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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 0BDB7C2D0A8 for ; Wed, 23 Sep 2020 11:44:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA042214D8 for ; Wed, 23 Sep 2020 11:44:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="bMOj5Tth" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726655AbgIWLox (ORCPT ); Wed, 23 Sep 2020 07:44:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbgIWLou (ORCPT ); Wed, 23 Sep 2020 07:44:50 -0400 Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC7B1C0613CE for ; Wed, 23 Sep 2020 04:44:49 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id d9so14881853pfd.3 for ; Wed, 23 Sep 2020 04:44:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=fGilIYrCbh50kTGRwzjJvVfohhOd0dHq1F9Kut44y9I=; b=bMOj5TthhClhPZZn3/SIzkBPxHYOZH75lTH2CcXUdw8UR/J+FzMyQ/KBz7hKRaA18E ZlSjrcfBhq5erVyx0j6CD66VdAJrqX0HfmM/0D3rabD6dkiKizTu6ztq1OKYtWN+y/75 hQj5pqVDvtbI5d65Og1ytt+GcllEe4wiB2FwEeV7M4suASAr+87Mnpsg8jCUvIhHLba/ 2rB2qF1Ho22sboU++zkzxz4bDO7QX1CKYUDkQ7WSU+5By9kHHdnQOGTW9zbUZWHsyNT1 2xPMaiq9HaTEvNN1xERZNOYTOplzVwhhoOw9R1DTo/979p3PKQjEeRPE5rznAiGDmRLW jO8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=fGilIYrCbh50kTGRwzjJvVfohhOd0dHq1F9Kut44y9I=; b=NU5bUrgjo9g8dpw9EaslD+UGMR2yQVyQePkkMMnIG3lO4zN76mfg7BiPhNz3T9goI7 xVVB3B5qYRqiCtky0nXUUUXd/U4ud6h4rX/VpjK00zF6Y/J+BSWr7AA2iLoHsqNikT8C ycnnRGp0Io4KEe3gXTS6V6lrJT2mBqX4nP2Phh0Dg2+T2TskZArHhnWVmjwffHZTMRmO CQXs+J1SlbwjzUCbq66lLWEOE6U2NDrBMovarcSwZ48FDEfoUJOeL7GSznJVnuhzXpN9 M9JkUfqmJ0UMufcmNIJ0b43fjIJslArgUki0SnMkz9CVxvyj1d1OmlHBPP9gqrpcNOTv iaXA== X-Gm-Message-State: AOAM530XgRAJgO9+QSghodsMnAoAk3OTongEeFPFiQS0aONlb85nQDgC OrvHoky547VziZwHY1DqUZdLLQ== X-Google-Smtp-Source: ABdhPJwPQPmp9mJ3CwnGnJmncLyVBkzdNV9o4SqscJ/GohWXP7zYQ0odT2RerJw29I0rw87VsNdsHw== X-Received: by 2002:a63:4d02:: with SMTP id a2mr7108482pgb.38.1600861489363; Wed, 23 Sep 2020 04:44:49 -0700 (PDT) Received: from Smcdef-MBP.local.net ([103.136.220.72]) by smtp.gmail.com with ESMTPSA id a13sm17632155pfl.184.2020.09.23.04.44.46 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Sep 2020 04:44:48 -0700 (PDT) From: Muchun Song To: axboe@kernel.dk, viro@zeniv.linux.org.uk Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, zhuyinyin@bytedance.com, Muchun Song Subject: [PATCH v2 2/5] io_uring: Fix missing smp_mb() in io_cancel_async_work() Date: Wed, 23 Sep 2020 19:44:16 +0800 Message-Id: <20200923114419.71218-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20200923114419.71218-1-songmuchun@bytedance.com> References: <20200923114419.71218-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The store to req->flags and load req->work_task should not be reordering in io_cancel_async_work(). We should make sure that either we store REQ_F_CANCE flag to req->flags or we see the req->work_task setted in io_sq_wq_submit_work(). Fixes: 1c4404efcf2c ("io_uring: make sure async workqueue is canceled on exit") Signed-off-by: Muchun Song --- fs/io_uring.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index a1350c7c50055..c80c37ef38513 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2252,6 +2252,12 @@ static void io_sq_wq_submit_work(struct work_struct *work) if (!ret) { req->work_task = current; + + /* + * Pairs with the smp_store_mb() (B) in + * io_cancel_async_work(). + */ + smp_mb(); /* A */ if (req->flags & REQ_F_CANCEL) { ret = -ECANCELED; goto end_req; @@ -3728,7 +3734,15 @@ static void io_cancel_async_work(struct io_ring_ctx *ctx, req = list_first_entry(&ctx->task_list, struct io_kiocb, task_list); list_del_init(&req->task_list); - req->flags |= REQ_F_CANCEL; + + /* + * The below executes an smp_mb(), which matches with the + * smp_mb() (A) in io_sq_wq_submit_work() such that either + * we store REQ_F_CANCEL flag to req->flags or we see the + * req->work_task setted in io_sq_wq_submit_work(). + */ + smp_store_mb(req->flags, req->flags | REQ_F_CANCEL); /* B */ + if (req->work_task && (!files || req->files == files)) send_sig(SIGINT, req->work_task, 1); } -- 2.11.0