Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757410AbcDJUyV (ORCPT ); Sun, 10 Apr 2016 16:54:21 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51533 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754090AbcDJShm (ORCPT ); Sun, 10 Apr 2016 14:37:42 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dietmar Eggemann , Byungchul Park , "Peter Zijlstra (Intel)" , Chris Metcalf , Christoph Lameter , Frederic Weisbecker , Linus Torvalds , Luiz Capitulino , Mike Galbraith , "Paul E . McKenney" , Rik van Riel , Thomas Gleixner , perterz@infradead.org, Ingo Molnar Subject: [PATCH 4.5 018/238] sched/fair: Avoid using decay_load_missed() with a negative value Date: Sun, 10 Apr 2016 11:33:15 -0700 Message-Id: <20160410183457.301824235@linuxfoundation.org> X-Mailer: git-send-email 2.8.0 In-Reply-To: <20160410183456.398741366@linuxfoundation.org> References: <20160410183456.398741366@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2061 Lines: 57 4.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Byungchul Park commit 7400d3bbaa229eb8e7631d28fb34afd7cd2c96ff upstream. decay_load_missed() cannot handle nagative values, so we need to prevent using the function with a negative value. Reported-by: Dietmar Eggemann Signed-off-by: Byungchul Park Signed-off-by: Peter Zijlstra (Intel) Cc: Chris Metcalf Cc: Christoph Lameter Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: perterz@infradead.org Fixes: 59543275488d ("sched/fair: Prepare __update_cpu_load() to handle active tickless") Link: http://lkml.kernel.org/r/20160115070749.GA1914@X58A-UD3R Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/sched/fair.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4459,9 +4459,17 @@ static void __update_cpu_load(struct rq /* scale is effectively 1 << i now, and >> i divides by scale */ - old_load = this_rq->cpu_load[i] - tickless_load; + old_load = this_rq->cpu_load[i]; old_load = decay_load_missed(old_load, pending_updates - 1, i); - old_load += tickless_load; + if (tickless_load) { + old_load -= decay_load_missed(tickless_load, pending_updates - 1, i); + /* + * old_load can never be a negative value because a + * decayed tickless_load cannot be greater than the + * original tickless_load. + */ + old_load += tickless_load; + } new_load = this_load; /* * Round up the averaging division if load is increasing. This