4.8 "Alternate system clock has died" error

[Uwe Doering]

Charles Sprickman wrote:
> On Mon, 21 Nov 2005, John Baldwin wrote:
>> On Saturday 19 November 2005 02:16 pm, Uwe Doering wrote:
>>> John Baldwin wrote:
>>>> [...]
>>>> 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.
> 
> I run ntp everywhere.
> 
> So it certainly looks easy enough for me to change the first two 
> sections of the diff referenced above, but I'm having issues finding 
> that last one in cpu_initclocks().  It looks like that section really 
> has changed quite a bit. (see v.1.206)

Just look for all instances of

   writertc(RTC_STATUSB, rtc_statusb);

and put

   rtcin(RTC_INTR);

directly behind them (into the next line).  There should be three of 
them, in 4.8 as well as RELENG_4 and CURRENT.

> Is there any interest in moving this back to 4-STABLE?

Interest there is, I suppose.  Plenty of people still run 4.x.  The 
question is rather whether there is any committer willing to do the 
backport.  As far as I can tell, most of them are more focused on newer 
branches.  Perhaps we need special backporting committers for legacy 
branches.  Just a thought. ;-)

> And lastly, is there any snippet of code that can twiddle the clock from 
> userspace and determine if it's wedged or dead?

You may want to look at adjkerntz(8).

    Uwe
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