Re: Regression: x86/tsc: Fix mark_tsc_unstable()

From: Peter Zijlstra
Date: Mon Jun 11 2018 - 10:17:59 EST

On Mon, Jun 11, 2018 at 01:59:15PM +0000, Jeremy Cline wrote:
> A user has bisected the problem to the v4.16 commit 1ab4ca7c59d4
> ("x86/tsc: Fix mark_tsc_unstable()"). According to the reporter,
> explicitly setting "tsc=" on the kernel command line causes the boot to
> always succeed. All the users have Thinkpad T500s or T400s (Core 2 Duos)

Weird. So Core2 typically triggers mark_tsc_unstable() in either
intel_idle or processor_idle. ISTR testing that when I did the patches.

When I make that mark_tsc_unstable() in the idle drivers unconditional
and boot my ivb with that, it doesn't want to fail. I've booted the
machine 5 consequctive times without issue.

Let me try and checkout -stable, maybe something's up with that.