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 24B67CD1288 for ; Wed, 3 Apr 2024 14:36:50 +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:In-Reply-To:MIME-Version:References: 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=8qr7s/RqHI78EW+RlEh3ZxVWXxQ0QeQ2YKAwnZH/HZc=; b=C/S/PlB+R6yzfo MN4g08dCY3AEDXQfQtoM5WnWzXAlOtjJ7QNVYzjJSSdG/MdQOhQ+O0Ae35+f6X8WhewgAKgxmBcXO XXZaASox18ysJN7Vhygq9EJHSl2U9GQKsJe0XnA/xcL0cK7wPibXDBM5yIhYVfQE/TcStNoSPqrho M/5Gs770gZpigq39diuGoIIXTcHpnj/vIq9DnlDrifejLnCP0A0+5s8TbLUh5DYGAHm3Q+t7mavet HMTCgI9qdTjfLR4SME10jkgcVYdOUKBhzmKK4lpobGgQDJSUou5h3gydD51vsoATXbglHGs2ymTUo gXsbPmVNvPEXi/tdUk6Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs1jD-0000000GVmD-1m5B; Wed, 03 Apr 2024 14:36:39 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs1jA-0000000GVln-2MDS for linux-arm-kernel@lists.infradead.org; Wed, 03 Apr 2024 14:36:38 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C1C301007; Wed, 3 Apr 2024 07:37:06 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 793C43F7B4; Wed, 3 Apr 2024 07:36:33 -0700 (PDT) Date: Wed, 3 Apr 2024 15:36:30 +0100 From: Mark Rutland To: Dawei Li Cc: will@kernel.org, yury.norov@gmail.com, linux@rasmusvillemoes.dk, xueshuai@linux.alibaba.com, renyu.zj@linux.alibaba.com, yangyicong@hisilicon.com, jonathan.cameron@huawei.com, andersson@kernel.org, konrad.dybcio@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH v2 09/10] perf/qcom_l2: Avoid placing cpumask var on stack Message-ID: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-10-dawei.li@shingroup.cn> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240403125109.2054881-10-dawei.li@shingroup.cn> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240403_073636_676885_4E4889A6 X-CRM114-Status: GOOD ( 24.14 ) 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, Apr 03, 2024 at 08:51:08PM +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 Mark. > --- > drivers/perf/qcom_l2_pmu.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c > index 148df5ae8ef8..b5a44dc1dc3a 100644 > --- a/drivers/perf/qcom_l2_pmu.c > +++ b/drivers/perf/qcom_l2_pmu.c > @@ -801,9 +801,8 @@ static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node) > > static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > { > - struct cluster_pmu *cluster; > struct l2cache_pmu *l2cache_pmu; > - cpumask_t cluster_online_cpus; > + struct cluster_pmu *cluster; > unsigned int target; > > l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node); > @@ -820,9 +819,8 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > cluster->on_cpu = -1; > > /* Any other CPU for this cluster which is still online */ > - cpumask_and(&cluster_online_cpus, &cluster->cluster_cpus, > - cpu_online_mask); > - target = cpumask_any_but(&cluster_online_cpus, cpu); > + target = cpumask_any_and_but(&cluster->cluster_cpus, > + cpu_online_mask, cpu); > if (target >= nr_cpu_ids) { > disable_irq(cluster->irq); > return 0; > -- > 2.27.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel