From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966469Ab3HHUSX (ORCPT ); Thu, 8 Aug 2013 16:18:23 -0400 Received: from mail-vb0-f45.google.com ([209.85.212.45]:52141 "EHLO mail-vb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966197Ab3HHUOK (ORCPT ); Thu, 8 Aug 2013 16:14:10 -0400 From: Tejun Heo To: lizefan@huawei.com Cc: containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo , Steven Rostedt , Frederic Weisbecker , Ingo Molnar Subject: [PATCH 04/14] cgroup: cgroup_css_from_dir() now should be called with RCU read locked Date: Thu, 8 Aug 2013 16:13:41 -0400 Message-Id: <1375992831-4650-5-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1375992831-4650-1-git-send-email-tj@kernel.org> References: <1375992831-4650-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org cgroup->subsys[] will become RCU protected and thus all cgroup_css() usages should either be under RCU read lock or cgroup_mutex. This patch updates cgroup_css_from_dir() which returns the matching cgroup_subsys_state given a directory file and subsys_id so that it requires RCU read lock and updates its sole user perf_cgroup_connect(). Signed-off-by: Tejun Heo Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Ingo Molnar --- kernel/cgroup.c | 12 ++++++++++-- kernel/events/core.c | 3 +++ 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 5c6dd7e..cbb6314 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5616,8 +5616,14 @@ struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id) } EXPORT_SYMBOL_GPL(css_lookup); -/* - * get corresponding css from file open on cgroupfs directory +/** + * cgroup_css_from_dir - get corresponding css from file open on cgroup dir + * @f: directory file of interest + * @id: subsystem id of interest + * + * Must be called under RCU read lock. The caller is responsible for + * pinning the returned css if it needs to be accessed outside the RCU + * critical section. */ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) { @@ -5625,6 +5631,8 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) struct inode *inode; struct cgroup_subsys_state *css; + WARN_ON_ONCE(!rcu_read_lock_held()); + inode = file_inode(f); /* check in cgroup filesystem dir */ if (inode->i_op != &cgroup_dir_inode_operations) diff --git a/kernel/events/core.c b/kernel/events/core.c index c199c4f..23261f9 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -591,6 +591,8 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, if (!f.file) return -EBADF; + rcu_read_lock(); + css = cgroup_css_from_dir(f.file, perf_subsys_id); if (IS_ERR(css)) { ret = PTR_ERR(css); @@ -617,6 +619,7 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event, ret = -EINVAL; } out: + rcu_read_unlock(); fdput(f); return ret; } -- 1.8.3.1