gcc/ada/s-taprop-linux.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --     S Y S T E M . T A S K _ P R I M I T I V E S . O P E R A T I O N S    --
   6 --                                                                          --
   7 --                                  B o d y                                 --
   8 --                                                                          --
   9 --         Copyright (C) 1992-2015, Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNARL was developed by the GNARL team at Florida State University.       --
  28 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This is a GNU/Linux (GNU/LinuxThreads) version of this package
  33
  34 --  This package contains all the GNULL primitives that interface directly with
  35 --  the underlying OS.
  36
  37 pragma Polling (Off);
  38 --  Turn off polling, we do not want ATC polling to take place during tasking
  39 --  operations. It causes infinite loops and other problems.
  40
  41 with Interfaces.C;
  42
  43 with System.Task_Info;
  44 with System.Tasking.Debug;
  45 with System.Interrupt_Management;
  46 with System.OS_Constants;
  47 with System.OS_Primitives;
  48 with System.Stack_Checking.Operations;
  49 with System.Multiprocessors;
  50
  51 with System.Soft_Links;
  52 --  We use System.Soft_Links instead of System.Tasking.Initialization
  53 --  because the later is a higher level package that we shouldn't depend on.
  54 --  For example when using the restricted run time, it is replaced by
  55 --  System.Tasking.Restricted.Stages.
  56
  57 package body System.Task_Primitives.Operations is
  58
  59    package OSC renames System.OS_Constants;
  60    package SSL renames System.Soft_Links;
  61    package SC renames System.Stack_Checking.Operations;
  62
  63    use System.Tasking.Debug;
  64    use System.Tasking;
  65    use Interfaces.C;
  66    use System.OS_Interface;
  67    use System.Parameters;
  68    use System.OS_Primitives;
  69    use System.Task_Info;
  70
  71    ----------------
  72    -- Local Data --
  73    ----------------
  74
  75    --  The followings are logically constants, but need to be initialized
  76    --  at run time.
  77
  78    Single_RTS_Lock : aliased RTS_Lock;
  79    --  This is a lock to allow only one thread of control in the RTS at
  80    --  a time; it is used to execute in mutual exclusion from all other tasks.
  81    --  Used mainly in Single_Lock mode, but also to protect All_Tasks_List
  82
  83    Environment_Task_Id : Task_Id;
  84    --  A variable to hold Task_Id for the environment task
  85
  86    Unblocked_Signal_Mask : aliased sigset_t;
  87    --  The set of signals that should be unblocked in all tasks
  88
  89    --  The followings are internal configuration constants needed
  90
  91    Next_Serial_Number : Task_Serial_Number := 100;
  92    --  We start at 100 (reserve some special values for using in error checks)
  93
  94    Time_Slice_Val : Integer;
  95    pragma Import (C, Time_Slice_Val, "__gl_time_slice_val");
  96
  97    Dispatching_Policy : Character;
  98    pragma Import (C, Dispatching_Policy, "__gl_task_dispatching_policy");
  99
 100    Locking_Policy : Character;
 101    pragma Import (C, Locking_Policy, "__gl_locking_policy");
 102
 103    Foreign_Task_Elaborated : aliased Boolean := True;
 104    --  Used to identified fake tasks (i.e., non-Ada Threads)
 105
 106    Use_Alternate_Stack : constant Boolean := Alternate_Stack_Size /= 0;
 107    --  Whether to use an alternate signal stack for stack overflows
 108
 109    Abort_Handler_Installed : Boolean := False;
 110    --  True if a handler for the abort signal is installed
 111
 112    Null_Thread_Id : constant pthread_t := pthread_t'Last;
 113    --  Constant to indicate that the thread identifier has not yet been
 114    --  initialized.
 115
 116    --------------------
 117    -- Local Packages --
 118    --------------------
 119
 120    package Specific is
 121
 122       procedure Initialize (Environment_Task : Task_Id);
 123       pragma Inline (Initialize);
 124       --  Initialize various data needed by this package
 125
 126       function Is_Valid_Task return Boolean;
 127       pragma Inline (Is_Valid_Task);
 128       --  Does executing thread have a TCB?
 129
 130       procedure Set (Self_Id : Task_Id);
 131       pragma Inline (Set);
 132       --  Set the self id for the current task
 133
 134       function Self return Task_Id;
 135       pragma Inline (Self);
 136       --  Return a pointer to the Ada Task Control Block of the calling task
 137
 138    end Specific;
 139
 140    package body Specific is separate;
 141    --  The body of this package is target specific
 142
 143    ----------------------------------
 144    -- ATCB allocation/deallocation --
 145    ----------------------------------
 146
 147    package body ATCB_Allocation is separate;
 148    --  The body of this package is shared across several targets
 149
 150    ---------------------------------
 151    -- Support for foreign threads --
 152    ---------------------------------
 153
 154    function Register_Foreign_Thread (Thread : Thread_Id) return Task_Id;
 155    --  Allocate and Initialize a new ATCB for the current Thread
 156
 157    function Register_Foreign_Thread
 158      (Thread : Thread_Id) return Task_Id is separate;
 159
 160    -----------------------
 161    -- Local Subprograms --
 162    -----------------------
 163
 164    procedure Abort_Handler (signo : Signal);
 165
 166    -------------------
 167    -- Abort_Handler --
 168    -------------------
 169
 170    procedure Abort_Handler (signo : Signal) is
 171       pragma Unreferenced (signo);
 172
 173       Self_Id : constant Task_Id := Self;
 174       Result  : Interfaces.C.int;
 175       Old_Set : aliased sigset_t;
 176
 177    begin
 178       --  It's not safe to raise an exception when using GCC ZCX mechanism.
 179       --  Note that we still need to install a signal handler, since in some
 180       --  cases (e.g. shutdown of the Server_Task in System.Interrupts) we
 181       --  need to send the Abort signal to a task.
