On Mon, Feb 22, 2010 at 01:07:32PM -0500, Vivek Goyal wrote:
> > > > +unsigned long mem_cgroup_dirty_bytes(void)
> > > > +{
> > > > + struct mem_cgroup *memcg;
> > > > + unsigned long dirty_bytes;
> > > > +
> > > > + if (mem_cgroup_disabled())
> > > > + return vm_dirty_bytes;
> > > > +
> > > > + rcu_read_lock();
> > > > + memcg = mem_cgroup_from_task(current);
> > > > + if (memcg == NULL)
> > > > + dirty_bytes = vm_dirty_bytes;
> > > > + else
> > > > + dirty_bytes = get_dirty_bytes(memcg);
> > > > + rcu_read_unlock();
> > >
> > > The rcu_read_lock() isn't protecting anything here.
> >
> > Right!
>
> Are we not protecting "memcg" pointer using rcu here?
Vivek, you are right:
mem_cgroup_from_task() -> task_subsys_state() -> rcu_dereference()
So, this *must* be RCU protected.
Thanks!
-Andrea
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