Hi,

On my EVO 15, running Slimbook OS with GNOME, video playback in Firefox sometimes causes the entire system to become extremely slow and unresponsive (I'm talking seconds of input latency on mouse movements, every animation being very slow and dropping frames... it seems like the entire GUI runs at barely one fps). This happens seemingly randomly, sometimes multiple times in a day, sometimes not at all. I've had the issue with at least three different video codecs (AV1, VP9 and HEVC) but others may be affected. The issue never occurred outside of video playback.

When the freeze happens, nothing appears in the syslog. There is still plenty of free RAM, and the CPU isn't at 100%. The only thing a bit weird : at any point one kthread seems to be using of full CPU core, but it alternates between a few ones, including at least kworker/u64:0-flush-259:0 and kworker/u64:5+events_unbound. The specific thread that shows up changes, but it's always just one using ~100% (out of 16000%) CPU, as reported by GNOME's system monitor.

I've tried to recover in a few ways : first of course restarting firefox, but even after it's closed the system remains in this state. Logging out then back in doesn't help either. I even tried to terminate every process with sysrq (tried both e and i) but even after the entire DE is restarted the issue is still the same. Only a full reboot can restore the machine to a usable state.

After the reboot, nothing seems out of place in the syslog or dmesg, it's as if nothing ever happened. The only log that I was able to get : when killing everything with sysrq e, after gnome is terminated the kernel output becomes visible and there, just one line : 

workqueue: drm_fb_helper_damage_work hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND

This line appeared twice, with just the amount of "times" being incremented between the two lines.

The fans are no ramping up, and the laptop does not seem hot to the touch (at least not more than when it's in use).

Has anyone had a similar issue before ?

Thanks.