netdev - Re: [Intel-wired-lan] [PATCH 1/1 iwl-net] idpf: disable local BH when scheduling napi for marker packets

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Date: Wed, 14 Feb 2024 15:54:31 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Alan Brady <alan.brady@...el.com>
CC: Jesse Brandeburg <jesse.brandeburg@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, <intel-wired-lan@...ts.osuosl.org>, "Emil
 Tantilov" <emil.s.tantilov@...el.com>, <netdev@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH 1/1 iwl-net] idpf: disable local BH when
 scheduling napi for marker packets

From: Alexander Lobakin <aleksander.lobakin@...el.com>
Date: Tue, 13 Feb 2024 14:16:47 +0100

> From: Alan Brady <alan.brady@...el.com>
> Date: Wed,  7 Feb 2024 16:42:43 -0800
> 
>> From: Emil Tantilov <emil.s.tantilov@...el.com>
>>
>> Fix softirq's not being handled during napi_schedule() call when
>> receiving marker packets for queue disable by disabling local bottom
>> half.
> 
> BTW, how exactly does this help?
> 
> __napi_schedule() already disables interrupts (local_irq_save()).
> napi_schedule_prep() only has READ_ONCE() and other atomic read/write
> helpers.
> 
> It's always been safe to call napi_schedule() with enabled BH, so I
> don't really understand how this works.

This also needs to be dropped from the fixes queue until investigated.
For now, it looks like a cheap hack (without the explanation how exactly
it does help), not a proper fix.

Thanks,
Olek