Re: [PATCH 3/4] mm,oom: Simplify exception case handling in out_of_memory().

[Michal Hocko <mhocko@kernel.org>]

On Thu 07-06-18 20:00:22, Tetsuo Handa wrote:
> To avoid oversights when adding the "mm, oom: cgroup-aware OOM killer"
> patchset, simplify the exception case handling in out_of_memory().
> This patch makes no functional changes.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Roman Gushchin <guro@fb.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Tejun Heo <tj@kernel.org>

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

with a minor nit

> ---
>  mm/oom_kill.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 23ce67f..5a6f1b1 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1073,15 +1073,18 @@ bool out_of_memory(struct oom_control *oc)
>  	}
>  
>  	select_bad_process(oc);
> +	if (oc->chosen == (void *)-1UL)

I think this one deserves a comment.
	/* There is an inflight oom victim *.

> +		return true;
>  	/* Found nothing?!?! Either we hang forever, or we panic. */
> -	if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
> +	if (!oc->chosen) {
> +		if (is_sysrq_oom(oc) || is_memcg_oom(oc))
> +			return false;
>  		dump_header(oc, NULL);
>  		panic("Out of memory and no killable processes...\n");
>  	}
> -	if (oc->chosen && oc->chosen != (void *)-1UL)
> -		oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
> -				 "Memory cgroup out of memory");
> -	return !!oc->chosen;
> +	oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
> +			 "Memory cgroup out of memory");
> +	return true;
>  }
>  
>  /*
> -- 
> 1.8.3.1
> 

-- 
Michal Hocko
SUSE Labs