 182
 183       if ZCX_By_Default then
 184          return;
 185       end if;
 186
 187       if Self_Id.Deferral_Level = 0
 188         and then Self_Id.Pending_ATC_Level < Self_Id.ATC_Nesting_Level
 189         and then not Self_Id.Aborting
 190       then
 191          Self_Id.Aborting := True;
 192
 193          --  Make sure signals used for RTS internal purpose are unmasked
 194
 195          Result :=
 196            pthread_sigmask
 197              (SIG_UNBLOCK,
 198               Unblocked_Signal_Mask'Access,
 199               Old_Set'Access);
 200          pragma Assert (Result = 0);
 201
 202          raise Standard'Abort_Signal;
 203       end if;
 204    end Abort_Handler;
 205
 206    --------------
 207    -- Lock_RTS --
 208    --------------
 209
 210    procedure Lock_RTS is
 211    begin
 212       Write_Lock (Single_RTS_Lock'Access, Global_Lock => True);
 213    end Lock_RTS;
 214
 215    ----------------
 216    -- Unlock_RTS --
 217    ----------------
 218
 219    procedure Unlock_RTS is
 220    begin
 221       Unlock (Single_RTS_Lock'Access, Global_Lock => True);
 222    end Unlock_RTS;
 223
 224    -----------------
 225    -- Stack_Guard --
 226    -----------------
 227
 228    --  The underlying thread system extends the memory (up to 2MB) when needed
 229
 230    procedure Stack_Guard (T : ST.Task_Id; On : Boolean) is
 231       pragma Unreferenced (T);
 232       pragma Unreferenced (On);
 233    begin
 234       null;
 235    end Stack_Guard;
 236
 237    --------------------
 238    -- Get_Thread_Id  --
 239    --------------------
 240
 241    function Get_Thread_Id (T : ST.Task_Id) return OSI.Thread_Id is
 242    begin
 243       return T.Common.LL.Thread;
 244    end Get_Thread_Id;
 245
 246    ----------
 247    -- Self --
 248    ----------
 249
 250    function Self return Task_Id renames Specific.Self;
 251
 252    ---------------------
 253    -- Initialize_Lock --
 254    ---------------------
 255
 256    --  Note: mutexes and cond_variables needed per-task basis are initialized
 257    --  in Initialize_TCB and the Storage_Error is handled. Other mutexes (such
 258    --  as RTS_Lock, Memory_Lock...) used in RTS is initialized before any
 259    --  status change of RTS. Therefore raising Storage_Error in the following
 260    --  routines should be able to be handled safely.
 261
 262    procedure Initialize_Lock
 263      (Prio : System.Any_Priority;
 264       L    : not null access Lock)
 265    is
 266       pragma Unreferenced (Prio);
 267
 268    begin
 269       if Locking_Policy = 'R' then
 270          declare
 271             RWlock_Attr : aliased pthread_rwlockattr_t;
 272             Result      : Interfaces.C.int;
 273
 274          begin
 275             --  Set the rwlock to prefer writer to avoid writers starvation
 276
 277             Result := pthread_rwlockattr_init (RWlock_Attr'Access);
 278             pragma Assert (Result = 0);
 279
 280             Result := pthread_rwlockattr_setkind_np
 281               (RWlock_Attr'Access,
 282                PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);
 283             pragma Assert (Result = 0);
 284
 285             Result := pthread_rwlock_init (L.RW'Access, RWlock_Attr'Access);
 286
 287             pragma Assert (Result = 0 or else Result = ENOMEM);
 288
 289             if Result = ENOMEM then
 290                raise Storage_Error with "Failed to allocate a lock";
 291             end if;
 292          end;
 293
 294       else
 295          declare
 296             Result : Interfaces.C.int;
 297
 298          begin
 299             Result := pthread_mutex_init (L.WO'Access, null);
 300
 301             pragma Assert (Result = 0 or else Result = ENOMEM);
 302
 303             if Result = ENOMEM then
 304                raise Storage_Error with "Failed to allocate a lock";
 305             end if;
 306          end;
 307       end if;
 308    end Initialize_Lock;
 309
 310    procedure Initialize_Lock
 311      (L     : not null access RTS_Lock;
 312       Level : Lock_Level)
 313    is
 314       pragma Unreferenced (Level);
 315
 316       Result : Interfaces.C.int;
 317
 318    begin
 319       Result := pthread_mutex_init (L, null);
 320
 321       pragma Assert (Result = 0 or else Result = ENOMEM);
 322
 323       if Result = ENOMEM then
 324          raise Storage_Error;
 325       end if;
 326    end Initialize_Lock;
 327
 328    -------------------
 329    -- Finalize_Lock --
 330    -------------------
 331
 332    procedure Finalize_Lock (L : not null access Lock) is
 333       Result : Interfaces.C.int;
 334    begin
 335       if Locking_Policy = 'R' then
 336          Result := pthread_rwlock_destroy (L.RW'Access);
 337       else
 338          Result := pthread_mutex_destroy (L.WO'Access);
 339       end if;
 340       pragma Assert (Result = 0);
 341    end Finalize_Lock;
 342
 343    procedure Finalize_Lock (L : not null access RTS_Lock) is
 344       Result : Interfaces.C.int;
 345    begin
 346       Result := pthread_mutex_destroy (L);
 347       pragma Assert (Result = 0);
 348    end Finalize_Lock;
 349
 350    ----------------
 351    -- Write_Lock --
 352    ----------------
 353
 354    procedure Write_Lock
 355      (L                 : not null access Lock;
 356       Ceiling_Violation : out Boolean)
 357    is
 358       Result : Interfaces.C.int;
 359    begin
 360       if Locking_Policy = 'R' then
 361          Result := pthread_rwlock_wrlock (L.RW'Access);
 362       else
 363          Result := pthread_mutex_lock (L.WO'Access);
 364       end if;
 365
 366       Ceiling_Violation := Result = EINVAL;
 367
 368       --  Assume the cause of EINVAL is a priority ceiling violation
 369
 370       pragma Assert (Result = 0 or else Result = EINVAL);
 371    end Write_Lock;
 372
 373    procedure Write_Lock
