From: Sergio Lopez <s...@redhat.com>
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
<kw...@redhat.com>.
--Stefan]
Signed-off-by: Sergio Lopez <s...@redhat.com>
Reviewed-by: Kevin Wolf <kw...@redhat.com>
Message-id: 20190916112411.21636-1-...@redhat.com
Message-Id: <20190916112411.21636-1-...@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
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 = {
--
2.21.0
