Original goal of addition of drain_call_rcu to qmp_device_add was to cover
the failure case of qdev_device_add. It seems call of drain_call_rcu was
misplaced in 7bed89958bfbf40df what led to waiting for pending RCU callbacks
under happy path too. What led to overall performance degradation of
qmp_device_add.
In this patch call of drain_call_rcu moved under handling of failure of
qdev_device_add.
Signed-off-by: Dmitrii Gavrilov <ds-g...@yandex-team.ru>
---
system/qdev-monitor.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c
index 1b8005a..dc7b02d 100644
--- a/system/qdev-monitor.c
+++ b/system/qdev-monitor.c
@@ -856,19 +856,18 @@ 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) {
+ /*
+ * 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();
+
qemu_opts_del(opts);
return;
}
--
2.34.1
