Quoting Alexey Kuznetsov <[EMAIL PROTECTED]>: Subject: Re: dst_ifdown breaks infiniband? > > Hello! > > > This is not new code, and should have triggered long time ago, > > so I am not sure how come we are triggering this only now, > > but somehow this did not lead to crashes in 2.6.20 > > I see. I guess this was plain luck. > > > > 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. > > We could not invalidate dst->neighbour but it looked safe to invalidate > neigh->dev after quiescent state. Obviosuly, it is not and it never was safe. > Was supposed to be repaired asap, but this did not happen. :-( > > > Can dst->neighbour be changed to point to NULL instead, and the neighbour > > released? > > It should be cleared and we should be sure it will not be destroyed > before quiescent state.
I'm confused. didn't you say dst_ifdown is called after quiescent state? > Seems, this is the only correct solution, but to do this we have > to audit all the places where dst->neighbour is dereferenced for > RCU safety. > > Actually, it is very good you caught this eventually, the bug was > so _disgusting_ that it was "forgotten" all the time, waiting for > someone who will point out that the king is naked. :-) > > Alexey This does not sound like something that's likely to be accepted in 2.6.21, right? Any simpler ideas? -- 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
