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------------------------------------------------------------------------------
--                                                                          --
--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
--                                                                          --
--     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    --
--                                                                          --
--                                  B o d y                                 --
--                                                                          --
--         Copyright (C) 1992-2005, Free Software Foundation, Inc.          --
--                                                                          --
-- GNARL is free software; you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNARL; see file COPYING.  If not, write --
-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
-- Boston, MA 02110-1301, USA.                                              --
--                                                                          --
-- As a special exception,  if other files  instantiate  generics from this --
-- unit, or you link  this unit with other files  to produce an executable, --
-- this  unit  does not  by itself cause  the resulting  executable  to  be --
-- covered  by the  GNU  General  Public  License.  This exception does not --
-- however invalidate  any other reasons why  the executable file  might be --
-- covered by the  GNU Public License.                                      --
--                                                                          --
-- GNARL was developed by the GNARL team at Florida State University.       --
-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
--                                                                          --
------------------------------------------------------------------------------
 
--  This is a OpenVMS/Alpha version of this package
 
--  This package contains all the GNULL primitives that interface directly
--  with the underlying OS.
 
pragma Polling (Off);
--  Turn off polling, we do not want ATC polling to take place during
--  tasking operations. It causes infinite loops and other problems.
 
with System.Tasking.Debug;
--  used for Known_Tasks
 
with System.OS_Primitives;
--  used for Delay_Modes
 
with Interfaces.C;
--  used for int
--           size_t
 
with System.Parameters;
--  used for Size_Type
 
with System.Soft_Links;
--  used for Get_Exc_Stack_Addr
 
with Unchecked_Conversion;
with Unchecked_Deallocation;
 
package body System.Task_Primitives.Operations is
 
   use System.Tasking.Debug;
   use System.Tasking;
   use Interfaces.C;
   use System.OS_Interface;
   use System.Parameters;
   use System.OS_Primitives;
   use type System.OS_Primitives.OS_Time;
 
   package SSL renames System.Soft_Links;
 
   ----------------
   -- Local Data --
   ----------------
 
   --  The followings are logically constants, but need to be initialized
   --  at run time.
 
   Single_RTS_Lock : aliased RTS_Lock;
   --  This is a lock to allow only one thread of control in the RTS at
   --  a time; it is used to execute in mutual exclusion from all other tasks.
   --  Used mainly in Single_Lock mode, but also to protect All_Tasks_List
 
   ATCB_Key : aliased pthread_key_t;
   --  Key used to find the Ada Task_Id associated with a thread
 
   Environment_Task_Id : Task_Id;
   --  A variable to hold Task_Id for the environment task.
 
   Time_Slice_Val : Integer;
   pragma Import (C, Time_Slice_Val, "__gl_time_slice_val");
 
   Dispatching_Policy : Character;
   pragma Import (C, Dispatching_Policy, "__gl_task_dispatching_policy");
 
   Foreign_Task_Elaborated : aliased Boolean := True;
   --  Used to identified fake tasks (i.e., non-Ada Threads).
 
   --------------------
   -- Local Packages --
   --------------------
 
   package Specific is
 
      procedure Initialize (Environment_Task : Task_Id);
      pragma Inline (Initialize);
      --  Initialize various data needed by this package.
 
      function Is_Valid_Task return Boolean;
      pragma Inline (Is_Valid_Task);
      --  Does executing thread have a TCB?
 
      procedure Set (Self_Id : Task_Id);
      pragma Inline (Set);
      --  Set the self id for the current task
 
      function Self return Task_Id;
      pragma Inline (Self);
      --  Return a pointer to the Ada Task Control Block of the calling task
 
   end Specific;
 
   package body Specific is separate;
   --  The body of this package is target specific.
 
