linux-kernel - Re: [PATCH] net: amd: xgbe: fix possible sleep-in-atomic-context bugs in xgbe

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Message-Id: <20191218.132601.160360469201947283.davem@davemloft.net>
Date:   Wed, 18 Dec 2019 13:26:01 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     baijiaju1990@...il.com
Cc:     thomas.lendacky@....com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: amd: xgbe: fix possible sleep-in-atomic-context
 bugs in xgbe_powerdown()

From: Jia-Ju Bai <baijiaju1990@...il.com>
Date: Wed, 18 Dec 2019 22:01:02 +0800

> @@ -1257,17 +1257,18 @@ int xgbe_powerdown(struct net_device *netdev, unsigned int caller)
>  	netif_tx_stop_all_queues(netdev);
>  
>  	xgbe_stop_timers(pdata);
> -	flush_workqueue(pdata->dev_workqueue);
>  
>  	hw_if->powerdown_tx(pdata);
>  	hw_if->powerdown_rx(pdata);
>  
> -	xgbe_napi_disable(pdata, 0);
> -
>  	pdata->power_down = 1;
>  
>  	spin_unlock_irqrestore(&pdata->lock, flags);
>  
> +	flush_workqueue(pdata->dev_workqueue);
> +
> +	xgbe_napi_disable(pdata, 0);
> +

Nope, this doesn't work at all.

You can't leave NAPI enabled, and thus packet processing, after the TX
and RX units of the chip have been powered down.