linux-kernel - Re: [PATCH net] net: xilinx: axienet: Schedule NAPI in two steps

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Message-ID: <f63bf0ad-2846-4108-9a3f-9ea113959af0@linux.dev>
Date: Thu, 12 Sep 2024 10:23:06 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 netdev@...r.kernel.org, Robert Hancock <robert.hancock@...ian.com>,
 linux-kernel@...r.kernel.org, Michal Simek <michal.simek@....com>,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net] net: xilinx: axienet: Schedule NAPI in two steps

On 9/10/24 21:58, Jakub Kicinski wrote:
> On Mon,  9 Sep 2024 19:19:04 -0400 Sean Anderson wrote:
>> Additionally, since we are running
>> in an IRQ context we can use the irqoff variant as well.
> 
> The _irqoff variant is a bit of a minefield. It causes issues if kernel
> is built with forced IRQ threading. With datacenter NICs forced
> threading is never used so we look the other way. Since this is a fix
> and driver is embedded I reckon we should stick to __napi_schedule().

Does it?

__napi_schedule_irqoff selects between __napi_schedule and
____napi_schedule based on whether PREEMPT_RT is enabled. Is there some
other way to force IRQ threading?

--Sean