Re: [PATCH 3/8] cgroup: add function to get task's cgroup
From: Tejun Heo <hidden>
Date: 2015-11-24 16:27:36
Also in:
cgroups, lkml
Hello, On Mon, Nov 16, 2015 at 01:51:40PM -0600, serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org wrote:
quoted hunk ↗ jump to hunk
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 22e3754..29f0b02 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h@@ -326,6 +326,7 @@ static inline bool css_tryget_online(struct cgroup_subsys_state *css) return percpu_ref_tryget_live(&css->refcnt); return true; } +struct cgroup *get_task_cgroup(struct task_struct *task);
Please move this where other prototypes are.
+/*
+ * get_task_cgroup - returns the cgroup of the task in the default cgroup
+ * hierarchy.
+ *
+ * @task: target task
+ * This function returns the @task's cgroup on the default cgroup hierarchy. The
+ * returned cgroup has its reference incremented (by calling cgroup_get()). So
+ * the caller must cgroup_put() the obtained reference once it is done with it.
+ */
+struct cgroup *get_task_cgroup(struct task_struct *task)
+{
+ struct cgroup *cgrp;
+
+ mutex_lock(&cgroup_mutex);
+ spin_lock_bh(&css_set_lock);
+
+ cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
+ cgroup_get(cgrp);
+
+ spin_unlock_bh(&css_set_lock);
+ mutex_unlock(&cgroup_mutex);
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(get_task_cgroup);So, exposing cgroup_mutex this way can lead to ugly lock dependency issues as cgroup_mutex is expected to be outside of pretty much everything. task_cgroup_path() does it but it has no users (should prolly removed) and cgroup_attach_task_all() is pretty specific. Hmmm... cc'ing Li (btw, please cc him and Johannes from the next posting). Li, I don't think cset_cgroup_from_root() really needs cgroup_mutex. css_set_lock seems to be enough. What do you think? Thanks. -- tejun