linux-kernel - Re: Regression: x86/tsc: Fix mark_tsc

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Date:   Mon, 11 Jun 2018 17:30:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jeremy Cline <jeremy@...ine.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        rui.zhang@...el.com, len.brown@...el.com, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, regressions@...mhuis.info,
        Diego Viola <diego.viola@...il.com>
Subject: Re: Regression: x86/tsc: Fix mark_tsc_unstable()

On Mon, Jun 11, 2018 at 04:38:01PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 11, 2018 at 04:17:42PM +0200, Peter Zijlstra wrote:
> > 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.
> 
> Nope -stable seems to be working as well on the IVB (with modification).
> I just dug up my T500 and that's actually still running the test kernel.
> Let me try and build the -stable kernel for that.

4.16.8 works without issue on my T500 with a debian/ubuntu like distro
config.