------------------------------------------------------------------------------
--                                                                          --
--                GNU ADA 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                                 --
--                                                                          --
--                             $Revision: 1.2 $
--                                                                          --
--             Copyright (C) 1991-2001, Florida State University            --
--                                                                          --
-- 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,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, 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. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com).                                  --
--                                                                          --
------------------------------------------------------------------------------

--  This is a GNU/Linux (GNU/LinuxThreads) 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 Interfaces.C;
--  used for int
--           size_t

with System.Interrupt_Management;
--  used for Keep_Unmasked
--           Abort_Task_Interrupt
--           Interrupt_ID

with System.Interrupt_Management.Operations;
--  used for Set_Interrupt_Mask
--           All_Tasks_Mask
pragma Elaborate_All (System.Interrupt_Management.Operations);

with System.Parameters;
--  used for Size_Type

with System.Tasking;
--  used for Ada_Task_Control_Block
--           Task_ID

with Ada.Exceptions;
--  used for Raise_Exception
--           Raise_From_Signal_Handler
--           Exception_Id

with System.Soft_Links;
--  used for Defer/Undefer_Abort

--  Note that we do not use System.Tasking.Initialization directly since
--  this 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.Initialization

with System.OS_Primitives;
--  used for Delay_Modes

with System.Soft_Links;
--  used for Get_Machine_State_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;

   package SSL renames System.Soft_Links;

   ------------------
   --  Local Data  --
   ------------------

   Max_Stack_Size : constant := 2000 * 1024;
   --  GNU/LinuxThreads does not return an error value when requesting
   --  a task stack size which is too large, so we have to check this
   --  ourselves.

   --  The followings are logically constants, but need to be initialized
   --  at run time.

   ATCB_Key : aliased pthread_key_t;
   --  Key used to find the Ada Task_ID associated with a thread

   All_Tasks_L : aliased System.Task_Primitives.RTS_Lock;
   --  See comments on locking rules in System.Tasking (spec).

   Environment_Task_ID : Task_ID;
   --  A variable to hold Task_ID for the environment task.

   Unblocked_Signal_Mask : aliased sigset_t;
   --  The set of signals that should unblocked in all tasks

   --  The followings are internal configuration constants needed.
   Priority_Ceiling_Emulation : constant Boolean := True;

   Next_Serial_Number : Task_Serial_Number := 100;
   --  We start at 100, to reserve some special values for
   --  using in error checking.
   --  The following are internal configuration constants needed.

   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");

   FIFO_Within_Priorities : constant Boolean := Dispatching_Policy = 'F';
   --  Indicates whether FIFO_Within_Priorities is set.

   --  The following are effectively constants, but they need to
   --  be initialized by calling a pthread_ function.

   Mutex_Attr   : aliased pthread_mutexattr_t;
   Cond_Attr    : aliased pthread_condattr_t;

   -----------------------
   -- Local Subprograms --
   -----------------------

   subtype unsigned_short is Interfaces.C.unsigned_short;
   subtype unsigned_long is Interfaces.C.unsigned_long;

   procedure Abort_Handler
     (signo         : Signal;
      gs            : unsigned_short;
      fs            : unsigned_short;
      es            : unsigned_short;
      ds            : unsigned_short;
      edi           : unsigned_long;
      esi           : unsigned_long;
      ebp           : unsigned_long;
      esp           : unsigned_long;
      ebx           : unsigned_long;
      edx           : unsigned_long;
      ecx           : unsigned_long;
      eax           : unsigned_long;
      trapno        : unsigned_long;
      err           : unsigned_long;
      eip           : unsigned_long;
      cs            : unsigned_short;
      eflags        : unsigned_long;
      esp_at_signal : unsigned_long;
      ss            : unsigned_short;
      fpstate       : System.Address;
      oldmask       : unsigned_long;
      cr2           : unsigned_long);

   function To_Task_ID is new Unchecked_Conversion (System.Address, Task_ID);

   function To_Address is new Unchecked_Conversion (Task_ID, System.Address);

   function To_pthread_t is new Unchecked_Conversion
     (Integer, System.OS_Interface.pthread_t);

   -------------------
   -- Abort_Handler --
   -------------------

   --  Target-dependent binding of inter-thread Abort signal to
   --  the raising of the Abort_Signal exception.

