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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 1F08EC282C4 for ; Mon, 4 Feb 2019 12:03:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DFDBD2087C for ; Mon, 4 Feb 2019 12:03:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YOgcOO1p" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729694AbfBDMDA (ORCPT ); Mon, 4 Feb 2019 07:03:00 -0500 Received: from merlin.infradead.org ([205.233.59.134]:35666 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729043AbfBDMC7 (ORCPT ); Mon, 4 Feb 2019 07:02:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=bg4hjxM5IGBEf79h/YG7PxQxXFu6QKqjbZsWvg+yTME=; b=YOgcOO1pIX+4vsm+OXVzah8p7 acFfb58No07LKiXH3dAMcG7yoAxlvMDiYfpQihTf6w9dk/FfSUmQhc0KNr8knY+g3XJW7Tz9LjNfi 6t34AZ1nDDYQAR7kcYBm0Y36dPIGiBFWdaSqJmomAxV4U40STrquMC2Ifb8EYl0oquS+jURZtjUgE nIqgPthb1YvPBRXlYpbrFVn+tEBvLZI3/IZkS0/HiVEQ8pg7hlG0xFY13CRQ4EqTda35cpOY20CbR D+2Fb54UAATaOhZKcIk3B0Tw8qpFhkKudjGnGUaW1A5fG8gfEvv1jKHqTbTW6dC2M8MqrnbZX3We5 I80cWQZcg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gqcxR-0002Fq-RL; Mon, 04 Feb 2019 12:02:38 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 985652029FA06; Mon, 4 Feb 2019 13:02:36 +0100 (CET) Date: Mon, 4 Feb 2019 13:02:36 +0100 From: Peter Zijlstra To: Juri Lelli 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 Subject: Re: [PATCH v6 3/5] cgroup/cpuset: make callback_lock raw Message-ID: <20190204120236.GC17550@hirez.programming.kicks-ass.net> References: <20190117084739.17078-1-juri.lelli@redhat.com> <20190117084739.17078-4-juri.lelli@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190117084739.17078-4-juri.lelli@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 17, 2019 at 09:47:37AM +0100, Juri Lelli wrote: > @@ -3233,11 +3233,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) > { > unsigned long flags; > > - spin_lock_irqsave(&callback_lock, flags); > + raw_spin_lock_irqsave(&callback_lock, flags); > rcu_read_lock(); > guarantee_online_cpus(task_cs(tsk), pmask); > rcu_read_unlock(); > - spin_unlock_irqrestore(&callback_lock, flags); > + raw_spin_unlock_irqrestore(&callback_lock, flags); > } > > void cpuset_cpus_allowed_fallback(struct task_struct *tsk) > @@ -3285,11 +3285,11 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk) > nodemask_t mask; > unsigned long flags; > > - spin_lock_irqsave(&callback_lock, flags); > + raw_spin_lock_irqsave(&callback_lock, flags); > rcu_read_lock(); > guarantee_online_mems(task_cs(tsk), &mask); > rcu_read_unlock(); > - spin_unlock_irqrestore(&callback_lock, flags); > + raw_spin_unlock_irqrestore(&callback_lock, flags); > > return mask; > } > @@ -3381,14 +3381,14 @@ bool __cpuset_node_allowed(int node, gfp_t gfp_mask) > return true; > > /* Not hardwall and node outside mems_allowed: scan up cpusets */ > - spin_lock_irqsave(&callback_lock, flags); > + raw_spin_lock_irqsave(&callback_lock, flags); > > rcu_read_lock(); > cs = nearest_hardwall_ancestor(task_cs(current)); > allowed = node_isset(node, cs->mems_allowed); > rcu_read_unlock(); > > - spin_unlock_irqrestore(&callback_lock, flags); > + raw_spin_unlock_irqrestore(&callback_lock, flags); > return allowed; > } These three appear to be a user-controlled O(n) (depth of cgroup tree). Which is basically bad for raw_spinlock_t. The Changelog should really have mentioned this; and ideally we'd somehow avoid this.