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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) 1992-2009, 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 3,  or (at your option) any later ver- --
-- sion.  GNAT 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.                                     --
--                                                                          --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception,   --
-- version 3.1, as published by the Free Software Foundation.               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- GNARL was developed by the GNARL team at Florida State University.       --
-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
--                                                                          --
------------------------------------------------------------------------------
 
--  This is a LynxOS version of this file, adapted to make SCHED_FIFO and
--  ceiling locking (Annex D compliance) work properly.
 
--  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_Deallocation;
 
with Interfaces.C;
 
with System.Tasking.Debug;
with System.Interrupt_Management;
with System.OS_Primitives;
with System.Task_Info;
 
with System.Soft_Links;
--  We use System.Soft_Links instead of System.Tasking.Initialization
--  because the later is a higher level package that we shouldn't depend on.
--  For example when using the restricted run time, it is replaced by
--  System.Tasking.Restricted.Stages.
 
package body System.Task_Primitives.Operations is
 
   package SSL renames System.Soft_Links;
 
   use System.Tasking.Debug;
   use System.Tasking;
   use Interfaces.C;
   use System.OS_Interface;
   use System.Parameters;
   use System.OS_Primitives;
 
   ----------------
   -- 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
 
   Locking_Policy : Character;
   pragma Import (C, Locking_Policy, "__gl_locking_policy");
   --  Value of the pragma Locking_Policy:
   --    'C' for Ceiling_Locking
   --    'I' for Inherit_Locking
   --    ' ' for none.
 
   Unblocked_Signal_Mask : aliased sigset_t;
   --  The set of signals that should unblocked in all tasks
 
   --  The followings are internal configuration constants needed
 
   Next_Serial_Number : Task_Serial_Number := 100;
   --  We start at 100, to reserve some special values for
   --  using in error checking.
 
   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 the current thread have an ATCB?
 
      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 --
   -----------------------
 
   procedure Abort_Handler (Sig : Signal);
   --  Signal handler used to implement asynchronous abort
 
   procedure Set_OS_Priority (T : Task_Id; Prio : System.Any_Priority);
   --  This procedure calls the scheduler of the OS to set thread's priority
 
   -------------------
   -- Abort_Handler --
   -------------------
 
   procedure Abort_Handler (Sig : Signal) is
      pragma Unreferenced (Sig);
 
      T       : constant Task_Id := Self;
      Result  : Interfaces.C.int;
      Old_Set : aliased sigset_t;
 
   begin
      --  It is not safe to raise an exception when using ZCX and the GCC
      --  exception handling mechanism.
 
      if ZCX_By_Default and then GCC_ZCX_Support then
         return;
      end if;
 
      if T.Deferral_Level = 0
        and then T.Pending_ATC_Level < T.ATC_Nesting_Level
        and then not T.Aborting
      then
         T.Aborting := True;
 
         --  Make sure signals used for RTS internal purpose are unmasked
 
         Result :=
           pthread_sigmask
             (SIG_UNBLOCK,
              Unblocked_Signal_Mask'Access,
              Old_Set'Access);
         pragma Assert (Result = 0);
 
         raise Standard'Abort_Signal;
      end if;
   end Abort_Handler;
 
   -----------------
   -- Stack_Guard --
   -----------------
 
   procedure Stack_Guard (T : ST.Task_Id; On : Boolean) is
      Stack_Base : constant Address := Get_Stack_Base (T.Common.LL.Thread);
      Guard_Page_Address : Address;
 
      Res : Interfaces.C.int;
 
   begin
      if Stack_Base_Available then
 
         --  Compute the guard page address
 
         Guard_Page_Address :=
           Stack_Base - (Stack_Base mod Get_Page_Size) + Get_Page_Size;
 
         if On then
            Res := mprotect (Guard_Page_Address, Get_Page_Size, PROT_ON);
         else
            Res := mprotect (Guard_Page_Address, Get_Page_Size, PROT_OFF);
         end if;
 
         pragma Assert (Res = 0);
      end if;
   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 --
   ---------------------
 
   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;
 
      if Locking_Policy = 'C' then
         L.Ceiling := Prio;
      end if;
 
      Result := pthread_mutex_init (L.Mutex'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;
 