   ---------------------------------
   -- Support for foreign threads --
   ---------------------------------
 
   function Register_Foreign_Thread (Thread : Thread_Id) return Task_Id;
   --  Allocate and Initialize a new ATCB for the current Thread
 
   function Register_Foreign_Thread
     (Thread : Thread_Id) return Task_Id is separate;
 
   -----------------------
   -- Local Subprograms --
   -----------------------
 
   function To_Task_Id is new Unchecked_Conversion (System.Address, Task_Id);
 
   function To_Address is new Unchecked_Conversion (Task_Id, System.Address);
 
   function Get_Exc_Stack_Addr return Address;
   --  Replace System.Soft_Links.Get_Exc_Stack_Addr_NT
 
   procedure Timer_Sleep_AST (ID : Address);
   --  Signal the condition variable when AST fires.
 
   procedure Timer_Sleep_AST (ID : Address) is
      Result  : Interfaces.C.int;
      Self_ID : constant Task_Id := To_Task_Id (ID);
   begin
      Self_ID.Common.LL.AST_Pending := False;
      Result := pthread_cond_signal_int_np (Self_ID.Common.LL.CV'Access);
      pragma Assert (Result = 0);
   end Timer_Sleep_AST;
 
   -----------------
   -- Stack_Guard --
   -----------------
 
   --  The underlying thread system sets a guard page at the
   --  bottom of a thread stack, so nothing is needed.
   --  ??? Check the comment above
 
   procedure Stack_Guard (T : ST.Task_Id; On : Boolean) is
      pragma Unreferenced (T);
      pragma Unreferenced (On);
   begin
      null;
   end Stack_Guard;
 
   --------------------
   -- Get_Thread_Id  --
   --------------------
 
   function Get_Thread_Id (T : ST.Task_Id) return OSI.Thread_Id is
   begin
      return T.Common.LL.Thread;
   end Get_Thread_Id;
 
   ----------
   -- Self --
   ----------
 
   function Self return Task_Id renames Specific.Self;
 
   ---------------------
   -- Initialize_Lock --
   ---------------------
 
   --  Note: mutexes and cond_variables needed per-task basis are
   --  initialized in Initialize_TCB and the Storage_Error is
   --  handled. Other mutexes (such as RTS_Lock, Memory_Lock...)
   --  used in RTS is initialized before any status change of RTS.
   --  Therefore rasing Storage_Error in the following routines
   --  should be able to be handled safely.
 
   procedure Initialize_Lock (Prio : System.Any_Priority; L : access Lock) is
      Attributes : aliased pthread_mutexattr_t;
      Result     : Interfaces.C.int;
 
   begin
      Result := pthread_mutexattr_init (Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         raise Storage_Error;
      end if;
 
      L.Prio_Save := 0;
      L.Prio := Interfaces.C.int (Prio);
 
      Result := pthread_mutex_init (L.L'Access, Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         raise Storage_Error;
      end if;
 
      Result := pthread_mutexattr_destroy (Attributes'Access);
      pragma Assert (Result = 0);
   end Initialize_Lock;
 
   procedure Initialize_Lock (L : access RTS_Lock; Level : Lock_Level) is
      pragma Unreferenced (Level);
 
      Attributes : aliased pthread_mutexattr_t;
      Result : Interfaces.C.int;
 
   begin
      Result := pthread_mutexattr_init (Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         raise Storage_Error;
      end if;
 
--      Don't use, see comment in s-osinte.ads about ERRORCHECK mutexes???
--      Result := pthread_mutexattr_settype_np
--        (Attributes'Access, PTHREAD_MUTEX_ERRORCHECK_NP);
--      pragma Assert (Result = 0);
 
--      Result := pthread_mutexattr_setprotocol
--        (Attributes'Access, PTHREAD_PRIO_PROTECT);
--      pragma Assert (Result = 0);
 
--      Result := pthread_mutexattr_setprioceiling
--         (Attributes'Access, Interfaces.C.int (System.Any_Priority'Last));
--      pragma Assert (Result = 0);
 
      Result := pthread_mutex_init (L, Attributes'Access);
 
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         raise Storage_Error;
      end if;
 
      Result := pthread_mutexattr_destroy (Attributes'Access);
      pragma Assert (Result = 0);
   end Initialize_Lock;
 
   -------------------
   -- Finalize_Lock --
   -------------------
 
   procedure Finalize_Lock (L : access Lock) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_destroy (L.L'Access);
      pragma Assert (Result = 0);
   end Finalize_Lock;
 
   procedure Finalize_Lock (L : access RTS_Lock) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_destroy (L);
      pragma Assert (Result = 0);
   end Finalize_Lock;
 
   ----------------
   -- Write_Lock --
   ----------------
 
   procedure Write_Lock (L : access Lock; Ceiling_Violation : out Boolean) is
      Self_ID        : constant Task_Id := Self;
      All_Tasks_Link : constant Task_Id := Self.Common.All_Tasks_Link;
      Current_Prio   : System.Any_Priority;
      Result         : Interfaces.C.int;
 
   begin
      Current_Prio := Get_Priority (Self_ID);
 
      --  If there is no other tasks, no need to check priorities
 
      if All_Tasks_Link /= Null_Task
        and then L.Prio < Interfaces.C.int (Current_Prio)
      then
         Ceiling_Violation := True;
         return;
      end if;
 
      Result := pthread_mutex_lock (L.L'Access);
      pragma Assert (Result = 0);
 
      Ceiling_Violation := False;
--  Why is this commented out ???
--      L.Prio_Save := Interfaces.C.int (Current_Prio);
--      Set_Priority (Self_ID, System.Any_Priority (L.Prio));
   end Write_Lock;
 
   procedure Write_Lock
     (L           : access RTS_Lock;
      Global_Lock : Boolean := False)
   is
      Result : Interfaces.C.int;
   begin
      if not Single_Lock or else Global_Lock then
         Result := pthread_mutex_lock (L);
         pragma Assert (Result = 0);
      end if;
   end Write_Lock;
 
   procedure Write_Lock (T : Task_Id) is
      Result : Interfaces.C.int;
   begin
      if not Single_Lock then
         Result := pthread_mutex_lock (T.Common.LL.L'Access);
         pragma Assert (Result = 0);
      end if;
   end Write_Lock;
 
   ---------------
   -- Read_Lock --
   ---------------
 
   procedure Read_Lock (L : access Lock; Ceiling_Violation : out Boolean) is
   begin
      Write_Lock (L, Ceiling_Violation);
   end Read_Lock;
 
   ------------
   -- Unlock --
   ------------
 
   procedure Unlock (L : access Lock) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_unlock (L.L'Access);
      pragma Assert (Result = 0);
   end Unlock;
 
   procedure Unlock (L : access RTS_Lock; Global_Lock : Boolean := False) is
      Result : Interfaces.C.int;
   begin
      if not Single_Lock or else Global_Lock then
         Result := pthread_mutex_unlock (L);
         pragma Assert (Result = 0);
      end if;
   end Unlock;
 
   procedure Unlock (T : Task_Id) is
      Result : Interfaces.C.int;
   begin
      if not Single_Lock then
         Result := pthread_mutex_unlock (T.Common.LL.L'Access);
         pragma Assert (Result = 0);
      end if;
   end Unlock;
 
   -----------
   -- Sleep --
   -----------
 
   procedure Sleep
     (Self_ID : Task_Id;
      Reason  : System.Tasking.Task_States)
   is
      pragma Unreferenced (Reason);
      Result : Interfaces.C.int;
 
   begin
      if Single_Lock then
         Result := pthread_cond_wait
           (Self_ID.Common.LL.CV'Access, Single_RTS_Lock'Access);
      else
         Result := pthread_cond_wait
           (Self_ID.Common.LL.CV'Access, Self_ID.Common.LL.L'Access);
      end if;
 
      --  EINTR is not considered a failure
 
      pragma Assert (Result = 0 or else Result = EINTR);
 
      if Self_ID.Deferral_Level = 0
        and then Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
      then
         Unlock (Self_ID);
         raise Standard'Abort_Signal;
      end if;
   end Sleep;
 
   -----------------
   -- Timed_Sleep --
   -----------------
 
   procedure Timed_Sleep
     (Self_ID  : Task_Id;
      Time     : Duration;
      Mode     : ST.Delay_Modes;
      Reason   : System.Tasking.Task_States;
      Timedout : out Boolean;
      Yielded  : out Boolean)
   is
      pragma Unreferenced (Reason);
 
      Sleep_Time : OS_Time;
      Result     : Interfaces.C.int;
      Status     : Cond_Value_Type;
 
      --  The body below requires more comments ???
 
   begin
      Timedout := False;
      Yielded := False;
 
      Sleep_Time := To_OS_Time (Time, Mode);
 
      if Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
        or else Self_ID.Pending_Priority_Change
      then
         return;
      end if;
 
      Self_ID.Common.LL.AST_Pending := True;
 
      Sys_Setimr
       (Status, 0, Sleep_Time,
        Timer_Sleep_AST'Access, To_Address (Self_ID), 0);
 
      if (Status and 1) /= 1 then
         raise Storage_Error;
      end if;
 
      if Single_Lock then
         Result := pthread_cond_wait
           (Self_ID.Common.LL.CV'Access, Single_RTS_Lock'Access);
         pragma Assert (Result = 0);
 
      else
         Result := pthread_cond_wait
           (Self_ID.Common.LL.CV'Access, Self_ID.Common.LL.L'Access);
         pragma Assert (Result = 0);
      end if;
 
      Yielded := True;
 
      if not Self_ID.Common.LL.AST_Pending then
         Timedout := True;
      else
         Sys_Cantim (Status, To_Address (Self_ID), 0);
         pragma Assert ((Status and 1) = 1);
      end if;
   end Timed_Sleep;
 
   -----------------
   -- Timed_Delay --
   -----------------
 
   procedure Timed_Delay
     (Self_ID : Task_Id;
      Time    : Duration;
      Mode    : ST.Delay_Modes)
   is
      Sleep_Time : OS_Time;
      Result     : Interfaces.C.int;
      Status     : Cond_Value_Type;
      Yielded    : Boolean := False;
 
   begin
      if Single_Lock then
         Lock_RTS;
      end if;
 
      --  More comments required in body below ???
 
      Write_Lock (Self_ID);
 
      if Time /= 0.0 or else Mode /= Relative then
         Sleep_Time := To_OS_Time (Time, Mode);
 
         if Mode = Relative or else OS_Clock < Sleep_Time then
            Self_ID.Common.State := Delay_Sleep;
            Self_ID.Common.LL.AST_Pending := True;
 
            Sys_Setimr
             (Status, 0, Sleep_Time,
              Timer_Sleep_AST'Access, To_Address (Self_ID), 0);
 
            if (Status and 1) /= 1 then
               raise Storage_Error;
            end if;
 
            loop
               if Self_ID.Pending_Priority_Change then
                  Self_ID.Pending_Priority_Change := False;
                  Self_ID.Common.Base_Priority := Self_ID.New_Base_Priority;
                  Set_Priority (Self_ID, Self_ID.Common.Base_Priority);
               end if;
 
               if Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level then
                  Sys_Cantim (Status, To_Address (Self_ID), 0);
                  pragma Assert ((Status and 1) = 1);
                  exit;
               end if;
 
               if Single_Lock then
                  Result := pthread_cond_wait
                    (Self_ID.Common.LL.CV'Access, Single_RTS_Lock'Access);
                  pragma Assert (Result = 0);
               else
                  Result := pthread_cond_wait
                    (Self_ID.Common.LL.CV'Access, Self_ID.Common.LL.L'Access);
                  pragma Assert (Result = 0);
               end if;
 
               Yielded := True;
 
               exit when not Self_ID.Common.LL.AST_Pending;
            end loop;
 
            Self_ID.Common.State := Runnable;
         end if;
      end if;
 
      Unlock (Self_ID);
 
      if Single_Lock then
         Unlock_RTS;
      end if;
 
      if not Yielded then
         Result := sched_yield;
         pragma Assert (Result = 0);
      end if;
   end Timed_Delay;
 
   ---------------------
   -- Monotonic_Clock --
   ---------------------
 
   function Monotonic_Clock return Duration
     renames System.OS_Primitives.Monotonic_Clock;
 
   -------------------
   -- RT_Resolution --
   -------------------
 
   function RT_Resolution return Duration is
   begin
      return 10#1.0#E-3;
   end RT_Resolution;
 
   ------------
   -- Wakeup --
   ------------
 
   procedure Wakeup (T : Task_Id; Reason : System.Tasking.Task_States) is
      pragma Unreferenced (Reason);
      Result : Interfaces.C.int;
   begin
      Result := pthread_cond_signal (T.Common.LL.CV'Access);
      pragma Assert (Result = 0);
   end Wakeup;
 
