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 9C4A3CD128A for ; Wed, 3 Apr 2024 14:21:28 +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=dEUJUDHkZzigGulz5EZHxWtDqFLw4Hrp13iYiSCBbxs=; b=GbBPfHJaXsY51V I/Vvs2EJ8K16J6ZqbckOObSvhgKisvN5DAKv1U3mB0f0GhU1k6cMu6vAHmATesxGIipKpCLm6Vici uWyJcCiaeDSANU+fN97j8jjeh96F7215rj07kY8HszWbPtHHWgsTDX/t5pSVlKWyGo5AlxEGUCZJO A67jLWN2s/IENY1I8QHIiMJnx+7YZ4qousGMm19IEPG8rG+PLFYU4LV++zYUaB2ll0wZqom+E38KH s1jM7TJGA6/2/QS2Dwjjm4QYrqKGQqPbw46Iel2zX1TjbX6mAtfpaBd3gy7nMaYTJ4GpWrRVbMe5N K63rEvnKl+UinYrL3O1Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs1UO-0000000GRZz-1FKv; Wed, 03 Apr 2024 14:21:20 +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 1rs1UL-0000000GRYp-3VrC for linux-arm-kernel@lists.infradead.org; Wed, 03 Apr 2024 14:21:18 +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 6C79E1007; Wed, 3 Apr 2024 07:21:46 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 226733F7B4; Wed, 3 Apr 2024 07:21:12 -0700 (PDT) Date: Wed, 3 Apr 2024 15:21:10 +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 04/10] perf/arm_cspmu: Avoid placing cpumask var on stack Message-ID: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-5-dawei.li@shingroup.cn> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240403125109.2054881-5-dawei.li@shingroup.cn> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240403_072117_938351_C7AD6DD8 X-CRM114-Status: GOOD ( 24.04 ) 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 08:51:03PM +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/arm_cspmu/arm_cspmu.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c > index b9a252272f1e..fd1004251665 100644 > --- a/drivers/perf/arm_cspmu/arm_cspmu.c > +++ b/drivers/perf/arm_cspmu/arm_cspmu.c > @@ -1322,8 +1322,7 @@ static int arm_cspmu_cpu_online(unsigned int cpu, struct hlist_node *node) > > static int arm_cspmu_cpu_teardown(unsigned int cpu, struct hlist_node *node) > { > - int dst; > - struct cpumask online_supported; > + unsigned int dst; > > struct arm_cspmu *cspmu = > hlist_entry_safe(node, struct arm_cspmu, cpuhp_node); > @@ -1333,9 +1332,8 @@ static int arm_cspmu_cpu_teardown(unsigned int cpu, struct hlist_node *node) > return 0; > > /* Choose a new CPU to migrate ownership of the PMU to */ > - cpumask_and(&online_supported, &cspmu->associated_cpus, > - cpu_online_mask); > - dst = cpumask_any_but(&online_supported, cpu); > + dst = cpumask_any_and_but(&cspmu->associated_cpus, > + cpu_online_mask, cpu); > if (dst >= nr_cpu_ids) > 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