On Mon, 30 Aug 2010 17:03:24 +0900
Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote:
> > Index: mmotm-0811/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0811.orig/mm/memcontrol.c
> > +++ mmotm-0811/mm/memcontrol.c
> > @@ -195,6 +195,7 @@ static void mem_cgroup_oom_notify(struct
> > */
> > struct mem_cgroup {
> > struct cgroup_subsys_state css;
> > + int valid; /* for checking validness under RCU access.*/
> > /*
> > * the counter to account for memory usage
> > */
> Do we really need to add this new member ?
> Can't we safely access "mem(=rcu_dereference(mem_cgroup[id]))" under rcu_read_lock() ?
> (iow, "mem" is not freed ?)
>
Maybe this can be removed. I'll check again.
>
> > @@ -4049,6 +4068,7 @@ static void __mem_cgroup_free(struct mem
> > mem_cgroup_remove_from_trees(mem);
> > free_css_id(&mem_cgroup_subsys, &mem->css);
> >
> > + atomic_dec(&mem_cgroup_num);
> > for_each_node_state(node, N_POSSIBLE)
> > free_mem_cgroup_per_zone_info(mem, node);
> >
> > @@ -4059,6 +4079,19 @@ static void __mem_cgroup_free(struct mem
> > vfree(mem);
> > }
> >
> > +static void mem_cgroup_free(struct mem_cgroup *mem)
> > +{
> > + /* No more lookup */
> > + mem->valid = 0;
> > + rcu_assign_pointer(mem_cgroups[css_id(&mem->css)], NULL);
> > + /*
> > + * Because we call vfree() etc...use synchronize_rcu() rather than
> > + * call_rcu();
> > + */
> > + synchronize_rcu();
> > + __mem_cgroup_free(mem);
> > +}
> > +
> > static void mem_cgroup_get(struct mem_cgroup *mem)
> > {
> > atomic_inc(&mem->refcnt);
> > @@ -4068,7 +4101,7 @@ static void __mem_cgroup_put(struct mem_
> > {
> > if (atomic_sub_and_test(count, &mem->refcnt)) {
> > struct mem_cgroup *parent = parent_mem_cgroup(mem);
> > - __mem_cgroup_free(mem);
> > + mem_cgroup_free(mem);
> > if (parent)
> > mem_cgroup_put(parent);
> > }
> > @@ -4189,9 +4222,11 @@ mem_cgroup_create(struct cgroup_subsys *
> > atomic_set(&mem->refcnt, 1);
> > mem->move_charge_at_immigrate = 0;
> > mutex_init(&mem->thresholds_lock);
> > + atomic_inc(&mem_cgroup_num);
> > + register_memcg_id(mem);
> > return &mem->css;
> > free_out:
> > - __mem_cgroup_free(mem);
> > + mem_cgroup_free(mem);
> > root_mem_cgroup = NULL;
> > return ERR_PTR(error);
> > }
> I think mem_cgroup_num should be increased at mem_cgroup_alloc(), because it
> is decreased at __mem_cgroup_free(). Otherwise, it can be decreased while it
> has not been increased, if mem_cgroup_create() fails after mem_cgroup_alloc().
>
Hmm. thank you for checking, I'll fix.
Thanks,
-Kame
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