From nobody Wed Feb 11 22:55:47 2026 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 E2E6FCA5507 for ; Wed, 13 Sep 2023 08:24:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238814AbjIMIYt (ORCPT ); Wed, 13 Sep 2023 04:24:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238724AbjIMIYp (ORCPT ); Wed, 13 Sep 2023 04:24:45 -0400 Received: from mail-pg1-x52a.google.com (mail-pg1-x52a.google.com [IPv6:2607:f8b0:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E281E73 for ; Wed, 13 Sep 2023 01:24:40 -0700 (PDT) Received: by mail-pg1-x52a.google.com with SMTP id 41be03b00d2f7-57795cb527dso1799933a12.1 for ; Wed, 13 Sep 2023 01:24:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1694593479; x=1695198279; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=NerOxo/Xet1iSR6t25Iug1uoSd/sPOYc1SroBY+3+S8=; b=F2i3wsZY1m/JmVFTUeBxm5668+ZihPYEW4MqtMvx8sjtq+xXZBeS9knHd90k8q5QQe /5mVvL/8HJy1OBPblVv1DVXE4zDzV2AYAnnaBHgi6PhJbfD0ZljHVTSMRU9vaQKgg2lA NIqIcH/iVx5nh91Z7WDB2NzHMP7WkwIqjbvFWYG0VSOmgHPbMGnIAWFDGkFHe5FkNAIh 4DU1ZHFUBGQ4B5Gsi5EiQdVv+82JuHaAZfOfOr6R/CzuEUzeWS0AVx4FqbYGAQrPIbJs F6+k/1rzvau6SKOdW3OSzPq+SZ182kTpf0ZhI0U1wPc9wmGgRK0FWZImMtqg6YY5dCgr BwFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694593479; x=1695198279; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=NerOxo/Xet1iSR6t25Iug1uoSd/sPOYc1SroBY+3+S8=; b=HjVBruX0VVqhUDGbMSfGZb1pWc5uedjj2VblqmXjPJXqQJILlrHnvOMvagZvlNEwN1 pq/M4AJ0lGkLuSLJn/XEEh/8YIXw2cnnC2gyIziLAvA44a2UZcrcvNiyqXR82vy6I41K BOl9/NAR/VvkdBPo2xGvmyKx092Ea2gP1dy2sM0FXONzQu/V7cB8gJLwgzop2C3rGoa1 69yoJG9jV1PPTyRhdIzfKjJ9p3T/J5lHORM+zjqYZJIl9SDDh0IJlDSvxEkhW2KYZnI6 OXgCAuq4mC5kbc4OSHuLUxMgWJT2LLhUF5HP3OBqviCidg7kM42APTMDT2K0kTpi4z/D t02A== X-Gm-Message-State: AOJu0Yx47EIo31VD5+RaP0xuEDSSRhmwXI5mA/vPwLsZ8/rakmHL8wjR 02j7F4zYoj7rT9oyEmYuQToRIQ== X-Google-Smtp-Source: AGHT+IG65wPuasuLxriLgRjy3n06qZHiH2RdjDj9cyh+QsrEvt28tN1EcUbBv9A5EfautCoYCYwcZw== X-Received: by 2002:a05:6a20:3956:b0:14c:5dc3:f1c9 with SMTP id r22-20020a056a20395600b0014c5dc3f1c9mr1921501pzg.49.1694593479512; Wed, 13 Sep 2023 01:24:39 -0700 (PDT) Received: from C02G87K0MD6R.bytedance.net ([203.208.167.146]) by smtp.gmail.com with ESMTPSA id z91-20020a17090a6d6400b0025c1cfdb93esm991443pjj.13.2023.09.13.01.24.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Sep 2023 01:24:39 -0700 (PDT) From: Hao Jia To: mingo@redhat.com, peterz@infradead.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com Cc: linux-kernel@vger.kernel.org, Hao Jia , stable@vger.kernel.org, Igor Raits , Bagas Sanjaya Subject: [PATCH] sched/core: Fix wrong warning check in rq_clock_start_loop_update() Date: Wed, 13 Sep 2023 16:24:24 +0800 Message-Id: <20230913082424.73252-1-jiahao.os@bytedance.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Igor Raits and Bagas Sanjaya report a RQCF_ACT_SKIP leak warning. Link: https://lore.kernel.org/all/a5dd536d-041a-2ce9-f4b7-64d8d85c86dc@gmai= l.com Commit ebb83d84e49b54 ("sched/core: Avoid multiple calling update_rq_clock() in __cfsb_csd_unthrottle()") add RQCF_ACT_SKIP leak warning in rq_clock_start_loop_update(). But this warning is inaccurate and may be triggered incorrectly in the following situations: CPU0 CPU1 __schedule() *rq->clock_update_flags <<=3D 1;* unregister_fair_sched_group() pick_next_task_fair+0x4a/0x410 destroy_cfs_bandwidth() newidle_balance+0x115/0x3e0 for_each_possible_cpu(i) *i=3D0* rq_unpin_lock(this_rq, rf) __cfsb_csd_unthrottle() raw_spin_rq_unlock(this_rq) rq_lock(*CPU0_rq*, &rf) rq_clock_start_loop_update() rq->clock_update_flags & RQCF_ACT_SKI= P <-- raw_spin_rq_lock(this_rq) So we remove this wrong check. Add assert_clock_updated() to check that rq clock has been updated before calling rq_clock_start_loop_update(). And we cannot unconditionally