From patchwork Sat Apr 9 07:38:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12807725 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 B3A02C433F5 for ; Sat, 9 Apr 2022 07:39:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3F7E68D0001; Sat, 9 Apr 2022 03:39:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A6A66B0074; Sat, 9 Apr 2022 03:39:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 295F18D0001; Sat, 9 Apr 2022 03:39:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 1B4BD6B0073 for ; Sat, 9 Apr 2022 03:39:03 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id F06EC6042B for ; Sat, 9 Apr 2022 07:39:02 +0000 (UTC) X-FDA: 79336539324.07.CF1B689 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf10.hostedemail.com (Postfix) with ESMTP id 40BE3C0002 for ; Sat, 9 Apr 2022 07:39:02 +0000 (UTC) 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 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 X-Stat-Signature: 77fj1ekdfk5fh9moibbqr9w5wu5ijypo Authentication-Results: imf10.hostedemail.com; dkim=none; spf=pass (imf10.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 40BE3C0002 X-HE-Tag: 1649489942-951021 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. Reviewed-by: Muchun Song Signed-off-by: Miaohe Lin Reviewed-by: Christoph Hellwig --- 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))