From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753511AbdK1SrR (ORCPT <rfc822;w@1wt.eu>);
        Tue, 28 Nov 2017 13:47:17 -0500
Received: from Galois.linutronix.de ([146.0.238.70]:35203 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752347AbdK1SrP (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 28 Nov 2017 13:47:15 -0500
Date: Tue, 28 Nov 2017 19:47:09 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Prarit Bhargava <prarit@redhat.com>
cc: Petr Mladek <pmladek@suse.com>, LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linuxfoundation.org>,
        Mark Salyzyn <salyzyn@android.com>, Ingo Molnar <mingo@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>, Joe Perches <joe@perches.com>
Subject: Re: [RFC patch 7/7] timekeeping: Hack to use fine grained timestamps
 during boot
In-Reply-To: <205229e2-fab4-31cb-60cd-f36bc2228804@redhat.com>
Message-ID: <alpine.DEB.2.20.1711281946140.2222@nanos>
References: <20171115181531.322572387@linutronix.de> <20171115182657.703928462@linutronix.de> <20171123125823.gnhwtnx6bxd3tb4q@pathway.suse.cz> <205229e2-fab4-31cb-60cd-f36bc2228804@redhat.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 28 Nov 2017, Prarit Bhargava wrote:
> On 11/23/2017 07:58 AM, Petr Mladek wrote:
> > On Wed 2017-11-15 19:15:38, Thomas Gleixner wrote:
> >> For demonstration purposes only.
> >>
> >> Add a disgusting hack to work around the fact that high resolution clock
> >> MONOTONIC accessors are not available during early boot and return stale
> >> time stamps accross suspend/resume when the current clocksource is not
> >> flagged with CLOCK_SOURCE_SUSPEND_ACCESS_OK.
> >>
> >> Use local_clock() to provide timestamps in early boot and when the
> >> clocksource is not accessible after timekeeping_suspend(). In the
> >> suspend/resume case this might cause non monotonic timestamps.
> > 
> > I get the non-monotonic times even during boot:
> > 
> > [    0.026709] smp: Bringing up secondary CPUs ...
> > [    0.027973] x86: Booting SMP configuration:
> > [    0.028006] .... node  #0, CPUs:      #1
> > [    0.004000] kvm-clock: cpu 1, msr 1:3ff51041, secondary cpu clock
> >      ^^^^^^^^

Which is interesting as this should happen even w/o those patches. 

Thanks,

	tglx