From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Martin KaFai Lau <kafai@fb.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
Hangbin Liu <liuhangbin@gmail.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Magnus Karlsson <magnus.karlsson@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH bpf-next] bpf/devmap: convert remaining READ_ONCE() to rcu_dereference()
Date: Tue, 29 Jun 2021 11:37:42 +0200 [thread overview]
Message-ID: <87h7hhj9jt.fsf@toke.dk> (raw)
In-Reply-To: <20210628235559.sgq7txsjmz3s2zeb@kafai-mbp.dhcp.thefacebook.com>
Martin KaFai Lau <kafai@fb.com> writes:
> On Tue, Jun 29, 2021 at 01:00:51AM +0200, Toke Høiland-Jørgensen wrote:
>> There were a couple of READ_ONCE()-invocations left-over by the devmap RCU
>> conversion. Convert these to rcu_dereference() as well to avoid complaints
>> from sparse.
>>
>> Fixes: 782347b6bcad ("xdp: Add proper __rcu annotations to redirect map entries")
>> Reported-by: kernel test robot <lkp@intel.com>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>> kernel/bpf/devmap.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
>> index 2f6bd75cd682..7a0c008f751b 100644
>> --- a/kernel/bpf/devmap.c
>> +++ b/kernel/bpf/devmap.c
>> @@ -558,7 +558,7 @@ int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
>>
>> if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
>> for (i = 0; i < map->max_entries; i++) {
>> - dst = READ_ONCE(dtab->netdev_map[i]);
>> + dst = rcu_dereference(dtab->netdev_map[i]);
> __dev_map_lookup_elem() uses rcu_dereference_check(dtab->netdev_map[key], rcu_read_lock_bh_held()).
> It is not needed here?
Hmm, I somehow managed to convince myself last night that it wasn't, but
looking at it again now I think you're right. Will send a v2.
-Toke
prev parent reply other threads:[~2021-06-29 9:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 23:00 [PATCH bpf-next] bpf/devmap: convert remaining READ_ONCE() to rcu_dereference() Toke Høiland-Jørgensen
2021-06-28 23:05 ` Paul E. McKenney
2021-06-28 23:55 ` Martin KaFai Lau
2021-06-29 9:37 ` Toke Høiland-Jørgensen [this message]
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