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Fri, 25 Oct 2019 09:40:36 -0700 (PDT) To: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <5badf1c0-9a7d-0950-2943-ff8db33e0929@gmail.com> <96446fe1-4f32-642b-7100-ebfa291d7127@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Subject: Re: [BUG] io_uring: defer logic based on shared data Message-ID: <31a7765b-bb6d-985a-454d-d998678100d1@gmail.com> Date: Fri, 25 Oct 2019 19:40:29 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wb6vixXjHWBLQL0aiNcZPh0cB85T4ITXv" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --wb6vixXjHWBLQL0aiNcZPh0cB85T4ITXv Content-Type: multipart/mixed; boundary="DvpRx4KljX6yzYynEe9WpMbne6GOEA6TB"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <31a7765b-bb6d-985a-454d-d998678100d1@gmail.com> Subject: Re: [BUG] io_uring: defer logic based on shared data References: <5badf1c0-9a7d-0950-2943-ff8db33e0929@gmail.com> <96446fe1-4f32-642b-7100-ebfa291d7127@kernel.dk> In-Reply-To: --DvpRx4KljX6yzYynEe9WpMbne6GOEA6TB Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 25/10/2019 19:32, Jens Axboe wrote: > On 10/25/19 10:27 AM, Jens Axboe wrote: >> On 10/25/19 10:21 AM, Pavel Begunkov wrote: >>> On 25/10/2019 19:03, Jens Axboe wrote: >>>> On 10/25/19 3:55 AM, Pavel Begunkov wrote: >>>>> I found 2 problems with __io_sequence_defer(). >>>>> >>>>> 1. it uses @sq_dropped, but doesn't consider @cq_overflow >>>>> 2. @sq_dropped and @cq_overflow are write-shared with userspace, so= >>>>> it can be maliciously changed. >>>>> >>>>> see sent liburing test (test/defer *_hung()), which left an unkilla= ble >>>>> process for me >>>> >>>> OK, how about the below. I'll split this in two, as it's really two >>>> separate fixes. >>> cached_sq_dropped is good, but I was concerned about cached_cq_overfl= ow. >>> io_cqring_fill_event() can be called in async, so shouldn't we do som= e >>> synchronisation then? >> >> We should probably make it an atomic just to be on the safe side, I'll= >> update the series. >=20 > Here we go, patch 1: >=20 > http://git.kernel.dk/cgit/linux-block/commit/?h=3Dfor-linus&id=3Df2a241= f596ed9e12b7c8f960e79ccda8053ea294 >=20 > patch 2: >=20 > http://git.kernel.dk/cgit/linux-block/commit/?h=3Dfor-linus&id=3Db7d029= 7d2df5bfa0d1ecf9d6c66d23676751ef6a >=20 1. submit rqs (not yet completed) 2. poll_list is empty, inflight =3D 0 3. async completed and placed into poll_list So, poll_list is not empty, but we won't get to polling again. At least until someone submitted something. --=20 Yours sincerely, Pavel Begunkov --DvpRx4KljX6yzYynEe9WpMbne6GOEA6TB-- --wb6vixXjHWBLQL0aiNcZPh0cB85T4ITXv Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl2zJYEACgkQWt5b1Glr +6Vrdg//dxuY82uWIRnNxVbgWmkiK/cDNvTjuwvEfrshkCo4grayfY7YT4tkZF0O yI7ogixxrylxoINEjMZBtd4IYaXuHHSt56GUPMTMw8q2ApBcEg5ZADEoXxFtq8hU eopPKMYzfecY6FGkTkM0gbrlrFhLAgcUNI3qkDGCwSpotaznjMaBQsCdvnzgSyil DJAN1WtFY2pk6xOYVTR97eXEq/n4Or/K5PBDXeNMB4bSDoAjDxq1+gIY6xGvdpbq AO24h+ckeFqdDPZInHHz7z7++gQhFvu0vIyrkIQDqIwH9rIjx17oyAkQZCdG2OqM CoTjR0JuCzR3OcPBTbPeDKAqjL6FTjR+hR0DX1NUAu7kj6MoRdWQ3YkDfmXP/Rfh UbN2wgBcpOLzxzxBsp3SNOEII/WTRMy23edMZsqfRAhbjbySXxkwGLLgUKMMCYv3 f5gI6iNTOuJE99OkhDKUTfhiurLYCMWrvBeA+DyP3bfCTTz6wrI+t5/Nq9sEWW0z 5seIu/dowvFzdLtkQXqoXcLjclp1RoEivRr1xoq+nn00sfw0anMf+U3yKOdsAP73 y28XZbmkSLci3Rm3/9cpscd7zw8D4NKW4yCM/n3SKL4jd8x1yw3wzgw/g93dG2E1 0vUKqKAyaUv1cIKRhpvkYtAswgnEFecDkGl/WEF5IbolANBFIVk= =uGsX -----END PGP SIGNATURE----- --wb6vixXjHWBLQL0aiNcZPh0cB85T4ITXv--