On Tue, 1 Dec 2020 16:16:33 -0800 Jakub Kicinski wrote:
> On Tue, 1 Dec 2020 11:44:38 -0800 Cong Wang wrote:
> > From: Dongdong Wang <wangdongdong@xxxxxxxxxxxxx>
> >
> > 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.
> >
> > Cc: Thomas Graf <tgraf@xxxxxxx>
> > Cc: bpf@xxxxxxxxxxxxxxx
> > Reviewed-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> > Signed-off-by: Dongdong Wang <wangdongdong@xxxxxxxxxxxxx>
>
> Fixes?
Ah, should have read the commit message first. Okay.