      Result := pthread_mutex_init (L, Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);
 
      if Result = ENOMEM then
         Result := pthread_mutexattr_destroy (Attributes'Access);
         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.Mutex'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
      Result : Interfaces.C.int;
      T      : constant Task_Id := Self;
 
   begin
      if Locking_Policy = 'C' then
         if T.Common.Current_Priority > L.Ceiling then
            Ceiling_Violation := True;
            return;
         end if;
 
         L.Saved_Priority := T.Common.Current_Priority;
 
         if T.Common.Current_Priority < L.Ceiling then
            Set_OS_Priority (T, L.Ceiling);
         end if;
      end if;
 
      Result := pthread_mutex_lock (L.Mutex'Access);
 
      --  Assume that the cause of EINVAL is a priority ceiling violation
 
      Ceiling_Violation := (Result = EINVAL);
      pragma Assert (Result = 0 or else Result = EINVAL);
   end Write_Lock;
 
   --  No tricks on RTS_Locks
 
   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;
      T      : constant Task_Id := Self;
 
   begin
      Result := pthread_mutex_unlock (L.Mutex'Access);
      pragma Assert (Result = 0);
 
      if Locking_Policy = 'C' then
         if T.Common.Current_Priority > L.Saved_Priority then
            Set_OS_Priority (T, L.Saved_Priority);
         end if;
      end if;
   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);
   end Sleep;
 
   -----------------
   -- Timed_Sleep --
   -----------------
 
   --  This is for use within the run-time system, so abort is
   --  assumed to be already deferred, and the caller should be
   --  holding its own ATCB lock.
 
   procedure Timed_Sleep
     (Self_ID  : Task_Id;
      Time     : Duration;
      Mode     : ST.Delay_Modes;
      Reason   : Task_States;
      Timedout : out Boolean;
      Yielded  : out Boolean)
   is
      pragma Unreferenced (Reason);
 
      Base_Time  : constant Duration := Monotonic_Clock;
      Check_Time : Duration := Base_Time;
      Rel_Time   : Duration;
      Abs_Time   : Duration;
      Request    : aliased timespec;
      Result     : Interfaces.C.int;
 
   begin
      Timedout := True;
      Yielded := False;
 
      if Mode = Relative then
         Abs_Time := Duration'Min (Time, Max_Sensible_Delay) + Check_Time;
 
         if Relative_Timed_Wait then
            Rel_Time := Duration'Min (Max_Sensible_Delay, Time);
         end if;
 
      else
         Abs_Time := Duration'Min (Check_Time + Max_Sensible_Delay, Time);
 
         if Relative_Timed_Wait then
            Rel_Time := Duration'Min (Max_Sensible_Delay, Time - Check_Time);
         end if;
      end if;
 
      if Abs_Time > Check_Time then
         if Relative_Timed_Wait then
            Request := To_Timespec (Rel_Time);
         else
            Request := To_Timespec (Abs_Time);
         end if;
 
         loop
            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;
 
            if Single_Lock then
               Result :=
                 pthread_cond_timedwait
                   (Self_ID.Common.LL.CV'Access, Single_RTS_Lock'Access,
                    Request'Access);
 
            else
               Result :=
                 pthread_cond_timedwait
                   (Self_ID.Common.LL.CV'Access, Self_ID.Common.LL.L'Access,
                    Request'Access);
            end if;
 
            Check_Time := Monotonic_Clock;
            exit when Abs_Time <= Check_Time or else Check_Time < Base_Time;
 
            if Result = 0 or Result = EINTR then
 
               --  Somebody may have called Wakeup for us
 
               Timedout := False;
               exit;
            end if;
 
            pragma Assert (Result = ETIMEDOUT);
         end loop;
      end if;
   end Timed_Sleep;
 
   -----------------
   -- Timed_Delay --
   -----------------
 
   --  This is for use in implementing delay statements, so we assume
   --  the caller is abort-deferred but is holding no locks.
 
   procedure Timed_Delay
     (Self_ID : Task_Id;
      Time    : Duration;
      Mode    : ST.Delay_Modes)
   is
      Base_Time  : constant Duration := Monotonic_Clock;
      Check_Time : Duration := Base_Time;
      Abs_Time   : Duration;
      Rel_Time   : Duration;
      Request    : aliased timespec;
 
      Result : Interfaces.C.int;
      pragma Warnings (Off, Result);
 
   begin
      if Single_Lock then
         Lock_RTS;
      end if;
 
      --  Comments needed in code below ???
 