 374      (L           : not null access RTS_Lock;
 375       Global_Lock : Boolean := False)
 376    is
 377       Result : Interfaces.C.int;
 378    begin
 379       if not Single_Lock or else Global_Lock then
 380          Result := pthread_mutex_lock (L);
 381          pragma Assert (Result = 0);
 382       end if;
 383    end Write_Lock;
 384
 385    procedure Write_Lock (T : Task_Id) is
 386       Result : Interfaces.C.int;
 387    begin
 388       if not Single_Lock then
 389          Result := pthread_mutex_lock (T.Common.LL.L'Access);
 390          pragma Assert (Result = 0);
 391       end if;
 392    end Write_Lock;
 393
 394    ---------------
 395    -- Read_Lock --
 396    ---------------
 397
 398    procedure Read_Lock
 399      (L                 : not null access Lock;
 400       Ceiling_Violation : out Boolean)
 401    is
 402       Result : Interfaces.C.int;
 403    begin
 404       if Locking_Policy = 'R' then
 405          Result := pthread_rwlock_rdlock (L.RW'Access);
 406       else
 407          Result := pthread_mutex_lock (L.WO'Access);
 408       end if;
 409
 410       Ceiling_Violation := Result = EINVAL;
 411
 412       --  Assume the cause of EINVAL is a priority ceiling violation
 413
 414       pragma Assert (Result = 0 or else Result = EINVAL);
 415    end Read_Lock;
 416
 417    ------------
 418    -- Unlock --
 419    ------------
 420
 421    procedure Unlock (L : not null access Lock) is
 422       Result : Interfaces.C.int;
 423    begin
 424       if Locking_Policy = 'R' then
 425          Result := pthread_rwlock_unlock (L.RW'Access);
 426       else
 427          Result := pthread_mutex_unlock (L.WO'Access);
 428       end if;
 429       pragma Assert (Result = 0);
 430    end Unlock;
 431
 432    procedure Unlock
 433      (L           : not null access RTS_Lock;
 434       Global_Lock : Boolean := False)
 435    is
 436       Result : Interfaces.C.int;
 437    begin
 438       if not Single_Lock or else Global_Lock then
 439          Result := pthread_mutex_unlock (L);
 440          pragma Assert (Result = 0);
 441       end if;
 442    end Unlock;
 443
 444    procedure Unlock (T : Task_Id) is
 445       Result : Interfaces.C.int;
 446    begin
 447       if not Single_Lock then
 448          Result := pthread_mutex_unlock (T.Common.LL.L'Access);
 449          pragma Assert (Result = 0);
 450       end if;
 451    end Unlock;
 452
 453    -----------------
 454    -- Set_Ceiling --
 455    -----------------
 456
 457    --  Dynamic priority ceilings are not supported by the underlying system
 458
 459    procedure Set_Ceiling
 460      (L    : not null access Lock;
 461       Prio : System.Any_Priority)
 462    is
 463       pragma Unreferenced (L, Prio);
 464    begin
 465       null;
 466    end Set_Ceiling;
 467
 468    -----------
 469    -- Sleep --
 470    -----------
 471
 472    procedure Sleep
 473      (Self_ID  : Task_Id;
 474       Reason   : System.Tasking.Task_States)
 475    is
 476       pragma Unreferenced (Reason);
 477
 478       Result : Interfaces.C.int;
 479
 480    begin
 481       pragma Assert (Self_ID = Self);
 482
 483       Result :=
 484         pthread_cond_wait
 485           (cond  => Self_ID.Common.LL.CV'Access,
 486            mutex => (if Single_Lock
 487                      then Single_RTS_Lock'Access
 488                      else Self_ID.Common.LL.L'Access));
 489
 490       --  EINTR is not considered a failure
 491
 492       pragma Assert (Result = 0 or else Result = EINTR);
 493    end Sleep;
 494
 495    -----------------
 496    -- Timed_Sleep --
 497    -----------------
 498
 499    --  This is for use within the run-time system, so abort is
 500    --  assumed to be already deferred, and the caller should be
 501    --  holding its own ATCB lock.
 502
 503    procedure Timed_Sleep
 504      (Self_ID  : Task_Id;
 505       Time     : Duration;
 506       Mode     : ST.Delay_Modes;
 507       Reason   : System.Tasking.Task_States;
 508       Timedout : out Boolean;
 509       Yielded  : out Boolean)
 510    is
 511       pragma Unreferenced (Reason);
 512
 513       Base_Time  : constant Duration := Monotonic_Clock;
 514       Check_Time : Duration := Base_Time;
 515       Abs_Time   : Duration;
 516       Request    : aliased timespec;
 517       Result     : Interfaces.C.int;
 518
 519    begin
 520       Timedout := True;
 521       Yielded := False;
 522
 523       Abs_Time :=
 524         (if Mode = Relative
 525          then Duration'Min (Time, Max_Sensible_Delay) + Check_Time
 526          else Duration'Min (Check_Time + Max_Sensible_Delay, Time));
 527
 528       if Abs_Time > Check_Time then
 529          Request := To_Timespec (Abs_Time);
 530
 531          loop
 532             exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;
 533
 534             Result :=
 535               pthread_cond_timedwait
 536                 (cond    => Self_ID.Common.LL.CV'Access,
 537                  mutex   => (if Single_Lock
 538                              then Single_RTS_Lock'Access
 539                              else Self_ID.Common.LL.L'Access),
 540                  abstime => Request'Access);
 541
 542             Check_Time := Monotonic_Clock;
 543             exit when Abs_Time <= Check_Time or else Check_Time < Base_Time;
 544
 545             if Result = 0 or else Result = EINTR then
 546
 547                --  Somebody may have called Wakeup for us
 548
 549                Timedout := False;
 550                exit;
 551             end if;
 552
 553             pragma Assert (Result = ETIMEDOUT);
 554          end loop;
 555       end if;
 556    end Timed_Sleep;
 557
 558    -----------------
 559    -- Timed_Delay --
 560    -----------------
 561
 562    --  This is for use in implementing delay statements, so we assume the
 563    --  caller is abort-deferred but is holding no locks.
