Created attachment 1792381 [details]
journalctl --no-hostname -k -b

1. Please describe the problem:
The system (desktop computer) sometimes freezes (yes, the whole system) or the UI is sometimes slow (opening GNOME Shell takes multiple seconds), as if it is under a high-load (which is not the case for in 80% of the cases).

This only happens on this desktop PC here.

I then have to powercycle it, i.e. use the hardware button to force-kill it and reboot. It then takes some time, but usually one a day it always happens, if the computer was running for some time.

I am under the impression that it does only happen, when the computer was in standby for some time (and is then used again for some time), but that may be a random correlation (i.e. no cause).
I.e. it e.g. never happened for the first <5h of usage. It only happens after some time… (thus, also after a reboot everything is okay again.)

2. What is the Version-Release number of the kernel:
5.12.9-300.fc34.x86_64 #1 SMP Thu Jun 3 13:51:40 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

3. Did it work previously in Fedora? If so, what kernel version did the issue
   *first* appear?  Old kernels are available for download at
   https://koji.fedoraproject.org/koji/packageinfo?packageID=8 :
Yes, AFAIK this issue did not occur in Fedora 33. Don’t know an exact kernel version, however and I’m also not quite sure.
I took some time to observe this and I almost want to blame some hardware failure (the system and SSD is quite old), but even if that should turn out to be the case, the system should in any case not randomly freeze, but show some error or gracefully fail or so IMHO.

Note: Before reporting this I did a SMART check of the SSD and it is fine, so maybe I'm again misjudging.

4. Can you reproduce this issue? If so, please provide the steps to reproduce
   the issue below:
As described above I can reproduce it by using the device for some time, but I cannot identify an exact trigger. I do different and usual tasks.

5. Does this problem occur with the latest Rawhide kernel? To install the
   Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by
   ``sudo dnf update --enablerepo=rawhide kernel``:
Sorry, but I don’t want to test such unstable versions here.

6. Are you running any modules that not shipped with directly Fedora's kernel?:
No.

7. Please attach the kernel logs. You can get the complete kernel log
   for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the
   issue occurred on a previous boot, use the journalctl ``-b`` flag.

Attached (from current boot!). Hostname replaced with `**hostname**`. File is not truncated.
Also attached “lshw” command output.

The log from the previous boot with that error has a size of ~500 MB, which I obviously cannot attach here.
However, I’ll attach the last 100 lines and from having q quick peek into the file, I also see that it mostly spam the log with the same line always:
> kernel: nouveau 0000:01:00.0: fifo: PBDMA0: 80206000 [ILLEGAL_MTHD] ch 3 [007fb04000 systemd-logind[1238]] subc 0 mthd 0008 data ffffffff

As I see some errors about nouveau in there, some descriptions about my setup:
* I used to use the included NVidia GPU in the system. (2 monitors)
* However, at some point of time, I switched the physical cables to connect both monitors to the integrated graphics Intel CPU, because well… we all know that was better than those nouveau driver. Since then I do have a “Launch with dedicated graphic card” menu in the GNOME shell when I right-click an app in that app list in the overview. This is quite fun, but I actually never use it. :)

Fedora 34 Workstation