netdev - Re: [PATCH net-next] r8169: set IRQF_NO

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Message-ID: <20201102000652.5i5o7ig56lymcjsv@skbuf>
Date:   Mon, 2 Nov 2020 02:06:52 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] r8169: set IRQF_NO_THREAD if MSI(X) is enabled

On Sun, Nov 01, 2020 at 11:30:44PM +0100, Heiner Kallweit wrote:
> We had to remove flag IRQF_NO_THREAD because it conflicts with shared
> interrupts in case legacy interrupts are used. Following up on the
> linked discussion set IRQF_NO_THREAD if MSI or MSI-X is used, because
> both guarantee that interrupt won't be shared.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> Link: https://www.spinics.net/lists/netdev/msg695341.html

I am not sure if this utilization of the Link: tag is valid. I think it
has a well-defined meaning and maintainers use it to provide a link to
the email where the patch was picked from:
https://lkml.org/lkml/2011/4/6/421

> ---
>  drivers/net/ethernet/realtek/r8169_main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 319399a03..4d6afaf7c 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -4690,6 +4690,7 @@ static int rtl_open(struct net_device *dev)
>  {
>  	struct rtl8169_private *tp = netdev_priv(dev);
>  	struct pci_dev *pdev = tp->pci_dev;
> +	unsigned long irqflags;
>  	int retval = -ENOMEM;
>  
>  	pm_runtime_get_sync(&pdev->dev);
> @@ -4714,8 +4715,9 @@ static int rtl_open(struct net_device *dev)
>  
>  	rtl_request_firmware(tp);
>  
> +	irqflags = pci_dev_msi_enabled(pdev) ? IRQF_NO_THREAD : IRQF_SHARED;
>  	retval = request_irq(pci_irq_vector(pdev, 0), rtl8169_interrupt,
> -			     IRQF_SHARED, dev->name, tp);
> +			     irqflags, dev->name, tp);
>  	if (retval < 0)
>  		goto err_release_fw_2;
>  
> -- 
> 2.29.2
> 

So all things considered, what do you want to achieve with this change?
Is there other benefit with disabling force threading of the
rtl8169_interrupt, or are you still looking to add back the
napi_schedule_irqoff call?