The ena 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. This
turns out to be harmless because it all happens in a single NAPI poll
cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock()
misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. 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: Guy Tzalik <redacted>
Cc: Saeed Bishara <redacted>
Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 881f88754bf6..cd5f03691b4c 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -385,7 +385,9 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp)
 	u64 *xdp_stat;
 	int qid;
 
-	rcu_read_lock();
+	/* This code is invoked within a single NAPI poll cycle and thus under
+	 * local_bh_disable(), which provides the needed RCU protection.
+	 */
 	xdp_prog = READ_ONCE(rx_ring->xdp_bpf_prog);
 
 	if (!xdp_prog)

@@ -443,8 +445,6 @@ static int ena_xdp_execute(struct ena_ring *rx_ring, struct xdp_buff *xdp)
 
 	ena_increase_stat(xdp_stat, 1, &rx_ring->syncp);
 out:
-	rcu_read_unlock();
-
 	return verdict;
 }
 

-- 
2.31.1