From 694cea395fded425008e93cd90cfdf7a451674af Mon Sep 17 00:00:00 2001 From: Toke Høiland-Jørgensen Date: Thu, 24 Jun 2021 18:05:54 +0200 Subject: bpf: Allow RCU-protected lookups to happen from bh context MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit XDP programs are called from a NAPI poll context, which means the RCU reference liveness is ensured by local_bh_disable(). Add rcu_read_lock_bh_held() as a condition to the RCU checks for map lookups so lockdep understands that the dereferences are safe from inside *either* an rcu_read_lock() section *or* a local_bh_disable() section. While both bh_disabled and rcu_read_lock() provide RCU protection, they are semantically distinct, so we need both conditions to prevent lockdep complaints. This change is done in preparation for removing the redundant rcu_read_lock()s from drivers. Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20210624160609.292325-5-toke@redhat.com --- kernel/bpf/helpers.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel/bpf/helpers.c') diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a2f1f15ce432..62cf00383910 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -29,7 +29,7 @@ */ BPF_CALL_2(bpf_map_lookup_elem, struct bpf_map *, map, void *, key) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return (unsigned long) map->ops->map_lookup_elem(map, key); } @@ -45,7 +45,7 @@ const struct bpf_func_proto bpf_map_lookup_elem_proto = { BPF_CALL_4(bpf_map_update_elem, struct bpf_map *, map, void *, key, void *, value, u64, flags) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return map->ops->map_update_elem(map, key, value, flags); } @@ -62,7 +62,7 @@ const struct bpf_func_proto bpf_map_update_elem_proto = { BPF_CALL_2(bpf_map_delete_elem, struct bpf_map *, map, void *, key) { - WARN_ON_ONCE(!rcu_read_lock_held()); + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); return map->ops->map_delete_elem(map, key); } -- cgit v1.2.3-70-g09d2