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Commit d62ac21aa075c8ddf3d02a98d28afce635e77e8e

Authored by john stultz
Committed by Linus Torvalds
1 parent b92c4f922b
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

[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>

Showing 1 changed file with 16 additions and 14 deletions Side-by-side Diff

... ... @@ -32,7 +32,7 @@
32 32 /* TIME_ERROR prevents overwriting the CMOS clock */
33 33 static int time_state = TIME_OK; /* clock synchronization status */
34 34 int time_status = STA_UNSYNC; /* clock status bits */
35   -static long time_offset; /* time adjustment (ns) */
  35 +static s64 time_offset; /* time adjustment (ns) */
36 36 static long time_constant = 2; /* pll time constant */
37 37 long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
38 38 long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
... ... @@ -196,7 +196,7 @@
196 196 */
197 197 int do_adjtimex(struct timex *txc)
198 198 {
199   - long ltemp, mtemp, save_adjust;
  199 + long mtemp, save_adjust, rem;
200 200 s64 freq_adj, temp64;
201 201 int result;
202 202  
203 203  
... ... @@ -277,14 +277,14 @@
277 277 time_adjust = txc->offset;
278 278 }
279 279 else if (time_status & STA_PLL) {
280   - ltemp = txc->offset * NSEC_PER_USEC;
  280 + time_offset = txc->offset * NSEC_PER_USEC;
281 281  
282 282 /*
283 283 * Scale the phase adjustment and
284 284 * clamp to the operating range.
285 285 */
286   - time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC);
287   - time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC);
  286 + time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC);
  287 + time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC);
288 288  
289 289 /*
290 290 * Select whether the frequency is to be controlled
291 291  
... ... @@ -297,11 +297,11 @@
297 297 mtemp = xtime.tv_sec - time_reftime;
298 298 time_reftime = xtime.tv_sec;
299 299  
300   - freq_adj = (s64)time_offset * mtemp;
  300 + freq_adj = time_offset * mtemp;
301 301 freq_adj = shift_right(freq_adj, time_constant * 2 +
302 302 (SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
303 303 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
304   - temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL);
  304 + temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL);
305 305 if (time_offset < 0) {
306 306 temp64 = -temp64;
307 307 do_div(temp64, mtemp);
... ... @@ -314,8 +314,10 @@
314 314 freq_adj += time_freq;
315 315 freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
316 316 time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
317   - time_offset = (time_offset / NTP_INTERVAL_FREQ)
318   - << SHIFT_UPDATE;
  317 + time_offset = div_long_long_rem_signed(time_offset,
  318 + NTP_INTERVAL_FREQ,
  319 + &rem);
  320 + time_offset <<= SHIFT_UPDATE;
319 321 } /* STA_PLL */
320 322 } /* txc->modes & ADJ_OFFSET */
321 323 if (txc->modes & ADJ_TICK)
322 324  
... ... @@ -328,12 +330,12 @@
328 330 result = TIME_ERROR;
329 331  
330 332 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
331   - txc->offset = save_adjust;
  333 + txc->offset = save_adjust;
332 334 else
333   - txc->offset = shift_right(time_offset, SHIFT_UPDATE)
334   - * NTP_INTERVAL_FREQ / 1000;
335   - txc->freq = (time_freq / NSEC_PER_USEC)
336   - << (SHIFT_USEC - SHIFT_NSEC);
  335 + txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *
  336 + NTP_INTERVAL_FREQ / 1000;
  337 + txc->freq = (time_freq / NSEC_PER_USEC) <<
  338 + (SHIFT_USEC - SHIFT_NSEC);
337 339 txc->maxerror = time_maxerror;
338 340 txc->esterror = time_esterror;
339 341 txc->status = time_status;