DSA performs non-trivial housekeeping of unicast and multicast addresses
on shared (CPU and DSA) ports, and puts a bit of pressure on higher
layers, requiring them to behave correctly (remove these addresses
exactly as many times as they were added). Otherwise, either addresses
linger around forever, or DSA returns -ENOENT complaining that entries
that were already deleted must be deleted again.

To aid debugging, introduce some trace points specifically for FDB and
MDB - that's where some of the bugs still are right now.

Some bugs I have seen were also due to race conditions, see:
- 630fd482 ("net: dsa: flush switchdev workqueue on bridge join error path")
- a2614140 ("net: dsa: mv88e6xxx: flush switchdev FDB workqueue before removing VLAN")

so it would be good to not disturb the timing too much, hence the choice
to use trace points vs regular dev_dbg().

I've had these for some time on my computer in a less polished form, and
they've proven useful. What I found most useful was to enable
CONFIG_BOOTTIME_TRACING, add "trace_event=dsa" to the kernel cmdline,
and run "cat /sys/kernel/debug/tracing/trace". This is to debug more
complex environments with network managers started by the init system,
things like that.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>