      Write_Lock (Self_ID);
 
      if Mode = Relative then
         Abs_Time := Duration'Min (Time, Max_Sensible_Delay) + Check_Time;
 
         if Relative_Timed_Wait then
            Rel_Time := Duration'Min (Max_Sensible_Delay, Time);
         end if;
 
      else
         Abs_Time := Duration'Min (Check_Time + Max_Sensible_Delay, Time);
 
         if Relative_Timed_Wait then
            Rel_Time := Duration'Min (Max_Sensible_Delay, Time - Check_Time);
         end if;
      end if;
 
      if Abs_Time > Check_Time then
         if Relative_Timed_Wait then
            Request := To_Timespec (Rel_Time);
         else
            Request := To_Timespec (Abs_Time);
         end if;
 
         Self_ID.Common.State := Delay_Sleep;
 
         loop
            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;
 
            if Single_Lock then
               Result :=
                 pthread_cond_timedwait
                   (Self_ID.Common.LL.CV'Access,
                    Single_RTS_Lock'Access,
                    Request'Access);
            else
               Result :=
                 pthread_cond_timedwait
                   (Self_ID.Common.LL.CV'Access,
                    Self_ID.Common.LL.L'Access,
                    Request'Access);
            end if;
 
            Check_Time := Monotonic_Clock;
            exit when Abs_Time <= Check_Time or else Check_Time < Base_Time;
 
            pragma Assert (Result = 0         or else
                           Result = ETIMEDOUT or else
                           Result = EINTR);
         end loop;
 
         Self_ID.Common.State := Runnable;
      end if;
 
      Unlock (Self_ID);
 
      if Single_Lock then
         Unlock_RTS;
      end if;
 
      Result := sched_yield;
   end Timed_Delay;
 
   ---------------------
   -- Monotonic_Clock --
   ---------------------
 
   function Monotonic_Clock return Duration is
      TS     : aliased timespec;
      Result : Interfaces.C.int;
   begin
      Result :=
        clock_gettime
          (clock_id => CLOCK_REALTIME, tp => TS'Unchecked_Access);
      pragma Assert (Result = 0);
      return To_Duration (TS);
   end Monotonic_Clock;
 
   -------------------
   -- RT_Resolution --
   -------------------
 
   function RT_Resolution return Duration is
      Res    : aliased timespec;
      Result : Interfaces.C.int;
   begin
      Result :=
        clock_getres
          (clock_id => CLOCK_REALTIME, res => Res'Unchecked_Access);
      pragma Assert (Result = 0);
      return To_Duration (Res);
   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_OS_Priority (T : Task_Id; Prio : System.Any_Priority) is
      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
      Param.sched_priority := Interfaces.C.int (Prio);
 
      if Time_Slice_Supported
        and then (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
         Result :=
           pthread_setschedparam
             (T.Common.LL.Thread, SCHED_OTHER, Param'Access);
      end if;
 
      pragma Assert (Result = 0);
   end Set_OS_Priority;
 
   type Prio_Array_Type is array (System.Any_Priority) of Integer;
   pragma Atomic_Components (Prio_Array_Type);
   Prio_Array : Prio_Array_Type;
   --  Comments needed for these declarations ???
 
   procedure Set_Priority
     (T                   : Task_Id;
      Prio                : System.Any_Priority;
      Loss_Of_Inheritance : Boolean := False)
   is
      Array_Item : Integer;
 
   begin
      Set_OS_Priority (T, Prio);
 
      if Locking_Policy = 'C' then
 
         --  Annex D requirements: loss of inheritance puts task at the start
         --  of the queue for that prio; copied from 5ztaprop (VxWorks).
 
         if Loss_Of_Inheritance
           and then Prio < T.Common.Current_Priority then
 
            Array_Item := Prio_Array (T.Common.Base_Priority) + 1;
            Prio_Array (T.Common.Base_Priority) := Array_Item;
 
            loop
               Yield;
               exit when Array_Item = Prio_Array (T.Common.Base_Priority)
                 or else Prio_Array (T.Common.Base_Priority) = 1;
            end loop;
 
            Prio_Array (T.Common.Base_Priority) :=
              Prio_Array (T.Common.Base_Priority) - 1;
         end if;
      end if;
 
      T.Common.Current_Priority := Prio;
   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;
      Self_ID.Common.LL.LWP := lwp_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
      --  Give the task a unique serial number
 
      Self_ID.Serial_Number := Next_Serial_Number;
      Next_Serial_Number := Next_Serial_Number + 1;
      pragma Assert (Next_Serial_Number /= 0);
 
      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;
      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;
 
   -----------------
   -- 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;
 
      use System.Task_Info;
 
   begin
      Adjusted_Stack_Size := Interfaces.C.size_t (Stack_Size);
 
      if Stack_Base_Available then
 
         --  If Stack Checking is supported then allocate 2 additional pages:
 
         --  In the worst case, stack is allocated at something like
         --  N * Get_Page_Size - epsilon, we need to add the size for 2 pages
         --  to be sure the effective stack size is greater than what
         --  has been asked.
 
