100% CPU usage when otherwise idle

[Patrick Gibson]

I've set up a master and slave server running MySQL 5.1.5x, and we're noticing that after a certain number of days running, the CPU usage will jump to 100%, but there's nothing going on that would explain it. The processlist just shows:

Id: 49
User: replicate
Host: xxx.xxxxx.xxx:14144
db: NULL
Command: Binlog Dump
Time: 1604403
State: Has sent all binlog to slave; waiting for binlog to be updated
Info: NULL

Has anyone ever seen this type of behaviour? It's on a FreeBSD (8.1) host, if that makes a difference.

Thanks,

Patrick