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=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 62A9BC43331 for ; Fri, 3 Apr 2020 16:32:26 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3521A206F8 for ; Fri, 3 Apr 2020 16:32:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3521A206F8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=proxmox.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jKPF3-0002bf-3m for qemu-devel@archiver.kernel.org; Fri, 03 Apr 2020 12:32:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38199) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jKPEP-00026f-3Y for qemu-devel@nongnu.org; Fri, 03 Apr 2020 12:31:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jKPEO-0002GM-2H for qemu-devel@nongnu.org; Fri, 03 Apr 2020 12:31:45 -0400 Received: from proxmox-new.maurer-it.com ([212.186.127.180]:51303) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jKPEK-00020n-Eu; Fri, 03 Apr 2020 12:31:41 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 8B4464297A; Fri, 3 Apr 2020 18:31:37 +0200 (CEST) Date: Fri, 3 Apr 2020 18:31:35 +0200 (CEST) From: Dietmar Maurer To: Kevin Wolf Message-ID: <1466731307.175.1585931495885@webmail.proxmox.com> In-Reply-To: <20200403084729.GB5336@linux.fritz.box> References: <20200401181256.GB27663@linux.fritz.box> <1403939459.52.1585765681569@webmail.proxmox.com> <20200401184431.GD27663@linux.fritz.box> <903538836.29.1585818619688@webmail.proxmox.com> <20200402121403.GB4006@linux.fritz.box> <20200402142524.GD4006@linux.fritz.box> <1043934808.59.1585842050330@webmail.proxmox.com> <20200402164744.GE4006@linux.fritz.box> <20200402171007.GF4006@linux.fritz.box> <2091214547.43.1585902379938@webmail.proxmox.com> <20200403084729.GB5336@linux.fritz.box> Subject: Re: bdrv_drained_begin deadlock with io-threads MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Priority: 3 Importance: Normal X-Mailer: Open-Xchange Mailer v7.10.2-Rev23 X-Originating-Client: open-xchange-appsuite X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 212.186.127.180 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Dietmar Maurer Cc: qemu-block@nongnu.org, Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , Stefan Hajnoczi , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > On April 3, 2020 10:47 AM Kevin Wolf wrote: > > > Am 03.04.2020 um 10:26 hat Dietmar Maurer geschrieben: > > > With the following patch, it seems to survive for now. I'll give it some > > > more testing tomorrow (also qemu-iotests to check that I didn't > > > accidentally break something else.) > > > > Wow, that was fast! Seems your patch fixes the bug! > > > > I wonder what commit introduced that problem, maybe: > > > > https://github.com/qemu/qemu/commit/cf3129323f900ef5ddbccbe86e4fa801e88c566e#diff-7cb66df56045598b75a219eebc27efb6 > > > > If so, version 4.1.X in not affected by this bug, but 4.2.0 and later? > > Yes, I'm pretty sure that's the one. I also wonder if we can loose an aio_wait_kick() by directly accessing blk->in_flight. I thought this should use atomic_mb_read()? diff --git a/block/block-backend.c b/block/block-backend.c index 8b8f2a80a0..48f3721505 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -2275,7 +2275,7 @@ static bool blk_root_drained_poll(BdrvChild *child) { BlockBackend *blk = child->opaque; assert(blk->quiesce_counter); - return !!blk->in_flight; + return !!atomic_mb_read(&blk->in_flight); } static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter)