- Remove a lot of superfluous locking during attach. There is no need
to lock access to the driver until some other thread has a way of getting
to it. For ethernet drivers the other ways include registering an
interrupt handler via bus_setup_intr(), calling ether_ifattach() to hook
into the network stack, and kicking off a callout-driven timer via
callout_reset().
- Use callout_* rather than timeout/untimeout.
- Break out of xl_rxeof() if IFF_DRV_RUNNING is clear after ifp->if_input
returns to handle the case where the interface was stopped while we were
passing a packet up the stack. Don't call xl_rxeof() in xl_rxeof_task()
unless IFF_DRV_RUNNING is set. With these fixes in place, any
outstanding task will gracefully terminate as soon as it gets a chance to
run after the interface has been stopped via xl_stop(). As a result,
taskqueue_drain() is no longer required in xl_stop(). The task is still
drained in detach() however to make sure that detach() can safely destroy
the driver mutex at the end of the function.
- Lock the driver lock in the ifmedia callouts and don't lock across
ifmedia_ioctl() in xl_ioctl().
Note: glebius came up with most of (3) as well independently. I took a
rather roundabout way of arriving at the same conclusion.
MFC after: 3 days
997452064e