linux-kernel - Re: [PATCH] mm: thp: minor lock simplification in __khugepaged

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Message-ID: <20110612103214.GB19493@tiehlicka.suse.cz>
Date:	Sun, 12 Jun 2011 12:32:15 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: thp: minor lock simplification in __khugepaged_exit

On Fri 10-06-11 16:33:55, Chris Wright wrote:
> The lock is released first thing in all three branches.  Simplify this
> by unconditionally releasing lock and remove else clause which was only
> there to be sure lock was released.
> 
> Signed-off-by: Chris Wright <chrisw@...s-sol.org>

Nice cleanup.
Reviewed-by: Michal Hocko <mhocko@...e.cz>

> ---
>  mm/huge_memory.c |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 615d974..a032ddd 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1596,14 +1596,13 @@ void __khugepaged_exit(struct mm_struct *mm)
>  		list_del(&mm_slot->mm_node);
>  		free = 1;
>  	}
> +	spin_unlock(&khugepaged_mm_lock);
>  
>  	if (free) {
> -		spin_unlock(&khugepaged_mm_lock);
>  		clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
>  		free_mm_slot(mm_slot);
>  		mmdrop(mm);
>  	} else if (mm_slot) {
> -		spin_unlock(&khugepaged_mm_lock);
>  		/*
>  		 * This is required to serialize against
>  		 * khugepaged_test_exit() (which is guaranteed to run
> @@ -1614,8 +1613,7 @@ void __khugepaged_exit(struct mm_struct *mm)
>  		 */
>  		down_write(&mm->mmap_sem);
>  		up_write(&mm->mmap_sem);
> -	} else
> -		spin_unlock(&khugepaged_mm_lock);
> +	}
>  }
>  
>  static void release_pte_page(struct page *page)
> 
> --
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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