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Date: Wed, 3 Dec 2014 13:14:59 -0800
Message-ID: <CA+55aFw8L06BxpsVnbdiNaU2WSFo=tafND25uV_SHUig=CC1AA@mail.gmail.com>
Subject: Re: frequent lockups in 3.18rc4
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Jones <davej@redhat.com>, Chris Mason <clm@fb.com>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        =?UTF-8?Q?D=C3=A2niel_Fraga?= <fragabr@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>
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Sender: linux-kernel-owner@vger.kernel.org

On Wed, Dec 3, 2014 at 12:55 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> But it's always negative, which means HPET is always ahead of
> TSC. That excludes pretty much the clocksource watchdog starvation
> issue which results in TSC being ahead of HPET due to a HPET
> wraparound (which takes ~300s).

Still, I'd be more likely to trust the TSC than the HPET on modern
machines.. And DaveJ's machine isn't some old one.

Of course, there's always BIOS games. Can we read the TSC offset
register and check it being constant (modulo sleep events)?

                     Linus
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