From: Tianyu Yuan tianyu.yuan@corigine.com

When CONFIG_PROVE_LOCKING and CONFIG_PROVE_RCU are enabled, using OVS with vf reprs on bridge will lead to following log in dmesg:

.../nfp/flower/main.c:269 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1 no locks held by swapper/15/0.

...... Call Trace: <IRQ> dump_stack_lvl+0x8c/0xa0 lockdep_rcu_suspicious+0x118/0x1a0 nfp_flower_dev_get+0xc1/0x240 [nfp] nfp_nfd3_rx+0x419/0xb90 [nfp] ? validate_chain+0x640/0x1880 nfp_nfd3_poll+0x3e/0x180 [nfp] __napi_poll+0x28/0x1d0 net_rx_action+0x2bd/0x3c0 ? _raw_spin_unlock_irqrestore+0x42/0x70 __do_softirq+0xc3/0x3c6 irq_exit_rcu+0xeb/0x130 common_interrupt+0xb9/0xd0 </IRQ> <TASK> ...... </TASK>

In previous patch rcu_read_lock()/unlock() are removed because rcu-lock may affect xdp_prog. However this removal will make RCU lockdep report above warning because of missing of rcu_read_lock()/unlock() pair around rcu_deference().

This patch resolves this problem by replacing rcu_deference() with rcu_dereference_check() to annotate that access is safe if rcu_read_lock/rcu_read_lock_bh is held.

Fixes: d5789621b658 ("nfp: Remove rcu_read_lock() around XDP program invocation") CC: stable@vger.kernel.org Signed-off-by: Tianyu Yuan tianyu.yuan@corigine.com Acked-by: Simon Horman simon.horman@corigine.com Signed-off-by: Louis Peens louis.peens@corigine.com --- v1 -> v2: Remove unnessary nfp_app_dev_get_locked() helper function Replace rcu_dereference() with rcu_dereference_check() in .get_dev() Improve commit message --- drivers/net/ethernet/netronome/nfp/abm/main.c | 4 ++-- drivers/net/ethernet/netronome/nfp/flower/main.c | 5 +++-- 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/abm/main.c b/drivers/net/ethernet/netronome/nfp/abm/main.c index 5d3df28c648f..10b73297a313 100644 --- a/drivers/net/ethernet/netronome/nfp/abm/main.c +++ b/drivers/net/ethernet/netronome/nfp/abm/main.c @@ -63,14 +63,14 @@ nfp_abm_repr_get(struct nfp_app *app, u32 port_id, bool *redir_egress) rtype = FIELD_GET(NFP_ABM_PORTID_TYPE, port_id); port = FIELD_GET(NFP_ABM_PORTID_ID, port_id);

- reprs = rcu_dereference(app->reprs[rtype]); + reprs = rcu_dereference_check(app->reprs[rtype], rcu_read_lock_bh_held()); if (!reprs) return NULL;

if (port >= reprs->num_reprs) return NULL;

- return rcu_dereference(reprs->reprs[port]); + return rcu_dereference_check(reprs->reprs[port], rcu_read_lock_bh_held()); }

static int diff --git a/drivers/net/ethernet/netronome/nfp/flower/main.c b/drivers/net/ethernet/netronome/nfp/flower/main.c index 83eaa5ae3cd4..d33cc22c788d 100644 --- a/drivers/net/ethernet/netronome/nfp/flower/main.c +++ b/drivers/net/ethernet/netronome/nfp/flower/main.c @@ -257,14 +257,15 @@ nfp_flower_dev_get(struct nfp_app *app, u32 port_id, bool *redir_egress) if (repr_type > NFP_REPR_TYPE_MAX) return NULL;

- reprs = rcu_dereference(app->reprs[repr_type]); + reprs = rcu_dereference_check(app->reprs[repr_type], + rcu_read_lock_bh_held()); if (!reprs) return NULL;

if (port >= reprs->num_reprs) return NULL;

- return rcu_dereference(reprs->reprs[port]); + return rcu_dereference_check(reprs->reprs[port], rcu_read_lock_bh_held()); }

static int