linux-kernel - RE: [PATCH net v1] mlxbf_gige: disable port during stop()

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Message-ID:
 <CY5PR12MB6646FAC499454E380A87D829C7952@CY5PR12MB6646.namprd12.prod.outlook.com>
Date: Wed, 28 Aug 2024 21:37:06 +0000
From: David Thompson <davthompson@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Benjamin Poirier <benjamin.poirier@...il.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"pabeni@...hat.com" <pabeni@...hat.com>, "andriy.shevchenko@...ux.intel.com"
	<andriy.shevchenko@...ux.intel.com>, "u.kleine-koenig@...gutronix.de"
	<u.kleine-koenig@...gutronix.de>, Asmaa Mnebhi <asmaa@...dia.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net v1] mlxbf_gige: disable port during stop()

> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Monday, August 19, 2024 8:47 PM
> To: David Thompson <davthompson@...dia.com>
> Cc: Benjamin Poirier <benjamin.poirier@...il.com>; davem@...emloft.net;
> edumazet@...gle.com; pabeni@...hat.com;
> andriy.shevchenko@...ux.intel.com; u.kleine-koenig@...gutronix.de; Asmaa
> Mnebhi <asmaa@...dia.com>; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH net v1] mlxbf_gige: disable port during stop()
> 
> On Mon, 19 Aug 2024 14:55:12 -0400 Benjamin Poirier wrote:
> > Is this memory barrier paired with another one?
> 
> +1
> You probably want synchronize_irq() here?
> You should explain in the cover letter, the mb() seems to not be mentioned.
> --
> pw-bot: cr

Hello Jakub and Benjamin, thanks for your input.

I will post a v2 adding information about the "mb()" call.

Regarding the "synchronize_irq()" call, I did some research and noticed that
some already merged driver patches (see list below for a sample) state that 
"synchronize_irq()" is unnecessary before "free_irq()":

3e0fcb782a9f i40e: Remove unnecessary synchronize_irq() before free_irq()
845517ed04ae RDMA/qedr: Remove unnecessary synchronize_irq() before free_irq()
d1e7f009bfff net: qede: Remove unnecessary synchronize_irq() before free_irq()
bd81bfb5a1d1 net: vxge: Remove unnecessary synchronize_irq() before free_irq()
29fd3ca1779f qed: Remove unnecessary synchronize_irq() before free_irq()
411dccf9d271 dmaengine: idxd: Remove unnecessary synchronize_irq() before free_irq()
d887ae3247e0 octeontx2-pf: Remove unnecessary synchronize_irq() before free_irq()

Given the above information, does my mlxbf_gige driver patch still need to
invoke "synchronize_irq()" in the stop() method?  The "mlxbf_gige_free_irq()"
call within the stop() method invokes "free_irq()" for each of the driver's IRQs, so
sounds like this "synchronize_irq()" is implicitly being invoked?

Regards, Dave