From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752542Ab1IDSBx (ORCPT ); Sun, 4 Sep 2011 14:01:53 -0400 Received: from mail-pz0-f42.google.com ([209.85.210.42]:51952 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752347Ab1IDSBl (ORCPT ); Sun, 4 Sep 2011 14:01:41 -0400 From: Tejun Heo To: rjw@sisk.pl, paul@paulmenage.org, lizf@cn.fujitsu.com Cc: linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, fweisbec@gmail.com, matthltc@us.ibm.com, akpm@linux-foundation.org, Tejun Heo , Oleg Nesterov , Paul Menage Subject: [PATCH 1/4] cgroup: change locking order in attach_task_by_pid() Date: Mon, 5 Sep 2011 03:01:17 +0900 Message-Id: <1315159280-25032-2-git-send-email-htejun@gmail.com> X-Mailer: git-send-email 1.7.6 In-Reply-To: <1315159280-25032-1-git-send-email-htejun@gmail.com> References: <1315159280-25032-1-git-send-email-htejun@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tejun Heo cgroup_mutex is updated to nest inside threadgroup_fork_lock instead of the other way around. threadgroup locking is scheduled to be updated to cover all threadgroup altering operations and nesting it inside cgroup_mutex complicates locking dependency unnecessarily. This also simplifies code a bit. The ugly "if (threadgroup)" conditionals for threadgroup locking will soon be removed. Signed-off-by: Tejun Heo Cc: Oleg Nesterov Cc: Andrew Morton Cc: Paul Menage Cc: Li Zefan --- kernel/cgroup.c | 22 ++++++++++------------ 1 files changed, 10 insertions(+), 12 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1d2b6ce..bd1fb5f 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2203,15 +2203,11 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) const struct cred *cred = current_cred(), *tcred; int ret; - if (!cgroup_lock_live_group(cgrp)) - return -ENODEV; - if (pid) { rcu_read_lock(); tsk = find_task_by_vpid(pid); if (!tsk) { rcu_read_unlock(); - cgroup_unlock(); return -ESRCH; } if (threadgroup) { @@ -2225,7 +2221,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) } else if (tsk->flags & PF_EXITING) { /* optimization for the single-task-only case */ rcu_read_unlock(); - cgroup_unlock(); return -ESRCH; } @@ -2238,7 +2233,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) cred->euid != tcred->uid && cred->euid != tcred->suid) { rcu_read_unlock(); - cgroup_unlock(); return -EACCES; } get_task_struct(tsk); @@ -2251,15 +2245,19 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) get_task_struct(tsk); } - if (threadgroup) { + if (threadgroup) threadgroup_fork_write_lock(tsk); - ret = cgroup_attach_proc(cgrp, tsk); - threadgroup_fork_write_unlock(tsk); - } else { - ret = cgroup_attach_task(cgrp, tsk); + ret = -ENODEV; + if (cgroup_lock_live_group(cgrp)) { + if (threadgroup) + ret = cgroup_attach_proc(cgrp, tsk); + else + ret = cgroup_attach_task(cgrp, tsk); + cgroup_unlock(); } + if (threadgroup) + threadgroup_fork_write_unlock(tsk); put_task_struct(tsk); - cgroup_unlock(); return ret; } -- 1.7.6