On Mon, May 11, 2020 at 07:09:47PM +0300, Maxim Levitsky wrote:
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index d87d989e72..ef47cb2d9c 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -3,6 +3,8 @@
>  
>  #include "qemu/queue.h"
>  #include "qemu/bitmap.h"
> +#include "qemu/rcu.h"
> +#include "qemu/rcu_queue.h"
>  #include "qom/object.h"
>  #include "hw/hotplug.h"
>  #include "hw/resettable.h"
> @@ -230,6 +232,7 @@ struct BusClass {
>  };
>  
>  typedef struct BusChild {
> +    struct rcu_head rcu;
>      DeviceState *child;
>      int index;
>      QTAILQ_ENTRY(BusChild) sibling;

Please add a doc comment to struct BusState saying the children field is
an RCU QTAILQ and writers must hold the QEMU global mutex.

Stefan