From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Wed, 1 Jul 2009 13:49:05 +0000 (+0200)
Subject: Try to minimize adjtime error
X-Git-Tag: 1.24-pre1~89
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8c0f3f4;p=thirdparty%2Fchrony.git

Try to minimize adjtime error

The offset is rounded before calling adjtime and the error below
microsecond is accumulated.
---

diff --git a/sys_linux.c b/sys_linux.c
index 2da7ed51..c60a7d3c 100644
--- a/sys_linux.c
+++ b/sys_linux.c
@@ -126,6 +126,17 @@ our_round(double x) {
   return y;
 }
 
+inline static long
+our_lround(double x) {
+  int y;
+
+  if (x > 0.0)
+	  y = x + 0.5;
+  else
+	  y = x - 0.5;
+  return y;
+}
+
 /* ================================================== */
 /* Amount of outstanding offset to process */
 static double offset_register;
@@ -255,14 +266,13 @@ initiate_slew(void)
 
   if (fabs(offset_register) < MAX_ADJUST_WITH_ADJTIME) {
     /* Use adjtime to do the shift */
-    offset = (long)(0.5 + 1.0e6*(-offset_register));
+    offset = our_lround(1.0e6 * -offset_register);
+
+    offset_register += offset * 1e-6;
 
     if (TMX_ApplyOffset(&offset) < 0) {
       CROAK("adjtimex() failed in initiate_slew");
     }
-
-    offset_register = 0.0;
-
   } else {
 
     /* If the system clock has a high drift rate, the combination of