diff mbox series

[Ada] Use the Monotonic Clock on Linux

Message ID 20171020170320.GA112533@adacore.com
State New
Headers show
Series [Ada] Use the Monotonic Clock on Linux | expand

Commit Message

Pierre-Marie de Rodat Oct. 20, 2017, 5:03 p.m. UTC
The Posix method of calculating absolute deadlines is adopted in
favor of latching the monotonic clock to a known epoch, as the Posix
method is simpler and meets all the requirements of the Ada LRM.

Tested on x86_64-pc-linux-gnu, committed on trunk

2017-10-20  Doug Rupp  <rupp@adacore.com>

	* libgnarl/s-osinte__linux.ads (Relative_Timed_Wait): Add variable
	needed for using monotonic clock.
	* libgnarl/s-taprop__linux.adb: Revert previous monotonic clock
	changes.
	* libgnarl/s-taprop__linux.adb, s-taprop__posix.adb: Unify and factor
	out monotonic clock related functions body.
	(Timed_Sleep, Timed_Delay, Montonic_Clock, RT_Resolution,
	Compute_Deadline): Move to...
	* libgnarl/s-tpopmo.adb: ... here. New separate package body.
diff mbox series

Patch

Index: libgnarl/s-osinte__linux.ads
===================================================================
--- libgnarl/s-osinte__linux.ads	(revision 253938)
+++ libgnarl/s-osinte__linux.ads	(working copy)
@@ -448,6 +448,9 @@ 
       abstime : access timespec) return int;
    pragma Import (C, pthread_cond_timedwait, "pthread_cond_timedwait");
 
+   Relative_Timed_Wait : constant Boolean := False;
+   --  pthread_cond_timedwait requires an absolute delay time
+
    --------------------------
    -- POSIX.1c  Section 13 --
    --------------------------
Index: libgnarl/s-taprop__posix.adb
===================================================================
--- libgnarl/s-taprop__posix.adb	(revision 253938)
+++ libgnarl/s-taprop__posix.adb	(working copy)
@@ -145,6 +145,38 @@ 
    package body Specific is separate;
    --  The body of this package is target specific
 
+   package Monotonic is
+
+      function Monotonic_Clock return Duration;
+      pragma Inline (Monotonic_Clock);
+      --  Returns "absolute" time, represented as an offset relative to "the
+      --  Epoch", which is Jan 1, 1970. This clock implementation is immune to
+      --  the system's clock changes.
+
+      function RT_Resolution return Duration;
+      pragma Inline (RT_Resolution);
+      --  Returns resolution of the underlying clock used to implement RT_Clock
+
+      procedure Timed_Sleep
+        (Self_ID  : ST.Task_Id;
+         Time     : Duration;
+         Mode     : ST.Delay_Modes;
+         Reason   : System.Tasking.Task_States;
+         Timedout : out Boolean;
+         Yielded  : out Boolean);
+      --  Combination of Sleep (above) and Timed_Delay
+
+      procedure Timed_Delay
+        (Self_ID : ST.Task_Id;
+         Time    : Duration;
+         Mode    : ST.Delay_Modes);
+      --  Implement the semantics of the delay statement.
+      --  The caller should be abort-deferred and should not hold any locks.
+
+   end Monotonic;
+
+   package body Monotonic is separate;
+
    ----------------------------------
    -- ATCB allocation/deallocation --
    ----------------------------------
@@ -183,18 +215,6 @@ 
    pragma Import (C,
      GNAT_pthread_condattr_setup, "__gnat_pthread_condattr_setup");
 
-   procedure Compute_Deadline
-     (Time       : Duration;
-      Mode       : ST.Delay_Modes;
-      Check_Time : out Duration;
-      Abs_Time   : out Duration;
-      Rel_Time   : out Duration);
-   --  Helper for Timed_Sleep and Timed_Delay: given a deadline specified by
-   --  Time and Mode, compute the current clock reading (Check_Time), and the
-   --  target absolute and relative clock readings (Abs_Time, Rel_Time). The
-   --  epoch for Time depends on Mode; the epoch for Check_Time and Abs_Time
-   --  is always that of CLOCK_RT_Ada.
-
    -------------------
    -- Abort_Handler --
    -------------------
@@ -253,67 +273,6 @@ 
       end if;
    end Abort_Handler;
 
