[PATCH bpf-next v2 14/16] netsec: remove rcu_read_lock() around XDP program invocation
From: Toke Høiland-Jørgensen <hidden>
Date: 2021-06-15 15:05:00
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 | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index dfc85cc68173..e07b7c870046 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);
@@ -1019,6 +1018,10 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget) pkt_len, false); if (xdp_prog) { + /* This code is invoked within a single NAPI poll cycle + * and thus under local_bh_disable(), which provides the + * needed RCU protection. + */ xdp_result = netsec_run_xdp(priv, xdp_prog, &xdp); if (xdp_result != NETSEC_XDP_PASS) { xdp_act |= xdp_result;
@@ -1069,8 +1072,6 @@ 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; }
--
2.31.1