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 4052FD272; Wed, 3 Apr 2024 14:32:08 +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=1712154729; cv=none; b=C+pX+icBgkaK37RYuW7+uwmNO+W3XJPEet0eeCjd8PExRvitTLlqDBjd2zUaVJSPsusG6vFCxPxOmfgQXWX3cCJy8nHODQR3U3EHhV/DbB3aCa10Ya2QaemDqHJRbD6WInWbLSJrRj18gBH28oW41kTWpJu3GkWhP7znRSK1hJE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712154729; c=relaxed/simple; bh=IfavOBHuNBC7BA6z+t/e9bZRoESBeEMspQVXwHiTgtQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bgyj43GdJcYpqvFuaQeKsC7TXazfjB2J2rusqURVCvQ8eTU8SugUIBYDCXcPo16yQ0PgyaYOpzeVY9YM5fjEvKyZ8b7DxgsAIC3Lwuq30Ex9NEpxNx9DpNos3A105PAbtOPE5PYEHXoYE4IDu068HEa1Sivu5HCSNb6ExFVZORE= 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 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> 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: <20240403125109.2054881-6-dawei.li@shingroup.cn> 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 >