[PATCH bpf-next v4 10/19] freescale: remove rcu_read_lock() around XDP program invocation

The dpaa and dpaa2 drivers have 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: Madalin Bucur <madalin.bucur@nxp.com>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Cc: Ioana Radulescu <redacted>
Reviewed-by: Camelia Groza <redacted>
Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c   | 8 +-------
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 3 ---
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index 177c020bf34a..e6826561cf11 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c

@@ -2558,13 +2558,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
 	u32 xdp_act;
 	int err;
 
-	rcu_read_lock();
-
 	xdp_prog = READ_ONCE(priv->xdp_prog);
-	if (!xdp_prog) {
-		rcu_read_unlock();
+	if (!xdp_prog)
 		return XDP_PASS;
-	}
 
 	xdp_init_buff(&xdp, DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE,
 		      &dpaa_fq->xdp_rxq);

@@ -2638,8 +2634,6 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
 		break;
 	}
 
-	rcu_read_unlock();
-
 	return xdp_act;
 }
 

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 8433aa730c42..973352393bd4 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c

@@ -352,8 +352,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
 	u32 xdp_act = XDP_PASS;
 	int err, offset;
 
-	rcu_read_lock();
-
 	xdp_prog = READ_ONCE(ch->xdp.prog);
 	if (!xdp_prog)
 		goto out;

@@ -414,7 +412,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
 
 	ch->xdp.res |= xdp_act;
 out:
-	rcu_read_unlock();
 	return xdp_act;
 }
 

-- 
2.32.0