A misplaced error check can cause this failure scenario, and does
so reliably as tested on Ubuntu 21.04 with KDE Plasma 5 desktop
within the first few seconds of login session startup, rendering
VRR under modesetting-ddx unusable:
1. Some X11 client application changes some window property.
2. ms_change_property() is called as part of the property change
handling call chain (client->requestVector[X_ChangeProperty]).
It removes itself temporarily from the call chain - or so it
thinks, hooking up saved_change_property instead.
3. ret = saved_change_property(client) is called and fails
temporarily for some non-critical reason.
4. The misplaced error check returns early (error abort), without
first restoring ms_change_property() as initial X_ChangeProperty
handler in the call chain again.
-> Now ms_change_property() has removed itself permanently from the
property handler call chain for the remainder of the X session
and VRR property changes on windows are no longer handled, ie.
VRR no longer gets enabled/disabled in response to window VRR
property changes.
Place the error check at the proper place, just as it is correctly
done by amdgpu-ddx, and in modesetting-ddx ms_delete_property()
function.
Verified to fix VRR handling with an AMD gpu under KDE desktop
session.
Please consider merging before branching the server 1.21 branch.
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
ab86be0ed9