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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 62FE3C433F5 for ; Mon, 13 Sep 2021 13:34:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 449E0619F5 for ; Mon, 13 Sep 2021 13:34:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242701AbhIMNeT (ORCPT ); Mon, 13 Sep 2021 09:34:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:34844 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240146AbhIMNT4 (ORCPT ); Mon, 13 Sep 2021 09:19:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3AF39610FB; Mon, 13 Sep 2021 13:17:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631539074; bh=TfMGfZX9sfpLJumnJiPgehJ4165p7DZonxEnbP0Pkr4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YHYBLui9JGz+kgGRGnyr7i/3rnMdRIqAMdtlMo+c8Askh3R0psmGgr4LHQohyx65r 5KHJUdSpLRUKVUjJKssKhKva0mEOnIQUgHDWBpZIbgcHgbCu3ggnGTaDn9UKbDZnYZ aFXcD1vS+tlFX6trp8OJj+g625RAuzqAOfTvGbi4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rick Yiu , Quentin Perret , "Peter Zijlstra (Intel)" , Qais Yousef , Dietmar Eggemann , Sasha Levin Subject: [PATCH 5.4 032/144] sched: Fix UCLAMP_FLAG_IDLE setting Date: Mon, 13 Sep 2021 15:13:33 +0200 Message-Id: <20210913131049.029454996@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131047.974309396@linuxfoundation.org> References: <20210913131047.974309396@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Quentin Perret [ Upstream commit ca4984a7dd863f3e1c0df775ae3e744bff24c303 ] The UCLAMP_FLAG_IDLE flag is set on a runqueue when dequeueing the last uclamp active task (that is, when buckets.tasks reaches 0 for all buckets) to maintain the last uclamp.max and prevent blocked util from suddenly becoming visible. However, there is an asymmetry in how the flag is set and cleared which can lead to having the flag set whilst there are active tasks on the rq. Specifically, the flag is cleared in the uclamp_rq_inc() path, which is called at enqueue time, but set in uclamp_rq_dec_id() which is called both when dequeueing a task _and_ in the update_uclamp_active() path. As a result, when both uclamp_rq_{dec,ind}_id() are called from update_uclamp_active(), the flag ends up being set but not cleared, hence leaving the runqueue in a broken state. Fix this by clearing the flag in update_uclamp_active() as well. Fixes: e496187da710 ("sched/uclamp: Enforce last task's UCLAMP_MAX") Reported-by: Rick Yiu Signed-off-by: Quentin Perret Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Qais Yousef Tested-by: Dietmar Eggemann Link: https://lore.kernel.org/r/20210805102154.590709-2-qperret@google.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8294debf68c4..5dc43d37e6a2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1110,6 +1110,23 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) uclamp_rq_dec_id(rq, p, clamp_id); } +static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p, + enum uclamp_id clamp_id) +{ + if (!p->uclamp[clamp_id].active) + return; + + uclamp_rq_dec_id(rq, p, clamp_id); + uclamp_rq_inc_id(rq, p, clamp_id); + + /* + * Make sure to clear the idle flag if we've transiently reached 0 + * active tasks on rq. + */ + if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE)) + rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; +} + static inline void uclamp_update_active(struct task_struct *p) { @@ -1133,12 +1150,8 @@ uclamp_update_active(struct task_struct *p) * affecting a valid clamp bucket, the next time it's enqueued, * it will already see the updated clamp bucket value. */ - for_each_clamp_id(clamp_id) { - if (p->uclamp[clamp_id].active) { - uclamp_rq_dec_id(rq, p, clamp_id); - uclamp_rq_inc_id(rq, p, clamp_id); - } - } + for_each_clamp_id(clamp_id) + uclamp_rq_reinc_id(rq, p, clamp_id); task_rq_unlock(rq, p, &rf); } -- 2.30.2