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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 B61E6C48BD1 for ; Fri, 11 Jun 2021 07:27:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D0F0613AE for ; Fri, 11 Jun 2021 07:27:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231555AbhFKH3A (ORCPT ); Fri, 11 Jun 2021 03:29:00 -0400 Received: from mail-wr1-f52.google.com ([209.85.221.52]:41489 "EHLO mail-wr1-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231289AbhFKH25 (ORCPT ); Fri, 11 Jun 2021 03:28:57 -0400 Received: by mail-wr1-f52.google.com with SMTP id o3so4899100wri.8 for ; Fri, 11 Jun 2021 00:26:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=5n7ASjdVQX9++neRCXsv7Z55wQbm+s4kD6dVvYNgYZU=; b=RkGhur84xEjQsrcwc17SY0Ez3fwuqcn5f5rlRsDo2lCJhNvFrLOeuP6kE4LZBVcoHJ 5nPcwz/cy8940sVu5oeagEQfRZ4DqX7vnn1dRk7+J8MZaWKGgPck/C2dGopKuSYUxWZQ 2kIeB/JLDWIlTLKDsd196FK0pbJsiVkIifD32EzDG/Z+wLswZ81khODnZEVFWqNthTK3 +3LbBXrt+orTfFFefYdpJl1iMNR3LWEnujy6HsW8QirKjUIF3U8zCeJDFSTsaZIwV9ib w7qmxIO7WP+0A1cTzFKMI8Jc22XfhERfpMzW5kv+/SMBtEOGHQnBAnNxsdJW8vC37j/0 zZFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5n7ASjdVQX9++neRCXsv7Z55wQbm+s4kD6dVvYNgYZU=; b=St0F/rbzQvMDzHU7GEI3X2+zZ/T9FEVjMDaFXwalToYPX7efBZcf1lbOU/PsR2aR2H RooLHzs0vN6n/wBjuGmmiIi2Td3JqZzd3ZgI2Q+3/GpnYuvvC8PFQa/T7xH0j0E/r0V5 qMQZtBKGxJK4zsGXdnYpG7hM7pTHk4OCa+fC5CcQ1ngF5G+RNaZOHPwPudgE4lnCmWH/ X4rGR6f4NX4nygs4lXkQnBqy7yOPnNFeg5GUq6C0TBv0bSuh1ORxxlIsCvuz0DNJTcMA R+RaRYFHdKgMCfobRgnVViQyMOlyuKSyLmT9k2aPcvb35whJcxYuU3Lt3W4FnGfYAIVo +rIA== X-Gm-Message-State: AOAM530nnyPJcjAZq1H7Hu/UE1okMfLUNr1/+TyUhdYYa4lmKoJcNXx9 cnRtu4p85I75t9JLtpSTWyFcBg== X-Google-Smtp-Source: ABdhPJywDjMPIVHmBZnMC7XwmDy67BVO5LvTdapfKfYTMXfIQtvsTZrpK5D1YCs4I7vz0/6bxoXg2A== X-Received: by 2002:a05:6000:232:: with SMTP id l18mr2382154wrz.88.1623396346083; Fri, 11 Jun 2021 00:25:46 -0700 (PDT) Received: from google.com (105.168.195.35.bc.googleusercontent.com. [35.195.168.105]) by smtp.gmail.com with ESMTPSA id a15sm7403125wrs.63.2021.06.11.00.25.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Jun 2021 00:25:45 -0700 (PDT) Date: Fri, 11 Jun 2021 07:25:42 +0000 From: Quentin Perret To: Peter Zijlstra Cc: mingo@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, qais.yousef@arm.com, rickyiu@google.com, wvw@google.com, patrick.bellasi@matbug.net, xuewen.yan94@gmail.com, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v2 1/3] sched: Fix UCLAMP_FLAG_IDLE setting Message-ID: References: <20210610151306.1789549-1-qperret@google.com> <20210610151306.1789549-2-qperret@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 10 Jun 2021 at 21:05:12 (+0200), Peter Zijlstra wrote: > On Thu, Jun 10, 2021 at 03:13:04PM +0000, Quentin Perret wrote: > > The UCLAMP_FLAG_IDLE flag is set on a runqueue when dequeueing the last > > active task 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 setting the flag in the uclamp_rq_inc_id() path to ensure > > things remain symmetrical. > > The code you moved is neither in uclamp_rq_inc_id(), although > uclamp_idle_reset() is called from there Yep, that is what I was trying to say. > nor does it _set_ the flag. Ahem. That I don't have a good excuse for ... > > I'm thinking it's been a long warm day? ;-) Indeed :-) Let me have another cup of coffee and try to write this again. Thanks, Quentin