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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A3F9AC5B578 for ; Mon, 1 Jul 2019 06:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D72F212F5 for ; Mon, 1 Jul 2019 06:52:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727615AbfGAGwj (ORCPT ); Mon, 1 Jul 2019 02:52:39 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:32972 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727279AbfGAGwi (ORCPT ); Mon, 1 Jul 2019 02:52:38 -0400 Received: by mail-wm1-f68.google.com with SMTP id h19so13817370wme.0 for ; Sun, 30 Jun 2019 23:52:37 -0700 (PDT) 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:user-agent; bh=ZanPqiEPVMdySHonMbQBl/5/VvjKUDnA16ZAnUCifwo=; b=qdSWVW2TSjRVT4hqR5Q1Un6Uov090iDyqZzRmHFRNfGjwcwJIEwnkhublC7h7Qr+vY M34ry4zO0B73wKNSZ2E6L0uY9/H72ZHMSf1nhnKWC5iadxSwEFNU0uL3Wdhn/iDazWt6 hDkStCYDG0JJtnLcrAK8DBtIVrJmBAmp0b3e/upEQ2k2fzbNNX2lKebYneuN3l30cZM5 uudrfc28TYm7vqCg+8jxW6p3u4TVapSkAsaApUp7BH2CZkKlLrf85Smt8/UIWcmbz6Ic rN4YOO9Jm6N2eN3Vy9YP+qzi4uQ0NI7ixZNUT7sBXDkVv7cKS3HvABv/2kgPCNFHCfbn 6k2w== X-Gm-Message-State: APjAAAWlyw+6vn3glGHGARCAFpssO02ns5xmG3nlcPhTwGh+0h0fGevH DVJ+WHNPE6DjeAb2NCutPnOmmA== X-Google-Smtp-Source: APXvYqyAJZ4botdtSJ3zU9ORTAwwQRPjpGAfhDs9AIdatmN70PBO8LqjP2idy/zV96eTgzly1dbG3w== X-Received: by 2002:a1c:dc07:: with SMTP id t7mr16638183wmg.164.1561963956698; Sun, 30 Jun 2019 23:52:36 -0700 (PDT) Received: from localhost.localdomain ([151.15.224.253]) by smtp.gmail.com with ESMTPSA id h21sm10492932wmb.47.2019.06.30.23.52.35 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 30 Jun 2019 23:52:35 -0700 (PDT) Date: Mon, 1 Jul 2019 08:52:33 +0200 From: Juri Lelli To: Peter Zijlstra Cc: mingo@redhat.com, rostedt@goodmis.org, tj@kernel.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it, bristot@redhat.com, mathieu.poirier@linaro.org, lizefan@huawei.com, cgroups@vger.kernel.org, Prateek Sood Subject: Re: [PATCH v8 6/8] cgroup/cpuset: Change cpuset_rwsem and hotplug lock order Message-ID: <20190701065233.GA26005@localhost.localdomain> References: <20190628080618.522-1-juri.lelli@redhat.com> <20190628080618.522-7-juri.lelli@redhat.com> <20190628130308.GU3419@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190628130308.GU3419@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 28/06/19 15:03, Peter Zijlstra wrote: > On Fri, Jun 28, 2019 at 10:06:16AM +0200, Juri Lelli wrote: > > cpuset_rwsem is going to be acquired from sched_setscheduler() with a > > following patch. There are however paths (e.g., spawn_ksoftirqd) in > > which sched_scheduler() is eventually called while holding hotplug lock; > > this creates a dependecy between hotplug lock (to be always acquired > > first) and cpuset_rwsem (to be always acquired after hotplug lock). > > > > Fix paths which currently take the two locks in the wrong order (after > > a following patch is applied). > > Signed-off-by: Juri Lelli > > This all reminds me of this: > > https://lkml.kernel.org/r/1510755615-25906-1-git-send-email-prsood@codeaurora.org > > Which sadly got reverted again. If we do this now (I've always been a > proponent), then we can make that rebuild synchronous again, which > should also help here IIRC. Why was that reverted? Perf regression of some type? Thanks, Juri