From e55ec34d3e459f1d0b77b1f7239be91638b57bd9 Mon Sep 17 00:00:00 2001 From: Dmitrii Gavrilov Date: Fri, 3 Nov 2023 13:56:02 +0300 Subject: [PATCH] system/qdev-monitor: move drain_call_rcu call under if (!dev) in qmp_device_add() 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 Message-ID: <20231103105602.90475-1-ds-gavr@yandex-team.ru> Fixes: 7bed89958bf ("device_core: use drain_call_rcu in in qmp_device_add", 2020-10-12) Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini (cherry picked from commit 012b170173bcaa14b9bc26209e0813311ac78489) Signed-off-by: Michael Tokarev --- softmmu/qdev-monitor.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c index 4b0ef657809..f4348443b05 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; } -- 2.39.5