openvswitch: meter: fix race when getting now_ms.
We have observed meters working unexpected if traffic is 3+Gbit/s with multiple connections. now_ms is not pretected by meter->lock, we may get a negative long_delta_ms when another cpu updated meter->used, then: delta_ms = (u32)long_delta_ms; which will be a large value. band->bucket += delta_ms * band->rate; then we get a wrong band->bucket. OpenVswitch userspace datapath has fixed the same issue[1] some time ago, and we port the implementation to kernel datapath. [1] https://patchwork.ozlabs.org/project/openvswitch/patch/20191025114436.9746-1-i.maximets@ovn.org/ Fixes: 96fbc13d ("openvswitch: Add meter infrastructure") Signed-off-by: Tao Liu <thomas.liu@ucloud.cn> Suggested-by: Ilya Maximets <i.maximets@ovn.org> Reviewed-by: Ilya Maximets <i.maximets@ovn.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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