linux-kernel - Re: [PATCH] mm: avoid livelock on !__GFP

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Date:	Wed, 16 Nov 2011 09:10:32 +0200 (EET)
From:	Pekka Enberg <penberg@...nel.org>
To:	Minchan Kim <minchan.kim@...il.com>
cc:	Colin Cross <ccross@...roid.com>, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: avoid livelock on !__GFP_FS allocations

On Wed, 16 Nov 2011, Minchan Kim wrote:
> Then, How about this?
>
> [barrios@...rios-laptop linux-2.6]$ git diff
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index fdd4263..01aa9b5 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -297,9 +297,11 @@ int enter_state(suspend_state_t state)
>                goto Finish;
>
>        pr_debug("PM: Entering %s sleep\n", pm_states[state]);
> +       oom_killer_disable();
>        pm_restrict_gfp_mask();
>        error = suspend_devices_and_enter(state);
>        pm_restore_gfp_mask();
> +       oom_killer_enable();
>
>  Finish:
>        pr_debug("PM: Finishing wakeup.\n");
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6e8ecb6..d8c31b7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2177,9 +2177,9 @@ rebalance:
>         * running out of options and have to consider going OOM
>         */
>        if (!did_some_progress) {
> -               if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
> -                       if (oom_killer_disabled)
> +               if (oom_killer_disabled)
>                                goto nopage;
> +               if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
>                        page = __alloc_pages_may_oom(gfp_mask, order,
>                                        zonelist, high_zoneidx,
>                                        nodemask, preferred_zone,
>

I'd prefer something like this. The whole 'gfp_allowed_flags' thing was 
designed to make GFP_KERNEL work during boot time where it's obviously 
safe to do that. I really don't think that's going to work suspend 
cleanly.

 			Pekka
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