kern/156481: commit references a PR

dfilter service dfilter at FreeBSD.ORG
Thu Aug 16 02:40:09 UTC 2012


The following reply was made to PR kern/156481; it has been noted by GNATS.

From: dfilter at FreeBSD.ORG (dfilter service)
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/156481: commit references a PR
Date: Thu, 16 Aug 2012 02:35:54 +0000 (UTC)

 Author: imp
 Date: Thu Aug 16 02:35:44 2012
 New Revision: 239320
 URL: http://svn.freebsd.org/changeset/base/239320
 
 Log:
   Limit popcorn limit to something sane (either 2ns or 2 ticks if that's
   longer).
   
   PR:		156481
   Submitted by:	Ian Lepore
 
 Modified:
   head/sys/kern/kern_ntptime.c
 
 Modified: head/sys/kern/kern_ntptime.c
 ==============================================================================
 --- head/sys/kern/kern_ntptime.c	Thu Aug 16 00:53:23 2012	(r239319)
 +++ head/sys/kern/kern_ntptime.c	Thu Aug 16 02:35:44 2012	(r239320)
 @@ -832,8 +832,15 @@ hardpps(tsp, nsec)
  	 * discarded. otherwise, if so enabled, the time offset is
  	 * updated. We can tolerate a modest loss of data here without
  	 * much degrading time accuracy.
 -	 */
 -	if (u_nsec > (pps_jitter << PPS_POPCORN)) {
 +	 *
 +	 * The measurements being checked here were made with the system
 +	 * timecounter, so the popcorn threshold is not allowed to fall below
 +	 * the number of nanoseconds in two ticks of the timecounter.  For a
 +	 * timecounter running faster than 1 GHz the lower bound is 2ns, just
 +	 * to avoid a nonsensical threshold of zero.
 +	*/
 +	if (u_nsec > lmax(pps_jitter << PPS_POPCORN, 
 +	    2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) {
  		time_status |= STA_PPSJITTER;
  		pps_jitcnt++;
  	} else if (time_status & STA_PPSTIME) {
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