linux-kernel - Re: [RFC][PATCH] PM: disable nonboot cpus before suspending devices

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Message-Id: <20100203174150.192a417a.akpm@linux-foundation.org>
Date:	Wed, 3 Feb 2010 17:41:50 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [RFC][PATCH] PM: disable nonboot cpus before suspending devices

On Wed, 3 Feb 2010 17:21:47 -0800 Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Thu, 4 Feb 2010 01:50:26 +0100 "Rafael J. Wysocki" <rjw@...k.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?
> 

I guess this:

mm/built-in.o: In function `clear_gfp_allowed_mask':
: undefined reference to `pm_mutex'
mm/built-in.o: In function `set_gfp_allowed_mask':
: undefined reference to `pm_mutex'

kinda answers my question.
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