   -----------
   -- Yield --
   -----------
 
   procedure Yield (Do_Yield : Boolean := True) is
      Result : Interfaces.C.int;
      pragma Unreferenced (Result);
   begin
      if Do_Yield then
         Result := sched_yield;
      end if;
   end Yield;
 
   ------------------
   -- Set_Priority --
   ------------------
 
   procedure Set_Priority
     (T                   : Task_Id;
      Prio                : System.Any_Priority;
      Loss_Of_Inheritance : Boolean := False)
   is
      pragma Unreferenced (Loss_Of_Inheritance);
 
      Result : Interfaces.C.int;
      Param  : aliased struct_sched_param;
 
   begin
      T.Common.Current_Priority := Prio;
      Param.sched_priority := Interfaces.C.int (Underlying_Priorities (Prio));
 
      if Time_Slice_Val > 0 then
         Result := pthread_setschedparam
           (T.Common.LL.Thread, SCHED_RR, Param'Access);
 
      elsif Dispatching_Policy = 'F' or else Time_Slice_Val = 0 then
         Result := pthread_setschedparam
           (T.Common.LL.Thread, SCHED_FIFO, Param'Access);
 
      else
         --  SCHED_OTHER priorities are restricted to the range 8 - 15.
         --  Since the translation from Underlying priorities results
         --  in a range of 16 - 31, dividing by 2 gives the correct result.
 
         Param.sched_priority := Param.sched_priority / 2;
         Result := pthread_setschedparam
           (T.Common.LL.Thread, SCHED_OTHER, Param'Access);
      end if;
 
      pragma Assert (Result = 0);
   end Set_Priority;
 
   ------------------
   -- Get_Priority --
   ------------------
 
   function Get_Priority (T : Task_Id) return System.Any_Priority is
   begin
      return T.Common.Current_Priority;
   end Get_Priority;
 
   ----------------
   -- Enter_Task --
   ----------------
 
   procedure Enter_Task (Self_ID : Task_Id) is
   begin
      Self_ID.Common.LL.Thread := pthread_self;
 
      Specific.Set (Self_ID);
 
      Lock_RTS;
 
      for J in Known_Tasks'Range loop
         if Known_Tasks (J) = null then
            Known_Tasks (J) := Self_ID;
            Self_ID.Known_Tasks_Index := J;
            exit;
         end if;
      end loop;
 
      Unlock_RTS;
   end Enter_Task;
 
   --------------
   -- New_ATCB --
   --------------
 
   function New_ATCB (Entry_Num : Task_Entry_Index) return Task_Id is
   begin
      return new Ada_Task_Control_Block (Entry_Num);
   end New_ATCB;
 
   -------------------
   -- Is_Valid_Task --
   -------------------
 
   function Is_Valid_Task return Boolean renames Specific.Is_Valid_Task;
 
   -----------------------------
   -- Register_Foreign_Thread --
   -----------------------------
 
   function Register_Foreign_Thread return Task_Id is
   begin
      if Is_Valid_Task then
         return Self;
      else
         return Register_Foreign_Thread (pthread_self);
      end if;
   end Register_Foreign_Thread;
 
   --------------------
   -- Initialize_TCB --
   --------------------
 
   procedure Initialize_TCB (Self_ID : Task_Id; Succeeded : out Boolean) is
      Mutex_Attr : aliased pthread_mutexattr_t;
      Result     : Interfaces.C.int;
      Cond_Attr  : aliased pthread_condattr_t;
 
   begin
      --  More comments required in body below ???
 
      if not Single_Lock then
         Result := pthread_mutexattr_init (Mutex_Attr'Access);
         pragma Assert (Result = 0 or else Result = ENOMEM);
 
         if Result = 0 then
            Result := pthread_mutex_init (Self_ID.Common.LL.L'Access,
              Mutex_Attr'Access);
            pragma Assert (Result = 0 or else Result = ENOMEM);
         end if;
 
         if Result /= 0 then
            Succeeded := False;
            return;
         end if;
 
