linux-kernel - Re: Setting large MTU size on slave interfaces may stall the whole system

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Date:   Wed, 13 Dec 2017 16:28:15 +0200
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Qing Huang <qing.huang@...cle.com>
Cc:     Linux Netdev List <netdev@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Aviv Heller <avivh@...lanox.com>,
        Moni Shoua <monis@...lanox.com>
Subject: Re: Setting large MTU size on slave interfaces may stall the whole system

On Tue, Dec 12, 2017 at 5:21 AM, Qing Huang <qing.huang@...cle.com> wrote:
> Hi,
>
> We found an issue with the bonding driver when testing Mellanox devices.
> The following test commands will stall the whole system sometimes, with
> serial console
> flooded with log messages from the bond_miimon_inspect() function. Setting
> mtu size
> to be 1500 seems okay but very rarely it may hit the same problem too.
>
> ip address flush dev ens3f0
> ip link set dev ens3f0 down
> ip address flush dev ens3f1
> ip link set dev ens3f1 down
> [root@...hcl629 etc]# modprobe bonding mode=0 miimon=250 use_carrier=1
> updelay=500 downdelay=500
> [root@...hcl629 etc]# ifconfig bond0 up
> [root@...hcl629 etc]# ifenslave bond0 ens3f0 ens3f1
> [root@...hcl629 etc]# ip link set bond0 mtu 4500 up

> Seiral console output:
>
> ** 4 printk messages dropped ** [ 3717.743761] bond0: link status down for
> interface ens3f0, disabling it in 500 ms
[..]


> It seems that when setting a large mtu size on an RoCE interface, the RTNL
> mutex may be held too long by the slave
> interface, causing bond_mii_monitor() to be called repeatedly at an interval
> of 1 tick (1K HZ kernel configuration) and kernel to become unresponsive.

Did you try/managed to reproduce that also with other NIC drivers?

Or.