From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 853E016C87F; Fri, 5 Apr 2024 09:52:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712310772; cv=none; b=Hgd5+xOHPTlK66IGF4TEiltDljKX5mUXN9FugZnzbGd92TQGKLlN8pXddD+MjPqiyfHNx37U9RQURAc4TYL2UGjyULNDShLWimR9ure06WvnB9PVlm3tg/ln4BNbgtD7lia5AMAiGQeam79ZTiFLsAPaneYOHcGYmSPzFImcqHw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712310772; c=relaxed/simple; bh=Cd32nAS4wjxMldROP8jmFEdqvn59+sAVNup8vx4Txdw=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lzMnXPEiCJRnoibN5KkFXtyiJ0SnQyYYsTFGBNwMSgFgBmjTjnUca8sgjZA08NuGrl9RIGOEAeutyh5L2/xeuHQAe+NbyRO+SGsWjz/IUsos25XygxnFn2ge7imZ2h8gfNb5e/UXenAkKvoFF4qiFmekWUIksh3piaw2tQ4ieJo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=Huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=Huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml100003.china.huawei.com (7.191.160.210) To lhrpeml500005.china.huawei.com (7.191.163.240) 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 > >