 564
 565    procedure Timed_Delay
 566      (Self_ID : Task_Id;
 567       Time    : Duration;
 568       Mode    : ST.Delay_Modes)
 569    is
 570       Base_Time  : constant Duration := Monotonic_Clock;
 571       Check_Time : Duration := Base_Time;
 572       Abs_Time   : Duration;
 573       Request    : aliased timespec;
 574
 575       Result : Interfaces.C.int;
 576       pragma Warnings (Off, Result);
 577
 578    begin
 579       if Single_Lock then
 580          Lock_RTS;
 581       end if;
 582
 583       Write_Lock (Self_ID);
 584
 585       Abs_Time :=
 586         (if Mode = Relative
 587          then Time + Check_Time
 588          else Duration'Min (Check_Time + Max_Sensible_Delay, Time));
 589
 590       if Abs_Time > Check_Time then
 591          Request := To_Timespec (Abs_Time);
 592          Self_ID.Common.State := Delay_Sleep;
 593
 594          loop
 595             exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;
 596
 597             Result :=
 598               pthread_cond_timedwait
 599                 (cond    => Self_ID.Common.LL.CV'Access,
 600                  mutex   => (if Single_Lock
 601                              then Single_RTS_Lock'Access
 602                              else Self_ID.Common.LL.L'Access),
 603                  abstime => Request'Access);
 604
 605             Check_Time := Monotonic_Clock;
 606             exit when Abs_Time <= Check_Time or else Check_Time < Base_Time;
 607
 608             pragma Assert (Result = 0 or else
 609               Result = ETIMEDOUT or else
 610               Result = EINTR);
 611          end loop;
 612
 613          Self_ID.Common.State := Runnable;
 614       end if;
 615
 616       Unlock (Self_ID);
 617
 618       if Single_Lock then
 619          Unlock_RTS;
 620       end if;
 621
 622       Result := sched_yield;
 623    end Timed_Delay;
 624
 625    ---------------------
 626    -- Monotonic_Clock --
 627    ---------------------
 628
 629    function Monotonic_Clock return Duration is
 630       TS     : aliased timespec;
 631       Result : int;
 632    begin
 633       Result := clock_gettime
 634         (clock_id => OSC.CLOCK_RT_Ada, tp => TS'Unchecked_Access);
 635       pragma Assert (Result = 0);
 636
 637       return To_Duration (TS);
 638    end Monotonic_Clock;
 639
 640    -------------------
 641    -- RT_Resolution --
 642    -------------------
 643
 644    function RT_Resolution return Duration is
 645       TS     : aliased timespec;
 646       Result : int;
 647
 648    begin
 649       Result := clock_getres (OSC.CLOCK_REALTIME, TS'Unchecked_Access);
 650       pragma Assert (Result = 0);
 651
 652       return To_Duration (TS);
 653    end RT_Resolution;
 654
 655    ------------
 656    -- Wakeup --
 657    ------------
 658
 659    procedure Wakeup (T : Task_Id; Reason : System.Tasking.Task_States) is
 660       pragma Unreferenced (Reason);
 661       Result : Interfaces.C.int;
 662    begin
 663       Result := pthread_cond_signal (T.Common.LL.CV'Access);
 664       pragma Assert (Result = 0);
 665    end Wakeup;
 666
 667    -----------
 668    -- Yield --
 669    -----------
 670
 671    procedure Yield (Do_Yield : Boolean := True) is
 672       Result : Interfaces.C.int;
 673       pragma Unreferenced (Result);
 674    begin
 675       if Do_Yield then
 676          Result := sched_yield;
 677       end if;
 678    end Yield;
 679
 680    ------------------
 681    -- Set_Priority --
 682    ------------------
 683
 684    procedure Set_Priority
 685      (T                   : Task_Id;
 686       Prio                : System.Any_Priority;
 687       Loss_Of_Inheritance : Boolean := False)
 688    is
 689       pragma Unreferenced (Loss_Of_Inheritance);
 690
 691       Result : Interfaces.C.int;
 692       Param  : aliased struct_sched_param;
 693
 694       function Get_Policy (Prio : System.Any_Priority) return Character;
 695       pragma Import (C, Get_Policy, "__gnat_get_specific_dispatching");
 696       --  Get priority specific dispatching policy
 697
 698       Priority_Specific_Policy : constant Character := Get_Policy (Prio);
 699       --  Upper case first character of the policy name corresponding to the
 700       --  task as set by a Priority_Specific_Dispatching pragma.
 701
 702    begin
 703       T.Common.Current_Priority := Prio;
 704
 705       --  Priorities are 1 .. 99 on GNU/Linux, so we map 0 .. 98 to 1 .. 99
 706
 707       Param.sched_priority := Interfaces.C.int (Prio) + 1;
 708
 709       if Dispatching_Policy = 'R'
 710         or else Priority_Specific_Policy = 'R'
 711         or else Time_Slice_Val > 0
 712       then
 713          Result :=
 714            pthread_setschedparam
 715              (T.Common.LL.Thread, SCHED_RR, Param'Access);
 716
 717       elsif Dispatching_Policy = 'F'
 718         or else Priority_Specific_Policy = 'F'
 719         or else Time_Slice_Val = 0
 720       then
 721          Result :=
 722            pthread_setschedparam
 723              (T.Common.LL.Thread, SCHED_FIFO, Param'Access);
 724
 725       else
 726          Param.sched_priority := 0;
 727          Result :=
 728            pthread_setschedparam
 729              (T.Common.LL.Thread,
 730               SCHED_OTHER, Param'Access);
 731       end if;
 732
 733       pragma Assert (Result = 0 or else Result = EPERM);
 734    end Set_Priority;
 735
 736    ------------------
 737    -- Get_Priority --
 738    ------------------
 739
 740    function Get_Priority (T : Task_Id) return System.Any_Priority is
 741    begin
 742       return T.Common.Current_Priority;
 743    end Get_Priority;
 744
 745    ----------------
 746    -- Enter_Task --
 747    ----------------
 748
 749    procedure Enter_Task (Self_ID : Task_Id) is
 750    begin
 751       if Self_ID.Common.Task_Info /= null
 752         and then Self_ID.Common.Task_Info.CPU_Affinity = No_CPU
 753       then
 754          raise Invalid_CPU_Number;
 755       end if;
 756
 757       Self_ID.Common.LL.Thread := pthread_self;
 758       Self_ID.Common.LL.LWP := lwp_self;
 759
 760       if Self_ID.Common.Task_Image_Len > 0 then
 761          declare
 762             Task_Name : String (1 .. Parameters.Max_Task_Image_Length + 1);
 763             Result    : int;
 764
 765          begin
 766             --  Set thread name to ease debugging
 767
 768             Task_Name (1 .. Self_ID.Common.Task_Image_Len) :=
 769               Self_ID.Common.Task_Image (1 .. Self_ID.Common.Task_Image_Len);
 770             Task_Name (Self_ID.Common.Task_Image_Len + 1) := ASCII.NUL;
 771
 772             Result := prctl (PR_SET_NAME, unsigned_long (Task_Name'Address));
