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>
Subject: Re: [PATCH bpf-next 03/17] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref
Date: Fri, 11 Jun 2021 01:05:38 +0200 [thread overview]
Message-ID: <87lf7huxq5.fsf@toke.dk> (raw)
In-Reply-To: <20210610193722.753tqgrovwyg2v6v@kafai-mbp>
Martin KaFai Lau <kafai@fb•com> writes:
> On Wed, Jun 09, 2021 at 12:33:12PM +0200, Toke Høiland-Jørgensen wrote:
>> Some of the XDP helpers (in particular, xdp_do_redirect()) will get a
>> struct net_device reference using dev_get_by_index_rcu(). These are called
>> from a NAPI poll context, which means the RCU reference liveness is ensured
>> by local_bh_disable(). Add rcu_read_lock_bh_held() as a condition to the
>> RCU list traversal in dev_get_by_index_rcu() so lockdep understands that
>> the dereferences are safe from *both* an rcu_read_lock() *and* with
>> local_bh_disable().
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat•com>
>> ---
>> net/core/dev.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index febb23708184..a499c5ffe4a5 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -1002,7 +1002,7 @@ struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex)
>> struct net_device *dev;
>> struct hlist_head *head = dev_index_hash(net, ifindex);
>>
>> - hlist_for_each_entry_rcu(dev, head, index_hlist)
>> + hlist_for_each_entry_rcu(dev, head, index_hlist, rcu_read_lock_bh_held())
> Is it needed? hlist_for_each_entry_rcu() checks for
> rcu_read_lock_any_held(). Did lockdep complain?
Ah, yes, I think you're right. I totally missed that
rcu_read_lock_any_held() includes a '!preemptible()' check at the end.
I'll drop this patch, then!
-Toke
next prev parent reply other threads:[~2021-06-10 23:05 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 10:33 [PATCH bpf-next 00/17] Clean up and document RCU-based object protection for XDP_REDIRECT Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 01/17] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 02/17] bpf: allow RCU-protected lookups to happen from bh context Toke Høiland-Jørgensen
2021-06-10 18:38 ` Alexei Starovoitov
2021-06-10 21:24 ` Daniel Borkmann
2021-06-10 22:27 ` Toke Høiland-Jørgensen
2021-06-10 19:33 ` Martin KaFai Lau
2021-06-09 10:33 ` [PATCH bpf-next 03/17] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref Toke Høiland-Jørgensen
2021-06-10 19:37 ` Martin KaFai Lau
2021-06-10 23:05 ` Toke Høiland-Jørgensen [this message]
2021-06-09 10:33 ` [PATCH bpf-next 04/17] xdp: add proper __rcu annotations to redirect map entries Toke Høiland-Jørgensen
2021-06-10 21:09 ` Martin KaFai Lau
2021-06-10 23:19 ` Toke Høiland-Jørgensen
2021-06-10 23:32 ` Martin KaFai Lau
2021-06-10 23:41 ` Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 05/17] ena: remove rcu_read_lock() around XDP program invocation Toke Høiland-Jørgensen
2021-06-09 13:57 ` Paul E. McKenney
2021-06-09 10:33 ` [PATCH bpf-next 06/17] bnxt: " Toke Høiland-Jørgensen
2021-06-09 13:58 ` Paul E. McKenney
2021-06-10 8:47 ` Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 07/17] thunderx: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 08/17] freescale: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 09/17] net: intel: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 10/17] marvell: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 11/17] mlx4: " Toke Høiland-Jørgensen
2021-06-10 7:10 ` Tariq Toukan
2021-06-09 10:33 ` [PATCH bpf-next 12/17] nfp: " Toke Høiland-Jørgensen
2021-06-11 16:30 ` Simon Horman
2021-06-09 10:33 ` [PATCH bpf-next 13/17] qede: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 14/17] sfc: " Toke Høiland-Jørgensen
2021-06-09 12:15 ` Edward Cree
2021-06-09 10:33 ` [PATCH bpf-next 15/17] netsec: " Toke Høiland-Jørgensen
2021-06-10 5:30 ` Ilias Apalodimas
2021-06-09 10:33 ` [PATCH bpf-next 16/17] stmmac: " Toke Høiland-Jørgensen
2021-06-09 10:33 ` [PATCH bpf-next 17/17] net: ti: " Toke Høiland-Jørgensen
2021-06-09 17:04 ` Grygorii Strashko
2021-06-10 0:18 ` [PATCH bpf-next 00/17] Clean up and document RCU-based object protection for XDP_REDIRECT Yonghong Song
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