Re: [PATCH net] net: wireless: intel: iwlwifi: fix GRO_NORMAL packet stalling

Luciano Coelho
2019-11-27T09:58:42Z

On Wed, 2019-11-27 at 12:41 +0300, Alexander Lobakin wrote:
> Commit 6570bc79c0df ("net: core: use listified Rx for GRO_NORMAL in
> napi_gro_receive()") has applied batched GRO_NORMAL packets processing
> to all napi_gro_receive() users, including mac80211-based drivers.
>
> However, this change has led to a regression in iwlwifi driver [1][2] as
> it is required for NAPI users to call napi_complete_done() or
> napi_complete() and the end of every polling iteration, whilst iwlwifi
> doesn't use NAPI scheduling at all and just calls napi_gro_flush().
> In that particular case, packets which have not been already flushed
> from napi->rx_list stall in it until at least next Rx cycle.
>
> Fix this by adding a manual flushing of the list to iwlwifi driver right
> before napi_gro_flush() call to mimic napi_complete() logics.
>
> I prefer to open-code gro_normal_list() rather than exporting it for 2
> reasons:
> * to prevent from using it and napi_gro_flush() in any new drivers,
> as it is the *really* bad way to use NAPI that should be avoided;
> * to keep gro_normal_list() static and don't lose any CC optimizations.
>
> I also don't add the "Fixes:" tag as the mentioned commit was only a
> trigger that only exposed an improper usage of NAPI in this particular
> driver.
>
> [1] https://lore.kernel.org/netdev/PSXP216MB04388962C411CD0B17A86F47804A0@PSXP216MB0438.KORP216.PROD.OUTLOOK.COM
> [2] https://bugzilla.kernel.org/show_bug.cgi?id=205647
>
> Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
> ---

We don't usually use "net: wireless: intel:" in the commit message, we
would use "iwlwifi: pcie:", but I don't care much.

Otherwise:

Acked-by: Luca Coelho <luciano.coelho@intel.com>

Thanks a lot for the fix!

Dave, I'm assuming you'll take this directly into your tree, right?

--
Cheers,
Luca.