linux-kernel - Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

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Message-ID: <20081106084727.GC11095@atrey.karlin.mff.cuni.cz>
Date:	Thu, 6 Nov 2008 09:47:27 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Yasunori Goto <y-goto@...fujitsu.com>,
	Nigel Cunningham <ncunningham@...a.org.au>,
	Matt Tolentino <matthew.e.tolentino@...el.com>,
	linux-pm@...ts.osdl.org, Dave Hansen <haveblue@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mel@...net.ie>, Andy Whitcroft <apw@...dowen.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

Hi!

> > To trigger "2", the user have special console to tell firmware "enable this memory".
> > Such firmware console or users have to know "the system works well." And, more important,
> > when the system is suspended, the firmware can't do hotplug because the kernel is sleeping.
> > So, such firmware console or operator have to know the system status.
> > 
> > Am I missing some ? Current linux can know PCI/USB hotplug while the
> > system is suspended ?
> 
> * echo 'disk' > /sys/power/state
> * count number of pages to write to disk
> * turn all interrupts off
> * copy pages to disk
> * power down
> 
> I think the race we're trying to close is the one between when we count
> pages and when we turn interrupts off.  I assume that there is a reason
> that we don't do the *entire* hibernation process with interrupts off,
> probably because it would "lock" the system up for too long, and can
> even possibly fail.

We need interrupts to write pages to the disk.
									Pavel
-- 
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