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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79C1DC433EF for ; Tue, 12 Apr 2022 03:21:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 09C076B0071; Mon, 11 Apr 2022 23:21:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 023EC6B0073; Mon, 11 Apr 2022 23:21:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E073F6B0074; Mon, 11 Apr 2022 23:21:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0249.hostedemail.com [216.40.44.249]) by kanga.kvack.org (Postfix) with ESMTP id CE6996B0071 for ; Mon, 11 Apr 2022 23:21:36 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7488D8248D52 for ; Tue, 12 Apr 2022 03:21:36 +0000 (UTC) X-FDA: 79346776992.26.1FE0E12 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by imf31.hostedemail.com (Postfix) with ESMTP id 70EBA20005 for ; Tue, 12 Apr 2022 03:21:35 +0000 (UTC) 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 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 Authentication-Results: imf31.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf31.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 70EBA20005 X-Stat-Signature: 4s34nkj3xaixin3677pxyfo1txftojf1 X-HE-Tag: 1649733695-629282 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 >> --- >> =C2=A0mm/migrate.c | 3 +-- >> =C2=A01 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) >> =C2=A0 return ERR_PTR(-ESRCH); >> =C2=A0 } >> =C2=A0 get_task_struct(task); >> + rcu_read_unlock(); >> =C2=A0 >> >> =C2=A0 /* >> =C2=A0 * Check if this process has the right to modify the specified >> =C2=A0 * process. Use the regular "ptrace_may_access()" checks. >> =C2=A0 */ >> =C2=A0 if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { >> - rcu_read_unlock(); >> =C2=A0 mm =3D ERR_PTR(-EPERM); >> =C2=A0 goto out; >> =C2=A0 } >> - rcu_read_unlock(); >> =C2=A0 >> >> =C2=A0 mm =3D ERR_PTR(security_task_movememory(task)); >> =C2=A0 if (IS_ERR(mm)) >=20 > Why do you ignore our discussion for the previous version? >=20 > https://lore.kernel.org/linux-mm/8735ju7as9.fsf@yhuang6-desk2.ccr.corp.= intel.com/ >=20 Sorry for confusing. I remember this patch is pending for verify. The rea= son 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 >=20 >=20 > . >=20