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Date: Fri, 12 Sep 2025 20:26:03 +0100
From: Simon Horman <horms@kernel.org>
To: Samiullah Khawaja <skhawaja@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
	"David S . Miller " <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>,
	willemb@google.com, netdev@vger.kernel.org
Subject: Re: [PATCH net] net: Use NAPI_* in test_bit when stopping napi
 kthread
Message-ID: <20250912192603.GF224143@horms.kernel.org>
References: <20250910203716.1016546-1-skhawaja@google.com>
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In-Reply-To: <20250910203716.1016546-1-skhawaja@google.com>

On Wed, Sep 10, 2025 at 08:37:16PM +0000, Samiullah Khawaja wrote:
> napi_stop_kthread waits for the NAPI_STATE_SCHED_THREADED to be unset
> before stopping the kthread. But it uses test_bit with the
> NAPIF_STATE_SCHED_THREADED and that might stop the kthread early before
> the flag is unset.
> 
> Use the NAPI_* variant of the NAPI state bits in test_bit instead.

I think it would be useful to mention the difference between 
NAPI_STATE_SCHED_THREADED and NAPIF_STATE_SCHED_THREADED.

For me, that would be that one is a bit number, while
the other is a mask with only the corresponding bit set.

> 
> Tested:
>  ./tools/testing/selftests/net/nl_netdev.py
>  TAP version 13
>  1..7
>  ok 1 nl_netdev.empty_check
>  ok 2 nl_netdev.lo_check
>  ok 3 nl_netdev.page_pool_check
>  ok 4 nl_netdev.napi_list_check
>  ok 5 nl_netdev.dev_set_threaded
>  ok 6 nl_netdev.napi_set_threaded
>  ok 7 nl_netdev.nsim_rxq_reset_down
>  # Totals: pass:7 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
>  ./tools/testing/selftests/drivers/net/napi_threaded.py
>  TAP version 13
>  1..2
>  ok 1 napi_threaded.change_num_queues
>  ok 2 napi_threaded.enable_dev_threaded_disable_napi_threaded
>  # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
> Fixes: 689883de94dd ("net: stop napi kthreads when THREADED napi is disabled")
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>

With the above addressed, feel free to add:

Reviewed-by: Simon Horman <horms@kernel.org>

...