From patchwork Tue Jan 15 16:19:38 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 212217 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 1AD6A2C00A5 for ; Wed, 16 Jan 2013 03:20:05 +1100 (EST) Received: from localhost ([::1]:55761 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tv9F5-0005bV-Gj for incoming@patchwork.ozlabs.org; Tue, 15 Jan 2013 11:20:03 -0500 Received: from eggs.gnu.org ([208.118.235.92]:53908) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tv9Ev-0005bO-Jb for qemu-devel@nongnu.org; Tue, 15 Jan 2013 11:19:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Tv9Ek-0004oB-Hm for qemu-devel@nongnu.org; Tue, 15 Jan 2013 11:19:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:11786) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Tv9Ek-0004o1-2I for qemu-devel@nongnu.org; Tue, 15 Jan 2013 11:19:42 -0500 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r0FGJf0L004180 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 15 Jan 2013 11:19:41 -0500 Received: from localhost (ovpn-112-16.ams2.redhat.com [10.36.112.16]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r0FGJdrZ008484; Tue, 15 Jan 2013 11:19:40 -0500 From: Stefan Hajnoczi To: Date: Tue, 15 Jan 2013 17:19:38 +0100 Message-Id: <1358266778-14621-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Kevin Wolf , Stefan Hajnoczi , "Michael S. Tsirkin" Subject: [Qemu-devel] [PATCH] dataplane: avoid reentrancy during virtio_blk_data_plane_stop() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org When dataplane is stopping, the s->vdev->binding->set_host_notifier(..., false) call can invoke the virtqueue handler if an ioeventfd notification is pending. This causes hw/virtio-blk.c to invoke virtio_blk_data_plane_start() before virtio_blk_data_plane_stop() returns! The result is that we try to restart dataplane while trying to stop it and the following assertion is raised: msix_set_mask_notifier: Assertion `!dev->msix_mask_notifier' failed. Although the code was intended to prevent this scenario, the s->started boolean isn't enough. Add s->stopping so that we can postpone clearing s->started until we've completely stopped dataplane. This way, virtqueue handler calls during virtio_blk_data_plane_stop() are ignored. When dataplane is legitimately started again later we already self-kick ourselves to resume processing. Signed-off-by: Stefan Hajnoczi --- hw/dataplane/virtio-blk.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c index 4b26faa..3f2da22 100644 --- a/hw/dataplane/virtio-blk.c +++ b/hw/dataplane/virtio-blk.c @@ -40,6 +40,7 @@ typedef struct { struct VirtIOBlockDataPlane { bool started; + bool stopping; QEMUBH *start_bh; QemuThread thread; @@ -357,7 +358,7 @@ static void *data_plane_thread(void *opaque) do { event_poll(&s->event_poll); - } while (s->started || s->num_reqs > 0); + } while (!s->stopping || s->num_reqs > 0); return NULL; } @@ -486,10 +487,10 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) { - if (!s->started) { + if (!s->started || s->stopping) { return; } - s->started = false; + s->stopping = true; trace_virtio_blk_data_plane_stop(s); /* Stop thread or cancel pending thread creation BH */ @@ -511,4 +512,6 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, false); vring_teardown(&s->vring); + s->started = false; + s->stopping = false; }