Messages in this thread Patch in this message | | | Date | Fri, 21 Nov 2008 16:49:46 +0800 | From | Lai Jiangshan <> | Subject | [PATCH 1/2] cgroups: enhance task_cgroup() |
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task_cgroup() calls cgroup_subsys_state(). and we must use rcu_read_lock() to protect cgroup_subsys_state(). so we must use rcu_read_lock() to protect task_cgroup().
but it'll not so friendly to caller: the callers of task_cgroup() have held cgroup_lock(). it means that struct cgroup will not be freed.
So this patch add rcu_read_lock() in task_cgroup() to enhance task_cgroup(). And we do NOT NEED FIX task_cgroup()'s callers, and cgroup_lock() can protect task_cgroup().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 1164963..22901ff 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -359,6 +360,10 @@ static inline struct cgroup* task_cgroup(struct task_struct *task, int subsys_id) { - return task_subsys_state(task, subsys_id)->cgroup; + struct cgroup *ret; + rcu_read_lock(); + ret = task_subsys_state(task, subsys_id)->cgroup; + rcu_read_unlock(); + return ret; } int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss,
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