Date: Wed, 3 Feb 2010 17:21:47 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>,
       linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [RFC][PATCH] PM: disable nonboot cpus before suspending devices
Message-Id: <20100203172147.2411966d.akpm@linux-foundation.org>
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On Thu, 4 Feb 2010 01:50:26 +0100 "Rafael J. Wysocki" <rjw@sisk.pl> wrote:

> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -76,6 +76,30 @@ unsigned long totalreserve_pages __read_
>  int percpu_pagelist_fraction;
>  gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
>  
> +/*
> + * The following functions are used by the suspend/hibernate code to temporarily
> + * change gfp_allowed_mask in order to avoid using I/O during memory allocations
> + * while devices are suspended.  To avoid races with the suspend/hibernate code,
> + * they should always be called with pm_mutex held (gfp_allowed_mask also should
> + * only be modified with pm_mutex held, unless the suspend/hibernate code is
> + * guaranteed not to run in parallel with that modification).
> + */
> +
> +void set_gfp_allowed_mask(gfp_t mask)
> +{
> +	WARN_ON(!mutex_is_locked(&pm_mutex));
> +	gfp_allowed_mask = mask;
> +}
> +
> +gfp_t clear_gfp_allowed_mask(gfp_t mask)
> +{
> +	gfp_t ret = gfp_allowed_mask;
> +
> +	WARN_ON(!mutex_is_locked(&pm_mutex));
> +	gfp_allowed_mask &= ~mask;
> +	return ret;
> +}

Maybe put an ifdef CONFIG_foo around these so they don't get included
when they're unneeded?

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