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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2F994C33CB3 for ; Tue, 28 Jan 2020 16:29:04 +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 F3E3A24681 for ; Tue, 28 Jan 2020 16:29:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F+tZehiF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F3E3A24681 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:32932 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iwTjb-0007jK-7t for qemu-devel@archiver.kernel.org; Tue, 28 Jan 2020 11:29:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55725) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iwTif-0006vf-4H for qemu-devel@nongnu.org; Tue, 28 Jan 2020 11:28:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iwTid-0002lU-Qk for qemu-devel@nongnu.org; Tue, 28 Jan 2020 11:28:04 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:33365 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iwTid-0002kz-Mn for qemu-devel@nongnu.org; Tue, 28 Jan 2020 11:28:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580228882; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=odW+lJDZ2Lmz7BsIl51gbc4/c2wH2TyvgUXdFuUpFw4=; b=F+tZehiF0sOF0Dn5LRSfNSO7sE0QEW8yHdET0s5a2tn4zcx4lZKF7FrM6PxiLjCdTJB3gp A3pqTClfO15p5Tg7rp0x9dyiNAn1Wv+lAuyVmVc+g+A2JIdVDOuaekCq+EX/ZVb9uVBQfK lATxdheDt45akbdYwphaGkvuqH2OhKM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-357-QxAxctJxPbaSRYz0R4NUVw-1; Tue, 28 Jan 2020 11:28:00 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 42EF68C30E8; Tue, 28 Jan 2020 16:27:59 +0000 (UTC) Received: from [10.3.117.16] (ovpn-117-16.phx2.redhat.com [10.3.117.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8795C7C35A; Tue, 28 Jan 2020 16:27:56 +0000 (UTC) Subject: Re: [PATCH 2/2] mirror: Don't let an operation wait for itself To: Kevin Wolf , qemu-block@nongnu.org References: <20200128151755.25162-1-kwolf@redhat.com> <20200128151755.25162-3-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <72ac830e-b8de-8c9e-4e80-b9af2bbfb9a0@redhat.com> Date: Tue, 28 Jan 2020 10:27:56 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200128151755.25162-3-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: QxAxctJxPbaSRYz0R4NUVw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 207.211.31.120 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: jsnow@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/28/20 9:17 AM, Kevin Wolf wrote: > mirror_wait_for_free_in_flight_slot() just picks a random operation to > wait for. However, when mirror_co_read() waits for free slots, its > MirrorOp is already in s->ops_in_flight, so if not enough slots are > immediately available, an operation can end up waiting for itself to > complete, which results in a hang. Eww. That can't have been fun to debug. > > Fix this by passing the current MirrorOp and skipping this operation > when picking an operation to wait for. > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1794692 > Signed-off-by: Kevin Wolf > --- > block/mirror.c | 21 ++++++++++++--------- > 1 file changed, 12 insertions(+), 9 deletions(-) > > diff --git a/block/mirror.c b/block/mirror.c > index 8959e4255f..cacbc70014 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -283,11 +283,14 @@ static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset, > } > > static inline void coroutine_fn > -mirror_wait_for_any_operation(MirrorBlockJob *s, bool active) > +mirror_wait_for_any_operation(MirrorBlockJob *s, MirrorOp *self, bool active) > { > MirrorOp *op; > > QTAILQ_FOREACH(op, &s->ops_in_flight, next) { > + if (self == op) { > + continue; > + } But this is the obvious fix. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org