set rq->clock_update_flags to RQCF_ACT_SKIP in rq_clock_start_loop_update(). So we use the variable rq_clock_flags in rq_clock_start_loop_update() to record the previous state of rq->clock_update_flags. Correspondingly, restore rq->clock_update_flags through rq_clock_flags in rq_clock_stop_loop_update() to prevent losing its previous information. Fixes: ebb83d84e49b ("sched/core: Avoid multiple calling update_rq_clock() = in __cfsb_csd_unthrottle()") Cc: stable@vger.kernel.org Reported-by: Igor Raits Reported-by: Bagas Sanjaya Signed-off-by: Hao Jia --- kernel/sched/fair.c | 10 ++++++---- kernel/sched/sched.h | 12 +++++++----- 2 files changed, 13 insertions(+), 9 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8dbff6e7ad4f..a64a002573d9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5679,6 +5679,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) #ifdef CONFIG_SMP static void __cfsb_csd_unthrottle(void *arg) { + unsigned int rq_clock_flags; struct cfs_rq *cursor, *tmp; struct rq *rq =3D arg; struct rq_flags rf; @@ -5691,7 +5692,7 @@ static void __cfsb_csd_unthrottle(void *arg) * Do it once and skip the potential next ones. */ update_rq_clock(rq); - rq_clock_start_loop_update(rq); + rq_clock_start_loop_update(rq, &rq_clock_flags); =20 /* * Since we hold rq lock we're safe from concurrent manipulation of @@ -5712,7 +5713,7 @@ static void __cfsb_csd_unthrottle(void *arg) =20 rcu_read_unlock(); =20 - rq_clock_stop_loop_update(rq); + rq_clock_stop_loop_update(rq, &rq_clock_flags); rq_unlock(rq, &rf); } =20 @@ -6230,6 +6231,7 @@ static void __maybe_unused update_runtime_enabled(str= uct rq *rq) /* cpu offline callback */ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) { + unsigned int rq_clock_flags; struct task_group *tg; =20 lockdep_assert_rq_held(rq); @@ -6239,7 +6241,7 @@ static void __maybe_unused unthrottle_offline_cfs_rqs= (struct rq *rq) * set_rq_offline(), so we should skip updating * the rq clock again in unthrottle_cfs_rq(). */ - rq_clock_start_loop_update(rq); + rq_clock_start_loop_update(rq, &rq_clock_flags); =20 rcu_read_lock(); list_for_each_entry_rcu(tg, &task_groups, list) { @@ -6264,7 +6266,7 @@ static void __maybe_unused unthrottle_offline_cfs_rqs= (struct rq *rq) } rcu_read_unlock(); =20 - rq_clock_stop_loop_update(rq); + rq_clock_stop_loop_update(rq, &rq_clock_flags); } =20 bool cfs_task_bw_constrained(struct task_struct *p) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 04846272409c..ff2864f202f5 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1558,20 +1558,22 @@ static inline void rq_clock_cancel_skipupdate(struc= t rq *rq) * when using list_for_each_entry_*) * rq_clock_start_loop_update() can be called after updating the clock * once and before iterating over the list to prevent multiple update. + * And use @rq_clock_flags to record the previous state of rq->clock_updat= e_flags. * After the iterative traversal, we need to call rq_clock_stop_loop_updat= e() - * to clear RQCF_ACT_SKIP of rq->clock_update_flags. + * to restore rq->clock_update_flags through @rq_clock_flags. */ -static inline void rq_clock_start_loop_update(struct rq *rq) +static inline void rq_clock_start_loop_update(struct rq *rq, unsigned int = *rq_clock_flags) { lockdep_assert_rq_held(rq); - SCHED_WARN_ON(rq->clock_update_flags & RQCF_ACT_SKIP); + assert_clock_updated(rq); + *rq_clock_flags =3D rq->clock_update_flags; rq->clock_update_flags |=3D RQCF_ACT_SKIP; } =20 -static inline void rq_clock_stop_loop_update(struct rq *rq) +static inline void rq_clock_stop_loop_update(struct rq *rq, unsigned int *= rq_clock_flags) { lockdep_assert_rq_held(rq); - rq->clock_update_flags &=3D ~RQCF_ACT_SKIP; + rq->clock_update_flags =3D *rq_clock_flags; } =20 struct rq_flags { --=20 2.39.2