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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DB5B7C67861 for ; Fri, 5 Apr 2024 09:53:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:CC:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=zkGusa2X3ZLYqdaTsQ5cVoWuzE6DQw4CqayPRtjlBXg=; b=msMzYKhpiBMPe/ GdKXuiQMWxIMlBDikohr8k5YaGRvFhdzV/51jYjFQDZH0QJN3obldhGN91M6LSah2TuN/Aik1k8H7 hvUG+d1iH+0a78rYVFEG0B7RnKy7l5Rjs5iAm+3lraDptTPGczQJREuYncLRtjgM3YVM7NB4on+30 7NZ8KnlvzdVNTfZ+e6pCfSrOSJhsy+GLwnd3cx9ZkxJKIDXhsLzQqs1ouRIk3WZA07wbKezKbEttu mX1ZMpzmrr3KCkqpZENwUZ8yW9Ov/d56Lz6/aQGkJuiDWQ0L92mBbxKOup3+5QFuuJ4DCTV1sSSZi 4jAkbOiDACJxiJSzO3Bw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rsgFq-00000006H7p-0Nzi; Fri, 05 Apr 2024 09:53:02 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rsgFl-00000006H3S-3rQ8 for linux-arm-kernel@lists.infradead.org; Fri, 05 Apr 2024 09:53:00 +0000 Received: from mail.maildlp.com (unknown [172.18.186.31]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4V9tvp1hqnz6J7pk; Fri, 5 Apr 2024 17:48:06 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id A3E05140A36; Fri, 5 Apr 2024 17:52:46 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Fri, 5 Apr 2024 10:52:46 +0100 Date: Fri, 5 Apr 2024 10:52:44 +0100 From: Jonathan Cameron To: Mark Rutland CC: Dawei Li , , , , , , , , , , , Subject: Re: [PATCH v2 07/10] perf/hisi_pcie: Avoid placing cpumask var on stack Message-ID: <20240405105244.00003eb8@Huawei.com> In-Reply-To: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-8-dawei.li@shingroup.cn> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100003.china.huawei.com (7.191.160.210) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240405_025258_341599_0ECDC473 X-CRM114-Status: GOOD ( 26.41 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 3 Apr 2024 15:35:10 +0100 Mark Rutland wrote: > On Wed, Apr 03, 2024 at 08:51:06PM +0800, Dawei Li wrote: > > For CONFIG_CPUMASK_OFFSTACK=y kernel, explicit allocation of cpumask > > variable on stack is not recommended since it can cause potential stack > > overflow. > > > > Instead, kernel code should always use *cpumask_var API(s) to allocate > > cpumask var in config-neutral way, leaving allocation strategy to > > CONFIG_CPUMASK_OFFSTACK. > > > > But dynamic allocation in cpuhp's teardown callback is somewhat problematic > > for if allocation fails(which is unlikely but still possible): > > - If -ENOMEM is returned to caller, kernel crashes for non-bringup > > teardown; > > - If callback pretends nothing happened and returns 0 to caller, it may > > trap system into an in-consisitent/compromised state; > > > > Use newly-introduced cpumask_any_and_but() to address all issues above. > > It eliminates usage of temporary cpumask var in generic way, no matter how > > the cpumask var is allocated. > > > > Suggested-by: Mark Rutland > > Signed-off-by: Dawei Li > > The logic looks good to me, but I'd like the commit message updated the same as > per my comment on patch 2. > > With that commit message: > > Reviewed-by: Mark Rutland Acked-by: Jonathan Cameron > > Mark. > > > --- > > drivers/perf/hisilicon/hisi_pcie_pmu.c | 9 ++++----- > > 1 file changed, 4 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c > > index 5d1f0e9fdb08..06b192cc31d5 100644 > > --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c > > +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c > > @@ -673,7 +673,6 @@ static int hisi_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > > { > > struct hisi_pcie_pmu *pcie_pmu = hlist_entry_safe(node, struct hisi_pcie_pmu, node); > > unsigned int target; > > - cpumask_t mask; > > int numa_node; > > > > /* Nothing to do if this CPU doesn't own the PMU */ > > @@ -684,10 +683,10 @@ static int hisi_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > > > > /* Choose a local CPU from all online cpus. */ > > numa_node = dev_to_node(&pcie_pmu->pdev->dev); > > - if (cpumask_and(&mask, cpumask_of_node(numa_node), cpu_online_mask) && > > - cpumask_andnot(&mask, &mask, cpumask_of(cpu))) > > - target = cpumask_any(&mask); > > - else > > + > > + target = cpumask_any_and_but(cpumask_of_node(numa_node), > > + cpu_online_mask, cpu); > > + if (target >= nr_cpu_ids) > > target = cpumask_any_but(cpu_online_mask, cpu); > > > > if (target >= nr_cpu_ids) { > > -- > > 2.27.0 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel