Re: [PATCH net] net: ethtool: keep rtnl_lock for ops using ethtool_op_get_link()

On Thu, Jun 25, 2026 at 08:48:03AM -0700, Stanislav Fomichev wrote:
> On 06/24, Jakub Kicinski wrote:
> > Breno reports following splats on mlx5:
> > 
> >   RTNL: assertion failed at net/core/dev.c (2241)
> >   WARNING: net/core/dev.c:2241 at netif_state_change+0xed/0x130, CPU#5: ethtool/1335
> >   RIP: 0010:netif_state_change+0xf9/0x130
> >   Call Trace:
> >     <TASK>
> >      __linkwatch_sync_dev+0xea/0x120
> >      ethtool_op_get_link+0xe/0x20
> >      __ethtool_get_link+0x26/0x40
> >      linkstate_prepare_data+0x51/0x200
> >      ethnl_default_doit+0x213/0x470
> >      genl_family_rcv_msg_doit+0xdd/0x110
> > 
> > Looks like I missed ethtool_op_get_link() trying to sync linkwatch,
> > which needs rtnl_lock. Not all drivers do this - bnxt doesn't,
> > it just returns the link state, so add an opt-in bit.
> > 
> > Reported-by: Breno Leitao <[email protected]>
> > Fixes: 45079e00133e ("net: ethtool: optionally skip rtnl_lock on Netlink path for GET ops")
> > Signed-off-by: Jakub Kicinski <[email protected]>
> 
> Acked-by: Stanislav Fomichev <[email protected]>

Reviewed-by: Breno Leitao <[email protected]>