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authorDongdong Wang <wangdongdong.6@bytedance.com>2020-12-04 23:59:45 -0800
committerAlexei Starovoitov <ast@kernel.org>2020-12-07 11:53:39 -0800
commitd9054a1ff585ba01029584ab730efc794603d68f (patch)
tree1423dfd779aad5f398dd1330a84e060306d1fa56 /lib
parent12c8a8ca117f3d734babc3fba131fdaa329d2163 (diff)
lwt: Disable BH too in run_lwt_bpf()
The per-cpu bpf_redirect_info is shared among all skb_do_redirect() and BPF redirect helpers. Callers on RX path are all in BH context, disabling preemption is not sufficient to prevent BH interruption. In production, we observed strange packet drops because of the race condition between LWT xmit and TC ingress, and we verified this issue is fixed after we disable BH. Although this bug was technically introduced from the beginning, that is commit 3a0af8fd61f9 ("bpf: BPF for lightweight tunnel infrastructure"), at that time call_rcu() had to be call_rcu_bh() to match the RCU context. So this patch may not work well before RCU flavor consolidation has been completed around v5.0. Update the comments above the code too, as call_rcu() is now BH friendly. Signed-off-by: Dongdong Wang <wangdongdong.6@bytedance.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Cong Wang <cong.wang@bytedance.com> Link: https://lore.kernel.org/bpf/20201205075946.497763-1-xiyou.wangcong@gmail.com
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