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author | Tejun Heo <tj@kernel.org> | 2013-08-13 11:01:54 -0400 |
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committer | Tejun Heo <tj@kernel.org> | 2013-08-13 11:01:54 -0400 |
commit | 0ae78e0bf10ac38ab53548e18383afc9997eca22 (patch) | |
tree | 8f3e828b1751966af779becd60a0ff432cfefc8d /include/linux/cgroup.h | |
parent | 35ef10da65d43211f4cd7e7822cbb3becdfc0ae1 (diff) | |
download | op-kernel-dev-0ae78e0bf10ac38ab53548e18383afc9997eca22.zip op-kernel-dev-0ae78e0bf10ac38ab53548e18383afc9997eca22.tar.gz |
cgroup: add cgroup_subsys_state->parent
With the planned unified hierarchy, css's (cgroup_subsys_state) will
be RCU protected and allowed to be attached and detached dynamically
over the course of a cgroup's lifetime. This means that css's will
stay accessible after being detached from its cgroup - the matching
pointer in cgroup->subsys[] cleared - for ref draining and RCU grace
period.
cgroup core still wants to guarantee that the parent css is never
destroyed before its children and css_parent() always returns the
parent regardless of the state of the child css as long as it's
accessible.
This patch makes css's hold onto their parents and adds css->parent so
that the parent css is never detroyed before its children and can be
determined without consulting the cgroups.
cgroup->dummy_css is also updated to point to the parent dummy_css;
however, it doesn't need to worry about object lifetime as the parent
cgroup is already pinned by the child.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'include/linux/cgroup.h')
-rw-r--r-- | include/linux/cgroup.h | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 12d66fe..8a5dc91 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -75,6 +75,9 @@ struct cgroup_subsys_state { /* reference count - access via css_[try]get() and css_put() */ struct percpu_ref refcnt; + /* the parent css */ + struct cgroup_subsys_state *parent; + unsigned long flags; /* ID for this css, if possible */ struct css_id __rcu *id; @@ -666,15 +669,7 @@ struct cgroup_subsys { static inline struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css) { - struct cgroup *parent_cgrp = css->cgroup->parent; - - if (!parent_cgrp) - return NULL; - - if (css->ss) - return parent_cgrp->subsys[css->ss->subsys_id]; - else - return &parent_cgrp->dummy_css; + return css->parent; } /** |