Prevent USB network devices to generate a page fault trap when detached

while UP and holding an open bpf handler by checking bpfilter_lookup()
for returning NULL in bpfpoll().  Added an XXX comment which reminds us
to recheck why this race condition happens in conjunction with the USB
stack.

Commented by miod@ and thib@ (would prefer to directly fix race condition,
if this is possible at all).

lot of help and OK claudio@

0 files changed, 0 insertions, 0 deletions