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 B4C6ACD128A for ; Wed, 3 Apr 2024 14:32:24 +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=rXidRx2IDEO2Aup1wWNa8W0O2Iqaf2EKBcoTAtWEpZI=; b=Sekxpgj8kxO8yS 34rgSQrhuwOfasUBJcXhqEXvbaUOEyeV2q3m5/1iPIZBxfcF18KLXQwT6fdMU7EP8+NRC13CiFO28 wEkg/e57OiVsCzxYYChCu26UQ3y0LLNrnQ2/6P5Pwcf8PL7OMMuOH7eUBc4eNcC5kJqMSjochG6jG +iJ/P+nY+I813Rkl+R2bT3LMNIlASLDlqlSvraNlU8Fjbpff07CBDVN5BrH1KPflTyacT8njMQKoU AE89fCpYyJilAWEsYq7jakRNKs+rtNXK3Mehw1vdedsTLN17crZn+Cjn931/8+9PqZU/ZrKAzOX2S 867KC53ZQ6v+eIRUBSww==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rs1et-0000000GUAq-3jf0; Wed, 03 Apr 2024 14:32:11 +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 1rs1eq-0000000GU9h-35YV for linux-arm-kernel@lists.infradead.org; Wed, 03 Apr 2024 14:32:10 +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 B81511007; Wed, 3 Apr 2024 07:32:38 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6C8843F7B4; Wed, 3 Apr 2024 07:32:05 -0700 (PDT) Date: Wed, 3 Apr 2024 15:32:02 +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 05/10] perf/arm_dsu: Avoid placing cpumask var on stack Message-ID: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-6-dawei.li@shingroup.cn> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240403125109.2054881-6-dawei.li@shingroup.cn> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240403_073208_862527_89D1252F X-CRM114-Status: GOOD ( 24.84 ) 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 08:51:04PM +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_dsu_pmu.c | 19 ++++++------------- > 1 file changed, 6 insertions(+), 13 deletions(-) > > diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c > index bae3ca37f846..adc0bbb5fafe 100644 > --- a/drivers/perf/arm_dsu_pmu.c > +++ b/drivers/perf/arm_dsu_pmu.c > @@ -230,15 +230,6 @@ static const struct attribute_group *dsu_pmu_attr_groups[] = { > NULL, > }; > > -static int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu) > -{ > - struct cpumask online_supported; > - > - cpumask_and(&online_supported, > - &dsu_pmu->associated_cpus, cpu_online_mask); > - return cpumask_any_but(&online_supported, cpu); > -} > - > static inline bool dsu_pmu_counter_valid(struct dsu_pmu *dsu_pmu, u32 idx) > { > return (idx < dsu_pmu->num_counters) || > @@ -827,14 +818,16 @@ static int dsu_pmu_cpu_online(unsigned int cpu, struct hlist_node *node) > > static int dsu_pmu_cpu_teardown(unsigned int cpu, struct hlist_node *node) > { > - int dst; > - struct dsu_pmu *dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, > - cpuhp_node); > + struct dsu_pmu *dsu_pmu; > + unsigned int dst; > + > + dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, cpuhp_node); > > if (!cpumask_test_and_clear_cpu(cpu, &dsu_pmu->active_cpu)) > return 0; > > - dst = dsu_pmu_get_online_cpu_any_but(dsu_pmu, cpu); > + dst = cpumask_any_and_but(&dsu_pmu->associated_cpus, > + cpu_online_mask, cpu); > /* If there are no active CPUs in the DSU, leave IRQ disabled */ > 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