Messages in this thread | | | From | Paul Menage <> | Date | Tue, 4 Jan 2011 17:31:47 -0800 | Subject | Re: [PATCH RESEND] cgroups: fix incorrect using rcu_dereference() in cgroup_subsys_state() |
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On Tue, Jan 4, 2011 at 12:18 AM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote: > From: Li Zefan <lizf@cn.fujitsu.com> > Date: Mon, 25 Aug 2008 11:05:28 +0800 > (Original) Subject: [PATCH] cgroup: fix wrong rcu_dereference() > > It is tsk->cgroups which is protected by RCU, not ->subsys[subsys_id]. > > laijs: updated it(the surrounding code have been changed since these two years). > > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > --- > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index ed4ba11..a798814 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -535,10 +535,11 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state( > * cgroup_subsys::attach() methods. > */ > #define task_subsys_state_check(task, subsys_id, __c) \ > - rcu_dereference_check(task->cgroups->subsys[subsys_id], \ > + rcu_dereference_check(task->cgroups, \ > rcu_read_lock_held() || \ > lockdep_is_held(&task->alloc_lock) || \ > - cgroup_lock_is_held() || (__c)) > + cgroup_lock_is_held() || \ > + (__c))->subsys[subsys_id]
Can you reformat this a bit? It took a fair bit of staring to realize that (__c))->subsys[subsys_id] wasn't trying to dereference __c.
Maybe make it:
#define task_subsys_state_check(task, subsys_id, __c) ({ \ struct css_set *_css = rcu_dereference_check(...); \ _css->subsys[subsys_id]; \ })
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