From 7bed89958bfbf40df9ca681cefbdca63abdde39d Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Tue, 6 Oct 2020 14:38:58 +0200 Subject: [PATCH] device_core: use drain_call_rcu in in qmp_device_add Soon, a device removal might only happen on RCU callback execution. This is okay for device-del which provides a DEVICE_DELETED event, but not for the failure case of device-add. To avoid changing monitor semantics, just drain all pending RCU callbacks on error. Signed-off-by: Maxim Levitsky Suggested-by: Stefan Hajnoczi Reviewed-by: Stefan Hajnoczi Message-Id: <20200913160259.32145-4-mlevitsk@redhat.com> [Don't use it in qmp_device_del. - Paolo] Signed-off-by: Paolo Bonzini --- softmmu/qdev-monitor.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c index e9b7228480..bcfb90a08f 100644 --- a/softmmu/qdev-monitor.c +++ b/softmmu/qdev-monitor.c @@ -803,6 +803,18 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp) return; } dev = qdev_device_add(opts, errp); + + /* + * Drain all pending RCU callbacks. This is done because + * some bus related operations can delay a device removal + * (in this case this can happen if device is added and then + * removed due to a configuration error) + * to a RCU callback, but user might expect that this interface + * will finish its job completely once qmp command returns result + * to the user + */ + drain_call_rcu(); + if (!dev) { qemu_opts_del(opts); return;