From patchwork Mon Sep 13 13:11:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 510517 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=ham 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 8C3F4C433FE for ; Mon, 13 Sep 2021 14:25:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7558360EC0 for ; Mon, 13 Sep 2021 14:25:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243294AbhIMO0X (ORCPT ); Mon, 13 Sep 2021 10:26:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:42328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344321AbhIMOWV (ORCPT ); Mon, 13 Sep 2021 10:22:21 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 44C8661B2F; Mon, 13 Sep 2021 13:47:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631540836; bh=zLWtLF0bywMH2Z+U3Bn9vPzzjC/86zuSJmRnWCSfUk0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tZM22hFbgMRDrdp25fsRfD2c4dcYbzT4hgeGntWecgLhfM3wyr3NPpMOok7oePBqu JgMj44R61/1dyHXHxBLMrw4axUkAXeAhD198gDtMy0iIlQlj9AVqq8ioviGTHYWmeg hTZCql4m8ao9oDB0wp41Sw7FGdru+Dr8W0GPzcRA= 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 5.14 054/334] sched: Fix UCLAMP_FLAG_IDLE setting Date: Mon, 13 Sep 2021 15:11:48 +0200 Message-Id: <20210913131115.248111333@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210913131113.390368911@linuxfoundation.org> References: <20210913131113.390368911@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 f3b27c6c5153..a2403432f3ab 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1633,6 +1633,23 @@ 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) { @@ -1656,12 +1673,8 @@ 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); }