The networking case is very different. The entire networking setup currently
assumes that an irq is not pre-empted by a BH or user, a bh is not pre-empted by
user space and two bh's may not run together. The tty code is evey tighter
on these assumptions.
The change given at least fixes the breakage of the assumption. Perhaps
2.1.31 someone cares to fix the assumption in about 50 drivers before breaking
it ?
Alan