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Commit e14880f7 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

cgroup: implement cgroup_from_id() 



This will be used as a replacement for css_lookup().

There's a difference with cgroup id and css id. cgroup id starts with 0,
while css id starts with 1.

v4:
- also check if cggroup_mutex is held.
- make it an inline function.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent b414dc09

include/linux/cgroup.h

+18 −0
Original line number Diff line number Diff line
@@ -720,6 +720,24 @@ static inline struct cgroup* task_cgroup(struct task_struct *task, 
	return task_subsys_state(task, subsys_id)->cgroup;

}



/**

 * cgroup_from_id - lookup cgroup by id

 * @ss: cgroup subsys to be looked into

 * @id: the cgroup id

 *

 * Returns the cgroup if there's valid one with @id, otherwise returns NULL.

 * Should be called under rcu_read_lock().

 */

static inline struct cgroup *cgroup_from_id(struct cgroup_subsys *ss, int id)

{

#ifdef CONFIG_PROVE_RCU

	rcu_lockdep_assert(rcu_read_lock_held() ||

			   lockdep_is_held(&cgroup_mutex),

			   "cgroup_from_id() needs proper protection");

#endif

	return idr_find(&ss->root->cgroup_idr, id);

}



struct cgroup *cgroup_next_sibling(struct cgroup *pos);



/**