-   ----------------------
-   -- Compute_Deadline --
-   ----------------------
-
-   procedure Compute_Deadline
-     (Time       : Duration;
-      Mode       : ST.Delay_Modes;
-      Check_Time : out Duration;
-      Abs_Time   : out Duration;
-      Rel_Time   : out Duration)
-   is
-   begin
-      Check_Time := Monotonic_Clock;
-
-      --  Relative deadline
-
-      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;
-
-         pragma Warnings (Off);
-         --  Comparison "OSC.CLOCK_RT_Ada = OSC.CLOCK_REALTIME" is compile
-         --  time known.
-
-      --  Absolute deadline specified using the tasking clock (CLOCK_RT_Ada)
-
-      elsif Mode = Absolute_RT
-        or else OSC.CLOCK_RT_Ada = OSC.CLOCK_REALTIME
-      then
-         pragma Warnings (On);
-         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;
-
-      --  Absolute deadline specified using the calendar clock, in the
-      --  case where it is not the same as the tasking clock: compensate for
-      --  difference between clock epochs (Base_Time - Base_Cal_Time).
-
-      else
-         declare
-            Cal_Check_Time : constant Duration := OS_Primitives.Clock;
-            RT_Time        : constant Duration :=
-                               Time + Check_Time - Cal_Check_Time;
-
-         begin
-            Abs_Time :=
-              Duration'Min (Check_Time + Max_Sensible_Delay, RT_Time);
-
-            if Relative_Timed_Wait then
-               Rel_Time :=
-                 Duration'Min (Max_Sensible_Delay, RT_Time - Check_Time);
-            end if;
-         end;
-      end if;
-   end Compute_Deadline;
-
    -----------------
    -- Stack_Guard --
    -----------------
@@ -600,61 +559,8 @@ 
       Mode     : ST.Delay_Modes;
       Reason   : Task_States;
       Timedout : out Boolean;
-      Yielded  : out Boolean)
-   is
-      pragma Unreferenced (Reason);
+      Yielded  : out Boolean) renames Monotonic.Timed_Sleep;
 
-      Base_Time  : Duration;
-      Check_Time : Duration;
-      Abs_Time   : Duration;
-      Rel_Time   : Duration;
-
-      Request    : aliased timespec;
-      Result     : Interfaces.C.int;
-
-   begin
-      Timedout := True;
-      Yielded := False;
-
-      Compute_Deadline
-        (Time       => Time,
-         Mode       => Mode,
-         Check_Time => Check_Time,
-         Abs_Time   => Abs_Time,
-         Rel_Time   => Rel_Time);
-      Base_Time := Check_Time;
-
-      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 --
    -----------------
@@ -665,96 +571,20 @@ 
    procedure Timed_Delay
      (Self_ID : Task_Id;
       Time    : Duration;
-      Mode    : ST.Delay_Modes)
-   is
-      Base_Time  : Duration;
-      Check_Time : Duration;
-      Abs_Time   : Duration;
-      Rel_Time   : Duration;
-      Request    : aliased timespec;
+      Mode    : ST.Delay_Modes) renames Monotonic.Timed_Delay;
 
-      Result : Interfaces.C.int;
-      pragma Warnings (Off, Result);
-
-   begin
-      if Single_Lock then
-         Lock_RTS;
-      end if;
-
-      Write_Lock (Self_ID);
-
-      Compute_Deadline
-        (Time       => Time,
-         Mode       => Mode,
-         Check_Time => Check_Time,
-         Abs_Time   => Abs_Time,
-         Rel_Time   => Rel_Time);
-      Base_Time := Check_Time;
-
-      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;
+   function Monotonic_Clock return Duration renames Monotonic.Monotonic_Clock;
 
    -------------------
    -- RT_Resolution --
    -------------------
 
-   function RT_Resolution return Duration is
-      TS     : aliased timespec;
-      Result : Interfaces.C.int;
-   begin
-      Result := clock_getres (OSC.CLOCK_REALTIME, TS'Unchecked_Access);
-      pragma Assert (Result = 0);
+   function RT_Resolution return Duration renames Monotonic.RT_Resolution;
 
