[PATCH] Flush buffer in time for global (un)lock xserver operation

[walter harms]

Am 12.12.2019 03:13, schrieb Chen Gang:
>> On Wed, 2019-12-04 at 18:24 +0800, chengang at emindsoft.com.cn wrote:
>>> From: Chen Gang <chengang at emindsoft.com.cn>
>>>
>>> The global (un)lock xserver operations will have effect to the whole
>>> system, and all the other gui apps have to be blocked, so the operations
>>> should not be buffered, or may cause sync issue, e.g. reboot machine.
>>
>> Enh. I can maybe see the point of this for XUngrabServer, but I think
>> doing this for XGrabServer may actually make interactivity worse. With
>> the code as it is currently, the GrabServer request will be buffered
>> inside the client until something happens to flush it out (presumably
>> something like QueryTree or GetImage that provokes a reply), and while
>> it stays buffered other clients may still interact with the server.
>> With this change you'll immediately write the request to the server,
>> and you might lose your scheduler timeslice as a result, in which case
>> not only will the grabbing client need to wait to reschedule but every
>> other client will need to wait in line behind the grabbing client.
>>
> 
> Oh, for me, what you said is reasonable. I got the issue because the
> XUngrabServer did not call _XFlush() immediately.
> 
> _XFlush for XGrabServer is not necesscary for my current issue, either
> not good for the performance.
> 
> Originally, I felt XGrabServer and XUngrabServer were a pair, and I was
> not quite sure enought. So I used _XFlush for both of them (it must be
> safe enough, altough it has negative effect with the performance).
> 
>> Do you have a scenario in mind that this helps with? Does doing _XFlush
>> only for XUngrabServer work just as well?
>>
> 
> At least for me, _XFlush only for XUngrabServer should be work well.
> 
> Welcome you to apply the patch with the new modification (only _XFlush
> for UngrabServer).
> 

short version,
  can you provide an example works.c vs. not_works.c ?

re,
 wh



> By the way, I can not join in xorg-devel at lists.x.org mailing list. I
> tried, but got "No ReCAPTCHA response provided". Welcome any ideas about it.
> 
> Thanks.
> 
> 
> _______________________________________________
> xorg-devel at lists.x.org: X.Org development
> Archives: http://lists.x.org/archives/xorg-devel
> Info: https://lists.x.org/mailman/listinfo/xorg-devel