Wraps task_dfl_cgroup() to also take a reference to the cgroup.
v2:
- Eliminate cgroup_mutex and make lighter-weight (Tejun)
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
---
include/linux/cgroup.h | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 63d22dfa00bd..74b435f913c1 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -527,6 +527,35 @@ static inline struct cgroup *task_dfl_cgroup(struct task_struct *task)
return task_css_set(task)->dfl_cgrp;
}
+/**
+ * task_get_dfl_cgroup() - find and get the cgroup for a task
+ * @task: the target task
+ *
+ * Find the cgroup in the v2 hierarchy that a task belongs to, increment its
+ * reference count, and return it.
+ *
+ * Returns:
+ * The appropriate cgroup from the default hierarchy.
+ */
+static inline struct cgroup *
+task_get_dfl_cgroup(struct task_struct *task)
+{
+ struct cgroup *cgrp;
+
+ rcu_read_lock();
+ while (true) {
+ cgrp = task_dfl_cgroup(task);
+
+ if (likely(cgroup_tryget(cgrp)))
+ break;
+
+ cpu_relax();
+ }
+ rcu_read_unlock();
+
+ return cgrp;
+}
+
static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
{
struct cgroup_subsys_state *parent_css = cgrp->self.parent;
--
2.14.3
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