Re: [PATCH] bpf: devmap: Pass lockdep expression to RCU lists
From: Jesper Dangaard Brouer <hidden>
Date: 2020-01-23 13:37:45
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bpf, linux-kernel-mentees, lkml
On Thu, 23 Jan 2020 17:34:38 +0530 Amol Grover [off-list ref] wrote:
head is traversed using hlist_for_each_entry_rcu outside an RCU read-side critical section but under the protection of dtab->index_lock.
We do hold the lock in update and delete cases, but not in the lookup cases. Is it then still okay to add the lockdep_is_held() annotation? If it is then it looks fine to me: Acked-by: Jesper Dangaard Brouer <redacted>
quoted hunk ↗ jump to hunk
Hence, add corresponding lockdep expression to silence false-positive lockdep warnings, and harden RCU lists. Signed-off-by: Amol Grover <redacted> --- kernel/bpf/devmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 3d3d61b5985b..b4b6b77f309c 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c@@ -293,7 +293,8 @@ struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key) struct hlist_head *head = dev_map_index_hash(dtab, key); struct bpf_dtab_netdev *dev; - hlist_for_each_entry_rcu(dev, head, index_hlist) + hlist_for_each_entry_rcu(dev, head, index_hlist, + lockdep_is_held(&dtab->index_lock)) if (dev->idx == key) return dev;
-- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer