Re: [PATCH net] net/mlx5: Fix double unregister of HCA_PORTS component

Moshe Shemesh
2025-12-04T17:07:57Z

On 12/4/2025 11:48 AM, Gerd Bayer wrote:
>
> On Wed, 2025-12-03 at 17:14 +0200, Moshe Shemesh wrote:
>>
>> On 12/2/2025 1:12 PM, Gerd Bayer wrote:
>>>
>
> [ ... snip ... ]
>
>>>
>>> Fixes: 5a977b5833b7 ("net/mlx5: Lag, move devcom registration to LAG layer")
>>> Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
>>
>> Reviewed-by: Moshe Shemesh <moshe@nvidia.com>> ---
>>> Hi Shay et al,
>>>
>>
>> Hi Gerd,
>> I stepped on this bug recently too, without s390 and was about to
>> submit same fix :) So as you wrote it is unrelated to Lukas' patches and
>> this fix is correct.
>
> Good to hear. I wonder if you could share how you got to run into this?
>

mlx5_unload_one() can be called from few flows.
Even that it is always called with devlink lock, serial of
mlx5_unload_one() twice caused it. I got it on fw_reset and shutdown. I
I will submit also a patch for calling mlx5_drain_fw_reset() on shutdown
soon.

>>
>>>
>>> I've spotted two additional places where the devcom reference is not
>>> cleared after calling mlx5_devcom_unregister_component() in
>>> drivers/net/ethernet/mellanox/mlx5/core/lib/sd.c that I have not
>>> addressed with a patch, since I'm unclear about how to test these
>>> paths.
>>
>> As for the other cases, we had the patch 664f76be38a1 ("net/mlx5: Fix
>> IPsec cleanup over MPV device") and two other cases on shared clock and
>> SD but I don't see any flow the shared clock or SD can fail,
>> specifically mlx5_sd_cleanup() checks sd pointer at beginning of the
>> function and nullify it right after sd_unregister() that free devcom.
>
> I didn't locate any calls to mxl5_devcom_unregister_component() in
> "shared clock" - is that not yet upstream?

mlx5_shared_clock_unregister() in
drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c

>
> Regarding SD, I follow that sd_cleanup() is followed immediately after
> sd_unregister() and does the clean-up. One path remains uncovered
> though: The error exit at
> https://elixir.bootlin.com/linux/v6.18/source/drivers/net/ethernet/mellanox/mlx5/core/lib/sd.c#L265
>
> Not sure, how likely that is...

It comes on error flow but after successful
mlx5_devcom_register_component() in sd_register(), and that error leads
to error flow in mlx5_sd_init(), which calls sd_cleanup() too.

>
> Thanks,
> Gerd