I experimented with this a bit this morning and I couldn't get it to happen.
it's most likely recursion due to interrupts like jason said.
can you get a backtrace?  we really should find out how this is happening.

-Chuck


Manuel Bouyer writes:
> With a kernel from wenesday sources, I got several panics
> 'pmap_zero_page: lock botch'. I also got a uvm_fault and random core dumps
> of processes. This was under mid-load (6-8 load average, several compilation
> running).
> A reliable way to get the pmap_zero_page: lock botch panic is to run
> 'make -j4 clean' in an already-clean /usr/src (lots of fork/exits).
> This is not likely a hardware problem, as this machine has run flawlessly for
> 2 years now, and I didn't change anything in the hardware config in the last
> months. (it's my home machine, so it's used to run a lot of gcc processes
> in parallel :)
> Did someone else notice this ? I'll see if I can reproduce this on another box
> later today.
> 
> --
> Manuel Bouyer <bouyer@antioche.eu.org>
> --