> Quoting David Miller <[EMAIL PROTECTED]>: > Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > > From: "Michael S. Tsirkin" <[EMAIL PROTECTED]> > Date: Mon, 19 Mar 2007 00:42:34 +0200 > > > > Quoting Michael S. Tsirkin <[EMAIL PROTECTED]>: > > > Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > > > > > > > Quoting Eric W. Biederman <ebiederman@lnxi.com>: > > > > Subject: Re: [ofa-general] Re: dst_ifdown breaks infiniband? > > > > > > > > "Michael S. Tsirkin" <[EMAIL PROTECTED]> writes: > > > > > > > > >> > Why is neighbour->dev changed here? > > > > >> > > > > >> It holds reference to device and prevents its destruction. > > > > >> If dst is held somewhere, we cannot destroy the device and deadlock > > > > >> while unregister. > > > > > > > > > > BTW, can this ever happen for the loopback device itself? > > > > > Is it ever unregistered? > > > > > > > > Well I don't think the loopback device is currently but as soon > > > > as we get network namespace support we will have multiple loopback > > > > devices and they will get unregistered when we remove the network > > > > namespace. > > > > > > Hmm. Then the code moving dst->dev to point to the loopback > > > device will have to be fixed too. I'll post a patch a bit later. > > > > Does this look sane (untested)? > > > > Signed-off-by: Michael S. Tsirkin <[EMAIL PROTECTED]> > > You can't point it at NULL, we don't point it at loopback > just for fun. > > There can be asynchronous paths elsewhere in the networking still > referencing the neigh or dst and they will (correctly) feel free to > derefence whatever device is hanging there. So transitioning > to NULL is invalid. > > You guys will need to come up with a better solution for this silly > situation with network namespaces. Loopback is always available to > point dead routes and neighbour entries at, and this assumption is > massively rooted in the networking.
Yes, I see this now. I guess it's best to focus on the original problem with dst_ifdown breaking infiniband for now. For that, we have to audit all the places where dst->neighbour is dereferenced for RCU safety, and this is already a massive task. -- MST - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
