ksoftirqd and the leap second issue

Last evening I spend quite a lot of time figuring out why tomcat was consuming 90% of CPU and ksoftirqd was consuming the rest of cpu. 
Typically tomcat uses all of the CPU when has gone out of memory (PermGen). So I restarted tomcat but cpu gone up to 100% immediately. 
After various attempts i saw that ksoftirqd was consuming 10% and the total consumed cpu was like after a DOS attack:

 4 root      20   0     0    0    0 S  0.0  0.0 567:44.72 ksoftirqd/0 

I found no DoS signs in the rest of the system, googling arround i found "the leap second issue". A kernel issue related to a second added between 30 June and 1 July.
This is the post:
http://www.mail-archive.com/user@cassandra.apache.org/msg23474.html

In fact this command line

date; date `date +"%m%d%H%M%C%y.%S"`; date

Reduced the cpu usage from 100% to the usual 5%

This is the related CPU load graph: