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 309CB56751; Wed, 3 Apr 2024 14:38:19 +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=1712155102; cv=none; b=iZQ8l0wl6DrJxq8IDqIv7BYPLWEveAHIKwXyhQjg9i4F/taslUPUagD5qsEQNbYqrsGXvTPWUwx6ADBMvl4Xuhixh8ESw+31Hfwa+A8UcVxx2XU+BqC38e1vcJTTYTDQpsquODfy5dHh9cfDMjHd/RfZNjyXP1n61eWxfAwKuVs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712155102; c=relaxed/simple; bh=hfRqXl7ehF2sHdQ1hQLBRdQcRua85KKZsoNUiS1ESF0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fZQPC9LzFThiarJeAy0RGGH9eQf2Yk8ZApiZkZ5k1mzaKhzHpfjlNwkWIXfKZegt5Gk/W58Nhci5R+djvTosFkhUehbMFPXmbUrFaHGWhdggrKJBzrSOTPFwOsKaDxi5TM6MN8rPcQz8n4Dej+RE9ZYPZa7kHJmGdwSt38GqWiA= 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 A15131007; Wed, 3 Apr 2024 07:38:50 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.212]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 58A0E3F7B4; Wed, 3 Apr 2024 07:38:17 -0700 (PDT) Date: Wed, 3 Apr 2024 15:38:14 +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 10/10] perf/thunderx2: Avoid placing cpumask var on stack Message-ID: References: <20240403125109.2054881-1-dawei.li@shingroup.cn> <20240403125109.2054881-11-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: <20240403125109.2054881-11-dawei.li@shingroup.cn> On Wed, Apr 03, 2024 at 08:51:09PM +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/thunderx2_pmu.c | 10 +++------- > 1 file changed, 3 insertions(+), 7 deletions(-) > > diff --git a/drivers/perf/thunderx2_pmu.c b/drivers/perf/thunderx2_pmu.c > index e16d10c763de..b3377b662ffc 100644 > --- a/drivers/perf/thunderx2_pmu.c > +++ b/drivers/perf/thunderx2_pmu.c > @@ -932,9 +932,8 @@ static int tx2_uncore_pmu_online_cpu(unsigned int cpu, > static int tx2_uncore_pmu_offline_cpu(unsigned int cpu, > struct hlist_node *hpnode) > { > - int new_cpu; > struct tx2_uncore_pmu *tx2_pmu; > - struct cpumask cpu_online_mask_temp; > + unsigned int new_cpu; > > tx2_pmu = hlist_entry_safe(hpnode, > struct tx2_uncore_pmu, hpnode); > @@ -945,11 +944,8 @@ static int tx2_uncore_pmu_offline_cpu(unsigned int cpu, > if (tx2_pmu->hrtimer_callback) > hrtimer_cancel(&tx2_pmu->hrtimer); > > - cpumask_copy(&cpu_online_mask_temp, cpu_online_mask); > - cpumask_clear_cpu(cpu, &cpu_online_mask_temp); > - new_cpu = cpumask_any_and( > - cpumask_of_node(tx2_pmu->node), > - &cpu_online_mask_temp); > + new_cpu = cpumask_any_and_but(cpumask_of_node(tx2_pmu->node), > + cpu_online_mask, cpu); > > tx2_pmu->cpu = new_cpu; > if (new_cpu >= nr_cpu_ids) > -- > 2.27.0 >