Messages in this thread Patch in this message | | | Date | Wed, 1 Nov 2017 15:13:51 +0100 | From | Stephen Hemminger <> | Subject | Re: [PATCH] tcp_nv: fix division by zero in tcpnv_acked() |
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On Wed, 1 Nov 2017 13:47:17 +0000 Lawrence Brakmo <brakmo@fb.com> wrote:
> Thank you for finding and fixing this. > > On 11/1/17, 6:32 AM, "Konstantin Khlebnikov" <khlebnikov@yandex-team.ru> wrote: > > Average RTT could become zero. This happened in real life at least twice. > This patch treats zero as 1us. > > Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru > Acked-by: Lawrence Brakmo <Brakmo@fb.com> > --- > net/ipv4/tcp_nv.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c > index 1ff73982e28c..125fc1450b01 100644 > --- a/net/ipv4/tcp_nv.c > +++ b/net/ipv4/tcp_nv.c > @@ -252,7 +252,7 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample) > > /* rate in 100's bits per second */ > rate64 = ((u64)sample->in_flight) * 8000000; > - rate = (u32)div64_u64(rate64, (u64)(avg_rtt * 100)); > + rate = (u32)div64_u64(rate64, (u64)(avg_rtt ?: 1) * 100);
Why is this code using expensive 64 bit by 64 bit divide when avg_rtt should never be bigger than 32 bits?
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