From bad34660344f37db8b55ce8bc139bddc7d83af1b Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Fri, 14 Feb 2014 16:54:28 +0800 Subject: [PATCH] cgroup: fix locking in cgroupstats_build() css_set_lock has been converted to css_set_rwsem, and rwsem can't nest inside rcu_read_lock. Signed-off-by: Li Zefan Signed-off-by: Tejun Heo --- kernel/cgroup.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 15dcae74b510..5606c0f08d95 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2995,6 +2995,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) kernfs_type(kn) != KERNFS_DIR) return -EINVAL; + mutex_lock(&cgroup_mutex); + /* * We aren't being called from kernfs and there's no guarantee on * @kn->priv's validity. For this and css_tryget_from_dir(), @@ -3002,10 +3004,12 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) */ rcu_read_lock(); cgrp = rcu_dereference(kn->priv); - if (!cgrp) { + if (!cgrp || cgroup_is_dead(cgrp)) { rcu_read_unlock(); + mutex_unlock(&cgroup_mutex); return -ENOENT; } + rcu_read_unlock(); css_task_iter_start(&cgrp->dummy_css, &it); while ((tsk = css_task_iter_next(&it))) { @@ -3030,7 +3034,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) } css_task_iter_end(&it); - rcu_read_unlock(); + mutex_unlock(&cgroup_mutex); return 0; } -- 2.39.2