         Result := pthread_mutexattr_destroy (Mutex_Attr'Access);
         pragma Assert (Result = 0);
      end if;
 
      Result := pthread_condattr_init (Cond_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = 0 then
         Result := pthread_cond_init (Self_ID.Common.LL.CV'Access,
           Cond_Attr'Access);
         pragma Assert (Result = 0 or else Result = ENOMEM);
      end if;
 
      if Result = 0 then
         Succeeded := True;
         Self_ID.Common.LL.Exc_Stack_Ptr := new Exc_Stack_T;
 
      else
         if not Single_Lock then
            Result := pthread_mutex_destroy (Self_ID.Common.LL.L'Access);
            pragma Assert (Result = 0);
         end if;
 
         Succeeded := False;
      end if;
 
      Result := pthread_condattr_destroy (Cond_Attr'Access);
      pragma Assert (Result = 0);
   end Initialize_TCB;
 
   ------------------------
   -- Get_Exc_Stack_Addr --
   ------------------------
 
   function Get_Exc_Stack_Addr return Address is
   begin
      return Self.Common.LL.Exc_Stack_Ptr (Exc_Stack_T'Last)'Address;
   end Get_Exc_Stack_Addr;
 
   -----------------
   -- Create_Task --
   -----------------
 
   procedure Create_Task
     (T          : Task_Id;
      Wrapper    : System.Address;
      Stack_Size : System.Parameters.Size_Type;
      Priority   : System.Any_Priority;
      Succeeded  : out Boolean)
   is
      Attributes          : aliased pthread_attr_t;
      Adjusted_Stack_Size : Interfaces.C.size_t;
      Result              : Interfaces.C.int;
 
      function Thread_Body_Access is new
        Unchecked_Conversion (System.Address, Thread_Body);
 
   begin
      if Stack_Size = Unspecified_Size then
         Adjusted_Stack_Size := Interfaces.C.size_t (Default_Stack_Size);
 
      elsif Stack_Size < Minimum_Stack_Size then
         Adjusted_Stack_Size := Interfaces.C.size_t (Minimum_Stack_Size);
 
      else
         Adjusted_Stack_Size := Interfaces.C.size_t (Stack_Size);
      end if;
 
      --  Since the initial signal mask of a thread is inherited from the
      --  creator, we need to set our local signal mask mask all signals
      --  during the creation operation, to make sure the new thread is
      --  not disturbed by signals before it has set its own Task_Id.
 
      Result := pthread_attr_init (Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result /= 0 then
         Succeeded := False;
         return;
      end if;
 
      Result := pthread_attr_setdetachstate
        (Attributes'Access, PTHREAD_CREATE_DETACHED);
      pragma Assert (Result = 0);
 
      Result := pthread_attr_setstacksize
        (Attributes'Access, Adjusted_Stack_Size);
      pragma Assert (Result = 0);
 
      --  This call may be unnecessary, not sure. ???
 
      Result :=
        pthread_attr_setinheritsched
          (Attributes'Access, PTHREAD_EXPLICIT_SCHED);
      pragma Assert (Result = 0);
 
      Result := pthread_create
        (T.Common.LL.Thread'Access,
         Attributes'Access,
         Thread_Body_Access (Wrapper),
         To_Address (T));
 
      --  ENOMEM is a valid run-time error.  Don't shut down.
 
      pragma Assert (Result = 0
        or else Result = EAGAIN or else Result = ENOMEM);
 
      Succeeded := Result = 0;
 
      Result := pthread_attr_destroy (Attributes'Access);
      pragma Assert (Result = 0);
 
      if Succeeded then
         Set_Priority (T, Priority);
      end if;
   end Create_Task;
 
   ------------------
   -- Finalize_TCB --
   ------------------
 
   procedure Finalize_TCB (T : Task_Id) is
      Result  : Interfaces.C.int;
      Tmp     : Task_Id := T;
      Is_Self : constant Boolean := T = Self;
 
      procedure Free is new
        Unchecked_Deallocation (Ada_Task_Control_Block, Task_Id);
 
      procedure Free is new Unchecked_Deallocation
       (Exc_Stack_T, Exc_Stack_Ptr_T);
 
   begin
      if not Single_Lock then
         Result := pthread_mutex_destroy (T.Common.LL.L'Access);
         pragma Assert (Result = 0);
      end if;
 
