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@xxxxxxx>
Cc: Ioana Ciornei <ioana.ciornei@xxxxxxx>
Cc: Ioana Radulescu <ruxandra.radulescu@xxxxxxx>
Reviewed-by: Camelia Groza <camelia.groza@xxxxxxx>
Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
---
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 11 ++++-------
drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 6 +++---
2 files changed, 7 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index 177c020bf34a..98fdcbde687a 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);
@@ -2585,6 +2581,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
}
#endif
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
/* Update the length and the offset of the FD */
@@ -2638,8 +2637,6 @@ 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..964d85c9e37d 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;
@@ -363,6 +361,9 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
xdp_prepare_buff(&xdp, vaddr + offset, XDP_PACKET_HEADROOM,
dpaa2_fd_get_len(fd), false);
+ /* This code is invoked within a single NAPI poll cycle and thus under
+ * local_bh_disable(), which provides the needed RCU protection.
+ */
xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
/* xdp.data pointer may have changed */
@@ -414,7 +415,6 @@ 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
