linux-kernel - Re: FYI: mmap

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Date:	Thu, 08 Jul 2010 11:02:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	linux-mm <linux-mm@...ck.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Divyesh Shah <dpshah@...gle.com>
Subject: Re: FYI: mmap_sem OOM patch

On Wed, 2010-07-07 at 16:11 -0700, Michel Lespinasse wrote:

> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index f627779..4b3a1c7 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1062,7 +1062,10 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
>  			bad_area_nosemaphore(regs, error_code, address);
>  			return;
>  		}
> -		down_read(&mm->mmap_sem);
> +		if (test_thread_flag(TIF_MEMDIE))
> +			down_read_unfair(&mm->mmap_sem);
> +		else
> +			down_read(&mm->mmap_sem);
>  	} else {
>  		/*
>  		 * The above down_read_trylock() might have succeeded in

I still think adding that _unfair interface is asking for trouble.
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