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modesetting: Fix VRR window property handling. 

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>
This commit is contained in:
Mario Kleiner 2021-08-27 19:27:29 +02:00
parent 18d3131f9a
commit ab86be0ed9
1 changed files with 3 additions and 2 deletions
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5
hw/xfree86/drivers/modesetting/driver.c
View File

@ -751,14 +751,15 @@ ms_change_property(ClientPtr client)
client->requestVector[X_ChangeProperty] = saved_change_property;
ret = saved_change_property(client);
if (ret != Success)
return ret;
if (restore_property_vector)
return ret;
client->requestVector[X_ChangeProperty] = ms_change_property;
if (ret != Success)
return ret;
ret = dixLookupWindow(&window, stuff->window, client, DixSetPropAccess);
if (ret != Success)
return ret;