Full-screen youtube hangs desktop

[Dave Jones]

On the current Mantic beta images of Ubuntu Desktop for Raspberry Pi, running on a Raspberry Pi 4B (either 4GB or 8GB), while attempting to play a YouTube video (as part of the ISO test procedure), attempting to switch the video to full-screen resulted in a hang of the desktop.

More precisely, I could still pause and resume the video with the spacebar (audio could be heard stopping or playing accordingly) but the display was frozen entirely, including the mouse pointer and I was unable to recover the desktop (attempting to switch to another virtual console with Ctrl+ a function key was unsuccessful, attempting keyboard shortcuts to shut down firefox, etc).

At the point that the desktop freezes the following messages appeared in journalctl (obtained over SSH):

Sep 21 22:05:52 miss-piggy kernel: vc4-drm gpu: swiotlb buffer is full (sz: 524288 bytes), total 32768 (slots), used 2104 (slots)
Sep 21 22:05:52 miss-piggy kernel: vc4-drm gpu: swiotlb buffer is full (sz: 524288 bytes), total 32768 (slots), used 2040 (slots)

The system is still responsive inasmuch as I can connect via SSH and kill the firefox process, but the desktop remains inaccessible. So far the only thing I've found that can bring it back is restarted the gdm service (effectively killing the running desktop) over SSH.

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
https://iso.qa.ubuntu.com/qatracker/reports/bugs/2037019

[Dave Jones (waveform)]

Also fixed in the currently daily, on both Pi 4 and 5. The recent of release of mutter is likely to have been the fix in this case (according to @vanvugt).