InnoDB semaphores resulted in extra CPU load

As you can see on picture below, at about 5:00, Sunday, July 1, CPU load raised up to 7% with no known reason. It’s slave server, and master faced same problem at same time.
The only visible correlation are InnoDB Semaphores.
But what is the reason?

CentOS Linux release 6.0

Sorry for long picture.

Denis, this could be your problem ond-high-cpu-and-the-fix/

Yes, that’s it!
Thank you!