Created attachment 1509890 [details]
Xorg.0.log - with the working kernel

Description of problem:

I have identical symptoms on two machines (which have identical hardware).

After updating to any of the 4.19.x kernels, on the desktop (which is XFCE), it appears that nothing happens when you click. Sometimes, the expected action happens a lot later. However, experimenting shows that it's actually a refresh problem. If you switch to a virtual console and switch back, then what you expected to see is there. If you leave it for the screensaver to start, then the mouse is actually constrained to the xscreensaver dialog even whilst you think you're still looking at the desktop. If you type in the password to unlock the screensaver, you don't see the desktop, but the mouse is released (you'll see it if you switch away and back).

If I reboot on the latest 4.18.18 kernel, it returns to working fine (as it always did - one of these machines began life on Fedora 27; the other is a completely fresh Fedora 29 install).

Version-Release number of selected component (if applicable):

kernel-4.19.4-300.fc29.x86_64 (and the earlier 4.19 kernels too).

How reproducible:

Every time. (And never on the older kernel).

Steps to Reproduce:
1. Log in to desktop.
2. Perform any action that should cause something different to appear on the screen.

Actual results:

In a desktop environment, the amount of time for the screen to update can vary from a few seconds to very many (I gave up waiting after a while). If you force a refresh somehow (e.g. switch to virtual console and return) you'll see what you expected.

Expected results:

Normal screen refresh.

Additional info:

- No errors are logged in ~/.xsession-errors .

- I have attached Xorg.0.log for both the working and non-working scenarios.

- I haven't seen anything like this happen on the greeter screen (lightdm)

- Happens on all logins, including newly-created ones