      Result := pthread_cond_destroy (T.Common.LL.CV'Access);
      pragma Assert (Result = 0);
 
      if T.Known_Tasks_Index /= -1 then
         Known_Tasks (T.Known_Tasks_Index) := null;
      end if;
 
      Free (T.Common.LL.Exc_Stack_Ptr);
 
      Free (Tmp);
 
      if Is_Self then
         Specific.Set (null);
      end if;
   end Finalize_TCB;
 
   ---------------
   -- Exit_Task --
   ---------------
 
   procedure Exit_Task is
   begin
      null;
   end Exit_Task;
 
   ----------------
   -- Abort_Task --
   ----------------
 
   procedure Abort_Task (T : Task_Id) is
   begin
      --  Interrupt Server_Tasks may be waiting on an event flag
 
      if T.Common.State = Interrupt_Server_Blocked_On_Event_Flag then
         Wakeup (T, Interrupt_Server_Blocked_On_Event_Flag);
      end if;
   end Abort_Task;
 
   ----------------
   -- Initialize --
   ----------------
 
   procedure Initialize (S : in out Suspension_Object) is
      Mutex_Attr : aliased pthread_mutexattr_t;
      Cond_Attr  : aliased pthread_condattr_t;
      Result     : Interfaces.C.int;
   begin
      --  Initialize internal state. It is always initialized to False (ARM
      --  D.10 par. 6).
 
      S.State := False;
      S.Waiting := False;
 
      --  Initialize internal mutex
 
      Result := pthread_mutexattr_init (Mutex_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         raise Storage_Error;
      end if;
 
      Result := pthread_mutex_init (S.L'Access, Mutex_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         Result := pthread_mutexattr_destroy (Mutex_Attr'Access);
         pragma Assert (Result = 0);
 
         raise Storage_Error;
      end if;
 
      Result := pthread_mutexattr_destroy (Mutex_Attr'Access);
      pragma Assert (Result = 0);
 
      --  Initialize internal condition variable
 
      Result := pthread_condattr_init (Cond_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result /= 0 then
         Result := pthread_mutex_destroy (S.L'Access);
         pragma Assert (Result = 0);
 
         if Result = ENOMEM then
            raise Storage_Error;
         end if;
      end if;
 
      Result := pthread_cond_init (S.CV'Access, Cond_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result /= 0 then
         Result := pthread_mutex_destroy (S.L'Access);
         pragma Assert (Result = 0);
 
         if Result = ENOMEM then
            Result := pthread_condattr_destroy (Cond_Attr'Access);
            pragma Assert (Result = 0);
 
            raise Storage_Error;
         end if;
      end if;
 
      Result := pthread_condattr_destroy (Cond_Attr'Access);
      pragma Assert (Result = 0);
   end Initialize;
 
   --------------
   -- Finalize --
   --------------
 
   procedure Finalize (S : in out Suspension_Object) is
      Result  : Interfaces.C.int;
   begin
      --  Destroy internal mutex
 
      Result := pthread_mutex_destroy (S.L'Access);
      pragma Assert (Result = 0);
 
      --  Destroy internal condition variable
 
      Result := pthread_cond_destroy (S.CV'Access);
      pragma Assert (Result = 0);
   end Finalize;
 
   -------------------
   -- Current_State --
   -------------------
 
   function Current_State (S : Suspension_Object) return Boolean is
   begin
      --  We do not want to use lock on this read operation. State is marked
      --  as Atomic so that we ensure that the value retrieved is correct.
 
      return S.State;
   end Current_State;
 
   ---------------
   -- Set_False --
   ---------------
 
   procedure Set_False (S : in out Suspension_Object) is
      Result  : Interfaces.C.int;
   begin
      Result := pthread_mutex_lock (S.L'Access);
      pragma Assert (Result = 0);
 
      S.State := False;
 
      Result := pthread_mutex_unlock (S.L'Access);
      pragma Assert (Result = 0);
   end Set_False;
 
