netdev - Re: Regression: [PATCH] mlx4: give precise rx/tx bytes/packets counters

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Message-ID: <CALzJLG-xERnkNEaC3+ikb6ZiWmzj9S1BAoJycYq1yp8AT+zuUQ@mail.gmail.com>
Date:   Sun, 4 Dec 2016 15:23:32 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: Regression: [PATCH] mlx4: give precise rx/tx bytes/packets counters

On Thu, Dec 1, 2016 at 7:36 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2016-12-01 at 08:08 -0800, Eric Dumazet wrote:
>> On Thu, 2016-12-01 at 07:55 -0800, Eric Dumazet wrote:
>>
>> > So removing the spinlock is doable, but needs to add a new parameter
>> > to mlx4_en_fold_software_stats() and call netdev_stats_to_stats64()
>> > before mlx4_en_fold_software_stats(dev)
>>
>> Untested patch would be :
>>
>>  drivers/net/ethernet/mellanox/mlx4/en_ethtool.c |    2 -
>>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c  |   10 +----
>>  drivers/net/ethernet/mellanox/mlx4/en_port.c    |   24 +++++++++-----
>>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h    |    3 +
>>  4 files changed, 23 insertions(+), 16 deletions(-)
>
> The patch is wrong, since priv->port_up could change to false while we
> are running and using the about to be deleted tx/rx rings.
>

Right, hence the regression Jesper saw ;).

>
> So the only safe thing to do is to remove the _bh suffix.
>
> Not worth trying to avoid taking a spinlock in this code.
>

Ack.