-      return To_Duration (TS);
-   end RT_Resolution;
-
    ------------
    -- Wakeup --
    ------------
Index: libgnarl/s-tpopmo.adb
===================================================================
--- libgnarl/s-tpopmo.adb	(revision 0)
+++ libgnarl/s-tpopmo.adb	(revision 0)
@@ -0,0 +1,283 @@ 
+------------------------------------------------------------------------------
+--                                                                          --
+--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --
+--                                                                          --
+--               SYSTEM.TASK_PRIMITIVES.OPERATIONS.MONOTONIC                --
+--                                                                          --
+--                                 B o d y                                  --
+--                                                                          --
+--         Copyright (C) 1992-2017, 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 the Monotonic version of this package for Posix and Linux targets.
+
+separate (System.Task_Primitives.Operations)
+package body Monotonic is
+
+   -----------------------
+   -- Local Subprograms --
+   -----------------------
+
+   procedure Compute_Deadline
+     (Time       : Duration;
+      Mode       : ST.Delay_Modes;
+      Check_Time : out Duration;
+      Abs_Time   : out Duration;
+      Rel_Time   : out Duration);
+   --  Helper for Timed_Sleep and Timed_Delay: given a deadline specified by
+   --  Time and Mode, compute the current clock reading (Check_Time), and the
+   --  target absolute and relative clock readings (Abs_Time, Rel_Time). The
+   --  epoch for Time depends on Mode; the epoch for Check_Time and Abs_Time
+   --  is always that of CLOCK_RT_Ada.
+
+   ---------------------
+   -- 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
+      TS     : aliased timespec;
+      Result : Interfaces.C.int;
+
+   begin
+      Result := clock_getres (OSC.CLOCK_REALTIME, TS'Unchecked_Access);
+      pragma Assert (Result = 0);
+
+      return To_Duration (TS);
+   end RT_Resolution;
+
+   ----------------------
+   -- Compute_Deadline --
+   ----------------------
+
+   procedure Compute_Deadline
+     (Time       : Duration;
+      Mode       : ST.Delay_Modes;
+      Check_Time : out Duration;
+      Abs_Time   : out Duration;
+      Rel_Time   : out Duration)
+   is
+   begin
+      Check_Time := Monotonic_Clock;
+
+      --  Relative deadline
+
+      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;
+
+         pragma Warnings (Off);
+         --  Comparison "OSC.CLOCK_RT_Ada = OSC.CLOCK_REALTIME" is compile
+         --  time known.
+
+      --  Absolute deadline specified using the tasking clock (CLOCK_RT_Ada)
+
+      elsif Mode = Absolute_RT
+        or else OSC.CLOCK_RT_Ada = OSC.CLOCK_REALTIME
+      then
+         pragma Warnings (On);
+         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;
+
+      --  Absolute deadline specified using the calendar clock, in the
+      --  case where it is not the same as the tasking clock: compensate for
+      --  difference between clock epochs (Base_Time - Base_Cal_Time).
+
+      else
+         declare
+            Cal_Check_Time : constant Duration := OS_Primitives.Clock;
+            RT_Time        : constant Duration :=
+                               Time + Check_Time - Cal_Check_Time;
+
+         begin
+            Abs_Time :=
+              Duration'Min (Check_Time + Max_Sensible_Delay, RT_Time);
+
+            if Relative_Timed_Wait then
+               Rel_Time :=
+                 Duration'Min (Max_Sensible_Delay, RT_Time - Check_Time);
+            end if;
+         end;
+      end if;
+   end Compute_Deadline;
+
+   -----------------
+   -- 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  : ST.Task_Id;
+      Time     : Duration;
+      Mode     : ST.Delay_Modes;
+      Reason   : System.Tasking.Task_States;
+      Timedout : out Boolean;
+      Yielded  : out Boolean)
+   is
+      pragma Unreferenced (Reason);
+
+      Base_Time  : Duration;
+      Check_Time : Duration;
+      Abs_Time   : Duration;
+      Rel_Time   : Duration;
+
+      Request    : aliased timespec;
+      Result     : Interfaces.C.int;
+
+   begin
+      Timedout := True;
+      Yielded := False;
+
+      Compute_Deadline
+        (Time       => Time,
+         Mode       => Mode,
+         Check_Time => Check_Time,
+         Abs_Time   => Abs_Time,
+         Rel_Time   => Rel_Time);
+      Base_Time := Check_Time;
+
+      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 in 0 | 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 : ST.Task_Id;
+      Time    : Duration;
+      Mode    : ST.Delay_Modes)
+   is
+      Base_Time  : Duration;
+      Check_Time : Duration;
+      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);
+
+      Compute_Deadline
+        (Time       => Time,
+         Mode       => Mode,
+         Check_Time => Check_Time,
+         Abs_Time   => Abs_Time,
+         Rel_Time   => Rel_Time);
+      Base_Time := Check_Time;
+
+      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 in 0 | ETIMEDOUT | 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;
+
+end Monotonic;
Index: libgnarl/s-taprop__linux.adb
===================================================================
--- libgnarl/s-taprop__linux.adb	(revision 253938)
+++ libgnarl/s-taprop__linux.adb	(working copy)
@@ -38,9 +38,7 @@ 
 --  Turn off polling, we do not want ATC polling to take place during tasking
 --  operations. It causes infinite loops and other problems.
 
