From patchwork Fri Mar 4 09:33:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12768808 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 066D1C433EF for ; Fri, 4 Mar 2022 09:35:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3EF0F8D0007; Fri, 4 Mar 2022 04:35:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2FF838D0005; Fri, 4 Mar 2022 04:35:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1EF918D0007; Fri, 4 Mar 2022 04:35:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id EB7F58D0005 for ; Fri, 4 Mar 2022 04:35:04 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B941920D32 for ; Fri, 4 Mar 2022 09:35:04 +0000 (UTC) X-FDA: 79206194928.02.D54AB95 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf03.hostedemail.com (Postfix) with ESMTP id 0C42F20013 for ; Fri, 4 Mar 2022 09:35:03 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4K92dQ3KPvzbcD4; Fri, 4 Mar 2022 17:30:18 +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 15.1.2308.21; Fri, 4 Mar 2022 17:35:00 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , , , , Subject: [PATCH 04/16] mm/migration: reduce the rcu lock duration Date: Fri, 4 Mar 2022 17:33:57 +0800 Message-ID: <20220304093409.25829-5-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220304093409.25829-1-linmiaohe@huawei.com> References: <20220304093409.25829-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0C42F20013 X-Stat-Signature: oxag5fa1bzj37unxo1h3iytd1a6jw6yo Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf03.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-HE-Tag: 1646386503-587906 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: 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. Signed-off-by: Miaohe Lin Reviewed-by: Muchun Song --- mm/migrate.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index da5a81052468..26943bd819e8 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))