Re: [Qemu-devel] [RFC PATCH V4 0/4] Introduce COLO-compare

[Jason Wang]

On 2016年06月20日 11:27, Zhang Chen wrote:
> On 06/20/2016 11:03 AM, Jason Wang wrote:
> > On 2016年06月17日 10:25, Zhang Chen wrote:
> > > Hi~ jason.
> > >
> > > I tried a lot of ways to make it run in compare thread, but it not 
> > > work.
> > >
> > > Because that:
> > > void g_main_context_push_thread_default (GMainContext *context);
> > > Acquires context and sets it as the thread-default context for the 
> > > current thread.
> > >
> > > So, this function g_main_context_push_thread_default() just can set 
> > > thread-default context,
> > > not the global default context. and I can't find a function to set 
> > > global default context in glib.
> > > The qemu's QIOChannel uses g_source_attach(source, NULL); to attach 
> > > GSource.
> > > g_source_attach (GSource *source,
> > >                  GMainContext *context);
> > >
> > > context
> > > a GMainContext (if NULL, the default context will be used).
> > >
> > > But he not say "the default context" is global default context or 
> > > thread-default context.
> > > So I read glib codes find that:
> > > guint
> > > g_source_attach (GSource *source,
> > >                  GMainContext *context)
> > > {
> > > .....
> > > if (!context)
> > >     context = g_main_context_default ();
> > > .....
> > > }
> > >
> > > g_main_context_default ()
> > > Returns the global default main context.
> > >
> > > So...I think we can't make qemu_chr_add_handlers() run in colo 
> > > thread in this way.
> > > Do you have any comments about that? 
> >
> > How about (like I suggest previously) just use
> >
> > g_souce_attach(x, g_main_context_get_thread_default());
> >
> > in qemu's QIOChannel code?
>
> I feel it seems can work, and will try it.
> but I don't know how this change in qemu's QIOChannel code
> will affect the other code. needs other people confirm it?

Yes, we need convince them. I believe we don't do this in the past is 
because there's no users.

> If no affect and works good,I will send a independent patch
> for this.

Right, if it works, please send a RFC and explain why it is needed.

Thanks

> Thanks
> Zhang Chen