Re: [RESEND PATCH V10 13/15] monitor/hmp: Add holders support for hmp_info_iothreads

On Tue, Jul 21, 2026 at 8:51 PM Markus Armbruster <[email protected]> wrote:
>
> Zhang Chen <[email protected]> writes:
>
> > Exposed the iothread holders via the Human Monitor Interface (HMP)
> > command 'info iothreads' to assist with manual debugging and
> > performance tuning.
> >
> > Signed-off-by: Zhang Chen <[email protected]>
> > ---
> >  monitor/hmp-cmds.c | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> >
> > diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> > index e9fb8d827a..cd2d9c1d59 100644
> > --- a/monitor/hmp-cmds.c
> > +++ b/monitor/hmp-cmds.c
> > @@ -240,11 +240,33 @@ void hmp_info_iothreads(Monitor *mon, const QDict *qdict)
> >      IOThreadInfoList *info_list = qmp_query_iothreads(NULL);
> >      IOThreadInfoList *info;
> >      IOThreadInfo *value;
> > +    IOThreadHolderList *h;
> >
> >      for (info = info_list; info; info = info->next) {
> >          value = info->value;
> >          monitor_printf(mon, "%s:\n", value->id);
> >          monitor_printf(mon, "  thread_id=%" PRId64 "\n", value->thread_id);
> > +        monitor_printf(mon, "  holders=");
>
> This is unconditional.
>
> > +        if (value->holders) {
> > +            for (h = value->holders; h; h = h->next) {
> > +                IOThreadHolder *holder = h->value;
> > +
> > +                switch (holder->type) {
> > +                case IO_THREAD_HOLDER_KIND_BLOCK_EXPORT:
> > +                    monitor_printf(mon, "[block-export: %s]",
> > +                                   holder->u.block_export.export_name);
> > +                    break;
> > +                case IO_THREAD_HOLDER_KIND_QOM_OBJECT:
> > +                    monitor_printf(mon, "[qom-path: %s]",
> > +                                   holder->u.qom_object.qom_path);
> > +                    break;
> > +                default:
> > +                    monitor_printf(mon, "[unknown]");
> > +                    break;
> > +                }
> > +            }
> > +            monitor_printf(mon, "\n");
>
> This isn't.  Results in messed-up output when there are no holders:
>
>     $ qemu-system-x86_64 -S -display none -monitor stdio -object iothread,id=iot0
>     QEMU 11.0.90 monitor - type 'help' for more information
>     (qemu) info iothreads
>     iot0:
>       thread_id=1035908
>       holders=  poll-max-ns=32768
>       poll-grow=2
>       poll-shrink=2
>       poll-weight=3
>       aio-max-batch=0
>
> There's no need for a conditional here, the loop does nothing just fine
> when the list is empty.

OK, will not display when the holders is absent.

Thanks
Chen

>
> > +        }
> >          monitor_printf(mon, "  poll-max-ns=%" PRId64 "\n", value->poll_max_ns);
> >          monitor_printf(mon, "  poll-grow=%" PRId64 "\n", value->poll_grow);
> >          monitor_printf(mon, "  poll-shrink=%" PRId64 "\n", value->poll_shrink);
>