freezing, hard locking, and debug.mpsafenet=0

Elvar elvar at
Tue Oct 9 09:41:07 PDT 2007

Hi there,

I'm sharing my experiences with this in the hopes that it saves someone 
else many many hours of troubleshooting and headaches. A client of mine 
has a Dell Poweredge tower server with FreeBSD 6-stable on it which was 
acting as their firewall. At some point in time about 6 months ago the 
box started locking up every day or couple of days. I imagine this was 
probably after a buildworld / installworld but I can't remember. It 
would hard lock with nothing logged or any sign of anything, and no 
response from the keyboard. In my experiences this usually resulted in 
bad memory but after swapping out the memory for new memory the issue 
still persisted. As time went on I eventually pulled the hard drives out 
of the server and put them into another server with completely different 
hardware (minus the transfered hard drives). After bringing the install 
up on the other server I still had the hard locks. I googled like mad 
and tried all sorts of things to narrow down the problem but kept coming 
up with nothing. Now, I admit I'm not an elite user so I'm sure lots of 
you could probably have figured it out quicker. Eventually I put new 
hard drives into the original firewall (the Dell Poweredge) and did a 
clean install of FreeBSD 6.2-RELEASE. Unfortunately after bringing the 
box online as the firewall again it continued locking up. I then updated 
to -STABLE and still experienced the issue. Finally, after even more 
countless hours of googling I found this thread 
which seemed to describe the same freezing I was having. One person 
mentioned setting debug.mpsafenet=0 in /boot/loader.conf and not having 
a problem since doing so. Well, I ended up doing the same thing and it's 
been about 25 days with not one freeze / lockup.

It's my understanding that the ability to even disable this has been 
taken out of 7.x, I only can hope that it's not an issue in 7.x like it 
is on some systems in 6.x. So anyway, I hope this helps someone out.

Kind regards,

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