[ntp:questions] Ntpd in uninterruptible sleep?
A C
agcarver+ntp at acarver.net
Sun Oct 23 23:19:30 UTC 2011
On 10/23/2011 16:06, unruh wrote:
> On 2011-10-23, A C<agcarver+ntp at acarver.net> wrote:
>> 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.
>
> Is there some problem with your ethernet card? Is ntpd polling and
> unresponsive card like mad? Ie, is hardware a problem?
The network interface (AUI with a 10BT transceiver, Lance Ethernet) was
up and running the entire time. I had xclock running on the system with
the display exported to another machine and I also had an ssh session in
an xterm up and running. Both of those continued to function (albeit
slowly) while ntpd was stuck in that sleep state. I actually used the
ssh-in-xterm session to kill and restart ntpd. There was no significant
polling on the interface (activity LEDs showed normal behavior).
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