[PATCH xf86-video-ati] Only change Set/MoveCursor hooks from what we expect

[Mario Kleiner]

On 03/07/2018 09:50 AM, Michel Dänzer wrote:
> On 2018-03-07 04:45 AM, Mario Kleiner wrote:
>> On 03/05/2018 10:56 PM, Alex Deucher wrote:
>>> On Mon, Mar 5, 2018 at 12:44 PM, Michel Dänzer <michel at daenzer.net>
>>> wrote:
>>>> From: Michel Dänzer <michel.daenzer at amd.com>
>>>>
>>>> Since xf86CursorCloseScreen runs after RADEONCloseScreen_KMS,
>>>> PointPriv->spriteFuncs doesn't point to the same struct in the latter as
>>>> in RADEONCursorInit_KMS. So we were restoring info->Set/MoveCursor to
>>>> the wrong struct. Then in the next server generation,
>>>> info->Set/MoveCursor would end up pointing to
>>>> drmmode_sprite_set/move_cursor, resulting in an infinite loop if one of
>>>> them was called.
>>>>
>>>> To avoid this, only change the Set/MoveCursor hooks if their values
>>>> match our expectations, otherwise leave them as is. This is kind of a
>>>> hack, but the alternative would be invasive and thus risky changes to
>>>> the way we're wrapping CloseScreen, and it's not even clear that can
>>>> work without changing xserver code.
>>>>
>>>> Fixes: 1fe8ca75974c ("Keep track of how many SW cursors are visible on
>>>>                         each screen")
>>>> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
>>>
>>> Acked-by: Alex Deucher <alexander.deucher at amd.com>
>>>
>>
>> Nope, not quite, unfortunately. Tested against x-server master, mesa
>> master, ati-ddx master, with sddm login manager. With a freshly started
>> server, now on a dual-x-screen setup, instead of an infinite loop, i get
>> a server crash as soon as i move the mouse cursor from X-Screen 0 to
>> X-Screen 1:
> 
> Well, that's not the same issue I was seeing after all. I'll take
> another look.
> 
> 

Bedtime here, but fwiw from some debug statements i added, it seems as 
if on dual-x-screen init, x-screen 1 somehow inherits the 
PointPriv->spriteFuncs->SetCursor = drmmode_sprite_set_cursor assignment 
done on x-screen 0, and therefore already has it == 
drmmode_sprite_set_cursor, so during RADEONCursorInit_KMS for x-screen 1 
the assignments get skipped, which leaves the info->SetCursor for 
x-screen 1 == NULL. Therefore cursor update for x-screen 1 = boom!

-mario