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=-14.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 30740C433ED for ; Thu, 8 Apr 2021 02:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0297E61074 for ; Thu, 8 Apr 2021 02:32:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229558AbhDHCck (ORCPT ); Wed, 7 Apr 2021 22:32:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbhDHCck (ORCPT ); Wed, 7 Apr 2021 22:32:40 -0400 Received: from mail-wr1-x433.google.com (mail-wr1-x433.google.com [IPv6:2a00:1450:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84758C061760 for ; Wed, 7 Apr 2021 19:32:29 -0700 (PDT) Received: by mail-wr1-x433.google.com with SMTP id s7so264924wru.6 for ; Wed, 07 Apr 2021 19:32:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:references:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=rhjdClddiLuYd1+F7XCIft4jFTYBq1xWxC+Xml7Q37A=; b=QxituHd69xkyIGxF0Vnc0vs6NLTuIHhUhitmn0HxrqL+fwsdtWkknjngMvyGxxSDq7 /LcvnJEoC/ItUwje2T7j36YC9r/FWL72U/MCyOxLGACLV7/JbwJwoOrX780kG636uCGC jA5IM0S7gsiWf59DBoFEDEEmG6vMkjwGUe+cZ5HeM8WhzYzmYSmHIFOg7WFbJGrtm83Y lBw6A6k1DfJwtkwkrdqBvBvP7k0bSkfMtBq7lhQSOBo86usuz28JVj2yS0laaiJIVzIh 5Z72iHCe5zGQHBn/Iqr/Rgspxlsarjgmh/XYpnkmJPjltkhwYtOuSBzAS9LLYtYavi+j rAKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:references:autocrypt:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=rhjdClddiLuYd1+F7XCIft4jFTYBq1xWxC+Xml7Q37A=; b=lHSQSmUedS3dAu/1NWmNJe2j29PK3yAO+dgVnL7oQEIswB77mX6DIonOhPS+fsOnox mAB9EeRiafX7ITjnLtUc1WhPK1sNEIr3k902YcCfgwuAMCs5fUT4WvgvitZlHV4z7SBc RhHEOIgkPcwQDRAJvx7gB80LP3unkpFD0bbZdjxiq4zUnxN6BDXHuOa3GojYVK6W/ewy IrpF/47EuYP3cjluTbzreMNOQUY23GSaTM3dMydx65/s+bil0ibwF6iJfjJv7wUtESI9 tfwVsI+EfbR56yx/nKIFZQH+rB8mm1dKt7De60qg5npHDqFp8JtFtW5HnMT/yr4Faqri tgbg== X-Gm-Message-State: AOAM5302CyLdr9gdYYcWzu5Gl8+Mu3pSSLkyPVrF7cFyciCDiH8ahEnw GGV7A9cpVFZOvGPJAi8iE1RF5xx3G7KaTw== X-Google-Smtp-Source: ABdhPJy2aa9gfnK3qJeHMMaVnaKAyN+hoAL2jDphMfdOY9tTaX32f4Jsj0lRc2mB2ftWN3zRSAEdoQ== X-Received: by 2002:a5d:6a4a:: with SMTP id t10mr37971wrw.422.1617849148066; Wed, 07 Apr 2021 19:32:28 -0700 (PDT) Received: from [192.168.8.155] ([148.252.132.202]) by smtp.gmail.com with ESMTPSA id n2sm11492388wrq.59.2021.04.07.19.32.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Apr 2021 19:32:27 -0700 (PDT) Subject: Re: [PATCH 3/4] io_uring: fix poll_rewait racing for ->canceled From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org References: 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: <04bcd0c7-4e13-a0eb-ebcd-e6abf08234e1@gmail.com> Date: Thu, 8 Apr 2021 03:28:22 +0100 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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 08/04/2021 01:54, Pavel Begunkov wrote: > poll->canceled may be set from different contexts, even async, so > io_poll_rewait() should be prepared that it can change and not read it > twice. Please disregard this one, apparently it's not a bug and will get in my way letter. Other 3 are fine. > > Signed-off-by: Pavel Begunkov > --- > fs/io_uring.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index de5822350345..376d9c875dc2 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -4897,15 +4897,16 @@ static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll) > __acquires(&req->ctx->completion_lock) > { > struct io_ring_ctx *ctx = req->ctx; > + bool canceled = READ_ONCE(poll->canceled); > > - if (!req->result && !READ_ONCE(poll->canceled)) { > + if (!req->result && !canceled) { > struct poll_table_struct pt = { ._key = poll->events }; > > req->result = vfs_poll(req->file, &pt) & poll->events; > } > > spin_lock_irq(&ctx->completion_lock); > - if (!req->result && !READ_ONCE(poll->canceled)) { > + if (!req->result && !canceled) { > add_wait_queue(poll->head, &poll->wait); > return true; > } > -- Pavel Begunkov