MySQL hangs server completely

[Alejandro Imass]

Hi,

We've been having this problem with a customer for a while and it
seems that some funky query makes MySQL use 100% of CPU. Nevertheless,
even though you can see in top that it's only 1 CPU in 100% (out of 8)
the server eventually becomes useless and stops responding completely.

So my question is, how does a user process hang the whole server? What
system resources could MySQL be draining to make the server stop
responding completely?

The MySQL database is running inside a Jail and perhaps that could
help limit the damage it can cause. Has anyone else run into this
problem?

Thanks,

-- 
Alejandro Imass