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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 9BB4EC34050 for ; Wed, 19 Feb 2020 15:47:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F6AD2465D for ; Wed, 19 Feb 2020 15:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582127266; bh=dBGpk8COWykA2HKIsIUCWVEXJBH0+ZiIy7I2ni2qit4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rzFOemoGA5qUyuxrfinbURzx70uMP1Kx8lRJM84j7auHNsUQeJGEo6dOkCKSbfD1+ zTx9m4Mx4dGpgyL7hdiOFNv99Er14esMXvA7zTzALYh34llLGDmvsCB+pw1wwo0Kaj TaiuscnuYPqG/3+LjOQIlvjl9Enwng2+SOePc3eg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726799AbgBSPrp (ORCPT ); Wed, 19 Feb 2020 10:47:45 -0500 Received: from mail-qt1-f172.google.com ([209.85.160.172]:44596 "EHLO mail-qt1-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726609AbgBSPrn (ORCPT ); Wed, 19 Feb 2020 10:47:43 -0500 Received: by mail-qt1-f172.google.com with SMTP id j23so496999qtr.11; Wed, 19 Feb 2020 07:47:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ar2wlN6dePLPhoLZZdzWfBNN9k6fU+94pITjgWF6huI=; b=sclZeeHgnDkV2FYKT4/orsaaiuStLqZ7oDvYPByVLnhQ45JVzoiKCg9SNfqUizUXM1 PdKKpACiSBRuyoCuBePSMjBUHNo4RiVhaQpzsZ0g7GEoD+iOQEGeIRwVuOnx3h26J1Ll f5WxGv/gxdwlLwPEZh458ue58Eg3YNYlrnY6R/Sku7ouKhgxM9m9fDbsXTYOg9cY3pqZ OyfPMBpISOolqyPwsuMfSyNBaRCjilHCmXNoPo5yFAw3iJv73AZ+2e5WTTAsqnTmKPn/ NyriSK0FpjMHtR07Ra8dLqT9DO+YQCvCmVSBG1mQ8yH0AkBapksPiboe4tPq1PuZCEzV R3mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=ar2wlN6dePLPhoLZZdzWfBNN9k6fU+94pITjgWF6huI=; b=LSfTOgjn1GwsFm1IhtzgTe8dTA8Gp6BD6q1Lt3vGquAoSvifKVqfMcznzL03UwaDl2 pFEXgqak5EB5Gv4gqmxzc3r9ftqIbC1BOHzkg8ylB/FPYUsllKAiN8LpFenqGd8MmMzf VvONEStyH3OEn5qqRgbZyopq5b6+710HDNEqkr9HwZQ1xVfsoBb+EKYNrR6lXEVpfTx9 V0998M/FrJXG6rwCxNzv/UmOv2YK0YrZZgCjVPIjYYrmYDbPchypxOhblmcLmoTW4DuS 3d2wC2XMj18EIECxW5u8nuqeY8G8HBiulcR2b2lW78wCRTcM6ZdnhH9KnVWllpY004yU TIIQ== X-Gm-Message-State: APjAAAUax0nOPIdurs47bvYYmnMuFUPia/J6hA4oh4uVStu+kkJPDrtL mx67GgnTHqjDWAaZbTC0epg= X-Google-Smtp-Source: APXvYqxiGhWxAr3upotVXemfaiuWz84Txa2Lq+b0+qGHZn+DYTYAHiXZHToFua0j8OQIpcpsuftSGw== X-Received: by 2002:ac8:a83:: with SMTP id d3mr22727495qti.228.1582127261138; Wed, 19 Feb 2020 07:47:41 -0800 (PST) Received: from localhost ([2620:10d:c091:500::2:e7ce]) by smtp.gmail.com with ESMTPSA id i28sm183939qtc.57.2020.02.19.07.47.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Feb 2020 07:47:40 -0800 (PST) Date: Wed, 19 Feb 2020 10:47:40 -0500 From: Tejun Heo To: Mathieu Desnoyers Cc: Li Zefan , cgroups , linux-kernel , Peter Zijlstra , Ingo Molnar , Valentin Schneider Subject: Re: [regression] cpuset: offlined CPUs removed from affinity masks Message-ID: <20200219154740.GD698990@mtj.thefacebook.com> References: <1251528473.590671.1579196495905.JavaMail.zimbra@efficios.com> <1317969050.4131.1581955387909.JavaMail.zimbra@efficios.com> <20200219151922.GB698990@mtj.thefacebook.com> <1589496945.670.1582126985824.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1589496945.670.1582126985824.JavaMail.zimbra@efficios.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 10:43:05AM -0500, Mathieu Desnoyers wrote: > The regression I'm talking about here is that CONFIG_CPUSET=y changes the > behavior of the sched_setaffinify system call, which existed prior to > cpusets. > > sched_setaffinity should behave in the same way for kernels configured with > CONFIG_CPUSET=y or CONFIG_CPUSET=n. > > The fact that cpuset decides to irreversibly change the task affinity mask > may not be considered a regression if it has always done that, but changing > the behavior of sched_setaffinity seems to fit the definition of a regression. We generally use "regression" for breakages which weren't in past versions but then appeared later. It has debugging implications because if we know something is a regression, we generally can point to the commit which introduced the bug either through examining the history or bisection. It is a silly bug, for sure, but slapping regression name on it just confuses rather than helping anything. -- tejun