linux-kernel - Re: [net v1] net: wwan: t7xx: Fix napi rx poll issue

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Message-ID: <20250515175251.58b5123f@kernel.org>
Date: Thu, 15 May 2025 17:52:51 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jinjian Song <jinjian.song@...ocom.com>
Cc: chandrashekar.devegowda@...el.com, chiranjeevi.rapolu@...ux.intel.com,
 haijun.liu@...iatek.com, m.chetan.kumar@...ux.intel.com,
 ricardo.martinez@...ux.intel.com, loic.poulain@...aro.org,
 ryazanov.s.a@...il.com, johannes@...solutions.net, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 angelogioacchino.delregno@...labora.com,
 linux-arm-kernel@...ts.infradead.org, matthias.bgg@...il.com,
 corbet@....net, linux-mediatek@...ts.infradead.org, helgaas@...nel.org,
 danielwinkler@...gle.com, andrew+netdev@...n.ch, horms@...nel.org
Subject: Re: [net v1] net: wwan: t7xx: Fix napi rx poll issue

On Thu, 15 May 2025 11:17:42 +0800 Jinjian Song wrote:
> diff --git a/drivers/net/wwan/t7xx/t7xx_netdev.c b/drivers/net/wwan/t7xx/t7xx_netdev.c
> index 91fa082e9cab..2116ff81728b 100644
> --- a/drivers/net/wwan/t7xx/t7xx_netdev.c
> +++ b/drivers/net/wwan/t7xx/t7xx_netdev.c
> @@ -324,6 +324,7 @@ static void t7xx_ccmni_wwan_dellink(void *ctxt, struct net_device *dev, struct l
>  	if (WARN_ON(ctlb->ccmni_inst[if_id] != ccmni))
>  		return;
>  
> +	ctlb->ccmni_inst[if_id] = NULL;
>  	unregister_netdevice(dev);

I don't see any synchronization between this write and NAPI processing.
Is this safe? NAPI can be at any point of processing as we set the ptr
to NULL
-- 
pw-bot: cr