   --------------
   -- Set_True --
   --------------
 
   procedure Set_True (S : in out Suspension_Object) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_lock (S.L'Access);
      pragma Assert (Result = 0);
 
      --  If there is already a task waiting on this suspension object then
      --  we resume it, leaving the state of the suspension object to False,
      --  as it is specified in ARM D.10 par. 9. Otherwise, it just leaves
      --  the state to True.
 
      if S.Waiting then
         S.Waiting := False;
         S.State := False;
 
         Result := pthread_cond_signal (S.CV'Access);
         pragma Assert (Result = 0);
      else
         S.State := True;
      end if;
 
      Result := pthread_mutex_unlock (S.L'Access);
      pragma Assert (Result = 0);
   end Set_True;
 
   ------------------------
   -- Suspend_Until_True --
   ------------------------
 
   procedure Suspend_Until_True (S : in out Suspension_Object) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_lock (S.L'Access);
      pragma Assert (Result = 0);
 
      if S.Waiting then
         --  Program_Error must be raised upon calling Suspend_Until_True
         --  if another task is already waiting on that suspension object
         --  (ARM D.10 par. 10).
 
         Result := pthread_mutex_unlock (S.L'Access);
         pragma Assert (Result = 0);
 
         raise Program_Error;
      else
         --  Suspend the task if the state is False. Otherwise, the task
         --  continues its execution, and the state of the suspension object
         --  is set to False (ARM D.10 par. 9).
 
         if S.State then
            S.State := False;
         else
            S.Waiting := True;
            Result := pthread_cond_wait (S.CV'Access, S.L'Access);
         end if;
      end if;
 
      Result := pthread_mutex_unlock (S.L'Access);
      pragma Assert (Result = 0);
   end Suspend_Until_True;
 
   ----------------
   -- Check_Exit --
   ----------------
 
   --  Dummy version
 
   function Check_Exit (Self_ID : ST.Task_Id) return Boolean is
      pragma Unreferenced (Self_ID);
   begin
      return True;
   end Check_Exit;
 
   --------------------
   -- Check_No_Locks --
   --------------------
 
   function Check_No_Locks (Self_ID : ST.Task_Id) return Boolean is
      pragma Unreferenced (Self_ID);
   begin
      return True;
   end Check_No_Locks;
 
   ----------------------
   -- Environment_Task --
   ----------------------
 
   function Environment_Task return Task_Id is
   begin
      return Environment_Task_Id;
   end Environment_Task;
 
   --------------
   -- Lock_RTS --
   --------------
 
   procedure Lock_RTS is
   begin
      Write_Lock (Single_RTS_Lock'Access, Global_Lock => True);
   end Lock_RTS;
 
   ----------------
   -- Unlock_RTS --
   ----------------
 
   procedure Unlock_RTS is
   begin
      Unlock (Single_RTS_Lock'Access, Global_Lock => True);
   end Unlock_RTS;
 
   ------------------
   -- Suspend_Task --
   ------------------
 
   function Suspend_Task
     (T           : ST.Task_Id;
      Thread_Self : Thread_Id) return Boolean
   is
      pragma Unreferenced (T);
      pragma Unreferenced (Thread_Self);
   begin
      return False;
   end Suspend_Task;
 
   -----------------
   -- Resume_Task --
   -----------------
 
   function Resume_Task
     (T           : ST.Task_Id;
      Thread_Self : Thread_Id) return Boolean
   is
      pragma Unreferenced (T);
      pragma Unreferenced (Thread_Self);
   begin
      return False;
   end Resume_Task;
 
   ----------------
   -- Initialize --
   ----------------
 
   procedure Initialize (Environment_Task : Task_Id) is
   begin
      Environment_Task_Id := Environment_Task;
 
      SSL.Get_Exc_Stack_Addr := Get_Exc_Stack_Addr'Access;
 
      --  Initialize the lock used to synchronize chain of all ATCBs
 
      Initialize_Lock (Single_RTS_Lock'Access, RTS_Lock_Level);
 
      Specific.Initialize (Environment_Task);
 
      Enter_Task (Environment_Task);
   end Initialize;
 
end System.Task_Primitives.Operations;