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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
	Hangbin Liu <liuhangbin@gmail.com>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	Magnus Karlsson <magnus.karlsson@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH RFC bpf-next 2/4] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref
Date: Fri, 23 Apr 2021 13:05:17 +0200	[thread overview]
Message-ID: <161917591778.102337.1084869564077259501.stgit@toke.dk> (raw)
In-Reply-To: <161917591559.102337.3558507780042453425.stgit@toke.dk>

From: Toke Høiland-Jørgensen <toke@redhat.com>

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

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 b4c67a5be606..a7b8e3289f7c 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())
 		if (dev->ifindex == ifindex)
 			return dev;

  parent reply	other threads:[~2021-04-23 11:05 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23 11:05 [PATCH RFC bpf-next 0/4] Clean up and document RCU-based object protection for XDP_REDIRECT Toke Høiland-Jørgensen
2021-04-23 11:05 ` [PATCH RFC bpf-next 1/4] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Toke Høiland-Jørgensen
2021-04-23 11:05 ` Toke Høiland-Jørgensen [this message]
2021-04-23 11:05 ` [PATCH RFC bpf-next 3/4] xdp: add proper __rcu annotations to redirect map entries Toke Høiland-Jørgensen
2021-04-23 11:05 ` [PATCH RFC bpf-next 4/4] i40e: remove rcu_read_lock() around XDP program invocation Toke Høiland-Jørgensen
2021-04-23 13:57   ` Maciej Fijalkowski
2021-04-23 20:33     ` Toke Høiland-Jørgensen

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