From patchwork Mon Jul 12 06:06:35 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: 475794 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=-19.4 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 39BFDC11F82 for ; Mon, 12 Jul 2021 07:10:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DB13610CD for ; Mon, 12 Jul 2021 07:10:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242812AbhGLHMK (ORCPT ); Mon, 12 Jul 2021 03:12:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:42642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244222AbhGLHKb (ORCPT ); Mon, 12 Jul 2021 03:10:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id AD1A06108B; Mon, 12 Jul 2021 07:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626073645; bh=zu502Br0QPCwapZx31JQYsfAnVnVVdPqxjJesmewIwE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dqMHAeAxo7IhT1PMEfZHEhc9IMsHOjOorLJz1hJekHKqcteTbCuyr4IGxiIvY7rof JEyfQd0+gQ5ISzFLA0WZC4TdgA/SI4aWeNpVIlcr4bEqqICmqQ46RpYIqPT73BZWpO bkz5Ap3JzvaCH9dRpM0Nb4jq8ckwO/m8xnlzt2K0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Xuewen Yan , Qais Yousef , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.12 312/700] sched/uclamp: Fix uclamp_tg_restrict() Date: Mon, 12 Jul 2021 08:06:35 +0200 Message-Id: <20210712061009.547812952@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qais Yousef [ Upstream commit 0213b7083e81f4acd69db32cb72eb4e5f220329a ] Now cpu.uclamp.min acts as a protection, we need to make sure that the uclamp request of the task is within the allowed range of the cgroup, that is it is clamp()'ed correctly by tg->uclamp[UCLAMP_MIN] and tg->uclamp[UCLAMP_MAX]. As reported by Xuewen [1] we can have some corner cases where there's inversion between uclamp requested by task (p) and the uclamp values of the taskgroup it's attached to (tg). Following table demonstrates 2 corner cases: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 60% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 20% -----------+-----+------+----------- With this fix we get: | p | tg | effective -----------+-----+------+----------- CASE 1 -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- CASE 2 -----------+-----+------+----------- uclamp_min | 0% | 30% | 30% -----------+-----+------+----------- uclamp_max | 20% | 50% | 30% -----------+-----+------+----------- Additionally uclamp_update_active_tasks() must now unconditionally update both UCLAMP_MIN/MAX because changing the tg's UCLAMP_MAX for instance could have an impact on the effective UCLAMP_MIN of the tasks. | p | tg | effective -----------+-----+------+----------- old -----------+-----+------+----------- uclamp_min | 60% | 0% | 50% -----------+-----+------+----------- uclamp_max | 80% | 50% | 50% -----------+-----+------+----------- *new* -----------+-----+------+----------- uclamp_min | 60% | 0% | *60%* -----------+-----+------+----------- uclamp_max | 80% |*70%* | *70%* -----------+-----+------+----------- [1] https://lore.kernel.org/lkml/CAB8ipk_a6VFNjiEnHRHkUMBKbA+qzPQvhtNjJ_YNzQhqV_o8Zw@mail.gmail.com/ Fixes: 0c18f2ecfcc2 ("sched/uclamp: Fix wrong implementation of cpu.uclamp.min") Reported-by: Xuewen Yan Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210617165155.3774110-1-qais.yousef@arm.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 49 +++++++++++++++++---------------------------- 1 file changed, 18 insertions(+), 31 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fe5da692dd7a..2b66c9a16cbe 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1055,8 +1055,10 @@ static void uclamp_sync_util_min_rt_default(void) static inline struct uclamp_se uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) { + /* Copy by value as we could modify it */ struct uclamp_se uc_req = p->uclamp_req[clamp_id]; #ifdef CONFIG_UCLAMP_TASK_GROUP + unsigned int tg_min, tg_max, value; /* * Tasks in autogroups or root task group will be @@ -1067,23 +1069,11 @@ uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) if (task_group(p) == &root_task_group) return uc_req; - switch (clamp_id) { - case UCLAMP_MIN: { - struct uclamp_se uc_min = task_group(p)->uclamp[clamp_id]; - if (uc_req.value < uc_min.value) - return uc_min; - break; - } - case UCLAMP_MAX: { - struct uclamp_se uc_max = task_group(p)->uclamp[clamp_id]; - if (uc_req.value > uc_max.value) - return uc_max; - break; - } - default: - WARN_ON_ONCE(1); - break; - } + tg_min = task_group(p)->uclamp[UCLAMP_MIN].value; + tg_max = task_group(p)->uclamp[UCLAMP_MAX].value; + value = uc_req.value; + value = clamp(value, tg_min, tg_max); + uclamp_se_set(&uc_req, value, false); #endif return uc_req; @@ -1282,8 +1272,9 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) } static inline void -uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id) +uclamp_update_active(struct task_struct *p) { + enum uclamp_id clamp_id; struct rq_flags rf; struct rq *rq; @@ -1303,9 +1294,11 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id) * affecting a valid clamp bucket, the next time it's enqueued, * it will already see the updated clamp bucket value. */ - 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) { + if (p->uclamp[clamp_id].active) { + uclamp_rq_dec_id(rq, p, clamp_id); + uclamp_rq_inc_id(rq, p, clamp_id); + } } task_rq_unlock(rq, p, &rf); @@ -1313,20 +1306,14 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id) #ifdef CONFIG_UCLAMP_TASK_GROUP static inline void -uclamp_update_active_tasks(struct cgroup_subsys_state *css, - unsigned int clamps) +uclamp_update_active_tasks(struct cgroup_subsys_state *css) { - enum uclamp_id clamp_id; struct css_task_iter it; struct task_struct *p; css_task_iter_start(css, 0, &it); - while ((p = css_task_iter_next(&it))) { - for_each_clamp_id(clamp_id) { - if ((0x1 << clamp_id) & clamps) - uclamp_update_active(p, clamp_id); - } - } + while ((p = css_task_iter_next(&it))) + uclamp_update_active(p); css_task_iter_end(&it); } @@ -8826,7 +8813,7 @@ static void cpu_util_update_eff(struct cgroup_subsys_state *css) } /* Immediately update descendants RUNNABLE tasks */ - uclamp_update_active_tasks(css, clamps); + uclamp_update_active_tasks(css); } }