On 05/27/2015 06:46 PM, Andrew Lunn wrote:

On Wed, May 27, 2015 at 03:51:59PM -0700, Guenter Roeck wrote:

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On 05/27/2015 02:05 PM, Andrew Lunn wrote:

quoted

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Do you have lock debugging enabled in your code ? I am getting a recursive
lock warning due to a recursive call to dev_mc_sync(). I think we may have
to implement lock nesting for dsa, similar to how it id done for vlan
support, but I have not been able to figure out how exactly it works yet.

I might be able to help, since i solve two similar problems already in
DSA, one for MDIO bus, and a second one for transmit buffers.

      Andrew

What I did is to create a vlan interface on one of the dsa slave ports
and enabling it.

This results in a call to dev_mc_sync() on the dsa interface, which is passed
on to the real interface. dev_mc_sync() calls netif_addr_lock_nested(to),
which results in the recursive lock message.

  ifconfig/2291 is trying to acquire lock:
   (_xmit_ETHER/1){+.....}, at: [<ffffffff8175b757>] dev_mc_sync+0x57/0xa0

  but task is already holding lock:
   (_xmit_ETHER/1){+.....}, at: [<ffffffff8175b757>] dev_mc_sync+0x57/0xa0

  other info that might help us debug this:
   Possible unsafe locking scenario:

         CPU0
         ----
    lock(_xmit_ETHER/1);
    lock(_xmit_ETHER/1);

Pretty much inevitable as far as I can see.

It looks like DSA needs to implement ndo_get_lock_subclass().

We can probably copy the code from macvlan.c.

Not entirely, but I think I have an idea. I'll give it a try.

Guenter