Messages in this thread | | | Date | Fri, 21 Nov 2008 10:58:44 -0800 | Subject | Re: [PATCH 1/2] cgroups: enhance task_cgroup() | From | Paul Menage <> |
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On Fri, Nov 21, 2008 at 12:49 AM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote: > > task_cgroup() calls cgroup_subsys_state().
No, it calls task_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().
Is there a reason to add an implicit rcu_read_lock() in task_cgroup() and not directly in task_subsys_state() ?
Paul
> > 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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