The cpsw 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: Grygorii Strashko <grygorii.strashko@xxxxxx>
Cc: linux-omap@xxxxxxxxxxxxxxx
Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
---
drivers/net/ethernet/ti/cpsw_priv.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/ti/cpsw_priv.c b/drivers/net/ethernet/ti/cpsw_priv.c
index 5862f0a4a975..ecc2a6b7e28f 100644
--- a/drivers/net/ethernet/ti/cpsw_priv.c
+++ b/drivers/net/ethernet/ti/cpsw_priv.c
@@ -1328,13 +1328,9 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp,
struct bpf_prog *prog;
u32 act;
- rcu_read_lock();
-
prog = READ_ONCE(priv->xdp_prog);
- if (!prog) {
- ret = CPSW_XDP_PASS;
- goto out;
- }
+ if (!prog)
+ return CPSW_XDP_PASS;
act = bpf_prog_run_xdp(prog, xdp);
/* XDP prog might have changed packet data and boundaries */
@@ -1378,10 +1374,8 @@ int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp,
ndev->stats.rx_bytes += *len;
ndev->stats.rx_packets++;
out:
- rcu_read_unlock();
return ret;
drop:
- rcu_read_unlock();
page_pool_recycle_direct(cpsw->page_pool[ch], page);
return ret;
}
--
2.31.1
