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[23.128.96.18]) by mx.google.com with ESMTP id bc15si9135191edb.334.2020.05.25.03.42.46; Mon, 25 May 2020 03:43:09 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@web.de header.s=dbaedf251592 header.b=OL+67yHV; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389867AbgEYKkj (ORCPT + 99 others); Mon, 25 May 2020 06:40:39 -0400 Received: from mout.web.de ([212.227.15.3]:45873 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389720AbgEYKkj (ORCPT ); Mon, 25 May 2020 06:40:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1590403230; bh=UAAySmjAxYuqZUoP+efpAcdgXj4UW8nezo8B+rRuNAA=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=OL+67yHV6Qz0iKD5yee8iW9W0gC+pYjR31ID31t7TyQuKaTdVp3V2RQfdDgDUFmTu lJ66wJ5soukyendWEg4eE52SS3vmvlgjFxTf1s2qr0DSytAdIt2nO8E3WG20U/h1kg PQBUAIZn++5fgrNrg+3KReWRJ7K0zEzj+fiYv8Lc= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.2] ([93.135.186.124]) by smtp.web.de (mrweb006 [213.165.67.108]) with ESMTPSA (Nemesis) id 1MoNZM-1jEp8g1JEG-00opIO; Mon, 25 May 2020 12:40:30 +0200 Subject: Re: [v2] workqueue: Fix double kfree for rescuer To: Zhang Qiang , Tejun Heo , Lai Jiangshan Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org References: <20200525075901.12699-1-qiang.zhang@windriver.com> <7d19381c-2c51-deb4-f82f-d54bc56c6ecf@web.de> From: Markus Elfring 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: <8b67c327-e70c-1e96-6a99-a5fd2667f666@web.de> Date: Mon, 25 May 2020 12:40:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:6441JMEiROh6sK8+BnPqqw3WrEthd5XUr+Kzdk6pmE+X9TQqB6A nPZqGV1WuN8t0Ug83lwopTfwhOLXgYMl0A1FBQTTL40z/En0u1vkxBK6o/EH5qe4ps+TE0t i9yzoQVL3n6/LX73+lFHsIocNLlluvTQzD8Ct+0WD1vJFYhmIPqbLTuEhAMKW/43+hA+S9O upkbkVVJzBnSGJiQqFggA== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:CCEENFUN3qw=:rhvh2m/C3Fq4w+hI58PLWZ W5RSOY0fHFNsFcRUHBR4HFGEMfQc89vrEmslrx4br1hbVL/xe897o9mi9yK9UZiIF0LMEWpXl dY9hSWKfpVws1bFSdVSS0RKSRkZ+ov6Vi3TNAfv7cIhxqxikt7yarfokGAsW+SISAab1P3ofb IAjZJt7zaVR25cgrqFNSJo4N79qWpGOud1OIzqdSbI1LRYL2HXyioyWKFyQXG0Amby3bFKNnz QDRU9p3J+cods9WHD+dPfAzRYLIYDVu4lOiSvcjKbyz91TxCk+y1sqO77Rc3n50fLGVegNju5 oB1pLec6ZG47yXyVQOeAVFXLsoiIdrOJs8rSTkCANS9mhgK2Dse1SVI9dvcdcEbwCl3TPdLmd 7O5uL1JaTHWjRr0mn87r0QobMCwZc6pDlumyBLVkykEpledNhmKGS0LU/edLxY5nGLY6/tNQ4 YzDRmqkUI6xr7o7DLxWGdySikmCGE47dfNBTIOrVBz6ktKMXWAJlti96lvHYmWbmHtEQeBAao dlmKr5ydrMXzSbqu8kERYxn59LLNjMohzNDXthFoQPMagBgfh10dv4y2Ov1+kcr8HlNhp+PAY zPz4qg5ayxdlrfalPd/gc11IwhhDhud69di7F0Nrp4QjFQAxvSp9tgUc6G2u/uLqs8nPz3MtK B1pwTD9LyWIxX4xinCHqzMYh8EI1aAIb0tfXNUZASRPi0Vzv7xCnjpIJhGdqUrarFvOA89tc1 bXYG5k/Z0XQvxb+H+s8wqDolGzXmMjIN4uGOM9MEgzHTEKyIwjmfaji+35Yw8MBCHt5lXGelR +9hESTrydfhrvRBp797EUTkFaJFCicN5TrFTuIr/ygAmn7D+dYubBMDFDFqLw6as94NyK3S35 t3FHtOyjEhMko3aYSP6ruGM0B65ie4bR7l3RrQVV238gt0eSy/+r4eAoLjhmX9vUHxOvxKbeY OoCIw8hI7I/puvXoLk/KaHtnXwQ0P1BfMTu2z+VUgQ2/TgW5+skp8Bl4TIexVGVXKz45jzqxA aSTpLTv4JqHXlRBHxz1SkSeKw+HMWn66m9lTF/jI2Ck1KmI790jF3WjO66O3OZfI1Abb4eGw4 CbMl0StdAa2CpMhmmLVlbYS2Rq9KaMsXzfIqSMTB0TxnyVrZ7qPoihtQK5G6cP5g3Kh7Er29y 5Hz/R0Tf31y9q3U3fQ57PZby7GG/GVJKHX+xV3/QZgB0Tj6lUCPJucxGlOhRUBbIVfhyuDiqW pV3dO5wSRt+olYd8U Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I see, kfree does nothing with null pointers and direct return. > but again kfree is not a good suggestion. I have got the impression that the implementation detail is important here if non-null pointers (according to valid rescuer objects) are occasionally passed by the corresponding data structure member for the callback function =E2=80=9Crcu_free_wq=E2=80=9D. Can another clarification attempt reduce unwanted confusion for this patch= review? Regards, Markus