[ovs-dev] [PATCH] dpif-netdev: Fix time delta overflow in case of race for meter lock.

[William Tu]

On Fri, Oct 25, 2019 at 4:44 AM Ilya Maximets <i.maximets at ovn.org> wrote:
>
> There is a race window between getting the time and getting the meter
> lock.  This could lead to situation where the thread with larger
> current time (this thread called time_{um}sec() later than others)
> will acquire meter lock first and update meter->used to the large
> value.  Next threads will try to calculate time delta by subtracting
> the large meter->used from their lower time getting the negative value
> which will be converted to a big unsigned delta.
>
> Fix that by assuming that all these threads received packets in the
> same time in this case, i.e. dropping negative delta to 0.
>
> CC: Jarno Rajahalme <jarno at ovn.org>
> Fixes: 4b27db644a8c ("dpif-netdev: Simple DROP meter implementation.")
> Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-September/363126.html
> Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
> ---

LGTM.
Thanks for the fix
Acked-by: William Tu <u9012063 at gmail.com>