On 2 laptops with Radeon graphics, all things related to Plasma panel (taskbar, clock, launcher, tray) freeze for an indefinite period of time; actually hang, they may start working again. The processor usage stays at 0, and Plasma can also be triggered to work correctly again: - press Ctrl+Alt+F1 and Ctrl+Alt+F7 again - press Alt+shift+f12 to change compositing settings - restart process plasmashell Other functions appear to work correctly (Alt+Tab switches windows correctly, Alt+CapsLock switches the input language, although the indicator remains still). May be Radeon related, doesn't happen on other computers with Intel or Nvidia graphics. Also seems more likely to happen if an video is displayed in a browser, but may not be relevant. Both on Debian Testing and Unstable.
More notes: - Alt+F2 (Krunner) works correctly during this type of freeze - right click on the desktop has no effect and the small square with three lines on the upper left doesn't work (but showing the window list by moving the cursor in the corner works correctly).
plasmashell process can be stopped with "kill", there's no need for "kill -9", I just notice today.
Can you try the change suggested here: https://www.linuxquestions.org/questions/slackware-14/lags-and-freezes-on-ati-rs880-%5Bradeon-hd-4290%5D-with-new-xf86-video-ati-7-8-0-a-4175594206/ and report back.
*** This bug has been marked as a duplicate of bug 373427 ***