 773             pragma Assert (Result = 0);
 774          end;
 775       end if;
 776
 777       Specific.Set (Self_ID);
 778
 779       if Use_Alternate_Stack
 780         and then Self_ID.Common.Task_Alternate_Stack /= Null_Address
 781       then
 782          declare
 783             Stack  : aliased stack_t;
 784             Result : Interfaces.C.int;
 785          begin
 786             Stack.ss_sp    := Self_ID.Common.Task_Alternate_Stack;
 787             Stack.ss_size  := Alternate_Stack_Size;
 788             Stack.ss_flags := 0;
 789             Result := sigaltstack (Stack'Access, null);
 790             pragma Assert (Result = 0);
 791          end;
 792       end if;
 793    end Enter_Task;
 794
 795    -------------------
 796    -- Is_Valid_Task --
 797    -------------------
 798
 799    function Is_Valid_Task return Boolean renames Specific.Is_Valid_Task;
 800
 801    -----------------------------
 802    -- Register_Foreign_Thread --
 803    -----------------------------
 804
 805    function Register_Foreign_Thread return Task_Id is
 806    begin
 807       if Is_Valid_Task then
 808          return Self;
 809       else
 810          return Register_Foreign_Thread (pthread_self);
 811       end if;
 812    end Register_Foreign_Thread;
 813
 814    --------------------
 815    -- Initialize_TCB --
 816    --------------------
 817
 818    procedure Initialize_TCB (Self_ID : Task_Id; Succeeded : out Boolean) is
 819       Cond_Attr : aliased pthread_condattr_t;
 820       Result    : Interfaces.C.int;
 821
 822    begin
 823       --  Give the task a unique serial number
 824
 825       Self_ID.Serial_Number := Next_Serial_Number;
 826       Next_Serial_Number := Next_Serial_Number + 1;
 827       pragma Assert (Next_Serial_Number /= 0);
 828
 829       Self_ID.Common.LL.Thread := Null_Thread_Id;
 830
 831       if not Single_Lock then
 832          Result :=
 833            pthread_mutex_init (Self_ID.Common.LL.L'Access, null);
 834          pragma Assert (Result = 0 or else Result = ENOMEM);
 835
 836          if Result /= 0 then
 837             Succeeded := False;
 838             return;
 839          end if;
 840       end if;
 841
 842       Result := pthread_condattr_init (Cond_Attr'Access);
 843       pragma Assert (Result = 0);
 844
 845       Result :=
 846         pthread_cond_init (Self_ID.Common.LL.CV'Access, Cond_Attr'Access);
 847       pragma Assert (Result = 0 or else Result = ENOMEM);
 848
 849       if Result = 0 then
 850          Succeeded := True;
 851       else
 852          if not Single_Lock then
 853             Result := pthread_mutex_destroy (Self_ID.Common.LL.L'Access);
 854             pragma Assert (Result = 0);
 855          end if;
 856
 857          Succeeded := False;
 858       end if;
 859    end Initialize_TCB;
 860
 861    -----------------
 862    -- Create_Task --
 863    -----------------
 864
 865    procedure Create_Task
 866      (T          : Task_Id;
 867       Wrapper    : System.Address;
 868       Stack_Size : System.Parameters.Size_Type;
 869       Priority   : System.Any_Priority;
 870       Succeeded  : out Boolean)
 871    is
 872       Attributes          : aliased pthread_attr_t;
 873       Adjusted_Stack_Size : Interfaces.C.size_t;
 874       Result              : Interfaces.C.int;
 875
 876       use type System.Multiprocessors.CPU_Range;
 877
 878    begin
 879       --  Check whether both Dispatching_Domain and CPU are specified for
 880       --  the task, and the CPU value is not contained within the range of
 881       --  processors for the domain.
 882
 883       if T.Common.Domain /= null
 884         and then T.Common.Base_CPU /= System.Multiprocessors.Not_A_Specific_CPU
 885         and then
 886           (T.Common.Base_CPU not in T.Common.Domain'Range
 887             or else not T.Common.Domain (T.Common.Base_CPU))
 888       then
 889          Succeeded := False;
 890          return;
 891       end if;
 892
 893       Adjusted_Stack_Size :=
 894          Interfaces.C.size_t (Stack_Size + Alternate_Stack_Size);
 895
 896       Result := pthread_attr_init (Attributes'Access);
 897       pragma Assert (Result = 0 or else Result = ENOMEM);
 898
 899       if Result /= 0 then
 900          Succeeded := False;
 901          return;
 902       end if;
 903
 904       Result :=
 905         pthread_attr_setstacksize (Attributes'Access, Adjusted_Stack_Size);
 906       pragma Assert (Result = 0);
 907
 908       Result :=
 909         pthread_attr_setdetachstate
 910           (Attributes'Access, PTHREAD_CREATE_DETACHED);
 911       pragma Assert (Result = 0);
 912
 913       --  Set the required attributes for the creation of the thread
 914
 915       --  Note: Previously, we called pthread_setaffinity_np (after thread
 916       --  creation but before thread activation) to set the affinity but it was
 917       --  not behaving as expected. Setting the required attributes for the
 918       --  creation of the thread works correctly and it is more appropriate.
 919
 920       --  Do nothing if required support not provided by the operating system
 921
 922       if pthread_attr_setaffinity_np'Address = System.Null_Address then
 923          null;
 924
 925       --  Support is available
 926
 927       elsif T.Common.Base_CPU /= System.Multiprocessors.Not_A_Specific_CPU then
 928          declare
 929             CPUs    : constant size_t :=
 930                         Interfaces.C.size_t
 931                           (System.Multiprocessors.Number_Of_CPUs);
 932             CPU_Set : constant cpu_set_t_ptr := CPU_ALLOC (CPUs);
 933             Size    : constant size_t := CPU_ALLOC_SIZE (CPUs);
 934
 935          begin
 936             CPU_ZERO (Size, CPU_Set);
 937             System.OS_Interface.CPU_SET
 938               (int (T.Common.Base_CPU), Size, CPU_Set);
 939             Result :=
 940               pthread_attr_setaffinity_np (Attributes'Access, Size, CPU_Set);
 941             pragma Assert (Result = 0);
 942
 943             CPU_FREE (CPU_Set);
 944          end;
 945
 946       --  Handle Task_Info
 947
 948       elsif T.Common.Task_Info /= null then
 949          Result :=
 950            pthread_attr_setaffinity_np
 951              (Attributes'Access,
 952               CPU_SETSIZE / 8,
 953               T.Common.Task_Info.CPU_Affinity'Access);
 954          pragma Assert (Result = 0);
 955
 956       --  Handle dispatching domains
 957
 958       --  To avoid changing CPU affinities when not needed, we set the
 959       --  affinity only when assigning to a domain other than the default
 960       --  one, or when the default one has been modified.
