From a72c9200fd70ca6e3c2a2232c1f27790dd891357 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 21 Jan 2013 17:16:52 +0100 Subject: [PATCH 2/5] dataplane: avoid reentrancy during virtio_blk_data_plane_stop() RH-Author: Stefan Hajnoczi Message-id: <1358788613-25421-2-git-send-email-stefanha@redhat.com> Patchwork-id: 47610 O-Subject: [PATCH RHEL6.4 qemu-kvm 1/2] dataplane: avoid reentrancy during virtio_blk_data_plane_stop() Bugzilla: 894995 RH-Acked-by: Paolo Bonzini RH-Acked-by: Miroslav Rezanina RH-Acked-by: Kevin Wolf RH-Acked-by: Laszlo Ersek 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 (cherry picked from commit cd7fdfe59f4f965665dcd9868fe3764f5256d6aa) Signed-off-by: Stefan Hajnoczi --- hw/dataplane/virtio-blk.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) Signed-off-by: Miroslav Rezanina --- hw/dataplane/virtio-blk.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c index 7703370..7d67e11 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; pthread_t thread; @@ -355,7 +356,7 @@ 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; } @@ -476,10 +477,10 @@ 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 */ @@ -501,4 +502,6 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, false); vring_teardown(&s->vring); + s->started = false; + s->stopping = false; } -- 1.7.1