From patchwork Wed Sep 25 17:44:00 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 11161167 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B47B21747 for ; Wed, 25 Sep 2019 17:46:35 +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 9502720872 for ; Wed, 25 Sep 2019 17:46:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9502720872 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:55502 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDBN3-0004gB-P8 for patchwork-qemu-devel@patchwork.kernel.org; Wed, 25 Sep 2019 13:46:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53404) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iDBL4-0002zF-Ox for qemu-devel@nongnu.org; Wed, 25 Sep 2019 13:44:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iDBL3-00038n-GF for qemu-devel@nongnu.org; Wed, 25 Sep 2019 13:44:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51046) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iDBL1-00036x-6j; Wed, 25 Sep 2019 13:44:27 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 7BE0285539; Wed, 25 Sep 2019 17:44:25 +0000 (UTC) Received: from localhost (ovpn-116-64.ams2.redhat.com [10.36.116.64]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8AC5961F40; Wed, 25 Sep 2019 17:44:16 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PULL 2/2] virtio-blk: schedule virtio_notify_config to run on main context Date: Wed, 25 Sep 2019 18:44:00 +0100 Message-Id: <20190925174400.8578-3-stefanha@redhat.com> In-Reply-To: <20190925174400.8578-1-stefanha@redhat.com> References: <20190925174400.8578-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 25 Sep 2019 17:44:25 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 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: Kevin Wolf , Peter Maydell , Sergio Lopez , qemu-block@nongnu.org, "Michael S. Tsirkin" , Max Reitz , Stefan Hajnoczi Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Sergio Lopez 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. [Removed unnecessary newline as suggested by Kevin Wolf . --Stefan] Signed-off-by: Sergio Lopez Reviewed-by: Kevin Wolf Message-id: 20190916112411.21636-1-slp@redhat.com Message-Id: <20190916112411.21636-1-slp@redhat.com> Signed-off-by: Stefan Hajnoczi --- hw/block/virtio-blk.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 18851601cb..ed2ddebd2b 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 +1087,24 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f, return 0; } +static void virtio_resize_cb(void *opaque) +{ + VirtIODevice *vdev = opaque; + + assert(qemu_get_current_aio_context() == qemu_get_aio_context()); + virtio_notify_config(vdev); +} + static void virtio_blk_resize(void *opaque) { VirtIODevice *vdev = VIRTIO_DEVICE(opaque); - 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); } static const BlockDevOps virtio_block_ops = {