 961
 962       elsif T.Common.Domain /= null and then
 963         (T.Common.Domain /= ST.System_Domain
 964           or else T.Common.Domain.all /=
 965                     (Multiprocessors.CPU'First ..
 966                      Multiprocessors.Number_Of_CPUs => True))
 967       then
 968          declare
 969             CPUs    : constant size_t :=
 970                         Interfaces.C.size_t
 971                           (System.Multiprocessors.Number_Of_CPUs);
 972             CPU_Set : constant cpu_set_t_ptr := CPU_ALLOC (CPUs);
 973             Size    : constant size_t := CPU_ALLOC_SIZE (CPUs);
 974
 975          begin
 976             CPU_ZERO (Size, CPU_Set);
 977
 978             --  Set the affinity to all the processors belonging to the
 979             --  dispatching domain.
 980
 981             for Proc in T.Common.Domain'Range loop
 982                if T.Common.Domain (Proc) then
 983                   System.OS_Interface.CPU_SET (int (Proc), Size, CPU_Set);
 984                end if;
 985             end loop;
 986
 987             Result :=
 988               pthread_attr_setaffinity_np (Attributes'Access, Size, CPU_Set);
 989             pragma Assert (Result = 0);
 990
 991             CPU_FREE (CPU_Set);
 992          end;
 993       end if;
 994
 995       --  Since the initial signal mask of a thread is inherited from the
 996       --  creator, and the Environment task has all its signals masked, we
 997       --  do not need to manipulate caller's signal mask at this point.
 998       --  All tasks in RTS will have All_Tasks_Mask initially.
 999
1000       --  Note: the use of Unrestricted_Access in the following call is needed
1001       --  because otherwise we have an error of getting a access-to-volatile
1002       --  value which points to a non-volatile object. But in this case it is
1003       --  safe to do this, since we know we have no problems with aliasing and
1004       --  Unrestricted_Access bypasses this check.
1005
1006       Result :=
1007         pthread_create
1008           (T.Common.LL.Thread'Unrestricted_Access,
1009            Attributes'Access,
1010            Thread_Body_Access (Wrapper),
1011            To_Address (T));
1012
1013       pragma Assert
1014         (Result = 0 or else Result = EAGAIN or else Result = ENOMEM);
1015
1016       if Result /= 0 then
1017          Succeeded := False;
1018          Result := pthread_attr_destroy (Attributes'Access);
1019          pragma Assert (Result = 0);
1020          return;
1021       end if;
1022
1023       Succeeded := True;
1024
1025       Result := pthread_attr_destroy (Attributes'Access);
1026       pragma Assert (Result = 0);
1027
1028       Set_Priority (T, Priority);
1029    end Create_Task;
1030
1031    ------------------
1032    -- Finalize_TCB --
1033    ------------------
1034
1035    procedure Finalize_TCB (T : Task_Id) is
1036       Result : Interfaces.C.int;
1037
1038    begin
1039       if not Single_Lock then
1040          Result := pthread_mutex_destroy (T.Common.LL.L'Access);
1041          pragma Assert (Result = 0);
1042       end if;
1043
1044       Result := pthread_cond_destroy (T.Common.LL.CV'Access);
1045       pragma Assert (Result = 0);
1046
1047       if T.Known_Tasks_Index /= -1 then
1048          Known_Tasks (T.Known_Tasks_Index) := null;
1049       end if;
1050
1051       SC.Invalidate_Stack_Cache (T.Common.Compiler_Data.Pri_Stack_Info'Access);
1052
1053       ATCB_Allocation.Free_ATCB (T);
1054    end Finalize_TCB;
1055
1056    ---------------
1057    -- Exit_Task --
1058    ---------------
1059
1060    procedure Exit_Task is
1061    begin
1062       Specific.Set (null);
1063    end Exit_Task;
1064
1065    ----------------
1066    -- Abort_Task --
1067    ----------------
1068
1069    procedure Abort_Task (T : Task_Id) is
1070       Result : Interfaces.C.int;
1071
1072       ESRCH : constant := 3; -- No such process
1073       --  It can happen that T has already vanished, in which case pthread_kill
1074       --  returns ESRCH, so we don't consider that to be an error.
1075
1076    begin
1077       if Abort_Handler_Installed then
1078          Result :=
1079            pthread_kill
1080              (T.Common.LL.Thread,
1081               Signal (System.Interrupt_Management.Abort_Task_Interrupt));
1082          pragma Assert (Result = 0 or else Result = ESRCH);
1083       end if;
1084    end Abort_Task;
1085
1086    ----------------
1087    -- Initialize --
1088    ----------------
1089
1090    procedure Initialize (S : in out Suspension_Object) is
1091       Result : Interfaces.C.int;
1092
1093    begin
1094       --  Initialize internal state (always to False (RM D.10(6)))
1095
1096       S.State := False;
1097       S.Waiting := False;
1098
1099       --  Initialize internal mutex
1100
1101       Result := pthread_mutex_init (S.L'Access, null);
1102
1103       pragma Assert (Result = 0 or else Result = ENOMEM);
1104
1105       if Result = ENOMEM then
1106          raise Storage_Error;
1107       end if;
1108
1109       --  Initialize internal condition variable
1110
1111       Result := pthread_cond_init (S.CV'Access, null);
1112
1113       pragma Assert (Result = 0 or else Result = ENOMEM);
1114
1115       if Result /= 0 then
1116          Result := pthread_mutex_destroy (S.L'Access);
1117          pragma Assert (Result = 0);
1118
1119          if Result = ENOMEM then
1120             raise Storage_Error;
1121          end if;
1122       end if;
1123    end Initialize;
1124
1125    --------------
1126    -- Finalize --
1127    --------------
1128
1129    procedure Finalize (S : in out Suspension_Object) is
1130       Result : Interfaces.C.int;
1131
1132    begin
1133       --  Destroy internal mutex
1134
1135       Result := pthread_mutex_destroy (S.L'Access);
1136       pragma Assert (Result = 0);
1137
1138       --  Destroy internal condition variable
1139
1140       Result := pthread_cond_destroy (S.CV'Access);
1141       pragma Assert (Result = 0);
1142    end Finalize;
1143
1144    -------------------
1145    -- Current_State --
1146    -------------------
1147
1148    function Current_State (S : Suspension_Object) return Boolean is
1149    begin
1150       --  We do not want to use lock on this read operation. State is marked
1151       --  as Atomic so that we ensure that the value retrieved is correct.
