From patchwork Wed Mar 25 15:50:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Reiter X-Patchwork-Id: 1261520 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=proxmox.com 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 ozlabs.org (Postfix) with ESMTPS id 48nXfj53Tpz9sPk for ; Thu, 26 Mar 2020 02:51:40 +1100 (AEDT) Received: from localhost ([::1]:38664 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jH8Jd-0003L1-Ah for incoming@patchwork.ozlabs.org; Wed, 25 Mar 2020 11:51:37 -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 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+incoming=patchwork.ozlabs.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 lock 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 main 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 = container_of(job, BackupBlockJob, common.job); - AioContext *aio_context = bdrv_get_aio_context(s->backup_top); - - aio_context_acquire(aio_context); bdrv_backup_top_drop(s->backup_top); - aio_context_release(aio_context); } void backup_do_checkpoint(BlockJob *job, Error **errp)