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Try to minimize adjtime error

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The offset is rounded before calling adjtime and the error below
microsecond is accumulated.
This commit is contained in:
Miroslav Lichvar
2009-07-01 15:49:05 +02:00
parent 735811b2b9
commit 8c0f3f4042
1 changed files with 14 additions and 4 deletions
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18
sys_linux.c
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@@ -126,6 +126,17 @@ our_round(double x) {
return y; 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 */ /* Amount of outstanding offset to process */
static double offset_register; static double offset_register;
@@ -255,14 +266,13 @@ initiate_slew(void)
if (fabs(offset_register) < MAX_ADJUST_WITH_ADJTIME) { if (fabs(offset_register) < MAX_ADJUST_WITH_ADJTIME) {
/* Use adjtime to do the shift */ /* 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) { if (TMX_ApplyOffset(&offset) < 0) {
CROAK("adjtimex() failed in initiate_slew"); CROAK("adjtimex() failed in initiate_slew");
} }
offset_register = 0.0;
} else { } else {
/* If the system clock has a high drift rate, the combination of /* If the system clock has a high drift rate, the combination of