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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 A02C1C49ED7 for ; Fri, 13 Sep 2019 11:00:27 +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 786592084F for ; Fri, 13 Sep 2019 11:00:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 786592084F 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]:42404 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8jJS-0003qH-Ly for qemu-devel@archiver.kernel.org; Fri, 13 Sep 2019 07:00:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40975) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i8jHx-0002Ow-IE for qemu-devel@nongnu.org; Fri, 13 Sep 2019 06:58:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i8jHv-0002gg-Lm for qemu-devel@nongnu.org; Fri, 13 Sep 2019 06:58:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44138) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i8jHt-0002f8-34; Fri, 13 Sep 2019 06:58:49 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6D3E010CC1E2; Fri, 13 Sep 2019 10:58:48 +0000 (UTC) Received: from dritchie.redhat.com (unknown [10.33.36.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id 43CA760C57; Fri, 13 Sep 2019 10:58:39 +0000 (UTC) From: Sergio Lopez To: qemu-block@nongnu.org Date: Fri, 13 Sep 2019 12:56:27 +0200 Message-Id: <20190913105626.22353-1-slp@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.65]); Fri, 13 Sep 2019 10:58:48 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2] virtio-blk: schedule virtio_notify_config to run on main context 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, Sergio Lopez , mst@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" virtio_notify_config() needs to acquire the global mutex, which isn't allowed from an iothread, and may lead to a deadlock like this: - main thead * Has acquired: qemu_global_mutex. * Is trying the acquire: iothread AioContext lock via AIO_WAIT_WHILE (after aio_poll). - iothread * Has acquired: AioContext lock. * Is trying to acquire: qemu_global_mutex (via virtio_notify_config->prepare_mmio_access). If virtio_blk_resize() is called from an iothread, schedule virtio_notify_config() to be run in the main context BH. Signed-off-by: Sergio Lopez --- Changelog v2: - Use aio_bh_schedule_oneshot instead of scheduling a coroutine (thanks Kevin Wolf). - Switch from RFC to v2 patch. --- hw/block/virtio-blk.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 18851601cb..669dc60f5b 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -16,6 +16,7 @@ #include "qemu/iov.h" #include "qemu/module.h" #include "qemu/error-report.h" +#include "qemu/main-loop.h" #include "trace.h" #include "hw/block/block.h" #include "hw/qdev-properties.h" @@ -1086,11 +1087,29 @@ static int virtio_blk_load_device(VirtIODevice *v= dev, QEMUFile *f, return 0; } =20 +static void virtio_resize_cb(void *opaque) +{ + VirtIODevice *vdev =3D opaque; + + assert(qemu_get_current_aio_context() =3D=3D qemu_get_aio_context())= ; + virtio_notify_config(vdev); +} + static void virtio_blk_resize(void *opaque) { VirtIODevice *vdev =3D VIRTIO_DEVICE(opaque); =20 - virtio_notify_config(vdev); + if (qemu_get_current_aio_context() !=3D qemu_get_aio_context()) { + /* + * virtio_notify_config() needs to acquire the global mutex, + * so it can't be called from an iothread. Instead, schedule + * it to be run in the main context BH. + */ + aio_bh_schedule_oneshot(qemu_get_aio_context(), + virtio_resize_cb, vdev); + } else { + virtio_notify_config(vdev); + } } =20 static const BlockDevOps virtio_block_ops =3D { --=20 2.21.0