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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) 1992-2011, 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 POSIX-like version of this package

--  This package contains all the GNULL primitives that interface directly with

--  the underlying OS.

--  Note: this file can only be used for POSIX compliant systems that implement

--  SCHED_FIFO and Ceiling Locking correctly.

--  For configurations where SCHED_FIFO and priority ceiling are not a

--  requirement, this file can also be used (e.g AiX threads)

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 Interfaces.C;

with System.Tasking.Debug;

with System.Interrupt_Management;

with System.OS_Constants;

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 OSC renames System.OS_Constants;

   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

   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)

   Use_Alternate_Stack : constant Boolean := Alternate_Stack_Size /= 0;

   --  Whether to use an alternate signal stack for stack overflows

   Abort_Handler_Installed : Boolean := False;

   --  True if a handler for the abort signal is installed

   --------------------

   -- 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

   ----------------------------------

   -- ATCB allocation/deallocation --

   ----------------------------------

   package body ATCB_Allocation is separate;

   --  The body of this package is shared across several targets

   ---------------------------------

   -- 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.

   --  See also comment before body, below.

   function To_Address is

     new Ada.Unchecked_Conversion (Task_Id, System.Address);

   function GNAT_pthread_condattr_setup

     (attr : access pthread_condattr_t) return int;

   pragma Import (C,

     GNAT_pthread_condattr_setup, "__gnat_pthread_condattr_setup");

   -------------------

   -- 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.

   procedure Abort_Handler (Sig : Signal) is

      pragma Unreferenced (Sig);

      T       : constant Task_Id := Self;

      Old_Set : aliased sigset_t;

      Result : Interfaces.C.int;

      pragma Warnings (Off, Result);

   begin

      --  It's not safe to raise an exception when using GCC ZCX mechanism.

      --  Note that we still need to install a signal handler, since in some

      --  cases (e.g. shutdown of the Server_Task in System.Interrupts) we

      --  need to send the Abort signal to a task.

      if ZCX_By_Default 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;

         Res :=

           mprotect (Guard_Page_Address, Get_Page_Size,

                     prot => (if On then PROT_ON else PROT_OFF));

         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 --

   ---------------------

   --  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;

      if Locking_Policy = 'C' then

         Result := pthread_mutexattr_setprotocol

           (Attributes'Access, PTHREAD_PRIO_PROTECT);

         pragma Assert (Result = 0);

         Result := pthread_mutexattr_setprioceiling

            (Attributes'Access, Interfaces.C.int (Prio));

         pragma Assert (Result = 0);

      elsif Locking_Policy = 'I' then

         Result := pthread_mutexattr_setprotocol

           (Attributes'Access, PTHREAD_PRIO_INHERIT);

         pragma Assert (Result = 0);

      end if;

      Result := pthread_mutex_init (L.WO'Access, 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;

   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;

      if Locking_Policy = 'C' then

         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);

      elsif Locking_Policy = 'I' then

         Result := pthread_mutexattr_setprotocol

           (Attributes'Access, PTHREAD_PRIO_INHERIT);

         pragma Assert (Result = 0);

      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.WO'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;

   begin

      Result := pthread_mutex_lock (L.WO'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;

   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.WO'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

      Result :=

        pthread_cond_wait

          (cond  => Self_ID.Common.LL.CV'Access,

           mutex => (if Single_Lock

                     then Single_RTS_Lock'Access

                     else 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   : 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

         Request :=

           To_Timespec (if Relative_Timed_Wait then Rel_Time else Abs_Time);

         loop

            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;

            Result :=

              pthread_cond_timedwait

                (cond    => Self_ID.Common.LL.CV'Access,

                 mutex   => (if Single_Lock

                             then Single_RTS_Lock'Access

                             else Self_ID.Common.LL.L'Access),

                 abstime => Request'Access);

            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;

      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

         Request :=

           To_Timespec (if Relative_Timed_Wait then Rel_Time else Abs_Time);

         Self_ID.Common.State := Delay_Sleep;

         loop

            exit when Self_ID.Pending_ATC_Level < Self_ID.ATC_Nesting_Level;

            Result :=

              pthread_cond_timedwait

                (cond    => Self_ID.Common.LL.CV'Access,

                 mutex   => (if Single_Lock

                             then Single_RTS_Lock'Access

                             else Self_ID.Common.LL.L'Access),

                 abstime => Request'Access);

            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 => OSC.CLOCK_RT_Ada, tp => TS'Unchecked_Access);

      pragma Assert (Result = 0);

      return To_Duration (TS);

   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

      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 := To_Target_Priority (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_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