Re: [Qemu-devel] [PATCH 1/3] iothread: provide helpers for internal use

[Daniel P. Berrange]

On Fri, Sep 22, 2017 at 05:14:30PM +0800, Peter Xu wrote:
> On Fri, Sep 22, 2017 at 10:04:33AM +0100, Daniel P. Berrange wrote:
> > On Fri, Sep 22, 2017 at 04:56:10PM +0800, Peter Xu wrote:
> > > IOThread is a general framework that contains IO loop environment and a
> > > real thread behind.  It's also good to be used internally inside qemu.
> > > Provide some helpers for it to create iothreads to be used internally.
> > > 
> > > Signed-off-by: Peter Xu <address@hidden>
> > > ---
> > >  include/sysemu/iothread.h |  8 ++++++++
> > >  iothread.c                | 21 +++++++++++++++++++++
> > >  2 files changed, 29 insertions(+)
> > > 
> > > diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
> > > index d2985b3..b07663f 100644
> > > --- a/include/sysemu/iothread.h
> > > +++ b/include/sysemu/iothread.h
> > > @@ -46,4 +46,12 @@ AioContext *iothread_get_aio_context(IOThread 
> > > *iothread);
> > >  void iothread_stop_all(void);
> > >  GMainContext *iothread_get_g_main_context(IOThread *iothread);
> > >  
> > > +/*
> > > + * Helpers used to allocate iothreads for internal use.  These
> > > + * iothreads will not be seen by monitor clients when query using
> > > + * "query-iothreads".
> > > + */
> > > +IOThread *iothread_create(const char *id, Error **errp);
> > > +void iothread_destroy(IOThread *iothread);
> > > +
> > >  #endif /* IOTHREAD_H */
> > > diff --git a/iothread.c b/iothread.c
> > > index 44c8944..74e400c 100644
> > > --- a/iothread.c
> > > +++ b/iothread.c
> > > @@ -354,3 +354,24 @@ GMainContext *iothread_get_g_main_context(IOThread 
> > > *iothread)
> > >  
> > >      return iothread->worker_context;
> > >  }
> > > +
> > > +static Object *iothread_get_internal_parent(void)
> > > +{
> > > +    return container_get(object_get_root(), "/internal-iothreads");
> > > +}
> > 
> > I tend to think we might benefit from having this generalized in the
> > QOM API instead. We have object_get_objects_root() for things that
> > are created by the mgmt app / user via CLI / QMP.  A parallel method
> > object_get_internal_root() could be useful for cases like this where
> > we want to create user-creatable objects, but not have them be
> > visible to the mgmt app / user, as that would confuse the mgmt app.
> > 
> > Example for this scenario - libvirt calls query-iothreads to identify
> > IO thread PIDs, and would get very unhappy if the IOThread used by
> > the monitor would appear in that response, which is why Peter has
> > put it under /internal-iothreads. I think this scenario will apply
> > more broadly, so benefit from us having a general helper in QOM.
> 
> Yeah, I can split the patch if we want it to be exposed to public.
> 
> In that case, would the name "object_get_internal_root" be good?

Yeah that's fine with me, but lets see if Paolo has any thoughts from
the QOM side.

Regards,
Daniel
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