From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 195CEC1B0F1 for ; Tue, 19 Jun 2018 22:52:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D160D20836 for ; Tue, 19 Jun 2018 22:52:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D160D20836 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754276AbeFSWw4 (ORCPT ); Tue, 19 Jun 2018 18:52:56 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:58495 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142AbeFSWwG (ORCPT ); Tue, 19 Jun 2018 18:52:06 -0400 Received: from p4fea482e.dip0.t-ipconnect.de ([79.234.72.46] helo=nanos.glx-home) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1fVPTW-0004qr-40; Wed, 20 Jun 2018 00:51:46 +0200 Date: Wed, 20 Jun 2018 00:51:45 +0200 (CEST) From: Thomas Gleixner To: Pavel Tatashin cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, linux@armlinux.org.uk, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, john.stultz@linaro.org, sboyd@codeaurora.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, douly.fnst@cn.fujitsu.com, peterz@infradead.org, prarit@redhat.com, feng.tang@intel.com, pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk Subject: Re: [PATCH v10 7/7] x86/tsc: use tsc early In-Reply-To: <20180615174204.30581-8-pasha.tatashin@oracle.com> Message-ID: References: <20180615174204.30581-1-pasha.tatashin@oracle.com> <20180615174204.30581-8-pasha.tatashin@oracle.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 15 Jun 2018, Pavel Tatashin wrote: > This patch adds early clock feature to x86 platforms. See Documentation about 'This patch' .... We already know that this is a patch otherwise it would not be marked as such ... > +/* > + * Finish clock for early time stamps, and hand over to permanent clock by > + * setting __sched_clock_offset appropriately for continued time keeping. > + */ > +static void __init tsc_early_fini(void) > +{ > + unsigned long long t; > + unsigned long r; > + > + t = -cyc2ns_early.cyc2ns_offset; > + r = do_div(t, NSEC_PER_SEC); > + > + __sched_clock_offset = sched_clock_early() - sched_clock(); As this is called _AFTER_ the TSC initialization which also includes sanitizing of TSC_ADJUST, this can result in a complete bogus __sched_clock_offset because sched_clock_early() will return nonsense when TSC_ADJUST has been modified. > + pr_info("early sched clock is finished, offset [%lld.%09lds]\n", t, r); That only gives useful information when the machine boots cold and when the machine has a sane BIOS. So it's almost guaranteed to print useless information. Thanks, tglx