| Message ID | 20210617212748.32456-7-toke@redhat.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | Clean up and document RCU-based object protection for XDP_REDIRECT | expand |
| Context | Check | Description |
|---|---|---|
| netdev/apply | fail | Patch does not apply to bpf-next |
| netdev/tree_selection | success | Clearly marked for bpf-next |
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c index c33b4e837515..1d752815c69a 100644 --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c @@ -555,9 +555,10 @@ static inline bool nicvf_xdp_rx(struct nicvf *nic, struct bpf_prog *prog, xdp_prepare_buff(&xdp, hard_start, data - hard_start, len, false); orig_data = xdp.data; - 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. + */ action = bpf_prog_run_xdp(prog, &xdp); - rcu_read_unlock(); len = xdp.data_end - xdp.data; /* Check if XDP program has changed headers */
The thunderx 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: Sunil Goutham <sgoutham@marvell.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> --- drivers/net/ethernet/cavium/thunder/nicvf_main.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)