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authorTejun Heo <tj@kernel.org>2014-05-07 21:31:17 -0400
committerTejun Heo <tj@kernel.org>2014-05-13 11:26:27 -0400
commit5024ae29cd285ce9e736776414da645d3a91828c (patch)
tree0afef891029af86947869d25b8a3c0e10b6ead69 /kernel/cgroup.c
parent36c38fb7144aa941dc072ba8f58b2dbe509c0345 (diff)
downloadlwn-5024ae29cd285ce9e736776414da645d3a91828c.tar.gz
lwn-5024ae29cd285ce9e736776414da645d3a91828c.zip
cgroup: introduce task_css_is_root()
Determining the css of a task usually requires RCU read lock as that's the only thing which keeps the returned css accessible till its reference is acquired; however, testing whether a task belongs to the root can be performed without dereferencing the returned css by comparing the returned pointer against the root one in init_css_set[] which never changes. Implement task_css_is_root() which can be invoked in any context. This will be used by the scheduled cgroup_freezer change. v2: cgroup no longer supports modular controllers. No need to export init_css_set. Pointed out by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 11a03d67635a..3f1ca934a237 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -348,7 +348,7 @@ struct cgrp_cset_link {
* reference-counted, to improve performance when child cgroups
* haven't been created.
*/
-static struct css_set init_css_set = {
+struct css_set init_css_set = {
.refcount = ATOMIC_INIT(1),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
.tasks = LIST_HEAD_INIT(init_css_set.tasks),