID := To_System (Interrupt_Manager'Identity);
1153
1154    --  During the elaboration of this package body we want RTS to inherit the
1155    --  interrupt mask from the Environment Task.
1156
1157    --  The Environment Task should have gotten its mask from the enclosing
1158    --  process during the RTS start up. (See in s-inmaop.adb). Pass the
1159    --  Interrupt_Mask of the Environment task to the Interrupt_Manager.
1160
1161    --  Note : At this point we know that all tasks (including RTS internal
1162    --  servers) are masked for non-reserved signals (see s-taprop.adb). Only
1163    --  the Interrupt_Manager will have masks set up differently inheriting the
1164    --  original Environment Task's mask.
1165
1166    Interrupt_Manager.Initialize (IMOP.Environment_Mask);
1167 end System.Interrupts;