   --  The technical issues and alternatives here are essentially
   --  the same as for raising exceptions in response to other
   --  signals (e.g. Storage_Error).  See code and comments in
   --  the package body System.Interrupt_Management.

   --  Some implementations may not allow an exception to be propagated
   --  out of a handler, and others might leave the signal or
   --  interrupt that invoked this handler masked after the exceptional
   --  return to the application code.

   --  GNAT exceptions are originally implemented using setjmp()/longjmp().
   --  On most UNIX systems, this will allow transfer out of a signal handler,
   --  which is usually the only mechanism available for implementing
   --  asynchronous handlers of this kind.  However, some
   --  systems do not restore the signal mask on longjmp(), leaving the
   --  abort signal masked.

   --  Alternative solutions include:

   --       1. Change the PC saved in the system-dependent Context
   --          parameter to point to code that raises the exception.
   --          Normal return from this handler will then raise
   --          the exception after the mask and other system state has
   --          been restored (see example below).
   --       2. Use siglongjmp()/sigsetjmp() to implement exceptions.
   --       3. Unmask the signal in the Abortion_Signal exception handler
   --          (in the RTS).

   --  Note that with the new exception mechanism, it is not correct to
   --  simply "raise" an exception from a signal handler, that's why we
   --  use Raise_From_Signal_Handler

   procedure Abort_Handler
     (signo   : Signal;
      gs            : unsigned_short;
      fs            : unsigned_short;
      es            : unsigned_short;
      ds            : unsigned_short;
      edi           : unsigned_long;
      esi           : unsigned_long;
      ebp           : unsigned_long;
      esp           : unsigned_long;
      ebx           : unsigned_long;
      edx           : unsigned_long;
      ecx           : unsigned_long;
      eax           : unsigned_long;
      trapno        : unsigned_long;
      err           : unsigned_long;
      eip           : unsigned_long;
      cs            : unsigned_short;
      eflags        : unsigned_long;
      esp_at_signal : unsigned_long;
      ss            : unsigned_short;
      fpstate       : System.Address;
      oldmask       : unsigned_long;
      cr2           : unsigned_long)
   is
      Self_Id : Task_ID := Self;
      Result  : Interfaces.C.int;
      Old_Set : aliased sigset_t;

      function To_Machine_State_Ptr is new
        Unchecked_Conversion (Address, Machine_State_Ptr);

      --  These are not directly visible

      procedure Raise_From_Signal_Handler
        (E : Ada.Exceptions.Exception_Id;
         M : System.Address);
      pragma Import
        (Ada, Raise_From_Signal_Handler,
         "ada__exceptions__raise_from_signal_handler");
      pragma No_Return (Raise_From_Signal_Handler);

      mstate  : Machine_State_Ptr;
      message : aliased constant String := "" & ASCII.Nul;
      --  a null terminated String.

   begin
      if Self_Id.Deferral_Level = 0
        and then Self_Id.Pending_ATC_Level < Self_Id.ATC_Nesting_Level
        and then not Self_Id.Aborting
      then
         Self_Id.Aborting := True;

         --  Make sure signals used for RTS internal purpose are unmasked

         Result := pthread_sigmask (SIG_UNBLOCK,
           Unblocked_Signal_Mask'Unchecked_Access, Old_Set'Unchecked_Access);
         pragma Assert (Result = 0);

         mstate := To_Machine_State_Ptr (SSL.Get_Machine_State_Addr.all);
         mstate.eip := eip;
         mstate.ebx := ebx;
         mstate.esp := esp_at_signal;
         mstate.ebp := ebp;
         mstate.esi := esi;
         mstate.edi := edi;

         Raise_From_Signal_Handler
           (Standard'Abort_Signal'Identity, message'Address);
      end if;
   end Abort_Handler;

   -------------------
   --  Stack_Guard  --
   -------------------

   --  The underlying thread system extends the memory (up to 2MB) when
   --  needed.

   procedure Stack_Guard (T : ST.Task_ID; On : Boolean) is
   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 is
      Result : System.Address;

   begin
      Result := pthread_getspecific (ATCB_Key);
      pragma Assert (Result /= System.Null_Address);
      return To_Task_ID (Result);
   end 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 All_Tasks_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
      Result : Interfaces.C.int;
   begin
      if Priority_Ceiling_Emulation then
         L.Ceiling := Prio;
      end if;

      Result := pthread_mutex_init (L.L'Access, Mutex_Attr'Access);

      pragma Assert (Result = 0 or else Result = ENOMEM);

      if Result = ENOMEM then
         Ada.Exceptions.Raise_Exception (Storage_Error'Identity,
           "Failed to allocate a lock");
      end if;
   end Initialize_Lock;

   procedure Initialize_Lock (L : access RTS_Lock; Level : Lock_Level) is
      Result : Interfaces.C.int;

   begin
      Result := pthread_mutex_init (L, Mutex_Attr'Access);

      pragma Assert (Result = 0 or else Result = ENOMEM);

      if Result = ENOMEM then
         raise Storage_Error;
      end if;
   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
      Result : Interfaces.C.int;

   begin
      if Priority_Ceiling_Emulation then
         declare
            Self_ID : constant Task_ID := Self;
         begin
            if Self_ID.Common.LL.Active_Priority > L.Ceiling then
               Ceiling_Violation := True;
               return;
            end if;
            L.Saved_Priority := Self_ID.Common.LL.Active_Priority;
            if Self_ID.Common.LL.Active_Priority < L.Ceiling then
               Self_ID.Common.LL.Active_Priority := L.Ceiling;
            end if;
            Result := pthread_mutex_lock (L.L'Access);
            pragma Assert (Result = 0);
            Ceiling_Violation := False;
         end;
      else
         Result := pthread_mutex_lock (L.L'Access);
         Ceiling_Violation := Result = EINVAL;
         --  assumes the cause of EINVAL is a priority ceiling violation
         pragma Assert (Result = 0 or else Result = EINVAL);
      end if;
   end Write_Lock;

   procedure Write_Lock (L : access RTS_Lock) is
      Result : Interfaces.C.int;

   begin
      Result := pthread_mutex_lock (L);
      pragma Assert (Result = 0);
   end Write_Lock;

   procedure Write_Lock (T : Task_ID) is
      Result : Interfaces.C.int;

   begin
      Result := pthread_mutex_lock (T.Common.LL.L'Access);
      pragma Assert (Result = 0);
   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
      if Priority_Ceiling_Emulation then
         declare
            Self_ID : constant Task_ID := Self;
         begin
            Result := pthread_mutex_unlock (L.L'Access);
            pragma Assert (Result = 0);
            if Self_ID.Common.LL.Active_Priority > L.Saved_Priority then
               Self_ID.Common.LL.Active_Priority := L.Saved_Priority;
            end if;
         end;
      else
         Result := pthread_mutex_unlock (L.L'Access);
         pragma Assert (Result = 0);
      end if;
   end Unlock;

   procedure Unlock (L : access RTS_Lock) is
      Result : Interfaces.C.int;
      --  Beware of any changes to this that might
      --  require access to the ATCB after the mutex is unlocked.
      --  This is the last operation performed by a task
      --  before it allows its ATCB to be deallocated, so it
      --  MUST NOT refer to the ATCB.

   begin
      Result := pthread_mutex_unlock (L);
      pragma Assert (Result = 0);
   end Unlock;

   procedure Unlock (T : Task_ID) is
      Result : Interfaces.C.int;

   begin
      Result := pthread_mutex_unlock (T.Common.LL.L'Access);
      pragma Assert (Result = 0);
   end Unlock;

   -------------
   --  Sleep  --
   -------------

   procedure Sleep (Self_ID : Task_ID;
                    Reason   : System.Tasking.Task_States) is
      Result : Interfaces.C.int;

   begin
      pragma Assert (Self_ID = Self);
      Result := pthread_cond_wait (Self_ID.Common.LL.CV'Access,
        Self_ID.Common.LL.L'Access);
      --  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   : System.Tasking.Task_States;
      Timedout : out Boolean;
      Yielded  : out Boolean)
   is
      Check_Time : constant Duration := Monotonic_Clock;
      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;
      else
         Abs_Time := Duration'Min (Check_Time + Max_Sensible_Delay, Time);
      end if;

      if Abs_Time > Check_Time then
         Request := To_Timespec (Abs_Time);

         loop
            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level
              or else Self_ID.Pending_Priority_Change;

