path: root/gcc/ada/s-taprop-vms.adb

------------------------------------------------------------------------------
--                                                                          --
--                 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) 1992-2008, 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 Ada.Unchecked_Conversion;
with Ada.Unchecked_Deallocation;

with Interfaces.C;

with System.Tasking.Debug;
with System.OS_Primitives;
with System.Soft_Links;
with System.Aux_DEC;

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 Ada.Unchecked_Conversion
       (System.Task_Primitives.Task_Address, Task_Id);

   function To_Address is
     new Ada.Unchecked_Conversion
       (Task_Id, System.Task_Primitives.Task_Address);

   function Get_Exc_Stack_Addr return Address;
   --  Replace System.Soft_Links.Get_Exc_Stack_Addr_NT

   procedure Timer_Sleep_AST (ID : Address);
   pragma Convention (C, Timer_Sleep_AST);
   --  Signal the condition variable when AST fires

   procedure Timer_Sleep_AST (ID : Address) is
      Result : Interfaces.C.int;
      pragma Warnings (Off, Result);
      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 raising Storage_Error in the following
   --  routines should be able to be handled safely.

   procedure Initialize_Lock
     (Prio : System.Any_Priority;
      L    : not null 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     : not null 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 : not null 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 : not null 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                 : not null 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           : not null 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                 : not null access Lock;
      Ceiling_Violation : out Boolean)
   is
   begin
      Write_Lock (L, Ceiling_Violation);
   end Read_Lock;

   ------------
   -- Unlock --
   ------------

   procedure Unlock (L : not null access Lock) is
      Result : Interfaces.C.int;
   begin
      Result := pthread_mutex_unlock (L.L'Access);
      pragma Assert (Result = 0);
   end Unlock;

   procedure Unlock
     (L           : not null 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;

   -----------------
   -- Set_Ceiling --
   -----------------

   --  Dynamic priority ceilings are not supported by the underlying system

   procedure Set_Ceiling
     (L    : not null access Lock;
      Prio : System.Any_Priority)
   is
      pragma Unreferenced (L, Prio);
   begin
      null;
   end Set_Ceiling;

   -----------
   -- 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 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);

            --  Comment following test

            if (Status and 1) /= 1 then
               raise Storage_Error;
            end if;

            loop
               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
      --  Document origin of this magic constant ???
      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;

      function Get_Policy (Prio : System.Any_Priority) return Character;
      pragma Import (C, Get_Policy, "__gnat_get_specific_dispatching");
      --  Get priority specific dispatching policy

      Priority_Specific_Policy : constant Character := Get_Policy (Prio);
      --  Upper case first character of the policy name corresponding to the
      --  task as set by a Priority_Specific_Dispatching pragma.

   begin
      T.Common.Current_Priority := Prio;
      Param.sched_priority := Interfaces.C.int (Underlying_Priorities (Prio));

      if Dispatching_Policy = 'R'
        or else Priority_Specific_Policy = 'R'
        or else Time_Slice_Val > 0
      then
         Result :=
           pthread_setschedparam
             (T.Common.LL.Thread, SCHED_RR, Param'Access);

      elsif Dispatching_Policy = 'F'
        or else Priority_Specific_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;
      Result     : Interfaces.C.int;

      function Thread_Body_Access is new
        Ada.Unchecked_Conversion (System.Aux_DEC.Short_Address, Thread_Body);

   begin
      --  Since the initial signal mask of a thread is inherited from the
      --  creator, we need to set our local signal mask to 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, Interfaces.C.size_t (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 -- do not 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
        Ada.Unchecked_Deallocation (Ada_Task_Control_Block, Task_Id);

      procedure Free is new Ada.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 (always to False (D.10 (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
      SSL.Abort_Defer.all;

      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);

      SSL.Abort_Undefer.all;
   end Set_False;

   --------------
   -- Set_True --
   --------------

   procedure Set_True (S : in out Suspension_Object) is
      Result : Interfaces.C.int;

   begin
      SSL.Abort_Defer.all;

      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 specified in (RM D.10(9)), otherwise leave state set 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);

      SSL.Abort_Undefer.all;
   end Set_True;

   ------------------------
   -- Suspend_Until_True --
   ------------------------

   procedure Suspend_Until_True (S : in out Suspension_Object) is
      Result : Interfaces.C.int;

   begin
      SSL.Abort_Defer.all;

      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
         --  (RM D.10(10)).

         Result := pthread_mutex_unlock (S.L'Access);
         pragma Assert (Result = 0);

         SSL.Abort_Undefer.all;

         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;

         Result := pthread_mutex_unlock (S.L'Access);
         pragma Assert (Result = 0);

         SSL.Abort_Undefer.all;
      end if;
   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;

   --------------------
   -- Stop_All_Tasks --
   --------------------

   procedure Stop_All_Tasks is
   begin
      null;
   end Stop_All_Tasks;

   ---------------
   -- Stop_Task --
   ---------------

   function Stop_Task (T : ST.Task_Id) return Boolean is
      pragma Unreferenced (T);
   begin
      return False;
   end Stop_Task;

   -------------------
   -- Continue_Task --
   -------------------

   function Continue_Task (T : ST.Task_Id) return Boolean is
      pragma Unreferenced (T);
   begin
      return False;
   end Continue_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;