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 38315C4332F for ; Tue, 12 Apr 2022 03:21:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344351AbiDLDX7 (ORCPT ); Mon, 11 Apr 2022 23:23:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344448AbiDLDXy (ORCPT ); Mon, 11 Apr 2022 23:23:54 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A37F33354 for ; Mon, 11 Apr 2022 20:21:34 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4KcrVz70JBzBsBC; Tue, 12 Apr 2022 11:17:15 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 12 Apr 2022 11:21:31 +0800 Subject: Re: [PATCH 1/4] mm/migration: reduce the rcu lock duration To: "ying.huang@intel.com" , CC: , , , , , , , , , , , , , , , , , References: <20220409073846.22286-1-linmiaohe@huawei.com> <20220409073846.22286-2-linmiaohe@huawei.com> <557be6cc7ecdee357391df3fe94e5573f9e1746d.camel@intel.com> From: Miaohe Lin Message-ID: <34f3aff7-0111-a8d6-a559-92bf6d0bd62a@huawei.com> Date: Tue, 12 Apr 2022 11:21:31 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <557be6cc7ecdee357391df3fe94e5573f9e1746d.camel@intel.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/12 10:07, ying.huang@intel.com wrote: > On Sat, 2022-04-09 at 15:38 +0800, Miaohe Lin wrote: >> rcu_read_lock is required by grabbing the task refcount but it's not >> needed for ptrace_may_access. So we could release the rcu lock after >> task refcount is successfully grabbed to reduce the rcu holding time. >> >> Reviewed-by: Muchun Song >> Signed-off-by: Miaohe Lin >> --- >>  mm/migrate.c | 3 +-- >>  1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index a3d8c2be2631..d8aae6c75990 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1907,17 +1907,16 @@ static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes) >>   return ERR_PTR(-ESRCH); >>   } >>   get_task_struct(task); >> + rcu_read_unlock(); >>   >> >>   /* >>   * Check if this process has the right to modify the specified >>   * process. Use the regular "ptrace_may_access()" checks. >>   */ >>   if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { >> - rcu_read_unlock(); >>   mm = ERR_PTR(-EPERM); >>   goto out; >>   } >> - rcu_read_unlock(); >>   >> >>   mm = ERR_PTR(security_task_movememory(task)); >>   if (IS_ERR(mm)) > > Why do you ignore our discussion for the previous version? > > https://lore.kernel.org/linux-mm/8735ju7as9.fsf@yhuang6-desk2.ccr.corp.intel.com/ > Sorry for confusing. I remember this patch is pending for verify. The reason I post this series is that I want to move the other patches in this series forward while this patch is still pending for verify. Thanks. > Best Regards, > Huang, Ying > > > . >