netsec: Remove rcu_read_lock() around XDP program invocation

The netsec driver has a rcu_read_lock()/rcu_read_unlock() pair around the
full RX loop, covering everything up to and including xdp_do_flush(). This
is actually the correct behaviour, but because it all happens in a single
NAPI poll cycle (and thus under local_bh_disable()), it is also technically
redundant.

With the addition of RCU annotations to the XDP_REDIRECT map types that
take bh execution into account, lockdep even understands this to be safe,
so there's really no reason to keep the rcu_read_lock() around anymore, so
let's just remove it.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Jassi Brar <jaswinder.singh@linaro.org>
Link: https://lore.kernel.org/bpf/20210624160609.292325-18-toke@redhat.com

diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index dfc85cc68173c4caabeb7cae2a3becdd4d9015e6..20d148c019d8de77ae16596908f3cae277e4789c 100644 (file)
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -958,7 +958,6 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
 
        xdp_init_buff(&xdp, PAGE_SIZE, &dring->xdp_rxq);
 
-       rcu_read_lock();
        xdp_prog = READ_ONCE(priv->xdp_prog);
        dma_dir = page_pool_get_dma_dir(dring->page_pool);
 
@@ -1069,8 +1068,6 @@ next:
        }
        netsec_finalize_xdp_rx(priv, xdp_act, xdp_xmit);
 
-       rcu_read_unlock();
-
        return done;
 }