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 CA9B09461; Wed, 3 Apr 2024 14:33:22 +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=1712154804; cv=none; b=YSxqUwnY69aWHmAJB+7AZ1EK0CDAwyh6xSOqAwZfXCOjcl9poYpe+09a3RyIGD5i7XblyxPwKDpx8WmdLFdwV7VWzK1nWJ8DY7NAoE0mKcFOriwY/suSgCZbosPFmWTD8rhwwX96kJK0duFYUFWNFQrf+0ZOn8uKsqoGsaMGy/s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712154804; c=relaxed/simple; bh=HqsbniXj2szSUCBQwyicUfJM4X8Rqg2MGkEXTwj3m1U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TlAio50/5WnahzJ017BfILDaExYk9H+dFa21NiIgCBcV6uQFqKyVueAyB5vJY2h9+N4MsmNJ3hFrQgO/XhtmCcuRtwhU4H2TD59u1Z0DSCewS/QUak1uXlb5J5D4rTEmIuMbJZMfNQHUHfiVf43g8PlYOrJQAn9I91tltO/ZvVw= 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 4E26F1007; Wed, 3 Apr 2024 07:33:53 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 01C423F7B4; Wed, 3 Apr 2024 07:33:19 -0700 (PDT) Date: Wed, 3 Apr 2024 15:33:17 +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 06/10] perf/dwc_pcie: Avoid placing cpumask var on stack Message-ID: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-7-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: <20240403125109.2054881-7-dawei.li@shingroup.cn> On Wed, Apr 03, 2024 at 08:51:05PM +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/dwc_pcie_pmu.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/perf/dwc_pcie_pmu.c b/drivers/perf/dwc_pcie_pmu.c > index 957058ad0099..c5e328f23841 100644 > --- a/drivers/perf/dwc_pcie_pmu.c > +++ b/drivers/perf/dwc_pcie_pmu.c > @@ -690,9 +690,8 @@ static int dwc_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_n > { > struct dwc_pcie_pmu *pcie_pmu; > struct pci_dev *pdev; > - int node; > - cpumask_t mask; > unsigned int target; > + int node; > > pcie_pmu = hlist_entry_safe(cpuhp_node, struct dwc_pcie_pmu, cpuhp_node); > /* Nothing to do if this CPU doesn't own the PMU */ > @@ -702,10 +701,9 @@ static int dwc_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_n > pcie_pmu->on_cpu = -1; > pdev = pcie_pmu->pdev; > node = dev_to_node(&pdev->dev); > - if (cpumask_and(&mask, cpumask_of_node(node), cpu_online_mask) && > - cpumask_andnot(&mask, &mask, cpumask_of(cpu))) > - target = cpumask_any(&mask); > - else > + > + target = cpumask_any_and_but(cpumask_of_node(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 >