[PATCH] ntp: avoid time_offset overflows
I've been seeing some odd NTP behavior recently on a few boxes and
finally narrowed it down to time_offset overflowing when converted to
SHIFT_UPDATE units (which was a side effect from my HZfreeNTP patch).
This patch converts time_offset from a long to a s64 which resolves the
issue.
[tglx@linutronix.de: signedness fixes]
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index eb12509..cb25649 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -32,7 +32,7 @@
/* TIME_ERROR prevents overwriting the CMOS clock */
static int time_state = TIME_OK; /* clock synchronization status */
int time_status = STA_UNSYNC; /* clock status bits */
-static long time_offset; /* time adjustment (ns) */
+static s64 time_offset; /* time adjustment (ns) */
static long time_constant = 2; /* pll time constant */
long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
@@ -196,7 +196,7 @@
*/
int do_adjtimex(struct timex *txc)
{
- long ltemp, mtemp, save_adjust;
+ long mtemp, save_adjust, rem;
s64 freq_adj, temp64;
int result;
@@ -277,14 +277,14 @@
time_adjust = txc->offset;
}
else if (time_status & STA_PLL) {
- ltemp = txc->offset * NSEC_PER_USEC;
+ time_offset = txc->offset * NSEC_PER_USEC;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
- time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
- time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
+ time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC);
+ time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC);
/*
* Select whether the frequency is to be controlled
@@ -297,11 +297,11 @@
mtemp = xtime.tv_sec - time_reftime;
time_reftime = xtime.tv_sec;
- freq_adj = (s64)time_offset * mtemp;
+ freq_adj = time_offset * mtemp;
freq_adj = shift_right(freq_adj, time_constant * 2 +
(SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
- temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL);
+ temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL);
if (time_offset < 0) {
temp64 = -temp64;
do_div(temp64, mtemp);
@@ -314,8 +314,10 @@
freq_adj += time_freq;
freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
- time_offset = (time_offset / NTP_INTERVAL_FREQ)
- << SHIFT_UPDATE;
+ time_offset = div_long_long_rem_signed(time_offset,
+ NTP_INTERVAL_FREQ,
+ &rem);
+ time_offset <<= SHIFT_UPDATE;
} /* STA_PLL */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK)
@@ -328,12 +330,12 @@
result = TIME_ERROR;
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
- txc->offset = save_adjust;
+ txc->offset = save_adjust;
else
- txc->offset = shift_right(time_offset, SHIFT_UPDATE)
- * NTP_INTERVAL_FREQ / 1000;
- txc->freq = (time_freq / NSEC_PER_USEC)
- << (SHIFT_USEC - SHIFT_NSEC);
+ txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *
+ NTP_INTERVAL_FREQ / 1000;
+ txc->freq = (time_freq / NSEC_PER_USEC) <<
+ (SHIFT_USEC - SHIFT_NSEC);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;