From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 54F7B56751; Wed, 3 Apr 2024 14:36:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712154997; cv=none; b=L9kFmEPWlk2lFi2vrJ15bvTGiKeO4TLLvZgKjxi4T88plfF6AX0NyCPRVcH+3P5WvJULIV+1XaO7HU1buHVxWUEvSIAjr0Z3QM+Tzaq0uEKO/J/umvw27WLh3FV7tGmCm4KOvxUz9EUv+ua8iCpQu77Qd9CgkXtx8t/xsqUMgeI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712154997; c=relaxed/simple; bh=T5ZryUJySmkQGCGluVYgzILkh9NuHRn6+M5l9AwVKbA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OTbl/ycZRUaORp7OuZKjEMfgO0cmavJo5VaxpX4aDYaeJ7VdGliDU38k9LXgXUKbEg01LnqResIc8OXIYHRUOYWSJo9UhV9hzHxgc70oXrNslcfhej5GWLeV3DoxHOLeZQ675//tEITSBexqyUtSt3ULronje9vdffzR0fUsaX0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240403125109.2054881-10-dawei.li@shingroup.cn> 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 >