Edward Cree wrote 27.11.2019 19:05:

On 27/11/2019 09:41, Alexander Lobakin wrote:

quoted

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 (local)
[2] https://bugzilla.kernel.org/show_bug.cgi?id=205647

Signed-off-by: Alexander Lobakin <redacted>

Reviewed-by: Edward Cree <redacted>

Thanks! And you were the first who's found the root of the issue.

Regards,
ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