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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 573EFC433EF for ; Fri, 27 May 2022 06:49:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344194AbiE0GtQ (ORCPT ); Fri, 27 May 2022 02:49:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236114AbiE0GtM (ORCPT ); Fri, 27 May 2022 02:49:12 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16C0B941A8; Thu, 26 May 2022 23:49:10 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4L8b4Z3QVBzDqT6; Fri, 27 May 2022 14:49:02 +0800 (CST) Received: from dggpemm500013.china.huawei.com (7.185.36.172) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 27 May 2022 14:49:08 +0800 Received: from [127.0.0.1] (10.67.108.67) by dggpemm500013.china.huawei.com (7.185.36.172) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 27 May 2022 14:49:08 +0800 Message-ID: Date: Fri, 27 May 2022 14:49:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v4] locking/csd_lock: change csdlock_debug from early_param to __setup Content-Language: en-US To: CC: , , , , , , , , , , , , , References: <20220510094639.106661-1-chenzhongjin@huawei.com> <9b3e61b8-ecab-08ff-a3b6-83d6862ead77@huawei.com> <20220518011101.GK1790663@paulmck-ThinkPad-P17-Gen-1> From: Chen Zhongjin In-Reply-To: <20220518011101.GK1790663@paulmck-ThinkPad-P17-Gen-1> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.108.67] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500013.china.huawei.com (7.185.36.172) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2022/5/18 9:11, Paul E. McKenney wrote: > On Tue, May 17, 2022 at 11:22:04AM +0800, Chen Zhongjin wrote: >> On 2022/5/10 17:46, Chen Zhongjin wrote: >>> csdlock_debug uses early_param and static_branch_enable() to enable >>> csd_lock_wait feature, which triggers a panic on arm64 with config: >>> CONFIG_SPARSEMEM=y >>> CONFIG_SPARSEMEM_VMEMMAP=n >>> >>> With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in >>> static_key_enable() and returns NULL which makes NULL dereference >>> because mem_section is initialized in sparse_init() which is later >>> than parse_early_param() stage. >>> >>> For powerpc this is also broken, because early_param stage is >>> earlier than jump_label_init() so static_key_enable won't work. >>> powerpc throws an warning: "static key 'xxx' used before call >>> to jump_label_init()". >>> >>> Thus, early_param is too early for csd_lock_wait to run >>> static_branch_enable(), so changes it to __setup to fix these. >>> >>> Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging") >>> Cc: stable@vger.kernel.org >>> Reported-by: Chen jingwen >>> Signed-off-by: Chen Zhongjin >>> --- >>> Change v3 -> v4: >>> Fix title and description because this fix is also applied >>> to powerpc. >>> For more detailed arm64 bug report see: >>> https://lore.kernel.org/linux-arm-kernel/e8715911-f835-059d-27f8-cc5f5ad30a07@huawei.com/t/ >>> >>> Change v2 -> v3: >>> Add module name in title >>> >>> Change v1 -> v2: >>> Fix return 1 for __setup >>> --- >>> kernel/smp.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/kernel/smp.c b/kernel/smp.c >>> index 65a630f62363..381eb15cd28f 100644 >>> --- a/kernel/smp.c >>> +++ b/kernel/smp.c >>> @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str) >>> if (val) >>> static_branch_enable(&csdlock_debug_enabled); >>> >>> - return 0; >>> + return 1; >>> } >>> -early_param("csdlock_debug", csdlock_debug); >>> +__setup("csdlock_debug=", csdlock_debug); >>> >>> static DEFINE_PER_CPU(call_single_data_t *, cur_csd); >>> static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); >> >> Ping for review. Thanks！ > > I have pulled it into -rcu for testing and further review. It might > well need to go through some other path, though. >> Thanx, Paul > . So did it have any result? Do we have any idea to fix that except delaying the set timing? I guess that maybe not using static_branch can work for this, but it still needs to be evaluated for performance influence of not enabled situation. Best, Chen