Re: [Qemu-devel] [PATCH v4 17/20] console: make screendump asynchronous

[Gerd Hoffmann]

> > > +        /*
> > > +         * FIXME: async save with coroutine? it would have to copy or
> > > +         * lock the surface.
> > > +         */
> > > +        ppm_save(dump->filename, surface, &err);
> >
> > DisplaySurface is just a thin layer above pixman images these days.
> > Pixman images are reference counted, so you can
> > pixman_image_ref(surface->image) to make sure it doesn't disappear
> > underneath you, then pass the pixman image to ppm_save.
> 
> ppm_save() is still synchronous. I suppose you suggested that for a
> future async version.

Yes.

> (note that in this case, ref the surface is
> probably not sufficient, as it could be mutated while it is being
> saved)

That can happen anyway.  The display surface / pixman image can be backed
by guest-writable memory (stdvga vram for example) and even when holding
the qemu lock the guest vcpu can write there ...

cheers,
  GerdY