4.8 "Alternate system clock has died" error

John Baldwin jhb at freebsd.org
Mon Nov 21 18:16:57 GMT 2005

On Saturday 19 November 2005 02:16 pm, Uwe Doering wrote:
> John Baldwin wrote:
> > On Friday 18 November 2005 10:05 pm, Charles Sprickman wrote:
> >>I tried this query on -stable, hoping someone here can help me further
> >>understand and troubleshoot this.
> >>
> >>Reference:
> >>http://thread.gmane.org/gmane.os.freebsd.stable/32837
> >>
> >>In short, top, ps report 0% CPU on all processes as of a few weeks ago.
> >>"systat -vmstat" hands out the "Alternate system clock has died" error.
> >>
> >>Box is running 4.8-p24 and has been up 425 days.  Nothing out of the
> >>ordinary except for the above symptoms.  In searching the various
> >>lists/newsgroups, it seems that the other folks with this problem have
> >>fixed it in various ways:
> >>
> >>-early 4.x users referenced a PR that was committed before 4.8
> >>-some 5.3 users reported this with unknown resolution/cause
> >>-sending init a HUP was suggested (tried it, no luck)
> >>-setting kern.timecounter.method: 1 (tried it, no luck)
> >>-one user seemed to actually have a dead timer
> >
> > Actually, there was a patch that was committed in 5.4 and 6.0 for this
> > issue. You can see the diff here:
> >
> > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/i386/isa/clock.c.diff?r1=1.
> >213&r2=1.214&f=h
> >
> > That patch would probably backport to 4.x fairly easily.
> I just looked at RELENG_4, and yes, backporting should be easy.  Though
> I haven't tried it yet on our machines.
> I wonder, however, what's writing to the RTC on a running server.  Could
> this event perhaps have been triggered by the recent Daylight Saving
> Time switch?

Yep.  Also, if you are using ntp, then the adjustments to the time are getting 
pushed back to the RTC as well.

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org

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