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Lu" , Xiaoliang Yang , "UNGLinuxDriver@microchip.com" , Claudiu Manoil , "alexandre.belloni@bootlin.com" , "andrew@lunn.ch" , "vivien.didelot@gmail.com" , "f.fainelli@gmail.com" , "kuba@kernel.org" , "richardcochran@gmail.com" Subject: Re: [PATCH net-next] net: mscc: ocelot: always pass skb clone to ocelot_port_add_txtstamp_skb Thread-Topic: [PATCH net-next] net: mscc: ocelot: always pass skb clone to ocelot_port_add_txtstamp_skb Thread-Index: AQHWkZwgfSWJjFtWWU2aMSGYdOEjdal2p0AAgAAEDoCAAAOhAIAAAuEA Date: Wed, 23 Sep 2020 20:45:48 +0000 Message-ID: <20200923204548.k2f44gjl7s4dwoim@skbuf> References: <20200923112420.2147806-1-vladimir.oltean@nxp.com> <20200923200800.t7y47fagvgffw4ya@soft-dev3.localdomain> <20200923202231.vr5ll2yu4gztqzwj@skbuf> <20200923203530.lenv5jedwmtefwqu@soft-dev3.localdomain> In-Reply-To: <20200923203530.lenv5jedwmtefwqu@soft-dev3.localdomain> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: microchip.com; dkim=none (message not signed) header.d=none;microchip.com; dmarc=none action=none header.from=nxp.com; x-originating-ip: [188.25.217.212] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: bf83fe14-5cf7-4017-4410-08d86001a73c x-ms-traffictypediagnostic: VI1PR04MB4222: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:10000; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: hWJZoEmnsDD8MY1bFiVEOTRe1uFiVQxZKr2enP9Ww6LFbm8AYIqv8WoBtZKXhZ8R0apl16OGb9RwCayJWGq2GfVcC2ehXelde337W+cGoPCwEy0vp8V9YQLkd3P1XmTWmT1uma1tXpQFP+gEX7yOaFG+7YhoRLJVnfG/SohF+wWead1uoZFpB01iP3zJu+zTeTPuGhqnhJD+X9bVXFBOzaviN0yCXfJyeiBzZXtcSPujWHGSgfpKC7NhU4Z6l7JMz6I0Vh2USUouuE5ZFHxiHv8yJ8VY7EpNzppowI4dkZ67mXhZozw3JPuKMhYWqhBnAxq9XAWvOFQ1wriNjFTo7Q== x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR04MB5696.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(7916004)(4636009)(136003)(396003)(346002)(376002)(366004)(39860400002)(6486002)(66946007)(1076003)(186003)(26005)(4326008)(6512007)(33716001)(6506007)(83380400001)(71200400001)(54906003)(9686003)(6916009)(316002)(76116006)(5660300002)(8676002)(8936002)(86362001)(478600001)(7416002)(91956017)(66556008)(44832011)(2906002)(66446008)(66476007)(64756008);DIR:OUT;SFP:1101; x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-ID: <953FCED5699B104CB187B509EDA03567@eurprd04.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5696.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: bf83fe14-5cf7-4017-4410-08d86001a73c X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Sep 2020 20:45:48.8734 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: DMp2F3z0TcVc0vx8c2H0cBPDdlm7K0CyRKTxrTZj/dw1Re9fa/lyZSesv4O9bfrXEp2oMKDqrRRxLKWQ5eaPzw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR04MB4222 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Sep 23, 2020 at 10:35:30PM +0200, Horatiu Vultur wrote: > The 09/23/2020 20:22, Vladimir Oltean wrote: > > On Wed, Sep 23, 2020 at 10:08:00PM +0200, Horatiu Vultur wrote: > > > The 09/23/2020 14:24, Vladimir Oltean wrote: > > > > + if (ocelot_port->ptp_cmd =3D=3D IFH_REW_OP_TWO_STEP= _PTP) { > > > > + struct sk_buff *clone; > > > > + > > > > + clone =3D skb_clone_sk(skb); > > > > + if (!clone) { > > > > + kfree_skb(skb); > > > > + return NETDEV_TX_OK; > > > > > > Why do you return NETDEV_TX_OK? > > > Because the frame is not sent yet. > > > > I suppose I _could_ increment the tx_dropped counters, if that's what > > you mean. > > Yeah, something like that I was thinking. > > Also I am just thinking, not sure if it is correct but, can you return > NETDEV_TX_BUSY and not free the skb? > Do you have a use case for NETDEV_TX_BUSY instead of plain dropping the skb, some situation where it would be better? I admit I haven't tested this particular code path, but my intuition tells me that under OOM, the last thing you need is some networking driver just trying and trying again to send a packet. Documentation/networking/driver.rst: 1) The ndo_start_xmit method must not return NETDEV_TX_BUSY under any normal circumstances. It is considered a hard error unless there is no way your device can tell ahead of time when it's transmit function will become busy. Looking up the uses of NETDEV_TX_BUSY, I see pretty much only congestion type of events. Thanks, -Vladimir=