driver-maintained ifnet fields (such as if_drv_flags).
- Use soft locks as the mutex that protects each interface's knote list
rather than using the global knote list lock. Also, use the softc
for kn_hook instead of the cdev.
- Use mtx_sleep() instead of tsleep() when blocking in the read routines.
This fixes a lost wakeup race.
- Remove D_NEEDGIANT now that the cdevsw routines use the softc lock
where locking is needed.
- Lock IFQ when calculating the result for FIONREAD in tap(4). tun(4)
already did this.
- Remove remaining spl calls.
Submitted by: Marcin Cieslak saper of saper|info (3)
MFC after: 2 weeks
b8914d3479