linux-kernel - Re: Deadlock possibly caused by too_many

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Message-ID: <4C90139A.1080809@redhat.com>
Date:	Tue, 14 Sep 2010 20:30:18 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Neil Brown <neilb@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: Deadlock possibly caused by too_many_isolated.

On 09/14/2010 07:11 PM, Neil Brown wrote:

> Index: linux-2.6.32-SLE11-SP1/mm/vmscan.c
> ===================================================================
> --- linux-2.6.32-SLE11-SP1.orig/mm/vmscan.c	2010-09-15 08:37:32.000000000 +1000
> +++ linux-2.6.32-SLE11-SP1/mm/vmscan.c	2010-09-15 08:38:57.000000000 +1000
> @@ -1106,6 +1106,11 @@ static unsigned long shrink_inactive_lis
>   		/* We are about to die and free our memory. Return now. */
>   		if (fatal_signal_pending(current))
>   			return SWAP_CLUSTER_MAX;
> +		if (!(sc->gfp_mask&  __GFP_IO))
> +			/* Not allowed to do IO, so mustn't wait
> +			 * on processes that might try to
> +			 */
> +			return SWAP_CLUSTER_MAX;
>   	}
>
>   	/*

Close.  We must also be sure that processes without __GFP_FS
set in their gfp_mask do not wait on processes that do have
__GFP_FS set.

Considering how many times we've run into a bug like this,
I'm kicking myself for not having thought of it :(

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