netdev - Re: mlx5 driver loading failing on v4.19 / net-next / bpf-next

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Date:   Fri, 14 Sep 2018 01:22:15 -0700
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Moshe Shemesh <moshe@...lanox.com>,
        Eli Cohen <eli@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>
Subject: Re: mlx5 driver loading failing on v4.19 / net-next / bpf-next

On Thu, Sep 13, 2018 at 11:36 PM, Jesper Dangaard Brouer
<brouer@...hat.com> wrote:
> On Thu, 13 Sep 2018 15:55:29 -0700
> Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
>
>> On Thu, Aug 30, 2018 at 1:35 AM, Tariq Toukan <tariqt@...lanox.com> wrote:
>> >
>> >
>> > On 29/08/2018 6:05 PM, Jesper Dangaard Brouer wrote:
>> >>
>> >> Hi Saeed,
>> >>
>> >> I'm having issues loading mlx5 driver on v4.19 kernels (tested both
>> >> net-next and bpf-next), while kernel v4.18 seems to work.  It happens
>> >> with a Mellanox ConnectX-5 NIC (and also a CX4-Lx but I removed that
>> >> from the system now).
>> >>
>> >
>> > Hi Jesper,
>> >
>> > Thanks for your report!
>> >
>> > We are working to analyze and debug the issue.
>>
>> looks like serious issue to me... while no news in 2 weeks.
>> any update?
>
> Mellanox took it offlist, and Sep 6th found that this is a regression
> introduced by commit 269d26f47f6f ("net/mlx5: Reduce command polling
> interval"), but only if CONFIG_PREEMPT is on.
>
> I can confirm that reverting this commit fixed the issue (and not the
> firmware upgrade I also did).
>
> I think Moshe (Cc) is responsible for this case, and I expect to soon
> see a revert or alternative solution to this!?
>
> Thanks for the kick Alexei :-)

Thanks you Alexei and Jesper for following up,
the fix is already being tested [1] and will be submitted tomorrow,
as Jesper pointed out the issue happens only with 269d26f47f6f
("net/mlx5: Reduce command polling
interval"), and only if CONFIG_PREEMPT is on.
the only affected kernel is 4.19 which is not GA yet.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux.git/commit/?h=net-mlx5

> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer