Re: [PATCH bpf-next 12/17] nfp: remove rcu_read_lock() around XDP program invocation
From: Simon Horman <hidden>
Date: 2021-06-11 16:31:05
Also in:
bpf
+Jakub On Wed, Jun 09, 2021 at 12:33:21PM +0200, Toke Høiland-Jørgensen wrote:
The nfp driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. While this is not actually an issue for the nfp driver because it doesn't support XDP_REDIRECT (and thus doesn't call xdp_do_flush()), the rcu_read_lock() is still unneeded. And 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 it around. Cc: Simon Horman <redacted> Cc: oss-drivers@netronome.com Signed-off-by: Toke Høiland-Jørgensen <redacted>
Reviewed-by: Simon Horman <redacted>
quoted hunk ↗ jump to hunk
--- drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 2 -- 1 file changed, 2 deletions(-)diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c index eeb30680b4dc..5dfa4799c34f 100644 --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c@@ -1819,7 +1819,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) struct xdp_buff xdp; int idx; - rcu_read_lock(); xdp_prog = READ_ONCE(dp->xdp_prog); true_bufsz = xdp_prog ? PAGE_SIZE : dp->fl_bufsz; xdp_init_buff(&xdp, PAGE_SIZE - NFP_NET_RX_BUF_HEADROOM,@@ -2036,7 +2035,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget) if (!nfp_net_xdp_complete(tx_ring)) pkts_polled = budget; } - rcu_read_unlock(); return pkts_polled; }-- 2.31.1