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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 53362C4CED0 for ; Mon, 23 Sep 2019 15:29:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25A4120835 for ; Mon, 23 Sep 2019 15:29:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569252545; bh=UusacmkEN6mDerkjQBRuvKA0NhZ5ib71ZM7nkpWnWzw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=pjipa1yMdMe4bY4jzCEdoOO1c0QhO3WQLxqo/ai4en4k9XCnjle/6nffemWiCYac3 QuksSg27Urwnr2xoElYrqGazWJ0RWVTnYAu23xQ1FpmkTrt8lGowKnAFE4cAH0ybHa lGNDmOMFkXDzWHxoVmml/UQZdi+mzmUyWx8Stj10= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731868AbfIWP3E (ORCPT ); Mon, 23 Sep 2019 11:29:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:51768 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725951AbfIWP3E (ORCPT ); Mon, 23 Sep 2019 11:29:04 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3DAA9AD85; Mon, 23 Sep 2019 15:28:59 +0000 (UTC) Date: Mon, 23 Sep 2019 17:28:56 +0200 From: Michal Hocko To: Peter Zijlstra Cc: Yunsheng Lin , catalin.marinas@arm.com, will@kernel.org, mingo@redhat.com, bp@alien8.de, rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, jiaxun.yang@flygoat.com, chenhc@lemote.com, akpm@linux-foundation.org, rppt@linux.ibm.com, anshuman.khandual@arm.com, tglx@linutronix.de, cai@lca.pw, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, len.brown@intel.com, axboe@kernel.dk, dledford@redhat.com, jeffrey.t.kirsher@intel.com, linux-alpha@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, tbogendoerfer@suse.de, linux-mips@vger.kernel.org, rafael@kernel.org, gregkh@linuxfoundation.org Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Message-ID: <20190923152856.GB17206@dhcp22.suse.cz> References: <1568724534-146242-1-git-send-email-linyunsheng@huawei.com> <20190923151519.GE2369@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190923151519.GE2369@hirez.programming.kicks-ass.net> 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 Mon 23-09-19 17:15:19, Peter Zijlstra wrote: > On Tue, Sep 17, 2019 at 08:48:54PM +0800, Yunsheng Lin wrote: > > When passing the return value of dev_to_node() to cpumask_of_node() > > without checking if the device's node id is NUMA_NO_NODE, there is > > global-out-of-bounds detected by KASAN. > > > > From the discussion [1], NUMA_NO_NODE really means no node affinity, > > which also means all cpus should be usable. So the cpumask_of_node() > > should always return all cpus online when user passes the node id as > > NUMA_NO_NODE, just like similar semantic that page allocator handles > > NUMA_NO_NODE. > > > > But we cannot really copy the page allocator logic. Simply because the > > page allocator doesn't enforce the near node affinity. It just picks it > > up as a preferred node but then it is free to fallback to any other numa > > node. This is not the case here and node_to_cpumask_map will only restrict > > to the particular node's cpus which would have really non deterministic > > behavior depending on where the code is executed. So in fact we really > > want to return cpu_online_mask for NUMA_NO_NODE. > > > > Also there is a debugging version of node_to_cpumask_map() for x86 and > > arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this > > patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map(). > > > > [1] https://lore.kernel.org/patchwork/patch/1125789/ > > That is bloody unusable, don't do that. Use: > > https://lkml.kernel.org/r/$MSGID > > if anything. Then I can find it in my local mbox without having to > resort to touching a mouse and shitty browser software. > > (also patchwork is absolute crap for reading email threads) > > Anyway, I found it -- I think, I refused to click the link. I replied > there. > > > Signed-off-by: Yunsheng Lin > > Suggested-by: Michal Hocko > > Acked-by: Michal Hocko > > > > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c > > index 4123100e..9859acb 100644 > > --- a/arch/x86/mm/numa.c > > +++ b/arch/x86/mm/numa.c > > @@ -861,6 +861,9 @@ void numa_remove_cpu(int cpu) > > */ > > const struct cpumask *cpumask_of_node(int node) > > { > > + if (node == NUMA_NO_NODE) > > + return cpu_online_mask; > > This mandates the caller holds cpus_read_lock() or something, I'm pretty > sure that if I put: > > lockdep_assert_cpus_held(); Is this documented somewhere? Also how does that differ from a normal case when a proper node is used? The cpumask will always be dynamic in the cpu hotplug presence, right? > here, it comes apart real quick. Without holding the cpu hotplug lock, > the online mask is gibberish. Can the returned cpu mask go away? -- Michal Hocko SUSE Labs