From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751663AbbKJIpB (ORCPT ); Tue, 10 Nov 2015 03:45:01 -0500 Received: from TYO202.gate.nec.co.jp ([210.143.35.52]:58497 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750893AbbKJIo7 convert rfc822-to-8bit (ORCPT ); Tue, 10 Nov 2015 03:44:59 -0500 From: Hiroshi Shimamoto To: Frederic Weisbecker , Peter Zijlstra CC: Ingo Molnar , "linux-kernel@vger.kernel.org" , Thomas Gleixner Subject: RE: [PATCH v3 1/2] cputime: fix invalid gtime in proc Thread-Topic: [PATCH v3 1/2] cputime: fix invalid gtime in proc Thread-Index: AQHRFYl6SKAHBF8RNkyCvP+4lQl5iJ6LdfKAgAmFcrA= Date: Tue, 10 Nov 2015 08:43:17 +0000 Message-ID: <7F861DC0615E0C47A872E6F3C5FCDDBD05F6B430@BPXM14GP.gisp.nec.co.jp> References: <7F861DC0615E0C47A872E6F3C5FCDDBD05F575AA@BPXM14GP.gisp.nec.co.jp> <20151102161351.GT3604@twins.programming.kicks-ass.net> <20151104161455.GB12889@lerouge> In-Reply-To: <20151104161455.GB12889@lerouge> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.205.5.123] Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Subject: Re: [PATCH v3 1/2] cputime: fix invalid gtime in proc > > On Mon, Nov 02, 2015 at 05:13:51PM +0100, Peter Zijlstra wrote: > > On Fri, Oct 30, 2015 at 12:46:39AM +0000, Hiroshi Shimamoto wrote: > > > +++ b/kernel/sched/cputime.c > > > @@ -786,6 +786,9 @@ cputime_t task_gtime(struct task_struct *t) > > > unsigned int seq; > > > cputime_t gtime; > > > > > > + if (!context_tracking_is_enabled()) > > > + return t->gtime; > > > + > > > > Yeah, not happy about that.. why do we have to touch context tracking > > muck to find vtime state etc. > > That's right, this is because it is deemed to be a quick and non invasive fix > to be backported. > > Then will come the more invasive but proper fix consisting in having > vtime_accounting_enabled() telling if vtime is running on any CPU and > vtime_accounting_cpu_enabled(). The first will be used for remote readers > (as in this patch) and the second for writers. > > Since we are dealing with a regression, it's better to minimize the changes. > AFAICT, the regression got introduced in 2012: > > 6a61671bb2f3a1bd12cd17b8fca811a624782632 > ("cputime: Safely read cputime of full dynticks CPUs") Is this patch going to apply to fix the regression? thanks, Hiroshi > > > > > > do { > > > seq = read_seqbegin(&t->vtime_seqlock); > > > > > > -- > > > 1.8.3.1 > > >