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 X-Spam-Level: X-Spam-Status: No, score=-15.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 963CFC07E95 for ; Tue, 13 Jul 2021 12:46:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7426E61289 for ; Tue, 13 Jul 2021 12:46:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236268AbhGMMtR (ORCPT ); Tue, 13 Jul 2021 08:49:17 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:6921 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236135AbhGMMtQ (ORCPT ); Tue, 13 Jul 2021 08:49:16 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GPKzb56FFz7Bwf; Tue, 13 Jul 2021 20:42:51 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 13 Jul 2021 20:46:20 +0800 Received: from [10.174.179.5] (10.174.179.5) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Tue, 13 Jul 2021 20:46:20 +0800 Subject: Re: [PATCH] cacheinfo: clear cache_leaves(cpu) in free_cache_attributes() To: Sudeep Holla CC: , , , References: <1626148058-55230-1-git-send-email-wangxiongfeng2@huawei.com> <20210713113315.thsvrvqvqptc7hje@bogus> From: Xiongfeng Wang Message-ID: <303cd2bf-7142-6ec9-548a-afe7f6e5ca8f@huawei.com> Date: Tue, 13 Jul 2021 20:46:19 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20210713113315.thsvrvqvqptc7hje@bogus> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.5] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sudeep, On 2021/7/13 19:33, Sudeep Holla wrote: > On Tue, Jul 13, 2021 at 11:47:38AM +0800, Xiongfeng Wang wrote: >> On ARM64, when PPTT(Processor Properties Topology Table) is not >> implemented in ACPI boot, we will goto 'free_ci' with the following >> print: >> Unable to detect cache hierarchy for CPU 0 >> > > The change itself looks good and I am fine with that. However,... > >> But some other codes may still use 'num_leaves' to iterate through the > > Can you point me exactly where it is used to make sure there are no > other issues associated with that. > >> 'info_list', such as get_cpu_cacheinfo_id(). If 'info_list' is NULL , it >> would crash. So clear 'num_leaves' in free_cache_attributes(). >> > > And can you provide the crash dump please ? If we are not hitting any > issue and you just figured this with code inspection, that is fine. It > helps to determine if this needs to be backport or just good to have > clean up. There is no issue in the mainline kernel. get_cpu_cacheinfo_id() is only called on x86. I didn't hit any issue using the mainline kernel. Actually, it's our own code that crashed. My colleague Shaobo(CCed) tried to add MPAM support on ARM64. His code called get_cpu_cacheinfo_id() and crashed when PPTT is not implemented. Maybe he should check whether PPTT is implemented before calling get_cpu_cacheinfo_id(), but we think it is also better to clear cache_leaves(cpu) in free_cache_attributes(). Sorry for not clearly expressed. Thanks, Xiongfeng > >> Signed-off-by: Xiongfeng Wang >> --- >> drivers/base/cacheinfo.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c >> index bfc0959..dad2962 100644 >> --- a/drivers/base/cacheinfo.c >> +++ b/drivers/base/cacheinfo.c >> @@ -297,6 +297,7 @@ static void free_cache_attributes(unsigned int cpu) >> >> kfree(per_cpu_cacheinfo(cpu)); >> per_cpu_cacheinfo(cpu) = NULL; >> + cache_leaves(cpu) = 0; > > I initially thought it might get used and crash in cache_shared_cpu_map_remove > but you are setting it later. So where do you suspect it to be used ? Sorry > if I am missing something obvious, looking at this code after long time. >