All,
Signed shifting must be done carefully, and the ntp code has quite a
number of conditionals to do the signed shifting. This patch makes use
of the shiftR() macro introduced in a previous patch to simplify a bit
of logic.
Any comments or feedback would be greatly appreciated.
thanks
-john
linux-2.6.13-rc6_timeofday-ntp-part7_B5.patch
============================================
diff --git a/kernel/ntp.c b/kernel/ntp.c
--- a/kernel/ntp.c
+++ b/kernel/ntp.c
@@ -162,28 +162,19 @@ void second_overflow(void)
}
ltemp = time_freq;
- if (ltemp < 0)
- time_adj -= -ltemp >> (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
- else
- time_adj += ltemp >> (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
+ time_adj += shiftR(ltemp, (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));
#if HZ == 100
/* Compensate for (HZ==100) != (1 << SHIFT_HZ).
* Add 25% and 3.125% to get 128.125; => only 0.125% error (p. 14)
*/
- if (time_adj < 0)
- time_adj -= (-time_adj >> 2) + (-time_adj >> 5);
- else
- time_adj += (time_adj >> 2) + (time_adj >> 5);
+ time_adj += shiftR(time_adj,2) + shiftR(time_adj,5);
#endif
#if HZ == 1000
/* Compensate for (HZ==1000) != (1 << SHIFT_HZ).
* Add 1.5625% and 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
*/
- if (time_adj < 0)
- time_adj -= (-time_adj >> 6) + (-time_adj >> 7);
- else
- time_adj += (time_adj >> 6) + (time_adj >> 7);
+ time_adj += shiftR(time_adj,6) + shiftR(time_adj,7);
#endif
}
@@ -349,10 +340,7 @@ int ntp_adjtimex(struct timex *txc)
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
txc->offset = save_adjust;
else {
- if (time_offset < 0)
- txc->offset = -(-time_offset >> SHIFT_UPDATE);
- else
- txc->offset = time_offset >> SHIFT_UPDATE;
+ txc->offset = shiftR(time_offset, SHIFT_UPDATE);
}
txc->freq = time_freq;
txc->maxerror = time_maxerror;
-
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