netdev - Re: ethtool physical identify vs netlink locking?

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Message-ID: <AANLkTi=um5CecqdXeqBNKHv4nWk7-bZ27aL5=bXFi0SE@mail.gmail.com>
Date:	Wed, 30 Mar 2011 03:35:40 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: ethtool physical identify vs netlink locking?

2011/3/30 Ben Hutchings <bhutchings@...arflare.com>:
> On Tue, 2011-03-29 at 13:52 -0700, Stephen Hemminger wrote:
>> 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.
[...]
>> 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
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