From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] tcp/fq: move back to CLOCK_MONOTONIC
Date: Mon, 01 Oct 2018 23:19:20 -0700 (PDT)
Message-ID: <20181001.231920.987040554483569743.davem@davemloft.net>
References: <20180928172844.182542-1-edumazet@google.com>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com,
        leonard.crestez@nxp.com
To: edumazet@google.com
Return-path: <netdev-owner@vger.kernel.org>
Received: from shards.monkeyblade.net ([23.128.96.9]:38202 "EHLO
        shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1726481AbeJBNAy (ORCPT
        <rfc822;netdev@vger.kernel.org>); Tue, 2 Oct 2018 09:00:54 -0400
In-Reply-To: <20180928172844.182542-1-edumazet@google.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

From: Eric Dumazet <edumazet@google.com>
Date: Fri, 28 Sep 2018 10:28:44 -0700

> In the recent TCP/EDT patch series, I switched TCP and sch_fq
> clocks from MONOTONIC to TAI, in order to meet the choice done
> earlier for sch_etf packet scheduler.
> 
> But sure enough, this broke some setups were the TAI clock
> jumps forward (by almost 50 year...), as reported
> by Leonard Crestez.
> 
> If we want to converge later, we'll probably need to add
> an skb field to differentiate the clock bases, or a socket option.
> 
> In the meantime, an UDP application will need to use CLOCK_MONOTONIC
> base for its SCM_TXTIME timestamps if using fq packet scheduler.
> 
> Fixes: 72b0094f9182 ("tcp: switch tcp_clock_ns() to CLOCK_TAI base")
> Fixes: 142537e41923 ("net_sched: sch_fq: switch to CLOCK_TAI")
> Fixes: fd2bca2aa789 ("tcp: switch internal pacing timer to CLOCK_TAI")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Leonard Crestez <leonard.crestez@nxp.com>

Applied.