1152
1153       return S.State;
1154    end Current_State;
1155
1156    ---------------
1157    -- Set_False --
1158    ---------------
1159
1160    procedure Set_False (S : in out Suspension_Object) is
1161       Result : Interfaces.C.int;
1162
1163    begin
1164       SSL.Abort_Defer.all;
1165
1166       Result := pthread_mutex_lock (S.L'Access);
1167       pragma Assert (Result = 0);
1168
1169       S.State := False;
1170
1171       Result := pthread_mutex_unlock (S.L'Access);
1172       pragma Assert (Result = 0);
1173
1174       SSL.Abort_Undefer.all;
1175    end Set_False;
1176
1177    --------------
1178    -- Set_True --
1179    --------------
1180
1181    procedure Set_True (S : in out Suspension_Object) is
1182       Result : Interfaces.C.int;
1183
1184    begin
1185       SSL.Abort_Defer.all;
1186
1187       Result := pthread_mutex_lock (S.L'Access);
1188       pragma Assert (Result = 0);
1189
1190       --  If there is already a task waiting on this suspension object then
1191       --  we resume it, leaving the state of the suspension object to False,
1192       --  as it is specified in ARM D.10 par. 9. Otherwise, it just leaves
1193       --  the state to True.
1194
1195       if S.Waiting then
1196          S.Waiting := False;
1197          S.State := False;
1198
1199          Result := pthread_cond_signal (S.CV'Access);
1200          pragma Assert (Result = 0);
1201
1202       else
1203          S.State := True;
1204       end if;
1205
1206       Result := pthread_mutex_unlock (S.L'Access);
1207       pragma Assert (Result = 0);
1208
1209       SSL.Abort_Undefer.all;
1210    end Set_True;
1211
1212    ------------------------
1213    -- Suspend_Until_True --
1214    ------------------------
1215
1216    procedure Suspend_Until_True (S : in out Suspension_Object) is
1217       Result : Interfaces.C.int;
1218
1219    begin
1220       SSL.Abort_Defer.all;
1221
1222       Result := pthread_mutex_lock (S.L'Access);
1223       pragma Assert (Result = 0);
1224
1225       if S.Waiting then
1226
1227          --  Program_Error must be raised upon calling Suspend_Until_True
1228          --  if another task is already waiting on that suspension object
1229          --  (RM D.10(10)).
1230
1231          Result := pthread_mutex_unlock (S.L'Access);
1232          pragma Assert (Result = 0);
1233
1234          SSL.Abort_Undefer.all;
1235
1236          raise Program_Error;
1237
1238       else
1239          --  Suspend the task if the state is False. Otherwise, the task
1240          --  continues its execution, and the state of the suspension object
1241          --  is set to False (ARM D.10 par. 9).
1242
1243          if S.State then
1244             S.State := False;
1245          else
1246             S.Waiting := True;
1247
1248             loop
1249                --  Loop in case pthread_cond_wait returns earlier than expected
1250                --  (e.g. in case of EINTR caused by a signal). This should not
1251                --  happen with the current Linux implementation of pthread, but
1252                --  POSIX does not guarantee it so this may change in future.
1253
1254                Result := pthread_cond_wait (S.CV'Access, S.L'Access);
1255                pragma Assert (Result = 0 or else Result = EINTR);
1256
1257                exit when not S.Waiting;
1258             end loop;
1259          end if;
1260
1261          Result := pthread_mutex_unlock (S.L'Access);
1262          pragma Assert (Result = 0);
1263
1264          SSL.Abort_Undefer.all;
1265       end if;
1266    end Suspend_Until_True;
1267
1268    ----------------
1269    -- Check_Exit --
1270    ----------------
1271
1272    --  Dummy version
1273
1274    function Check_Exit (Self_ID : ST.Task_Id) return Boolean is
1275       pragma Unreferenced (Self_ID);
1276    begin
1277       return True;
1278    end Check_Exit;
1279
1280    --------------------
1281    -- Check_No_Locks --
1282    --------------------
1283
1284    function Check_No_Locks (Self_ID : ST.Task_Id) return Boolean is
1285       pragma Unreferenced (Self_ID);
1286    begin
1287       return True;
1288    end Check_No_Locks;
1289
1290    ----------------------
1291    -- Environment_Task --
1292    ----------------------
1293
1294    function Environment_Task return Task_Id is
1295    begin
1296       return Environment_Task_Id;
1297    end Environment_Task;
1298
1299    ------------------
1300    -- Suspend_Task --
1301    ------------------
1302
1303    function Suspend_Task
1304      (T           : ST.Task_Id;
1305       Thread_Self : Thread_Id) return Boolean
1306    is
1307    begin
1308       if T.Common.LL.Thread /= Thread_Self then
1309          return pthread_kill (T.Common.LL.Thread, SIGSTOP) = 0;
1310       else
1311          return True;
1312       end if;
1313    end Suspend_Task;
1314
1315    -----------------
1316    -- Resume_Task --
1317    -----------------
1318
1319    function Resume_Task
1320      (T           : ST.Task_Id;
1321       Thread_Self : Thread_Id) return Boolean
1322    is
1323    begin
1324       if T.Common.LL.Thread /= Thread_Self then
1325          return pthread_kill (T.Common.LL.Thread, SIGCONT) = 0;
1326       else
1327          return True;
1328       end if;
1329    end Resume_Task;
1330
1331    --------------------
1332    -- Stop_All_Tasks --
1333    --------------------
1334
1335    procedure Stop_All_Tasks is
1336    begin
1337       null;
1338    end Stop_All_Tasks;
1339
1340    ---------------
1341    -- Stop_Task --
1342    ---------------
1343
1344    function Stop_Task (T : ST.Task_Id) return Boolean is
1345       pragma Unreferenced (T);
1346    begin
1347       return False;
1348    end Stop_Task;
1349
1350    -------------------
1351    -- Continue_Task --
1352    -------------------
1353
1354    function Continue_Task (T : ST.Task_Id) return Boolean is
1355       pragma Unreferenced (T);
1356    begin
1357       return False;
1358    end Continue_Task;
1359
1360    ----------------
1361    -- Initialize --
1362    ----------------
1363
1364    procedure Initialize (Environment_Task : Task_Id) is
1365       act     : aliased struct_sigaction;
1366       old_act : aliased struct_sigaction;
1367       Tmp_Set : aliased sigset_t;
1368       Result  : Interfaces.C.int;
1369       --  Whether to use an alternate signal stack for stack overflows
1370
1371       function State
1372         (Int : System.Interrupt_Management.Interrupt_ID) return Character;
