From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755270AbaEFUTv (ORCPT ); Tue, 6 May 2014 16:19:51 -0400 Received: from mail-qc0-f177.google.com ([209.85.216.177]:52766 "EHLO mail-qc0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755126AbaEFUTs (ORCPT ); Tue, 6 May 2014 16:19:48 -0400 From: Tejun Heo To: lizefan@huawei.com Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 6/8] cgroup: use cgroup_kn_lock_live() in other cgroup kernfs methods Date: Tue, 6 May 2014 16:19:32 -0400 Message-Id: <1399407574-21472-7-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1399407574-21472-1-git-send-email-tj@kernel.org> References: <1399407574-21472-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Make __cgroup_procs_write() and cgroup_release_agent_write() use cgroup_kn_lock_live() and cgroup_kn_unlock() instead of cgroup_lock_live_group(). This puts the operations under both cgroup_tree_mutex and cgroup_mutex protection without circular dependency from kernfs active protection. Also, this means that cgroup_mutex is no longer nested below kernfs active protection. There is no longer any place where the two locks interact. This leaves cgroup_lock_live_group() without any user. Removed. This will help simplifying cgroup locking. Signed-off-by: Tejun Heo --- kernel/cgroup.c | 39 ++++++++++++--------------------------- 1 file changed, 12 insertions(+), 27 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 1d0d5f7..281fce5 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -386,23 +386,6 @@ static int notify_on_release(const struct cgroup *cgrp) ; \ else -/** - * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive. - * @cgrp: the cgroup to be checked for liveness - * - * On success, returns true; the mutex should be later unlocked. On - * failure returns false with no lock held. - */ -static bool cgroup_lock_live_group(struct cgroup *cgrp) -{ - mutex_lock(&cgroup_mutex); - if (cgroup_is_dead(cgrp)) { - mutex_unlock(&cgroup_mutex); - return false; - } - return true; -} - /* the list of cgroups eligible for automatic release. Protected by * release_list_lock */ static LIST_HEAD(release_list); @@ -2306,14 +2289,15 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf, { struct task_struct *tsk; const struct cred *cred = current_cred(), *tcred; - struct cgroup *cgrp = of_css(of)->cgroup; + struct cgroup *cgrp; pid_t pid; int ret; if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0) return -EINVAL; - if (!cgroup_lock_live_group(cgrp)) + cgrp = cgroup_kn_lock_live(of->kn); + if (!cgrp) return -ENODEV; retry_find_task: @@ -2379,7 +2363,7 @@ retry_find_task: put_task_struct(tsk); out_unlock_cgroup: - mutex_unlock(&cgroup_mutex); + cgroup_kn_unlock(of->kn); return ret ?: nbytes; } @@ -2429,17 +2413,18 @@ static ssize_t cgroup_procs_write(struct kernfs_open_file *of, static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { - struct cgroup *cgrp = of_css(of)->cgroup; - struct cgroup_root *root = cgrp->root; + struct cgroup *cgrp; - BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX); - if (!cgroup_lock_live_group(cgrp)) + BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); + + cgrp = cgroup_kn_lock_live(of->kn); + if (!cgrp) return -ENODEV; spin_lock(&release_agent_path_lock); - strlcpy(root->release_agent_path, strstrip(buf), - sizeof(root->release_agent_path)); + strlcpy(cgrp->root->release_agent_path, strstrip(buf), + sizeof(cgrp->root->release_agent_path)); spin_unlock(&release_agent_path_lock); - mutex_unlock(&cgroup_mutex); + cgroup_kn_unlock(of->kn); return nbytes; } -- 1.9.0