Bugzilla – Bug 1080488
Updating to libLLVM5 5.0.1-4.2 makes KDE unusable
Last modified: 2018-02-12 15:12:40 UTC
Yesterday after updating my Tumbleweed system, I realized I could not reboot via the the desktop (I'm on KDE). The normal logoff greeter would not appear and I would get a notification saying it had crashed. I rebooted my system by hitting ctrl-alt-F2 to get to a text console.
After the system rebooted, I could never get it to boot again, the mouse cursor would appear but instead of the logon page, it would only display a white background.
Booting from previous snapshots and installing updates for different things one by one, I managed to narrow it down to libLLVM5 5.0.1-4.2 (previous version was 5.0.1-4.1, and it worked fine). As soon as that gets updated, the desktop stops working normally and it will no longer boot again. Booting from the pre-update snapshot makes things work again.
This system is running an AMD FX-8350 CPU, 16GB of RAM and two Radeon 290X's.
I don't think libLLVM5 5.0.1-4.2 is the culprit here. The version 5.0.1-4.2 only differs from 5.0.1-4.1 by optimizations and fixes in the build process. Nothing changed in the final package.
Mesa uses LLVM for AMD cards and it is possible that changing LLVM invalidates the shader cache. There is a bug in Qt5 that causes bad rendering if shader caches entries are rejected. The symptom - white screen in place of sddm - also matches: bug 1080578
You can temporary solve it by deleting ~/.cache and /var/lib/sddm/.cache. However, if you upgrade or downgrade Mesa, it will come back and you have to delete the cache again. We are working on a fix and plan to release it before any update to Mesa.
If this workaround does not help, please reopen.
*** This bug has been marked as a duplicate of bug 1080578 ***