1373       pragma Import (C, State, "__gnat_get_interrupt_state");
1374       --  Get interrupt state.  Defined in a-init.c
1375       --  The input argument is the interrupt number,
1376       --  and the result is one of the following:
1377
1378       Default : constant Character := 's';
1379       --    'n'   this interrupt not set by any Interrupt_State pragma
1380       --    'u'   Interrupt_State pragma set state to User
1381       --    'r'   Interrupt_State pragma set state to Runtime
1382       --    's'   Interrupt_State pragma set state to System (use "default"
1383       --           system handler)
1384
1385       use type System.Multiprocessors.CPU_Range;
1386
1387    begin
1388       Environment_Task_Id := Environment_Task;
1389
1390       Interrupt_Management.Initialize;
1391
1392       --  Prepare the set of signals that should be unblocked in all tasks
1393
1394       Result := sigemptyset (Unblocked_Signal_Mask'Access);
1395       pragma Assert (Result = 0);
1396
1397       for J in Interrupt_Management.Interrupt_ID loop
1398          if System.Interrupt_Management.Keep_Unmasked (J) then
1399             Result := sigaddset (Unblocked_Signal_Mask'Access, Signal (J));
1400             pragma Assert (Result = 0);
1401          end if;
1402       end loop;
1403
1404       Initialize_Lock (Single_RTS_Lock'Access, RTS_Lock_Level);
1405
1406       --  Initialize the global RTS lock
1407
1408       Specific.Initialize (Environment_Task);
1409
1410       if Use_Alternate_Stack then
1411          Environment_Task.Common.Task_Alternate_Stack :=
1412            Alternate_Stack'Address;
1413       end if;
1414
1415       --  Make environment task known here because it doesn't go through
1416       --  Activate_Tasks, which does it for all other tasks.
1417
1418       Known_Tasks (Known_Tasks'First) := Environment_Task;
1419       Environment_Task.Known_Tasks_Index := Known_Tasks'First;
1420
1421       Enter_Task (Environment_Task);
1422
1423       if State
1424           (System.Interrupt_Management.Abort_Task_Interrupt) /= Default
1425       then
1426          act.sa_flags := 0;
1427          act.sa_handler := Abort_Handler'Address;
1428
1429          Result := sigemptyset (Tmp_Set'Access);
1430          pragma Assert (Result = 0);
1431          act.sa_mask := Tmp_Set;
1432
1433          Result :=
1434            sigaction
1435            (Signal (Interrupt_Management.Abort_Task_Interrupt),
1436             act'Unchecked_Access,
1437             old_act'Unchecked_Access);
1438          pragma Assert (Result = 0);
1439          Abort_Handler_Installed := True;
1440       end if;
1441
1442       --  pragma CPU and dispatching domains for the environment task
1443
1444       Set_Task_Affinity (Environment_Task);
1445    end Initialize;
1446
1447    -----------------------
1448    -- Set_Task_Affinity --
1449    -----------------------
1450
1451    procedure Set_Task_Affinity (T : ST.Task_Id) is
1452       use type System.Multiprocessors.CPU_Range;
1453
1454    begin
1455       --  Do nothing if there is no support for setting affinities or the
1456       --  underlying thread has not yet been created. If the thread has not
1457       --  yet been created then the proper affinity will be set during its
1458       --  creation.
1459
1460       if pthread_setaffinity_np'Address /= System.Null_Address
1461         and then T.Common.LL.Thread /= Null_Thread_Id
1462       then
1463          declare
1464             CPUs    : constant size_t :=
1465                         Interfaces.C.size_t
1466                           (System.Multiprocessors.Number_Of_CPUs);
1467             CPU_Set : cpu_set_t_ptr := null;
1468             Size    : constant size_t := CPU_ALLOC_SIZE (CPUs);
1469
1470             Result  : Interfaces.C.int;
1471
1472          begin
1473             --  We look at the specific CPU (Base_CPU) first, then at the
1474             --  Task_Info field, and finally at the assigned dispatching
1475             --  domain, if any.
1476
1477             if T.Common.Base_CPU /= Multiprocessors.Not_A_Specific_CPU then
1478
1479                --  Set the affinity to an unique CPU
1480
1481                CPU_Set := CPU_ALLOC (CPUs);
1482                System.OS_Interface.CPU_ZERO (Size, CPU_Set);
1483                System.OS_Interface.CPU_SET
1484                  (int (T.Common.Base_CPU), Size, CPU_Set);
1485
1486             --  Handle Task_Info
1487
1488             elsif T.Common.Task_Info /= null then
1489                CPU_Set := T.Common.Task_Info.CPU_Affinity'Access;
1490
1491             --  Handle dispatching domains
1492
1493             elsif T.Common.Domain /= null and then
1494               (T.Common.Domain /= ST.System_Domain
1495                 or else T.Common.Domain.all /=
1496                           (Multiprocessors.CPU'First ..
1497                            Multiprocessors.Number_Of_CPUs => True))
1498             then
1499                --  Set the affinity to all the processors belonging to the
1500                --  dispatching domain. To avoid changing CPU affinities when
1501                --  not needed, we set the affinity only when assigning to a
1502                --  domain other than the default one, or when the default one
1503                --  has been modified.
1504
1505                CPU_Set := CPU_ALLOC (CPUs);
1506                System.OS_Interface.CPU_ZERO (Size, CPU_Set);
1507
1508                for Proc in T.Common.Domain'Range loop
1509                   if T.Common.Domain (Proc) then
1510                      System.OS_Interface.CPU_SET (int (Proc), Size, CPU_Set);
1511                   end if;
1512                end loop;
1513             end if;
1514
1515             --  We set the new affinity if needed. Otherwise, the new task
1516             --  will inherit its creator's CPU affinity mask (according to
1517             --  the documentation of pthread_setaffinity_np), which is
1518             --  consistent with Ada's required semantics.
1519
1520             if CPU_Set /= null then
1521                Result :=
1522                  pthread_setaffinity_np (T.Common.LL.Thread, Size, CPU_Set);
1523                pragma Assert (Result = 0);
1524
1525                CPU_FREE (CPU_Set);
1526             end if;
1527          end;
1528       end if;
1529    end Set_Task_Affinity;
1530
1531 end System.Task_Primitives.Operations;