Bug on df command-unable to kill a hanging df process

[Ernesto Quiroz]

Hello

 

I am unable to kill a hanging df process by using kill -9 <PID>.

 

Situation: We have an NFS mount on one of our servers. The network link
went down before the NFS mount was properly unmounted. We have a cron
job that runs df every so often to check for disk space. We noticed that
the load on this box was getting high. After doing research we found
that the df command would hang because the NFS mount is "still there"
when it's not thus causing the load to slowly increase. We tried killing
all df processes by PID using kill -9 PID and kill -KILL PID, but we
were unable to do it. We ran top and under the S column (Process Status)
all the df processes had a D. We did a man top, and under the Process
Status -> D it says uninterruptible sleep which explains why the kill
command is unable to kill hanging df processes.

We think this is a bug because normally one can execute kill -9 <PID>
and the process goes away, but not in this case. At this moment the
"fix" is to restart the box.

 

Thank you,

Ernesto