Re: New lock-order reversal

On Fri, Sep 06, 2024 at 06:49:48PM +0200, Kristof Provost wrote:
> Hi Steve,
> 
> On 6 Sep 2024, at 17:54, Steve Kargl wrote:
> > FYI (and return hackers to a non-language)
> > 
> > Update my old system to circa Aug 10, 2024 top-of-tree
> > and rebuilts all installed ports.  I'm now see a new
> > lock-order reversal while using openvpn.
> > 

(trace elided)

> I don’t think that’s new. It’s an order issue between if_ovpn establishing
> the UDP tunnel callback (which requires the UDP lock) and the normal traffic
> flow, where the UDP lock is taken, the tunnel function is called and that
> then takes the if_ovpn lock.

Yeah, I should have looked at bugzilla.  There is a report of the LoR.

> I’ve had another look at this, and while I can probably avoid this for
> setting the tunnel function (basically by assuming setting it never fails or
> is already done, which is currently the case), I’m not happy with the only
> solution I see on the removal side (i.e. “don’t, just trust that the socket
> will be closed soon”).

Thanks for the patch.  I'll add to my kernel when I rebuild it.
Unfortuantely, I have way too little understanding about locking
within the kernel to be of much help.

--
steve