linux-kernel - Re: [patch 01/12] mm: oom_kill: remove unnecessary locking in oom

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Message-ID: <20150326114306.GB15257@dhcp22.suse.cz>
Date:	Thu, 26 Mar 2015 12:43:06 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Huang Ying <ying.huang@...el.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Chinner <david@...morbit.com>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [patch 01/12] mm: oom_kill: remove unnecessary locking in
 oom_enable()

On Wed 25-03-15 02:17:05, Johannes Weiner wrote:
> Setting oom_killer_disabled to false is atomic, there is no need for
> further synchronization with ongoing allocations trying to OOM-kill.

True, races with an ongoing allocations are not harmful.

> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

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

> ---
>  mm/oom_kill.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 2b665da1b3c9..73763e489e86 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -488,9 +488,7 @@ bool oom_killer_disable(void)
>   */
>  void oom_killer_enable(void)
>  {
> -	down_write(&oom_sem);
>  	oom_killer_disabled = false;
> -	up_write(&oom_sem);
>  }
>  
>  #define K(x) ((x) << (PAGE_SHIFT-10))
> -- 
> 2.3.3
> 
> --
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-- 
Michal Hocko
SUSE Labs
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