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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79914C433EF for ; Tue, 19 Apr 2022 19:35:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355857AbiDSTh4 (ORCPT ); Tue, 19 Apr 2022 15:37:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232518AbiDSThq (ORCPT ); Tue, 19 Apr 2022 15:37:46 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D4A023BF6; Tue, 19 Apr 2022 12:35:02 -0700 (PDT) Date: Tue, 19 Apr 2022 19:35:00 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1650396901; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DlvWHJF8b1esV8seniJmC7hs+4b+46cXWx9FKu3RKeE=; b=AjrSK1Jf+eA3xEsL0w2WRsT/5P5iPQqG3F1uzhLKY8QcOH1W4RHJm/Rs6adS43K1lUDa6N ZmBjXaK3+GegEH1udrzu9uFtXEjcPKUatANvrTkmjQJOEqqjeAtn8oujgE6VRNhFCTsu/g V84/jDo9Eg6MgMZMreqzO6S/lzYiZe+LoeolKhyLdOhVPtH6x4InqFt8kbtAsphDFDrVVA cBGNA/Eb5xQSGB36pka3v9/WtaGflmNpm9GulZYPh+JaMV77XgHWshRUQ+0f9ZBAwZj/jx 9tBxhWwHvfiCOqUa0NtRiELzXT8zFdm17wbqsIsAPKu3QxuHHCf8I1FnvcBRWw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1650396901; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DlvWHJF8b1esV8seniJmC7hs+4b+46cXWx9FKu3RKeE=; b=bbgxh0jBmBkSb1Y13c0FT3K8pnDSaqINV9HcWN2lhT0cz2IlRFLW7KtnfP1N/SRO9rU5BP syd5RsFGFaXDnfAA== From: "tip-bot2 for kuyo chang" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/pelt: Fix attach_entity_load_avg() corner case Cc: kuyo chang , "Peter Zijlstra (Intel)" , Vincent Guittot , Dietmar Eggemann , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220414090229.342-1-kuyo.chang@mediatek.com> References: <20220414090229.342-1-kuyo.chang@mediatek.com> MIME-Version: 1.0 Message-ID: <165039690015.4207.4030717443778774474.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 40f5aa4c5eaebfeaca4566217cb9c468e28ed682 Gitweb: https://git.kernel.org/tip/40f5aa4c5eaebfeaca4566217cb9c468e28ed682 Author: kuyo chang AuthorDate: Thu, 14 Apr 2022 17:02:20 +08:00 Committer: Peter Zijlstra CommitterDate: Tue, 19 Apr 2022 21:15:41 +02:00 sched/pelt: Fix attach_entity_load_avg() corner case The warning in cfs_rq_is_decayed() triggered: SCHED_WARN_ON(cfs_rq->avg.load_avg || cfs_rq->avg.util_avg || cfs_rq->avg.runnable_avg) There exists a corner case in attach_entity_load_avg() which will cause load_sum to be zero while load_avg will not be. Consider se_weight is 88761 as per the sched_prio_to_weight[] table. Further assume the get_pelt_divider() is 47742, this gives: se->avg.load_avg is 1. However, calculating load_sum: se->avg.load_sum = div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); se->avg.load_sum = 1*47742/88761 = 0. Then enqueue_load_avg() adds this to the cfs_rq totals: cfs_rq->avg.load_avg += se->avg.load_avg; cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum; Resulting in load_avg being 1 with load_sum is 0, which will trigger the WARN. Fixes: f207934fb79d ("sched/fair: Align PELT windows between cfs_rq and its se") Signed-off-by: kuyo chang [peterz: massage changelog] Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Tested-by: Dietmar Eggemann Link: https://lkml.kernel.org/r/20220414090229.342-1-kuyo.chang@mediatek.com --- kernel/sched/fair.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d4bd299..a68482d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3829,11 +3829,11 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s se->avg.runnable_sum = se->avg.runnable_avg * divider; - se->avg.load_sum = divider; - if (se_weight(se)) { - se->avg.load_sum = - div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se)); - } + se->avg.load_sum = se->avg.load_avg * divider; + if (se_weight(se) < se->avg.load_sum) + se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se)); + else + se->avg.load_sum = 1; enqueue_load_avg(cfs_rq, se); cfs_rq->avg.util_avg += se->avg.util_avg;