From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: bpf@vger.kernel.org, netdev@vger.kernel.org
Cc: "Martin KaFai Lau" <kafai@fb.com>,
"Hangbin Liu" <liuhangbin@gmail.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Magnus Karlsson" <magnus.karlsson@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
"Jakub Kicinski" <kuba@kernel.org>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
"Simon Horman" <simon.horman@netronome.com>,
oss-drivers@netronome.com
Subject: [PATCH bpf-next v4 14/19] nfp: remove rcu_read_lock() around XDP program invocation
Date: Wed, 23 Jun 2021 13:07:22 +0200 [thread overview]
Message-ID: <20210623110727.221922-15-toke@redhat.com> (raw)
In-Reply-To: <20210623110727.221922-1-toke@redhat.com>
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 <simon.horman@netronome.com>
Cc: oss-drivers@netronome.com
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
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;
}
--
2.32.0
next prev parent reply other threads:[~2021-06-23 11:14 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 11:07 [PATCH bpf-next v4 00/19] Clean up and document RCU-based object protection for XDP and TC BPF Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 01/19] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 02/19] doc: Clarify and expand RCU updaters and corresponding readers Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 03/19] doc: Give XDP as example of non-obvious RCU reader/updater pairing Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 04/19] bpf: allow RCU-protected lookups to happen from bh context Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 05/19] xdp: add proper __rcu annotations to redirect map entries Toke Høiland-Jørgensen
2021-06-24 13:12 ` Daniel Borkmann
2021-06-24 14:52 ` Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 06/19] sched: remove unneeded rcu_read_lock() around BPF program invocation Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 07/19] ena: remove rcu_read_lock() around XDP " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 08/19] bnxt: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 09/19] thunderx: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 10/19] freescale: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 11/19] net: intel: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 12/19] marvell: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 13/19] mlx4: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` Toke Høiland-Jørgensen [this message]
2021-06-23 11:07 ` [PATCH bpf-next v4 15/19] qede: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 16/19] sfc: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 17/19] netsec: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 18/19] stmmac: " Toke Høiland-Jørgensen
2021-06-23 11:07 ` [PATCH bpf-next v4 19/19] net: ti: " Toke Høiland-Jørgensen
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