Ubuntu
linux package

  1. Bug #1973434
  2. Comment #51

Comment 51 for bug 1973434

Revision history for this message
Roland Lewis (roland-l) wrote (last edit ):

I've seen many of the OP's symptoms too, including pinning one CPU at 100%. Makes the machine unusable. However I can be a little more precise as to when they started:

- 20.04 was fine at first;
- 20.04 later under kernel 5.13-generic saw the problems start, at which pointed I switched to low-latency in desperation;
- 20.04 kernel 5.13-low-latency, which (unlike generic) still worked fine;
- 20.04 under kernel 5.15-generic and 5.15-low-latency were both problematic;
   ... then upgraded to 22.04 to see if resolved;
- 22.04 kernel 6.2 is still problematic.

My guess is a kernel config change which was brought in first for 5.13-generic, and then also introduced to low-latency a version later. I attach diffs for the configs for (a) 5.11-5.13-generic, and for (b) 5.13-5.15-low-latency. I've tried to isolate a changed variable which is common to both, though I have not been able to yet.

Any help appreciated. intel_iommu=off doesn't help.

I'm using a Mac Pro 1,1 with clean EFI boot (and 'noefi' grub params). Woodcrest Xeon X5160 and AMD 5770 (official Mac edition).