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| Started by | Michal Hocko <mhocko@kernel.org> |
|---|---|
| First post | 2016-08-02 14:50 +0200 |
| Last post | 2016-08-03 00:00 +0200 |
| Articles | 2 — 1 participant |
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Re: [PATCH 3/3] mm: memcontrol: add sanity checks for memcg->id.ref on get/put Michal Hocko <mhocko@kernel.org> - 2016-08-02 14:50 +0200
Re: [PATCH 3/3] mm: memcontrol: add sanity checks for memcg->id.ref on get/put Michal Hocko <mhocko@kernel.org> - 2016-08-03 00:00 +0200
| From | Michal Hocko <mhocko@kernel.org> |
|---|---|
| Date | 2016-08-02 14:50 +0200 |
| Subject | Re: [PATCH 3/3] mm: memcontrol: add sanity checks for memcg->id.ref on get/put |
| Message-ID | <s1HiX-4uK-61@gated-at.bofh.it> |
On Mon 01-08-16 16:26:26, Vladimir Davydov wrote:
[...]
> static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
> {
> - while (!atomic_inc_not_zero(&memcg->id.ref))
> + while (!atomic_inc_not_zero(&memcg->id.ref)) {
> + VM_BUG_ON(mem_cgroup_is_root(memcg));
> memcg = parent_mem_cgroup(memcg);
> + }
why is this BUG_ON ok? What if the root.use_hierarchy=true?
> return memcg;
> }
--
Michal Hocko
SUSE Labs
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| From | Michal Hocko <mhocko@kernel.org> |
|---|---|
| Date | 2016-08-03 00:00 +0200 |
| Message-ID | <s1PTb-1PI-1@gated-at.bofh.it> |
| In reply to | #1454181 |
On Tue 02-08-16 14:45:03, Michal Hocko wrote:
> On Mon 01-08-16 16:26:26, Vladimir Davydov wrote:
> [...]
> > static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
> > {
> > - while (!atomic_inc_not_zero(&memcg->id.ref))
> > + while (!atomic_inc_not_zero(&memcg->id.ref)) {
> > + VM_BUG_ON(mem_cgroup_is_root(memcg));
> > memcg = parent_mem_cgroup(memcg);
> > + }
>
> why is this BUG_ON ok? What if the root.use_hierarchy=true?
Scratch that. I got it. root will never get its count down to 0. Sorry
about the noise.
--
Michal Hocko
SUSE Labs
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