-with Interfaces.C; use Interfaces;
-use type Interfaces.C.int;
-use type Interfaces.C.long;
+with Interfaces.C; use Interfaces; use type Interfaces.C.int;
 
 with System.Task_Info;
 with System.Tasking.Debug;
@@ -112,8 +110,6 @@ 
    --  Constant to indicate that the thread identifier has not yet been
    --  initialized.
 
-   Base_Monotonic_Clock : Duration := 0.0;
-
    --------------------
    -- Local Packages --
    --------------------
@@ -141,6 +137,38 @@ 
    package body Specific is separate;
    --  The body of this package is target specific
 
+   package Monotonic is
+
+      function Monotonic_Clock return Duration;
+      pragma Inline (Monotonic_Clock);
+      --  Returns "absolute" time, represented as an offset relative to "the
+      --  Epoch", which is Jan 1, 1970. This clock implementation is immune to
+      --  the system's clock changes.
+
+      function RT_Resolution return Duration;
+      pragma Inline (RT_Resolution);
+      --  Returns resolution of the underlying clock used to implement RT_Clock
+
+      procedure Timed_Sleep
+        (Self_ID  : ST.Task_Id;
+         Time     : Duration;
+         Mode     : ST.Delay_Modes;
+         Reason   : System.Tasking.Task_States;
+         Timedout : out Boolean;
+         Yielded  : out Boolean);
+      --  Combination of Sleep (above) and Timed_Delay
+
+      procedure Timed_Delay
+        (Self_ID : ST.Task_Id;
+         Time    : Duration;
+         Mode    : ST.Delay_Modes);
+      --  Implement the semantics of the delay statement.
+      --  The caller should be abort-deferred and should not hold any locks.
+
+   end Monotonic;
+
+   package body Monotonic is separate;
+
    ----------------------------------
    -- ATCB allocation/deallocation --
    ----------------------------------
@@ -169,11 +197,6 @@ 
 
    procedure Abort_Handler (signo : Signal);
 
-   function Compute_Base_Monotonic_Clock return Duration;
-   --  The monotonic clock epoch is set to some undetermined time in the past
-   --  (typically system boot time). In order to use the monotonic clock for
-   --  absolute time, the offset from a known epoch is needed.
-
    function GNAT_pthread_condattr_setup
      (attr : access pthread_condattr_t) return C.int;
    pragma Import
@@ -275,100 +298,6 @@ 
       end if;
    end Abort_Handler;
 
-   ----------------------------------
-   -- Compute_Base_Monotonic_Clock --
-   ----------------------------------
-
-   function Compute_Base_Monotonic_Clock return Duration is
-      Aft     : Duration;
-      Bef     : Duration;
-      Mon     : Duration;
-      Res_A   : Interfaces.C.int;
-      Res_B   : Interfaces.C.int;
-      Res_M   : Interfaces.C.int;
-      TS_Aft  : aliased timespec;
-      TS_Aft0 : aliased timespec;
-      TS_Bef  : aliased timespec;
-      TS_Bef0 : aliased timespec;
-      TS_Mon  : aliased timespec;
-      TS_Mon0 : aliased timespec;
-
-   begin
-      Res_B :=
-        clock_gettime
-          (clock_id => OSC.CLOCK_REALTIME,
-           tp       => TS_Bef0'Unchecked_Access);
-      pragma Assert (Res_B = 0);
-
-      Res_M :=
-        clock_gettime
-          (clock_id => OSC.CLOCK_RT_Ada,
-           tp       => TS_Mon0'Unchecked_Access);
-      pragma Assert (Res_M = 0);
-
-      Res_A :=
-        clock_gettime
-          (clock_id => OSC.CLOCK_REALTIME,
-           tp       => TS_Aft0'Unchecked_Access);
-      pragma Assert (Res_A = 0);
-
-      for I in 1 .. 10 loop
-
-         --  Guard against a leap second that will cause CLOCK_REALTIME to jump
-         --  backwards. In the extrenmely unlikely event we call clock_gettime
-         --  before and after the jump the epoch, the result will be off
-         --  slightly.
-         --  Use only results where the tv_sec values match, for the sake of
-         --  convenience.
-         --  Also try to calculate the most accurate epoch by taking the
-         --  minimum difference of 10 tries.
-
-         Res_B :=
-           clock_gettime
-             (clock_id => OSC.CLOCK_REALTIME,
-              tp       => TS_Bef'Unchecked_Access);
-         pragma Assert (Res_B = 0);
-
-         Res_M :=
-           clock_gettime
-             (clock_id => OSC.CLOCK_RT_Ada,
-              tp       => TS_Mon'Unchecked_Access);
-         pragma Assert (Res_M = 0);
-
-         Res_A :=
-           clock_gettime
-             (clock_id => OSC.CLOCK_REALTIME,
-              tp       => TS_Aft'Unchecked_Access);
-         pragma Assert (Res_A = 0);
-
-         --  The calls to clock_gettime before the loop were no good
-
-         if (TS_Bef0.tv_sec /= TS_Aft0.tv_sec
-               and then TS_Bef.tv_sec  = TS_Aft.tv_sec)
-
-           --  The most recent calls to clock_gettime were better
-
-           or else
-             (TS_Bef0.tv_sec = TS_Aft0.tv_sec
-                and then TS_Bef.tv_sec = TS_Aft.tv_sec
-                and then (TS_Aft.tv_nsec - TS_Bef.tv_nsec
-                            < TS_Aft0.tv_nsec - TS_Bef0.tv_nsec))
-         then
-            TS_Bef0 := TS_Bef;
-            TS_Aft0 := TS_Aft;
-            TS_Mon0 := TS_Mon;
-         end if;
-      end loop;
-
-      Bef := To_Duration (TS_Bef0);
-      Mon := To_Duration (TS_Mon0);
-      Aft := To_Duration (TS_Aft0);
-
-      --  Distribute the division, to avoid potential type overflow someday
-
-      return Bef / 2 + Aft / 2 - Mon;
-   end Compute_Base_Monotonic_Clock;
-
    --------------
    -- Lock_RTS --
    --------------
@@ -690,57 +619,8 @@ 
       Mode     : ST.Delay_Modes;
       Reason   : System.Tasking.Task_States;
       Timedout : out Boolean;
-      Yielded  : out Boolean)
-   is
-      pragma Unreferenced (Reason);
+      Yielded  : out Boolean) renames Monotonic.Timed_Sleep;
 
