Re: [PATCHv4 09/11] memcg: Use *_dec_not_zero instead of *_add_unless

Michal Hocko
2011-07-27T11:58:21Z

On Wed 27-07-11 11:47:48, Sven Eckelmann wrote:
> atomic_dec_not_zero is defined for each architecture through
> <linux/atomic.h> to provide the functionality of
> atomic_add_unless(x, -1, 0).

yes, I like it because atomic_dec_* is more consistent (at least from
the code reading) with atomic_inc used by mem_cgroup_mark_under_oom
which.

>
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: linux-mm@kvack.org

Acked-by: Michal Hocko <mhocko@suse.cz>

> ---
> mm/memcontrol.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5f84d23..00a7580 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1909,10 +1909,10 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *mem)
> /*
> * When a new child is created while the hierarchy is under oom,
> * mem_cgroup_oom_lock() may not be called. We have to use
> - * atomic_add_unless() here.
> + * atomic_dec_not_zero() here.
> */
> for_each_mem_cgroup_tree(iter, mem)
> - atomic_add_unless(&iter->under_oom, -1, 0);
> + atomic_dec_not_zero(&iter->under_oom);
> }
>
> static DEFINE_SPINLOCK(memcg_oom_lock);
> --
> 1.7.5.4
>
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic