[RFC] Fix attempt for Mesa + X-Server 1.20 + modesetting-ddx hangs on KDE5.

[Michel Dänzer]

On 2018-05-08 06:41 PM, Adam Jackson wrote:
> On Fri, 2018-05-04 at 15:45 +0200, Mario Kleiner wrote:
> 
>> The real problem, if i understand it correctly, is the way the life-time
>> of dri3_drawables and loader_dri3_drawables is managed atm. by Mesa's
>> bindContext() functions. Whenever glXMakeCurrent() etc. are called to
>> assign new/different GLXDrawables to the same context (ie. one context
>> reused for drawing into many different drawables, as opposed to using
>> one dedicated context for each drawable), we destroy the underlying
>> DRIDrawables/dri3_drawables_loader_dri3_drawables and they lose all
>> state wrt. pending bufferswaps, msc, sbc, ust.
> 
> That's utterly, utterly, utterly broken.
> 
>> Therefore one of these patches is either a good enough fix for the KDE
>> hang problems atm. or a diagnosis of the problem as a starting point for
>> brighter people to deal with the root cause ;-)
> 
> I'll see what I can come up with. I'm not sure there's a great fix for
> this that doesn't involve a few more roundtrips at MakeCurrent time,
> since we can lose drawables asynchronously, but such is life.

I had an idea, at least for SBC:

In dri3_destroy_drawable, store the drawable's send_sbc value in a hash
table (keyed on the XID) in struct dri3_screen. Then in
dri3_create_drawable, if there's an entry for the drawable's XID in the
hash table, initialize send_sbc and recv_sbc to that.

If nobody beats me to it, I'll try this tomorrow.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer