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

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Message-ID: <20180611141742.GP12198@hirez.programming.kicks-ass.net>
Date:   Mon, 11 Jun 2018 16:17:42 +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 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.