iotests: add 238 for throttling tgm unregister iothread segfault

Hot-unplug a scsi-hd using an iothread.  The previous patch fixes a
segfault in this scenario.

This patch adds a regression test.

Suggested-by: Alberto Garcia <berto@igalia.com>
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20190114133257.30299-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/238

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+#
+# Regression test for throttle group member unregister segfault with iothread
+#
+# Copyright (c) 2019 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import sys
+import os
+import iotests
+from iotests import log
+
+sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'scripts'))
+
+from qemu import QEMUMachine
+
+if iotests.qemu_default_machine == 's390-ccw-virtio':
+    virtio_scsi_device = 'virtio-scsi-ccw'
+else:
+    virtio_scsi_device = 'virtio-scsi-pci'
+
+vm = QEMUMachine(iotests.qemu_prog)
+vm.add_args('-machine', 'accel=kvm')
+vm.launch()
+
+log(vm.qmp('blockdev-add', node_name='hd0', driver='null-co'))
+log(vm.qmp('object-add', qom_type='iothread', id='iothread0'))
+log(vm.qmp('device_add', id='scsi0', driver=virtio_scsi_device, iothread='iothread0'))
+log(vm.qmp('device_add', id='scsi-hd0', driver='scsi-hd', drive='hd0'))
+log(vm.qmp('block_set_io_throttle', id='scsi-hd0', bps=0, bps_rd=0, bps_wr=0,
+           iops=1000, iops_rd=0, iops_wr=0, conv_keys=False))
+log(vm.qmp('device_del', id='scsi-hd0'))
+
+vm.shutdown()

tests/qemu-iotests/238.out

@@ -0,0 +1,6 @@
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}
+{"return": {}}

tests/qemu-iotests/group

@@ -234,3 +234,4 @@
 234 auto quick migration
 235 auto quick
 236 auto quick
+238 auto quick