From nobody Wed Nov 12 03:45:33 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1568633212; cv=none; d=zoho.com; s=zohoarc; b=oOG2P+I5vUfMlxOrtUgtVXdpyd6A3GIvGkewr8yoqWjNqHEUlfEt9ia6HGu+HEJELEAvjDNQU37WKVDWRgvygaCzDdUsHWfN3kfC4xLlXQOXTpjZ2tz3xRy/4d1CgrOsoXOr14E+OBfu3K/eL+kphQ4ysDiktUMuPoV2XinVOHY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1568633212; h=Content-Transfer-Encoding:Cc:Date:From:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:To:ARC-Authentication-Results; bh=GTtyU19pXuVA/SuY+sJj1gWZgfn8eOJbesTGSc7j+tQ=; b=Xj+BJUrsZHJ6nHRQcK5IRVnJ9qVJGsUCeIvtqeWxuqFQ8SBPPPYqGKjcM2spFwDTqiUA2Sgzn9UL/9TK9/Dq3sUhahs94wYD8+awjC4A42/jHshMiHzFsn9mAfOgwGapFubka36V+d1JIKgMubVioS1zM0bOv71tR7COBs2g9t8= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (209.51.188.17 [209.51.188.17]) by mx.zohomail.com with SMTPS id 1568633212777943.2846175196987; Mon, 16 Sep 2019 04:26:52 -0700 (PDT) Received: from localhost ([::1]:32990 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i9p9X-0006Vf-UV for importer@patchew.org; Mon, 16 Sep 2019 07:26:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54157) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i9p8R-0005zg-C3 for qemu-devel@nongnu.org; Mon, 16 Sep 2019 07:25:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i9p8Q-0006xF-86 for qemu-devel@nongnu.org; Mon, 16 Sep 2019 07:25:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2827) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i9p8M-0006va-Rz; Mon, 16 Sep 2019 07:25:30 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C588F4E926; Mon, 16 Sep 2019 11:25:29 +0000 (UTC) Received: from dritchie.redhat.com (unknown [10.33.36.134]) by smtp.corp.redhat.com (Postfix) with ESMTP id 146FA5D9DC; Mon, 16 Sep 2019 11:25:20 +0000 (UTC) From: Sergio Lopez To: qemu-block@nongnu.org Date: Mon, 16 Sep 2019 13:24:12 +0200 Message-Id: <20190916112411.21636-1-slp@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 16 Sep 2019 11:25:29 +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 v3] 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Kevin Wolf --- Changelog v3: - Unconditionally schedule the work to be done in the main context BH (thanks John Snow and Kevin Wolf). 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 | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 18851601cb..0163285f6f 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 +1087,25 @@ static int virtio_blk_load_device(VirtIODevice *vde= v, 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); + /* + * 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); } =20 static const BlockDevOps virtio_block_ops =3D { --=20 2.21.0