From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C37B5C10F11 for ; Wed, 10 Apr 2019 11:36:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A4872083E for ; Wed, 10 Apr 2019 11:36:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="N848gfrF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731302AbfDJLgP (ORCPT ); Wed, 10 Apr 2019 07:36:15 -0400 Received: from mout.web.de ([212.227.17.12]:35081 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727206AbfDJLgO (ORCPT ); Wed, 10 Apr 2019 07:36:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1554896153; bh=EpmGjf0QE/uQH049jh3E1+zrAi2YhnCQzfXxngPbYhA=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=N848gfrFZuwmTClIH37FbfwmouB2hyvTfqA29qF7xQl3HuhTJTduN5CpOv+qUuh8J cyllwtbk525f0k/xeNolJtudRohK81OxVdHCXxmIkpCjQpXOb8hTcrekLpmz47e3wj LTH9aeQ5ZE9faVZtG9OV/2tRlVm4796OgNqJJ5sI= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.2] ([93.135.98.93]) by smtp.web.de (mrweb101 [213.165.67.124]) with ESMTPSA (Nemesis) id 0LsQLM-1glQMj1qXY-011yfK; Wed, 10 Apr 2019 13:35:53 +0200 Subject: Re: [v2] ethernet: ti: eliminate a bit of duplicate code in gbe_probe() To: Wen Yang , netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Yi Wang , Wingman Kwok , Murali Karicheri , "David S. Miller" References: <201904101838229475340@zte.com.cn> From: Markus Elfring Openpgp: preference=signencrypt Autocrypt: addr=Markus.Elfring@web.de; prefer-encrypt=mutual; keydata= mQINBFg2+xABEADBJW2hoUoFXVFWTeKbqqif8VjszdMkriilx90WB5c0ddWQX14h6w5bT/A8 +v43YoGpDNyhgA0w9CEhuwfZrE91GocMtjLO67TAc2i2nxMc/FJRDI0OemO4VJ9RwID6ltwt mpVJgXGKkNJ1ey+QOXouzlErVvE2fRh+KXXN1Q7fSmTJlAW9XJYHS3BDHb0uRpymRSX3O+E2 lA87C7R8qAigPDZi6Z7UmwIA83ZMKXQ5stA0lhPyYgQcM7fh7V4ZYhnR0I5/qkUoxKpqaYLp YHBczVP+Zx/zHOM0KQphOMbU7X3c1pmMruoe6ti9uZzqZSLsF+NKXFEPBS665tQr66HJvZvY GMDlntZFAZ6xQvCC1r3MGoxEC1tuEa24vPCC9RZ9wk2sY5Csbva0WwYv3WKRZZBv8eIhGMxs rcpeGShRFyZ/0BYO53wZAPV1pEhGLLxd8eLN/nEWjJE0ejakPC1H/mt5F+yQBJAzz9JzbToU 5jKLu0SugNI18MspJut8AiA1M44CIWrNHXvWsQ+nnBKHDHHYZu7MoXlOmB32ndsfPthR3GSv jN7YD4Ad724H8fhRijmC1+RpuSce7w2JLj5cYj4MlccmNb8YUxsE8brY2WkXQYS8Ivse39MX BE66MQN0r5DQ6oqgoJ4gHIVBUv/ZwgcmUNS5gQkNCFA0dWXznQARAQABtCZNYXJrdXMgRWxm cmluZyA8TWFya3VzLkVsZnJpbmdAd2ViLmRlPokCVAQTAQgAPhYhBHDP0hzibeXjwQ/ITuU9 Figxg9azBQJYNvsQAhsjBQkJZgGABQsJCAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEOU9Figx g9azcyMP/iVihZkZ4VyH3/wlV3nRiXvSreqg+pGPI3c8J6DjP9zvz7QHN35zWM++1yNek7Ar OVXwuKBo18ASlYzZPTFJZwQQdkZSV+atwIzG3US50ZZ4p7VyUuDuQQVVqFlaf6qZOkwHSnk+ CeGxlDz1POSHY17VbJG2CzPuqMfgBtqIU1dODFLpFq4oIAwEOG6fxRa59qbsTLXxyw+PzRaR LIjVOit28raM83Efk07JKow8URb4u1n7k9RGAcnsM5/WMLRbDYjWTx0lJ2WO9zYwPgRykhn2 sOyJVXk9xVESGTwEPbTtfHM+4x0n0gC6GzfTMvwvZ9G6xoM0S4/+lgbaaa9t5tT/PrsvJiob kfqDrPbmSwr2G5mHnSM9M7B+w8odjmQFOwAjfcxoVIHxC4Cl/GAAKsX3KNKTspCHR0Yag78w i8duH/eEd4tB8twcqCi3aCgWoIrhjNS0myusmuA89kAWFFW5z26qNCOefovCx8drdMXQfMYv g5lRk821ZCNBosfRUvcMXoY6lTwHLIDrEfkJQtjxfdTlWQdwr0mM5ye7vd83AManSQwutgpI q+wE8CNY2VN9xAlE7OhcmWXlnAw3MJLW863SXdGlnkA3N+U4BoKQSIToGuXARQ14IMNvfeKX NphLPpUUnUNdfxAHu/S3tPTc/E/oePbHo794dnEm57LuuQINBFg2+xABEADZg/T+4o5qj4cw