On Mon 23-05-16 19:02:10, Vladimir Davydov wrote:
> mem_cgroup_oom may be invoked multiple times while a process is handling
> a page fault, in which case current->memcg_in_oom will be overwritten
> leaking the previously taken css reference.
Have you seen this happening? I was under impression that the page fault
paths that have oom enabled will not retry allocations.
> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
That being said I do not have anything against the patch. It is a good
safety net I am just not sure this might happen right now and so the
patch is not stable candidate.
After clarification
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/memcontrol.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5b48cd25951b..ef8797d34039 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1608,7 +1608,7 @@ static void memcg_oom_recover(struct mem_cgroup *memcg)
>
> static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
> {
> - if (!current->memcg_may_oom)
> + if (!current->memcg_may_oom || current->memcg_in_oom)
> return;
> /*
> * We are in the middle of the charge context here, so we
> --
> 2.1.4
--
Michal Hocko
SUSE Labs
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