            Result := pthread_cond_timedwait
              (Self_ID.Common.LL.CV'Access, Self_ID.Common.LL.L'Access,
               Request'Access);

            exit when Abs_Time <= Monotonic_Clock;

            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
      Check_Time : constant Duration := Monotonic_Clock;
      Abs_Time   : Duration;
      Request    : aliased timespec;
      Result     : Interfaces.C.int;
   begin

      --  Only the little window between deferring abort and
      --  locking Self_ID is the reason we need to
      --  check for pending abort and priority change below! :(

      SSL.Abort_Defer.all;
      Write_Lock (Self_ID);

      if Mode = Relative then
         Abs_Time := Time + Check_Time;
      else
         Abs_Time := Duration'Min (Check_Time + Max_Sensible_Delay, Time);
      end if;

      if Abs_Time > Check_Time then
         Request := To_Timespec (Abs_Time);
         Self_ID.Common.State := Delay_Sleep;

         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;

            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;

            Result := pthread_cond_timedwait (Self_ID.Common.LL.CV'Access,
              Self_ID.Common.LL.L'Access, Request'Access);

            exit when Abs_Time <= Monotonic_Clock;

            pragma Assert (Result = 0 or else
              Result = ETIMEDOUT or else
              Result = EINTR);
         end loop;

         Self_ID.Common.State := Runnable;
      end if;

      Unlock (Self_ID);
      Result := sched_yield;
      SSL.Abort_Undefer.all;
   end Timed_Delay;

   ---------------------
   -- Monotonic_Clock --
   ---------------------

   function Monotonic_Clock return Duration is
      TV     : aliased struct_timeval;
      Result : Interfaces.C.int;

   begin
      Result := gettimeofday (TV'Access, System.Null_Address);
      pragma Assert (Result = 0);
      return To_Duration (TV);
   end Monotonic_Clock;

   -------------------
   -- RT_Resolution --
   -------------------

   function RT_Resolution return Duration is
   begin
      return 10#1.0#E-6;
   end RT_Resolution;

   ------------
   -- Wakeup --
   ------------

   procedure Wakeup (T : Task_ID; Reason : System.Tasking.Task_States) is
      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;

   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
      Result : Interfaces.C.int;
      Param  : aliased struct_sched_param;

   begin
      T.Common.Current_Priority := Prio;

      if Priority_Ceiling_Emulation then
         if T.Common.LL.Active_Priority < Prio then
            T.Common.LL.Active_Priority := Prio;
         end if;
      end if;

      --  Priorities are in range 1 .. 99 on GNU/Linux, so we map
      --  map 0 .. 31 to 1 .. 32

      Param.sched_priority := Interfaces.C.int (Prio) + 1;

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

      elsif FIFO_Within_Priorities 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 or else Result = EPERM);
   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
      Result : Interfaces.C.int;

   begin
      Self_ID.Common.LL.Thread := pthread_self;

      Result := pthread_setspecific (ATCB_Key, To_Address (Self_ID));
      pragma Assert (Result = 0);

      Lock_All_Tasks_List;
      for I in Known_Tasks'Range loop
         if Known_Tasks (I) = null then
            Known_Tasks (I) := Self_ID;
            Self_ID.Known_Tasks_Index := I;
            exit;
         end if;
      end loop;
      Unlock_All_Tasks_List;
   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;

   --------------------
   -- Initialize_TCB --
   --------------------

   procedure Initialize_TCB (Self_ID : Task_ID; Succeeded : out Boolean) is
      Result : Interfaces.C.int;

   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);

      Self_ID.Common.LL.Thread := To_pthread_t (-1);

      Result := pthread_mutex_init (Self_ID.Common.LL.L'Access,
        Mutex_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);

      if Result /= 0 then
         Succeeded := False;
         return;
      end if;

