Re: wm_intr may lead wm_start unexpectedly

[Matt Thomas <matt%3am-software.com@localhost>]

On Jun 24, 2014, at 10:43 PM, Ryota Ozaki <ozaki-r%netbsd.org@localhost> wrote:

> Hi,
> 
> I found a strange behavior of if_wm that
> its interrupt handler may call its if_start
> (xmit function) eventually. I don't think
> it's sane. It makes difficult to use mutex for MP.
> 
> Here is a call trace:
> wm_intr => wm_linkintr => wm_linkintr_gmii =>
> mii_pollstat => makphy_service => mii_phy_update =>
> if_link_state_change => in6_if_link_up =>
> nd6_dad_start => nd6_dad_ns_output => ... =>
> => ether_output => ... => wm_start
> 
> The interrupt handler calls mii, mii notifies
> a link state change to inet6, and inet6 tries DAD.
> This IPv6 DAD code (nd6_dad_start and
> nd6_dad_ns_output) is the main issue of my claim.
> nd6_dad_start normally sets up a callout for
> nd6_dad_ns_output, however, it may call
> nd6_dad_ns_output directly at random.

Simple, set IFF_OACTIVE before calling mii