Thread (21 messages) 21 messages, 2 authors, 2021-06-24
STALE1827d LANDED: 3 (3M)
Revisions (2)
  1. v4 [diff vs current]
  2. v5 current

[PATCH bpf-next v5 17/19] netsec: remove rcu_read_lock() around XDP program invocation

From: Toke Høiland-Jørgensen <hidden>
Date: 2021-06-24 16:13:56
Also in: bpf
Subsystem: networking drivers, socionext (sni) netsec network driver, the rest · Maintainers: Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Ilias Apalodimas, Masahisa Kojima, Linus Torvalds

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.

Cc: Jassi Brar <redacted>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
 drivers/net/ethernet/socionext/netsec.c | 3 ---
 1 file changed, 3 deletions(-)
diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index dfc85cc68173..20d148c019d8 100644
--- 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 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
 	}
 	netsec_finalize_xdp_rx(priv, xdp_act, xdp_xmit);
 
-	rcu_read_unlock();
-
 	return done;
 }
 
-- 
2.32.0
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