Comment 529 for bug 1690085

Revision history for this message
In , kernel (kernel-linux-kernel-bugs) wrote :

(In reply to Vladyslav Yamkovyi from comment #441)
> (In reply to Owen Swerkstrom from comment #439)
> > This comes up as a Linux problem, but it sure smells like a hardware defect
> > to me.
> Any system that does not provides a software workaround must be affected
> according to published errata, not even a question. I've published one of
> their revision guides in my previous comments. They have no plans on fixing
> this and suggest using software workarounds. We're left on our own.

What is the "this" that AMD have no plans to fix ?

I had a look at <https://www.amd.com/system/files/TechDocs/55449_Fam_17h_M_00h-0Fh_Rev_Guide.pdf> which you referenced earlier. I found 3 MWAIT issues:

  1057 MWAIT or MWAITX Instructions May Fail to Correctly Exit From
       the Monitor Event Pending State

  1059 In Real Mode or Virtual-8086 Mode MWAIT or MWAITX Instructions May
       Fail to Correctly Exit From the Monitor Event Pending State

  1109 MWAIT Instruction May Hang a Thread

but I could not find anything else that might be related to the "freeze when idle" problem.

FWIW, here's the full text for the Erratum 1109:

  1109 MWAIT Instruction May Hang a Thread

       Description: Under a highly specific and detailed set of internal timing
                    conditions, the MWAIT instruction may cause a thread to
                    hang in SMT (Simultaneous Multithreading) Mode.

       Potential Effect on System: The system may hang or reset.

       Suggested Workaround: System software may contain the workaround for
                             this erratum.

       Fix Planned: No fix planned

so there ! I guess "idle=nomwait" is "the workaround" ?

"Typical Current Idle" appears to work for some (including me) but not for everyone. If one or more of these MWAIT errata is the root cause of the "freeze when idle" problem, I wonder why AMD introduced "Typical Current Idle" and how that relates to these MWAIT issues ??