System hangs but ping when remounting read-only

[David Demelier]

Hello folks,

I have a machine that runs on a compact flash so I try to mount read-only as 
much as possible, but when I need to do some maintainance I remount read-write 
with

mount -u -w /

It works, but when I try to remount read only the prompt never get back using 

mount -u -r /

and the ssh does not respond anymore. I have also a serial cable and it is not 
accessible anymore. However pings are still working so I can't debug anything 
at all..

This problem appears on a 9.1-RELEASE i386 with /var and /tmp mounted as md 
devices.

Regards,

-- 
David Demelier