linux-kernel - Re: [PATCH] x86/ioapic: don't use unstable TSC to detect timer IRQ

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Message-ID: <alpine.DEB.2.21.1803201000380.6506@nanos.tec.linutronix.de>
Date:   Tue, 20 Mar 2018 10:03:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Liu, Changcheng" <changcheng.liu@...el.com>
cc:     Peter Zijlstra <peterz@...radead.org>, hpa@...or.com,
        douly.fnst@...fujitsu.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/ioapic: don't use unstable TSC to detect timer IRQ

On Tue, 20 Mar 2018, Liu, Changcheng wrote:

> On 09:49 Tue 20 Mar, Peter Zijlstra wrote:
> > On Tue, Mar 20, 2018 at 04:42:55PM +0800, Liu, Changcheng wrote:
> > > In rare case, the TSC is every unstable or can't sync with
> > > real time hardware clock. 
> > 
> > However did you manage that? Please provide _FAR_ more details.
> [Changcheng] TSC is simulated and HPET is hardware implemented.
> TSC can't sync with HPET. When running linux, the TSC grows too
> fast and HPET can't trigger periodic timer interrupt in time which
> is used to update jiffies.

Why on earth is that system claiming it has a TSC at all? That's just
broken.

Thanks,

	tglx