      Result := pthread_cond_init (Self_ID.Common.LL.CV'Access,
        Cond_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);

      if Result = 0 then
         Succeeded := True;
      else
         Result := pthread_mutex_destroy (Self_ID.Common.LL.L'Access);
         pragma Assert (Result = 0);
         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;
      Result     : Interfaces.C.int;

      function Thread_Body_Access is new
        Unchecked_Conversion (System.Address, Thread_Body);

   begin
      Result := pthread_attr_init (Attributes'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);

      if Result /= 0 or else Stack_Size > Max_Stack_Size then
         Succeeded := False;
         return;
      end if;

      Result := pthread_attr_setdetachstate
        (Attributes'Access, PTHREAD_CREATE_DETACHED);
      pragma Assert (Result = 0);

      --  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);

      Set_Priority (T, Priority);
   end Create_Task;

   ------------------
   -- Finalize_TCB --
   ------------------

   procedure Finalize_TCB (T : Task_ID) is
      Result : Interfaces.C.int;
      Tmp    : Task_ID := T;

      procedure Free is new
        Unchecked_Deallocation (Ada_Task_Control_Block, Task_ID);

   begin
      Result := pthread_mutex_destroy (T.Common.LL.L'Access);
      pragma Assert (Result = 0);
      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);
   end Finalize_TCB;

   ---------------
   -- Exit_Task --
   ---------------

   procedure Exit_Task is
   begin
      pthread_exit (System.Null_Address);
   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;

   ----------------
   -- Check_Exit --
   ----------------

   --  Dummy versions.  The only currently working versions is for solaris
   --  (native).

   function Check_Exit (Self_ID : ST.Task_ID) return Boolean is
   begin
      return True;
   end Check_Exit;

   --------------------
   -- Check_No_Locks --
   --------------------

   function Check_No_Locks (Self_ID : ST.Task_ID) return Boolean is
   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_All_Tasks_List --
   -------------------------

   procedure Lock_All_Tasks_List is
   begin
      Write_Lock (All_Tasks_L'Access);
   end Lock_All_Tasks_List;

   ---------------------------
   -- Unlock_All_Tasks_List --
   ---------------------------

   procedure Unlock_All_Tasks_List is
   begin
      Unlock (All_Tasks_L'Access);
   end Unlock_All_Tasks_List;

   ------------------
   -- Suspend_Task --
   ------------------

   function Suspend_Task
     (T           : ST.Task_ID;
      Thread_Self : Thread_Id) return Boolean is
   begin
      if T.Common.LL.Thread /= Thread_Self then
         return pthread_kill (T.Common.LL.Thread, SIGSTOP) = 0;
      else
         return True;
      end if;
   end Suspend_Task;

   -----------------
   -- Resume_Task --
   -----------------

   function Resume_Task
     (T           : ST.Task_ID;
      Thread_Self : Thread_Id) return Boolean is
   begin
      if T.Common.LL.Thread /= Thread_Self then
         return pthread_kill (T.Common.LL.Thread, SIGCONT) = 0;
      else
         return True;
      end if;
   end Resume_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;

   begin
      Environment_Task_ID := Environment_Task;

      Result := pthread_mutexattr_init (Mutex_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);

      Result := pthread_condattr_init (Cond_Attr'Access);
      pragma Assert (Result = 0 or else Result = ENOMEM);

      Initialize_Lock (All_Tasks_L'Access, All_Tasks_Level);
      --  Initialize the lock used to synchronize chain of all ATCBs.

      Enter_Task (Environment_Task);

      --  Install the abort-signal handler

      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 (Interrupt_Management.Abort_Task_Interrupt),
           act'Unchecked_Access,
           old_act'Unchecked_Access);
      pragma Assert (Result = 0);
   end Initialize;

begin
   declare
      Result : Interfaces.C.int;
   begin
      --  Mask Environment task for all signals. The original mask of the
      --  Environment task will be recovered by Interrupt_Server task
      --  during the elaboration of s-interr.adb.

      System.Interrupt_Management.Operations.Set_Interrupt_Mask
        (System.Interrupt_Management.Operations.All_Tasks_Mask'Access);

      --  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;

      Result := pthread_key_create (ATCB_Key'Access, null);
      pragma Assert (Result = 0);
   end;

end System.Task_Primitives.Operations;