From: Dmitrii Gavrilov <ds-g...@yandex-team.ru>
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>
Message-ID: <20231103105602.90475-1-ds-g...@yandex-team.ru>
Fixes: 7bed89958bf ("device_core: use drain_call_rcu in in qmp_device_add",
2020-10-12)
Cc: qemu-sta...@nongnu.org
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
(cherry picked from commit 012b170173bcaa14b9bc26209e0813311ac78489)
Signed-off-by: Michael Tokarev <m...@tls.msk.ru>
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index 4b0ef65780..f4348443b0 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -853,19 +853,18 @@ 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;
}
--
2.39.2
