From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755421AbaEHSrd (ORCPT ); Thu, 8 May 2014 14:47:33 -0400 Received: from mail-ob0-f180.google.com ([209.85.214.180]:51172 "EHLO mail-ob0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752485AbaEHSrc (ORCPT ); Thu, 8 May 2014 14:47:32 -0400 Message-ID: <536BD141.7030000@mvista.com> Date: Thu, 08 May 2014 13:47:29 -0500 From: Corey Minyard User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Peter Zijlstra , minyard@acm.org CC: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched: Initialize rq->age_stamp on processor start References: <1399405857-14056-1-git-send-email-minyard@acm.org> <20140508161337.GF30445@twins.programming.kicks-ass.net> In-Reply-To: <20140508161337.GF30445@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/08/2014 11:13 AM, Peter Zijlstra wrote: > On Tue, May 06, 2014 at 02:50:57PM -0500, minyard@acm.org wrote: >> From: Corey Minyard >> >> If the sched_clock time starts at a large value, the kernel will spin >> in sched_avg_update for a long time while rq->age_stamp catches up >> with rq->clock. >> >> The comment in kernel/sched/clock.c says that there is no strict promise >> that it starts at zero. So initialize rq->age_stamp when a cpu starts up >> to avoid this. >> >> I was seeing long delays on a simulator that didn't start the clock at >> zero. This might also be an issue on reboots on processors that don't >> re-initialize the timer to zero on reset, and when using kexec. >> >> Signed-off-by: Corey Minyard > This patch made my cris-defconfig build fail. Dang, I missed propagating a change. Yes, it's broken. One more time... -corey