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 DFEF5C433EF for ; Sat, 9 Apr 2022 07:38:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240327AbiDIHkp (ORCPT ); Sat, 9 Apr 2022 03:40:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238317AbiDIHki (ORCPT ); Sat, 9 Apr 2022 03:40:38 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D05C14016 for ; Sat, 9 Apr 2022 00:38:32 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kb6P45dZyzDq5x; Sat, 9 Apr 2022 15:36:08 +0800 (CST) Received: from huawei.com (10.175.124.27) 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; Sat, 9 Apr 2022 15:38:29 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , , , , , Subject: [PATCH 1/4] mm/migration: reduce the rcu lock duration Date: Sat, 9 Apr 2022 15:38:43 +0800 Message-ID: <20220409073846.22286-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220409073846.22286-1-linmiaohe@huawei.com> References: <20220409073846.22286-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) 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 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)) -- 2.23.0