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

[Jason Wang <jasowang@redhat.com>]

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