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[109.152.100.164]) by smtp.gmail.com with ESMTPSA id 4sm4521744wrp.58.2020.11.04.13.23.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2020 13:23:22 -0800 (PST) Subject: Re: [PATCH v3 RESEND] io_uring: add timeout support for io_uring_enter() To: Jens Axboe , Hao Xu Cc: io-uring@vger.kernel.org, metze@samba.org, Jiufei Xue , Joseph Qi References: <1604307047-50980-1-git-send-email-haoxu@linux.alibaba.com> <1604372077-179941-1-git-send-email-haoxu@linux.alibaba.com> <052a2b54-017f-8617-5d1a-074408d164fd@kernel.dk> <13c05478-5363-cfae-69b1-8022b9736088@gmail.com> <1d7cbae3-c284-e01d-7f7d-2ae2ab9cbb54@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== Message-ID: <310a29cd-0dc2-69b0-7700-975af8025b71@gmail.com> Date: Wed, 4 Nov 2020 21:20:22 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <1d7cbae3-c284-e01d-7f7d-2ae2ab9cbb54@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 04/11/2020 20:28, Jens Axboe wrote: > On 11/4/20 1:16 PM, Pavel Begunkov wrote: >> On 04/11/2020 19:34, Jens Axboe wrote: >>> On 11/4/20 12:27 PM, Pavel Begunkov wrote: >>>> On 04/11/2020 18:32, Jens Axboe wrote: >>>>> On 11/4/20 10:50 AM, Jens Axboe wrote: >>>>>> +struct io_uring_getevents_arg { >>>>>> + sigset_t *sigmask; >>>>>> + struct __kernel_timespec *ts; >>>>>> +}; >>>>>> + >>>>> >>>>> I missed that this is still not right, I did bring it up in your last >>>>> posting though - you can't have pointers as a user API, since the size >>>>> of the pointer will vary depending on whether this is a 32-bit or 64-bit >>>>> arch (or 32-bit app running on 64-bit kernel). >>>> >>>> Maybe it would be better >>>> >>>> 1) to kill this extra indirection? >>>> >>>> struct io_uring_getevents_arg { >>>> - sigset_t *sigmask; >>>> - struct __kernel_timespec *ts; >>>> + sigset_t sigmask; >>>> + struct __kernel_timespec ts; >>>> }; >>>> >>>> then, >>>> >>>> sigset_t *sig = (...)arg; >>>> __kernel_timespec* ts = (...)(arg + offset); >>> >>> But then it's kind of hard to know which, if any, of them are set... I >>> did think about this, and any solution seemed worse than just having the >>> extra indirection. >> >> struct io_uring_getevents_arg { >> sigset_t sigmask; >> u32 mask; >> struct __kernel_timespec ts; >> }; >> >> if size > sizeof(sigmask), then use mask to determine that. >> Though, not sure how horrid the rest of the code would be. > > I'm not saying it's not possible, just that I think the end result would > be worse in terms of both kernel code and how the user applications (or > liburing) would need to use it. I'd rather sacrifice an extra copy for > something that's straight forward (and logical) to use, rather than > needing weird setups or hoops to jump through. And this mask vs > sizeof(mask) thing seems pretty horrendeous to me :-) If you think so, I'll spare my time then :) > >>> Yeah, not doing the extra indirection would save a copy, but don't think >>> it's worth it for this path. >> >> I much more don't like branching like IORING_ENTER_GETEVENTS_TIMEOUT, >> from conceptual point. I may try it out to see how it looks like while >> it's still for-next. > > One thing I think we should change is the name, > IORING_ENTER_GETEVENTS_TIMEOUT will quickly be a bad name if we end up > adding just one more thing to the struct. Would be better to call it > IORING_ENTER_EXTRA_DATA or something, meaning that the sigmask pointer > is a pointer to the aux data instead of a sigmask. Better name > suggestions welcome... _EXT_ARG from extended Also, a minor one -- s/sigsz/argsz/ -- Pavel Begunkov