Re: [Qemu-devel] [Qemu-block] [PATCH RFC v3 4/8] block: convert ThrottleGroup to object with QOM

[Manos Pitsidianakis]

On Mon, Jun 26, 2017 at 03:52:34PM +0100, Stefan Hajnoczi wrote:
> On Fri, Jun 23, 2017 at 03:46:56PM +0300, Manos Pitsidianakis wrote:
> > +static bool throttle_group_exists(const char *name)
> > +{
> > +    ThrottleGroup *iter;
> > +    bool ret = false;
> > +
> > +    qemu_mutex_lock(&throttle_groups_lock);
>
> Not sure if this lock or the throttle_groups list are necessary.
>
> Have you seen iothread.c:qmp_query_iothreads()?  All objects are put
> into a container (the parent object), so you can just iterate over its
> children.  There's no need for a separate list because QOM already has
> all the objects.

> > +static void throttle_group_obj_complete(UserCreatable *obj, Error **errp)
> > +{
> > +    char *name = NULL;
> > +    Error *local_error = NULL;
> > +    ThrottleGroup *tg = THROTTLE_GROUP(obj);
> > +
> > +    name = object_get_canonical_path_component(OBJECT(obj));
> > +    if (throttle_group_exists(name)) {
> > +        error_setg(&local_error, "A throttle group with this name already \
> > +                                  exists.");
> > +        goto ret;
> > +    }
>
> QOM should enforce unique id=<ID>.  I don't think this is necessary.
>
> > +
> > +    qemu_mutex_lock(&throttle_groups_lock);
> > +    tg->name = name;
> > +    qemu_mutex_init(&tg->lock);
> > +    QLIST_INIT(&tg->head);
> > +    QTAILQ_INSERT_TAIL(&throttle_groups, tg, list);
> > +    tg->refcount++;
> > +    qemu_mutex_unlock(&throttle_groups_lock);
> > +

Sorry for the multiple replies but I just remembered this.

This is necessary because throttle groups are created by other 
interfaces as well. Of course block/throttle-groups.c could use only QOM 
objects internally to eliminate the housekeeping.

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