         Adjusted_Stack_Size := Adjusted_Stack_Size + 2 * Get_Page_Size;
      end if;
 
      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);
 
      if T.Common.Task_Info /= Default_Scope then
 
         --  We are assuming that Scope_Type has the same values than the
         --  corresponding C macros
 
         Result :=
           pthread_attr_setscope
             (Attributes'Access, Task_Info_Type'Pos (T.Common.Task_Info));
         pragma Assert (Result = 0);
      end if;
 
      --  Since the initial signal mask of a thread is inherited from the
      --  creator, and the Environment task has all its signals masked, we
      --  do not need to manipulate caller's signal mask at this point.
      --  All tasks in RTS will have All_Tasks_Mask initially.
 
      Result :=
        pthread_create
          (T.Common.LL.Thread'Access,
           Attributes'Access,
           Thread_Body_Access (Wrapper),
           To_Address (T));
      pragma Assert (Result = 0 or else Result = EAGAIN);
 
      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);
 
   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 (Tmp);
 
      if Is_Self then
         Result := st_setspecific (ATCB_Key, System.Null_Address);
         pragma Assert (Result = 0);
      end if;
   end Finalize_TCB;
 
   ---------------
   -- Exit_Task --
   ---------------
 
   procedure Exit_Task is
   begin
      Specific.Set (null);
   end Exit_Task;
 
   ----------------
   -- Abort_Task --
   ----------------
 
   procedure Abort_Task (T : Task_Id) is
      Result : Interfaces.C.int;
   begin
      Result :=
        pthread_kill
          (T.Common.LL.Thread,
           Signal (System.Interrupt_Management.Abort_Task_Interrupt));
      pragma Assert (Result = 0);
   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 (RM 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, just leave state set 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 (RM D.10(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
      act     : aliased struct_sigaction;
      old_act : aliased struct_sigaction;
      Tmp_Set : aliased sigset_t;
      Result  : Interfaces.C.int;
 
      function State
        (Int  : System.Interrupt_Management.Interrupt_ID) return Character;
      pragma Import (C, State, "__gnat_get_interrupt_state");
      --  Get interrupt state.  Defined in a-init.c
      --  The input argument is the interrupt number,
      --  and the result is one of the following:
 
      Default : constant Character := 's';
      --    'n'   this interrupt not set by any Interrupt_State pragma
      --    'u'   Interrupt_State pragma set state to User
      --    'r'   Interrupt_State pragma set state to Runtime
      --    's'   Interrupt_State pragma set state to System (use "default"
      --           system handler)
 
   begin
      Environment_Task_Id := Environment_Task;
 
      Interrupt_Management.Initialize;
 
      --  Prepare the set of signals that should unblocked in all tasks
 
      Result := sigemptyset (Unblocked_Signal_Mask'Access);
      pragma Assert (Result = 0);
 
      for J in Interrupt_Management.Interrupt_ID loop
         if System.Interrupt_Management.Keep_Unmasked (J) then
            Result := sigaddset (Unblocked_Signal_Mask'Access, Signal (J));
            pragma Assert (Result = 0);
         end if;
      end loop;
 
      --  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);
 
      --  Install the abort-signal handler
 
      if State
          (System.Interrupt_Management.Abort_Task_Interrupt) /= Default
      then
         act.sa_flags := 0;
         act.sa_handler := Abort_Handler'Address;
 
         Result := sigemptyset (Tmp_Set'Access);
         pragma Assert (Result = 0);
         act.sa_mask := Tmp_Set;
 
         Result :=
           sigaction
             (Signal (System.Interrupt_Management.Abort_Task_Interrupt),
              act'Unchecked_Access,
              old_act'Unchecked_Access);
 
         pragma Assert (Result = 0);
      end if;
   end Initialize;
 
end System.Task_Primitives.Operations;