linux-kernel - Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine support

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Message-ID: <20231006143230.4230fdc2@kernel.org>
Date:   Fri, 6 Oct 2023 14:32:30 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "Simek, Michal" <michal.simek@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "git (AMD-Xilinx)" <git@....com>
Subject: Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine
 support

On Fri, 6 Oct 2023 19:04:29 +0000 Pandey, Radhey Shyam wrote:
> > > +		netif_stop_queue(ndev);
> > > +		if (net_ratelimit())
> > > +			netdev_warn(ndev, "TX ring unexpectedly full\n");  
> > 
> > I don't see you stopping the queue when the ring gets full, am I not looking
> > into the right place? Otherwise this is sort of expected to occasionally hapen  
> 
> We are calling stop_queue if TX ring is full. Is that what you meant?
> netif_stop_queue(ndev);

But somewhere else or just here after printing the warning?

The recommended flow is to stop the queue after enqueuing
a packet successfully, if the remaining space is not enough
to hold an skb with all frags populated. That avoids ever
returning BUSY.