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device_core: use drain_call_rcu in in qmp_device_add

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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 <mlevitsk@redhat.com>
Suggested-by: Stefan Hajnoczi <stefanha@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200913160259.32145-4-mlevitsk@redhat.com>
[Don't use it in qmp_device_del. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Maxim Levitsky 2020-10-06 14:38:58 +02:00 committed by Paolo Bonzini
parent 7a8202c521
commit 7bed89958b
1 changed files with 12 additions and 0 deletions
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12
softmmu/qdev-monitor.c
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@ -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;