-      Base_Time  : constant Duration := Monotonic_Clock;
-      Check_Time : Duration := Base_Time - Base_Monotonic_Clock;
-      Abs_Time   : Duration;
-      Request    : aliased timespec;
-      Result     : C.int;
-
-   begin
-      Timedout := True;
-      Yielded := False;
-
-      Abs_Time :=
-        (if Mode = Relative
-         then Duration'Min (Time, Max_Sensible_Delay) + Check_Time
-         else Duration'Min (Check_Time + Max_Sensible_Delay,
-                            Time - Base_Monotonic_Clock));
-
-      if Abs_Time > Check_Time then
-         Request := To_Timespec (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 + Base_Monotonic_Clock <= Check_Time
-                      or else Check_Time < Base_Time;
-
-            if Result in 0 | 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 --
    -----------------
@@ -751,93 +631,20 @@ 
    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 - Base_Monotonic_Clock;
-      Abs_Time   : Duration;
-      Request    : aliased timespec;
+      Mode    : ST.Delay_Modes) renames Monotonic.Timed_Delay;
 
-      Result : C.int;
-      pragma Warnings (Off, Result);
-
-   begin
-      if Single_Lock then
-         Lock_RTS;
-      end if;
-
-      Write_Lock (Self_ID);
-
-      Abs_Time :=
-        (if Mode = Relative
-         then Time + Check_Time
-         else Duration'Min (Check_Time + Max_Sensible_Delay,
-                            Time - Base_Monotonic_Clock));
-
-      if Abs_Time > Check_Time then
-         Request := To_Timespec (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 + Base_Monotonic_Clock <= Check_Time
-                      or else Check_Time < Base_Time;
-
-            pragma Assert (Result in 0 | ETIMEDOUT | 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);
+   function Monotonic_Clock return Duration renames Monotonic.Monotonic_Clock;
 
-      return Base_Monotonic_Clock + To_Duration (TS);
-   end Monotonic_Clock;
-
    -------------------
    -- RT_Resolution --
    -------------------
 
-   function RT_Resolution return Duration is
-      TS     : aliased timespec;
-      Result : C.int;
+   function RT_Resolution return Duration renames Monotonic.RT_Resolution;
 
-   begin
-      Result := clock_getres (OSC.CLOCK_REALTIME, TS'Unchecked_Access);
-      pragma Assert (Result = 0);
-
-      return To_Duration (TS);
-   end RT_Resolution;
-
    ------------
    -- Wakeup --
    ------------
@@ -1612,8 +1419,6 @@ 
 
       Interrupt_Management.Initialize;
 
-      Base_Monotonic_Clock := Compute_Base_Monotonic_Clock;
-
       --  Prepare the set of signals that should be unblocked in all tasks
 
       Result := sigemptyset (Unblocked_Signal_Mask'Access);