From: Ido Schimmel <idosch@idosch.org>
To: Nikolay Aleksandrov <razor@blackwall.org>
Cc: netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org,
dsahern@gmail.com, Nikolay Aleksandrov <nikolay@nvidia.com>
Subject: Re: [PATCH net 0/3] net: nexthop: fix refcount issues when replacing groups
Date: Sun, 21 Nov 2021 19:55:17 +0200 [thread overview]
Message-ID: <YZqIBVcFwIzj6VZG@shredder> (raw)
In-Reply-To: <20211121152453.2580051-1-razor@blackwall.org>
On Sun, Nov 21, 2021 at 05:24:50PM +0200, Nikolay Aleksandrov wrote:
> From: Nikolay Aleksandrov <nikolay@nvidia.com>
>
> Hi,
> This set fixes a refcount bug when replacing nexthop groups and
> modifying routes. It is complex because the objects look valid when
> debugging memory dumps, but we end up having refcount dependency between
> unlinked objects which can never be released, so in turn they cannot
> free their resources and refcounts. The problem happens because we can
> have stale IPv6 per-cpu dsts in nexthops which were removed from a
> group. Even though the IPv6 gen is bumped, the dsts won't be released
> until traffic passes through them or the nexthop is freed, that can take
> arbitrarily long time, and even worse we can create a scenario[1] where it
> can never be released. The fix is to release the IPv6 per-cpu dsts of
> replaced nexthops after an RCU grace period so no new ones can be
> created. To do that we add a new IPv6 stub - fib6_nh_release_dsts, which
> is used by the nexthop code only when necessary. We can further optimize
> group replacement, but that is more suited for net-next as these patches
> would have to be backported to stable releases.
Will run regression with these patches tonight and report tomorrow
next prev parent reply other threads:[~2021-11-21 17:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-21 15:24 [PATCH net 0/3] net: nexthop: fix refcount issues when replacing groups Nikolay Aleksandrov
2021-11-21 15:24 ` [PATCH net 1/3] net: ipv6: add fib6_nh_release_dsts stub Nikolay Aleksandrov
2021-11-21 15:24 ` [PATCH net 2/3] net: nexthop: release IPv6 per-cpu dsts when replacing a nexthop group Nikolay Aleksandrov
2021-11-21 17:17 ` Ido Schimmel
2021-11-21 17:35 ` Ido Schimmel
2021-11-21 18:02 ` Nikolay Aleksandrov
2021-11-21 15:24 ` [PATCH net 3/3] selftests: net: fib_nexthops: add test for group refcount imbalance bug Nikolay Aleksandrov
2021-11-21 17:53 ` Ido Schimmel
2021-11-21 17:59 ` Nikolay Aleksandrov
2021-11-21 17:55 ` Ido Schimmel [this message]
2021-11-21 18:17 ` [PATCH net 0/3] net: nexthop: fix refcount issues when replacing groups Nikolay Aleksandrov
2021-11-22 9:48 ` Ido Schimmel
2021-11-22 9:53 ` Nikolay Aleksandrov
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