From patchwork Fri Mar 24 12:36:19 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9642779 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 57FA560327 for ; Fri, 24 Mar 2017 12:36:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5237327F07 for ; Fri, 24 Mar 2017 12:36:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 471B52823E; Fri, 24 Mar 2017 12:36:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 099AD27F07 for ; Fri, 24 Mar 2017 12:36:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933751AbdCXMgo (ORCPT ); Fri, 24 Mar 2017 08:36:44 -0400 Received: from mail-pg0-f66.google.com ([74.125.83.66]:34744 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932434AbdCXMgn (ORCPT ); Fri, 24 Mar 2017 08:36:43 -0400 Received: by mail-pg0-f66.google.com with SMTP id w20so226597pgc.1 for ; Fri, 24 Mar 2017 05:36:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=8D5ChyTj/gDVUmQzwxUm3qiKfp+0a0NqaXtPgvQ3ZAc=; b=lE72YpU5hVMDv53qKUZO78D8RDQ64DxHmcylJIEtx42IwHBBGfCxbbYo3BP+0SDigK /3g8egdPh3cneROAhXE/m8v+x9BRIzlX1LtRPxojSiWCtGwvBTkBWojE8kpF2DJTK3kh XyL6d0sXfvVenHBrJu1e5aSRPBHQlLPBbqf65YDNKeSpxEalUyOZy0/auI4k+Kv6h+m5 rTihGHb/6i5msAmBd28sled6J0lYVyqhHFXfvoQ3g1rCKmCIBTiddTMdnElRjjP7ZZbC NWDABxVdeXz12EmdEZ66omdqV5dCuwgTiNRgFkzO69HhjYQXANelDfDBiKInH85hMSYN 9SoQ== 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; bh=8D5ChyTj/gDVUmQzwxUm3qiKfp+0a0NqaXtPgvQ3ZAc=; b=p8pkwt1zU7iE3YKPIx+FLJ4na+WDuRZZJaflt61h0CnLxDTa+k07CuX6ZReaG/ZTaj +9eEfUBPza2xp/GqgR32MAw0qQ9G4wbpj34VsADJJ8T2pWPDE5Woj0V83d1gDVqXYgMp z+u/QjYuQ8wCNJ5UsPUP0YKJjSSQ2weZIwpwArx8LX+ApkS9tIXSvzQdZE0XHG5g10Ha aaSHZqM2SntDXsNTRh3wde5FKZwSzZMlIVAhaW5KzcYiEEKTqi4X8uCDKmi4yjkNjeZF 10sp4DIrF7/6Vv2v0IIEDSZZSTJXSOu79UDyK4TUDpt8YWP0MvamEjb5HY35sTq4XRx3 +hQA== X-Gm-Message-State: AFeK/H1dhUxFi+XuTtEjo7I35jYUia223TjQSfWsv0Belahz1BgXRVL2u+1U8dbuxF55tg== X-Received: by 10.84.229.10 with SMTP id b10mr10704631plk.148.1490359001012; Fri, 24 Mar 2017 05:36:41 -0700 (PDT) Received: from localhost (li405-222.members.linode.com. [106.187.53.222]) by smtp.gmail.com with ESMTPSA id d3sm3648736pfd.57.2017.03.24.05.36.39 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 24 Mar 2017 05:36:40 -0700 (PDT) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig Cc: Bart Van Assche , Hannes Reinecke , Ming Lei Subject: [PATCH v2 2/4] block: add a read barrier in blk_queue_enter() Date: Fri, 24 Mar 2017 20:36:19 +0800 Message-Id: <20170324123621.5227-3-tom.leiming@gmail.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170324123621.5227-1-tom.leiming@gmail.com> References: <20170324123621.5227-1-tom.leiming@gmail.com> Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Without the barrier, reading DEAD flag of .q_usage_counter and reading .mq_freeze_depth may be reordered, then the following wait_event_interruptible() may never return. Signed-off-by: Ming Lei Reviewed-by: Hannes Reinecke --- block/blk-core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/block/blk-core.c b/block/blk-core.c index ad388d5e309a..44eed17319c0 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -669,6 +669,14 @@ int blk_queue_enter(struct request_queue *q, bool nowait) if (nowait) return -EBUSY; + /* + * read pair of barrier in blk_mq_freeze_queue_start(), + * we need to order reading DEAD flag of .q_usage_counter + * and reading .mq_freeze_depth, otherwise the following + * wait may never return if the two read are reordered. + */ + smp_rmb(); + ret = wait_event_interruptible(q->mq_freeze_wq, !atomic_read(&q->mq_freeze_depth) || blk_queue_dying(q));