nd0G5pFy7ACxk28mSrLuva9tyzqPgRZ2bdPiwNXJUvBg1es2u81urekeUvGvnERB/TKekp25 4wU3I2lEhIXj5NVdLc6eU5czZQs4YEZbu1U5iqhhZmKhlLrhLlZv2whLOXRlLwi4jAzXIZAu 76mT813jbczl2dwxFxcT8XRzk9+dwzNTdOg75683uinMgskiiul+dzd6sumdOhRZR7YBT+xC wzfykOgBKnzfFscMwKR0iuHNB+VdEnZw80XGZi4N1ku81DHxmo2HG3icg7CwO1ih2jx8ik0r riIyMhJrTXgR1hF6kQnX7p2mXe6K0s8tQFK0ZZmYpZuGYYsV05OvU8yqrRVL/GYvy4Xgplm3 DuMuC7/A9/BfmxZVEPAS1gW6QQ8vSO4zf60zREKoSNYeiv+tURM2KOEj8tCMZN3k3sNASfoG fMvTvOjT0yzMbJsI1jwLwy5uA2JVdSLoWzBD8awZ2X/eCU9YDZeGuWmxzIHvkuMj8FfX8cK/ 2m437UA877eqmcgiEy/3B7XeHUipOL83gjfq4ETzVmxVswkVvZvR6j2blQVr+MhCZPq83Ota xNB7QptPxJuNRZ49gtT6uQkyGI+2daXqkj/Mot5tKxNKtM1Vbr/3b+AEMA7qLz7QjhgGJcie qp4b0gELjY1Oe9dBAXMiDwARAQABiQI8BBgBCAAmFiEEcM/SHOJt5ePBD8hO5T0WKDGD1rMF Alg2+xACGwwFCQlmAYAACgkQ5T0WKDGD1rOYSw/+P6fYSZjTJDAl9XNfXRjRRyJSfaw6N1pA Ahuu0MIa3djFRuFCrAHUaaFZf5V2iW5xhGnrhDwE1Ksf7tlstSne/G0a+Ef7vhUyeTn6U/0m +/BrsCsBUXhqeNuraGUtaleatQijXfuemUwgB+mE3B0SobE601XLo6MYIhPh8MG32MKO5kOY hB5jzyor7WoN3ETVNQoGgMzPVWIRElwpcXr+yGoTLAOpG7nkAUBBj9n9TPpSdt/npfok9ZfL /Q+ranrxb2Cy4tvOPxeVfR58XveX85ICrW9VHPVq9sJf/a24bMm6+qEg1V/G7u/AM3fM8U2m tdrTqOrfxklZ7beppGKzC1/WLrcr072vrdiN0icyOHQlfWmaPv0pUnW3AwtiMYngT96BevfA qlwaymjPTvH+cTXScnbydfOQW8220JQwykUe+sHRZfAF5TS2YCkQvsyf7vIpSqo/ttDk4+xc Z/wsLiWTgKlih2QYULvW61XU+mWsK8+ZlYUrRMpkauN4CJ5yTpvp+Orcz5KixHQmc5tbkLWf x0n1QFc1xxJhbzN+r9djSGGN/5IBDfUqSANC8cWzHpWaHmSuU3JSAMB/N+yQjIad2ztTckZY pwT6oxng29LzZspTYUEzMz3wK2jQHw+U66qBFk8whA7B2uAU1QdGyPgahLYSOa4XAEGb6wbI FEE= Message-ID: Date: Wed, 10 Apr 2019 13:35:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <201904101838229475340@zte.com.cn> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:ifja0MMk/p4oUEtpltUgZVwYhg5lVRdc43h/BO/ygYOpL4jFa+l F30DMvuvOAYmtbvioaMztybr7bK0Hs4PhLtYZSMLyqpK6MB/9T+gtdJM0QewN+Q8gVq6WQ0 2/JtQ7QtgyWPZcQ1Up90XPnPezRzNLjWNerbuYP8PWur+0CFUHt7/YuxBNjQFW+xXm6DgmF XeNm3p85woHxp6kvDMj+A== X-UI-Out-Filterresults: notjunk:1;V03:K0:sHdVSIsVKMs=:9zPzv7Mo0NxL+lFszc8qLQ Y684bP2MilBi3yx1N8Fbmx5MefSSxmrO0ve7Zf3KrH9ZiNDDr361ZS/NtLCIszLN8pYdbdRsm 9iH0jO6m13SPqNET63SVUfBZXZA9VK7cOPxyvQ9JABG+1j4i2V1MXm73fc1j787G73SIpCdyf Ox8juhFPnDAO/3yWX6oekUDtSrYQQNP9asb86EpBWkTQ6I7cflPS8TRYuWfSGHuW1UhgkySEJ eMFb/VoXeGGIuJGflTDj39pbPFAGU+6/5SceugNNT/9CJdioEeXqeF5U3XXX9lx89S8gkfSDT RPqp/GOqtpJSNgaueVcZHo+jxUcRzwS+8xNzIHGihfS8DBopu4gwv1/oH0yOMmwZd3v7VMreB TFuhmvCWmKsJyqshyzOQelTN8bQyh+0P6lW2szXaqSvlO4SfLhkvLvDTde6A28NFdHFlI0o8/ UCAutjP0QJS6uqYMk1ZLZZaSPBgDLsZDrmTt/HIar1BH8G6dByqzQBE6QAO8aUCPNhi839rMP +xvFCp/yR4js3MQOwnP0YCXLtdaINY9aTy3LOcmbksyMCy5A+/XocnDkkeTAFlgVrCl1rWJW1 A2QeLgqvB2JIWRoOGYhdMJNJixdXgTOMv9FToNjWbgirhfTuyjM42j7V4xdYcHM+CPUX0n2eP YCLo7Y1nL91devZRe5RC3UoaYBVKcAb9zoLpFR9SqkWp+Gz8pme7s5JYiHaOYbggmYzU2Qadu /RRPvC56IkyKYA3lFGisNaWlF/XahcYrfgTARMRHy6WgWqgUE/3v/6uTyuTgCZz1YdcOl1we4 EjIFiOVNB8km4oaUkMaG8lcfnRKZs6azdeX2phMLIf0CiRHgQlOm2xhTv9vZLtmbGFiPhEu++ Qs1tJWxfPo6jg+AyuXalIxbb56pnJBsmWozJ8A/9PAQEZ289WxtafcWHM2vT2w+Vy9WU3WiZy bFg3fd6DDvQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> @@ -3651,22 +3651,18 @@ static int gbe_probe(struct netcp_device *ne= tcp_device, struct device *dev, >>>>> if (ret) >>>>> return ret; >>>>> >>>>> - interfaces =3D of_get_child_by_name(node, "interfaces"); >>>>> - if (!interfaces) >>>>> - dev_err(dev, "could not find interfaces\n"); >>>>> - >>>> >>>> How do you think about to skip a bit of statements as a reaction for >>>> such a null pointer? >>>> https://elixir.bootlin.com/linux/v5.1-rc4/source/drivers/net/ethernet= /ti/netcp_ethss.c#L3562 >> =E2=80=A6 >>> Maybe you need to look at the implementation of for_each_child_of_node= () and of_node_put(). >>> NULL check before those functions is not needed. >> >> This information is reasonable in principle. >> >> Was the reference counter incremented even if a null pointer was return= ed >> by such a function call? > > The situation you assume is an issue that the of_get_child_by_name() fun= ction needs to consider > and has been irrelevant to our patch. I suggest to reconsider the software situation a bit more. > 1, when returning NULL, the of_get_child_by_name () function needs to en= sure that the resources > it has allocated are released; > 2, when returning NULL, if of_get_child_by_name() can't release its= resources, then the > outer function has no way to release these resources. > > If you are interested, you can check the of_get_child_by_name() function= further It seems that the corresponding software documentation can be improved als= o here. https://elixir.bootlin.com/linux/v5.1-rc4/source/drivers/of/base.c#L863 > and send it to me if you find any problems. I find the exception handling suspicious in the discussed function impleme= ntation. >>>>> ret =3D netcp_txpipe_init(&gbe_dev->tx_pipe, netcp_device, >>>>> gbe_dev->dma_chan_name, gbe_dev->tx_queue_id); >>>>> - if (ret) { >>>>> - of_node_put(interfaces); >>>>> + if (ret) >>>>> return ret; >>>>> - } >>>>> >>>>> ret =3D netcp_txpipe_open(&gbe_dev->tx_pipe); >>>>> - if (ret) { >>>>> - of_node_put(interfaces); >>>>> + if (ret) >>>>> return ret; >>>>> - } >> >> Does the preparation of the NetCP pipe still matter in this special use= case? =E2=80=A6 > Please refer to my reply above. I propose to take additional software design possibilities into account. > We have checked the netcp_txpipe_init() and the netcp_txpipe_open() func= tion. I wonder if such function calls are still relevant if a questionable syste= m configuration would be detected before. > However, your questions may not actually be related to our patch. Your update suggestion triggered related adjustment ideas. >>>> + >>>> + interfaces =3D of_get_child_by_name(node, "interfaces"); >>>> + if (!interfaces) >>>> + dev_err(dev, "could not find interfaces\n"); >>>> >>>> /* Create network interfaces */ >>>> INIT_LIST_HEAD(&gbe_dev->gbe_intf_head); >>>> >>>> Can code like the following trigger corresponding software developmen= t concerns? >>>> >>>> for_each_child_of_node(interfaces, interface) { >>>> =E2=80=A6 >>>> } >>>> of_node_put(interfaces); >>>> >> =E2=80=A6 >>>> if (!gbe_dev->num_slaves) >>>> dev_warn(dev, "No network interface configured\n"); > >> Is this message really required as another response then? Is the exception handling still questionable in this function? Regards, Markus