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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 E1204C1975A for ; Wed, 25 Mar 2020 15:51:55 +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 BE77F20719 for ; Wed, 25 Mar 2020 15:51:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE77F20719 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]:38666 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jH8Ju-0003lG-Sn for qemu-devel@archiver.kernel.org; Wed, 25 Mar 2020 11:51:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46791) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jH8JL-0003IE-I3 for qemu-devel@nongnu.org; Wed, 25 Mar 2020 11:51:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jH8JK-0006OR-Ez for qemu-devel@nongnu.org; Wed, 25 Mar 2020 11:51:19 -0400 Received: from proxmox-new.maurer-it.com ([212.186.127.180]:62947) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jH8JH-0006Em-VF; Wed, 25 Mar 2020 11:51:16 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 9FA8242E95; Wed, 25 Mar 2020 16:51:11 +0100 (CET) From: Stefan Reiter To: qemu-devel@nongnu.org, qemu-block@nongnu.org Subject: [PATCH] backup: don't acquire aio_context in backup_clean Date: Wed, 25 Mar 2020 16:50:55 +0100 Message-Id: <20200325155055.730633-1-s.reiter@proxmox.com> X-Mailer: git-send-email 2.25.2 In-Reply-To: <76edbead-7ccf-833b-a3f2-15dff7f0748c@virtuozzo.com> References: <76edbead-7ccf-833b-a3f2-15dff7f0748c@virtuozzo.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: , Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, mreitz@redhat.com, stefanha@redhat.com, jsnow@redhat.com, dietmar@proxmox.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" backup_clean is only ever called as a handler via job_exit, which already acquires the job's context. The job's context is guaranteed to be the same as the one used by backup_top via backup_job_create. Since the previous logic effectively acquired the lock twice, this broke cleanup of backups for disks using IO threads, since the BDRV_POLL_= WHILE in bdrv_backup_top_drop -> bdrv_do_drained_begin would only release the l= ock once, thus deadlocking with the IO thread. Signed-off-by: Stefan Reiter --- This is a fix for the issue discussed in this part of the thread: https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg07639.html ...not the original problem (core dump) posted by Dietmar. I've still seen it occasionally hang during a backup abort. I'm trying to= figure out why that happens, stack trace indicates a similar problem with the ma= in thread hanging at bdrv_do_drained_begin, though I have no clue why as of = yet. block/backup.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/block/backup.c b/block/backup.c index 7430ca5883..a7a7dcaf4c 100644 --- a/block/backup.c +++ b/block/backup.c @@ -126,11 +126,7 @@ static void backup_abort(Job *job) static void backup_clean(Job *job) { BackupBlockJob *s =3D container_of(job, BackupBlockJob, common.job); - AioContext *aio_context =3D bdrv_get_aio_context(s->backup_top); - - aio_context_acquire(aio_context); bdrv_backup_top_drop(s->backup_top); - aio_context_release(aio_context); } =20 void backup_do_checkpoint(BlockJob *job, Error **errp) --=20 2.25.2