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authorTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
committerTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
commit6387698699afd72d6304566fb6ccf84bffe07c56 (patch)
tree9440e96fa8e5adce62409a5b0e40984dfedaada3 /kernel/sched/core.c
parenta7c6d554aa01236ac2a9f851ab0f75704f76dfa2 (diff)
downloadblackbird-op-linux-6387698699afd72d6304566fb6ccf84bffe07c56.tar.gz
blackbird-op-linux-6387698699afd72d6304566fb6ccf84bffe07c56.zip
cgroup: add css_parent()
Currently, controllers have to explicitly follow the cgroup hierarchy to find the parent of a given css. cgroup is moving towards using cgroup_subsys_state as the main controller interface construct, so let's provide a way to climb the hierarchy using just csses. This patch implements css_parent() which, given a css, returns its parent. The function is guarnateed to valid non-NULL parent css as long as the target css is not at the top of the hierarchy. freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices are converted to use css_parent() instead of accessing cgroup->parent directly. * __parent_ca() is dropped from cpuacct and its usage is replaced with parent_ca(). The only difference between the two was NULL test on cgroup->parent which is now embedded in css_parent() making the distinction moot. Note that eventually a css->parent field will be added to css and the NULL check in css_parent() will go away. This patch shouldn't cause any behavior differences. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/sched/core.c')
-rw-r--r--kernel/sched/core.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5bccb0277129..7a10742b389a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7114,13 +7114,10 @@ static struct cgroup_subsys_state *cpu_cgroup_css_alloc(struct cgroup *cgrp)
static int cpu_cgroup_css_online(struct cgroup *cgrp)
{
struct task_group *tg = cgroup_tg(cgrp);
- struct task_group *parent;
+ struct task_group *parent = css_tg(css_parent(&tg->css));
- if (!cgrp->parent)
- return 0;
-
- parent = cgroup_tg(cgrp->parent);
- sched_online_group(tg, parent);
+ if (parent)
+ sched_online_group(tg, parent);
return 0;
}
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