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Date: Thu, 2 May 2019 09:19:47 -0400 From: Eric Dumazet <eric.dumazet@...il.com> To: Tom Hughes <tom@...pton.nu>, David Ahern <dsahern@...il.com> Cc: netdev@...r.kernel.org Subject: Re: ndisc_cache garbage collection issue On 5/2/19 5:42 AM, Tom Hughes wrote: > I recently upgraded a machine from a 4.20.13 kernel to 5.0.9 and am > finding that after a few days I start getting a lot of these messages: > > neighbour: ndisc_cache: neighbor table overflow! > > and IPv6 networking starts to fail intermittently as a result. > > The neighbour table doesn't appear to have much in it however so I've > been looking at the code, and especially your recent changes to garbage > collection in the neighbour tables and my working theory is that the > value of gc_entries is somehow out of sync with the actual list of what > needs to be garbage collected. > > Looking at the code I think I see a possible way that this could be > happening post 8cc196d6ef8 which moved the addition of new entries to > the gc list out of neigh_alloc into ___neigh_create. > > The problem is that neigh_alloc is doing the increment of gc_entries, so > if ___neigh_create winds up taking an error path gc_entries will have > been incremented but the neighbour will never be added to the gc list. > > I don't know for sure yet that this is the cause of my problem, but it > seems to be incorrect in any case unless I have misunderstood something? > > Tom > Hi Tom This seems to match your report : https://patchwork.ozlabs.org/patch/1093973/
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