port-alpha/42189: System clock unstable when using PCC as the timecounter when running under SMP

[jailbird%sky.fdf.net@localhost]

>Number:         42189
>Category:       port-alpha
>Synopsis:       System clock unstable when using PCC as the timecounter when 
>running under SMP
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    port-alpha-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Oct 16 06:05:00 +0000 2009
>Originator:     Dustin Marquess
>Release:        NetBSD 5.0_STABLE (200910110000Z)
>Organization:
>Environment:
System: NetBSD sky.fdf.net 5.0_STABLE NetBSD 5.0_STABLE (GENERIC-$Revision: 
1.325.4.1 $) #0: Sun Oct 11 02:37:40 UTC 2009 
builds%b8.netbsd.org@localhost:/home/builds/ab/netbsd-5/alpha/200910110000Z-obj/home/builds/ab/netbsd-5/src/sys/arch/alpha/compile/GENERIC.MP
 alpha
Architecture: alpha
Machine: alpha
>Description:
        When running under SMP, using the default timecounter (PCC)
        results in the system clock running at roughly half-speed.  ntpd
        is also unable to perform a lock, and the clock ends up free
        running.  Switching the timecounter to use clockinterrupt
        appears to work around the problem.  This does not appear to
        happen when running under UP.
>How-To-Repeat:
        Boot a SMP kernel using the default PCC timecounter.
>Fix:
        Workaround: sysctl -w kern.timecounter.hardware = clockinterrupt