2011/3/30 Ben Hutchings [off-list ref]:

On Tue, 2011-03-29 at 13:52 -0700, Stephen Hemminger wrote:

quoted

Right now if an administrator uses the ethtool function to identify network
interface, the netlink lock can be held indefinitely. In other words, doing
"ethtool -p eth1" will stop all other netlink activity. This is bad, imagine
the case of an operator doing that to find a NIC in a rack, and because of
the netlink lockout all routing daemon activity stops.

[...]

quoted

There are several possible solutions but most involve fixing all the device
drivers (24). Options:

1. Have device driver drop and reacquire rtnl() while blinking
2. Have ethtool core drop rtnl before calling device driver
3. Add per-device ethtool rtnl lock

4. Define a ethtool operation 'set_id_state' with an argument that sets
identification on/off/inactive/active (the last optional, for any driver
that really wants to do this differently).  When this is defined, the
ethtool core runs the loop and acquires the lock each time it calls this
operation.

5. Have a driver register a LED class device instead of implementing
an ethtool op.

Hmm. This would require changes to userspace ethtool command. I wonder
if anything else uses this call?

Best Regards,
Michał Mirosław