[ntp:questions] Ntpd in uninterruptible sleep?

A C agcarver+ntp at acarver.net
Sun Oct 23 19:28:08 UTC 2011


A continuation of my debugging ntpd on a sparc system running NetBSD. 
First, using -N results in a system lockup after a period of time if I 
am polling ntpd remotely with ntpq.  I removed the -N option from 
startup and the system stayed stable even when querying at 5 second 
intervals.

However, I just ran into a new problem.  Here's the output of ps ax for 
the ntpd entry:

22887 ?     Ds     20:17.58 /usr/sbin/ntpd


Uninterruptible sleep?  The daemon is indeed asleep because it stopped 
responding to my ntpq queries but this time the system stayed up.  I 
suspect it was this same sleep that occurred in the other condition but 
the high priority locked up the machine.  I was able to kill and restart 
ntpd without having to fully reboot.  All other processes were still 
running normally but slowly (see below).

More interesting is that the cpu was pegged until I was able to kill and 
restart ntpd.  Most of the cpu was devoted to ntpd during this locked up 
period.  Simple things like typing at the console were difficult.  It 
would take a few seconds for a keypress to register on the screen.  Once 
ntpd was restarted the system responded normally and the cpu usage 
dropped to normal levels.

This is still version 4.2.6p3.  I should probably go ahead and compile 
the most recently released version but I'm at a loss to understand why 
it happened.


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