On Wed, Oct 18, 2017 at 05:31:15PM +0200, Stefan Hajnoczi wrote:
> On Mon, Oct 16, 2017 at 03:50:39PM +0800, Peter Xu wrote:
> > On Thu, Oct 12, 2017 at 01:50:45PM +0100, Stefan Hajnoczi wrote:
> > > On Fri, Sep 29, 2017 at 11:38:35AM +0800, Peter Xu wrote:
> > > > + qdict = qobject_to_qdict(req);
> > > > + if (qdict) {
> > > > + id = qdict_get(qdict, "id");
> > > > + qobject_incref(id);
> > > > + qdict_del(qdict, "id");
> > > > + } /* else will fail qmp_dispatch() */
> > > > +
> > > > + req_obj = g_new0(QMPRequest, 1);
> > > > + req_obj->mon = mon;
> > > > + req_obj->id = id;
> > > > + req_obj->req = req;
> > > > +
> > > > + /*
> > > > + * Put the request to the end of queue so that requests will be
> > > > + * handled in time order. Ownership for req_obj, req, id,
> > > > + * etc. will be delivered to the handler side.
> > > > + */
> > > > + g_queue_push_tail(mon->qmp_requests, req_obj);
> > > > +
> > > > + /* Kick the dispatcher routine */
> > > > + qemu_bh_schedule(mon_global.qmp_dispatcher_bh);
> > >
> > > How is thread-safety ensured when accessing qmp_requests?
> >
> > It's a GQueue. I assume GQueue is thread safe itself as long as
> > g_thread_init() is called?
>
> No, glib data structures are not automatically thread-safe unless the
> documentation says so.
>
> Here is the implementation where you can see that no locking is
> performed:
>
> void
> g_queue_push_tail (GQueue *queue,
> gpointer data)
> {
> g_return_if_fail (queue != NULL);
>
> queue->tail = g_list_append (queue->tail, data);
> if (queue->tail->next)
> queue->tail = queue->tail->next;
> else
> queue->head = queue->tail;
> queue->length++;
> }
Oops. Yes then I possibly need a lock... Thanks.
I think maybe I can rename the Monitor.out_lock into a more general
name, then to use it as a per-monitor lock (instead of introducing
another one).
--
Peter Xu
