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 0F086C61DA4 for ; Tue, 31 Jan 2023 02:36:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229961AbjAaCgY (ORCPT ); Mon, 30 Jan 2023 21:36:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229524AbjAaCgW (ORCPT ); Mon, 30 Jan 2023 21:36:22 -0500 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5950432E7B for ; Mon, 30 Jan 2023 18:35:35 -0800 (PST) Received: by mail-pj1-x1033.google.com with SMTP id nm12-20020a17090b19cc00b0022c2155cc0bso13021997pjb.4 for ; Mon, 30 Jan 2023 18:35:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=1u9t1H+HU2zMGcldkE0dm5tbD5OiqV0vr+NJule6bo4=; b=sv0Ug0Nx3GH7aSZw2rGsbY9445qEURy0pSDjIZzQNTwWE+2lGDsk4S4f9xH1Cm+qg5 ohsdSe8vfsxko7NrbTAv8K6FoHu7lN0vMgd77MYzBEMCC/XDVWe67WvkKvGxibw7XzXm mcLTmxluoQ4i7UDR0W4pirKHaXXA50hThF55xMCaBtBaH2Tgyk1PJXTXnwE2me88JKzg HuWkNNJNCdvNAPlQGLP+NO6Y8BY+fRojljEzUp4QILvT18kxpzSI6vr+xef9lHPW8XM0 Hv/1DM3bnMXEcVHxGYWnXIrUNvju5pULXOp6ztJmduFaBMc6/laLQtc7d+4Yp5cXSa5r tdfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=1u9t1H+HU2zMGcldkE0dm5tbD5OiqV0vr+NJule6bo4=; b=IXhkIt+I40PnVten23R8ytzwn10Sz7PB5HPNu+GzSWV52KAkckaKNrDxb3ye8gkFbY ENa952Sqdzy9dBkMPFl8S6Xshz9S/oZKEwbY1zf8VXPExdzGniwul8jlLX9ldm1GgnDc w+DUobEaghdu1kFQZ2n8FPazo5BQl8/pBlk1HuQ2olnslc2GQHtpb/uLFYl/2Kee66VT N3gfjAPWCATxMucjsslV2nflyOhuHwZ2xkq8s7hbN/qjaHO/CnnIiG0efIkrZgek4Rs1 YDPsz+dDVL4ROxY1r8Lf1D66V1YQoFfH+uYo1gcKOeOSbPO/06umYBUnbOZzHf8eHVYv 0WBw== X-Gm-Message-State: AFqh2krsTR4U86OMM/JZi/MFOmP5GD8Y0pxd0DUkCDlh+dkWqBx7tAYf 6Bf+aCmI+G37YiXa918n9akNiA== X-Google-Smtp-Source: AMrXdXvZ7w2pgJoZao2G3m2UeAYyGOLEuTL+d74ltOyW34bdTVIXAjHHDS0QkESi+QheJv6okUlp8w== X-Received: by 2002:a17:902:f789:b0:192:9550:339a with SMTP id q9-20020a170902f78900b001929550339amr55698184pln.52.1675132529308; Mon, 30 Jan 2023 18:35:29 -0800 (PST) Received: from [10.85.115.102] ([139.177.225.244]) by smtp.gmail.com with ESMTPSA id v3-20020a17090331c300b001869ba04c83sm8449593ple.245.2023.01.30.18.35.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Jan 2023 18:35:28 -0800 (PST) Message-ID: Date: Tue, 31 Jan 2023 10:35:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [External] Re: [PATCH] sched/core: Avoid WARN_DOUBLE_CLOCK warning when CONFIG_SCHED_CORE To: Peter Zijlstra Cc: mingo@redhat.com, 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, mgorman@techsingularity.net, linux-kernel@vger.kernel.org References: <20221206070550.31763-1-jiahao.os@bytedance.com> From: Hao Jia In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/1/16 Peter Zijlstra wrote: > On Tue, Dec 06, 2022 at 03:05:50PM +0800, Hao Jia wrote: >> When we need to call update_rq_clock() to update the rq clock of >> other CPUs on the same core, before that we need to clear RQCF_UPDATED >> of rq->clock_update_flags to avoid the WARN_DOUBLE_CLOCK warning. >> Because at this time the rq->clock_update_flags of other CPUs >> may be RQCF_UPDATED. > > So you've found that the WARN_DOUBLE_CLOCK machinery doesn't work for > core-sched -- but then instead of fixing that machinery, you put > band-aids on it :/ > > Hi, Peter Sorry for the late reply. I just finished my holiday. I am trying to adapt WARN_DOUBLE_CLOCK machinery for core-sched. If sched_core_enabled(), we will get a core wide rq->lock, so we can safely clear RQCF_UPDATED of rq->clock_update_flags of all CPUs on this core. This avoids a WARN_DOUBLE_CLOCK warning when we call update_rq_clock() to update the rq clock of other cpus on the same core. We cannot clear rq->clock_update_flags of other cpus on the same core in rq_pin_lock(). Because in some functions, we will temporarily give up core wide rq->lock, and then use raw_spin_rq_lock() to obtain core wide rq->lock, such as newidle_balance() and _double_lock_balance(). Thanks, Hao --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e838feb6adc5..f279912e30b3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -435,6 +435,21 @@ sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { } #endif /* CONFIG_SCHED_CORE */ +static inline void sched_core_rq_clock_clear_update(struct rq *rq) +{ +#ifdef CONFIG_SCHED_DEBUG + const struct cpumask *smt_mask; + int i; + if (rq->core_enabled) { + smt_mask = cpu_smt_mask(rq->cpu); + for_each_cpu(i, smt_mask) { + if (rq->cpu != i) + cpu_rq(i)->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); + } + } +#endif +} + /* * Serialization rules: * @@ -546,6 +561,7 @@ void raw_spin_rq_lock_nested(struct rq *rq, int subclass) if (likely(lock == __rq_lockp(rq))) { /* preempt_count *MUST* be > 1 */ preempt_enable_no_resched(); + sched_core_rq_clock_clear_update(rq); return; } raw_spin_unlock(lock);