mbuf LOR

[Nate Lawson]

I was testing some changes to make fxp MPSAFE and got a LOR in allocating
the mbuf cluster and then finally a panic when trying to dereference the
cluster header.  Is the mbuf system MPSAFE?  Is it ok to call m_getcl
with a device lock held (but not Giant)?

The lock reversal was: 1. fxp softc lock, 2. Giant.

Traceback:
zalloc...
malloc()
mb_pop_cont()
mb_alloc()
m_getcl()
fxp_add_rfabuf()
fxp_intr_body()
fxp_intr() -- locks fxp softc

-Nate